CN115526026A - Physical model test method for seashore evolution and channel siltation under storm surge effect - Google Patents
Physical model test method for seashore evolution and channel siltation under storm surge effect Download PDFInfo
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Abstract
The invention discloses a physical model test method for seashore evolution and channel siltation under the action of storm surge, which determines the median particle size of prototype sand, the particle density of the prototype sand and the apparent dry density of the prototype sand; determining the median particle diameter, particle density and apparent dry density of the model sand: manufacturing a fixed bed terrain and a moving bed terrain in a test pool; adding water into a test pool to a model water level corresponding to the average water level of the prototype coastal storm before the storm surge, setting a wave which does not start the sediment through a wave making machine, and starting the test; calculating the test operation time according to the prototype coastal wind storm surge action time and the erosion and deposition time scale; draining water in the test water tank, measuring the terrain after the test operation is finished, and subtracting the moving bed terrain before the test from the terrain after the test operation is finished to obtain silt scouring distribution under the action of storm surge.
Description
Technical Field
The invention relates to a physical model test method for seashore evolution and channel siltation under the action of storm surge, belonging to the technical field of coastal engineering.
Background
Coastal evolution is the result of the interaction of coastal hydrodynamic forces with the terrain, in which silt movements play the role of coupling processes. Under certain sand coming conditions, when hydrodynamic force is matched with underwater topography, sediment transport is usually balanced, and a beach and a seabed are also stable; when the hydrodynamic force is not matched with the underwater topography, the coastal hydrodynamic force can cause the sediment to start, suspend, transport, settle and the like, so that the sediment is redistributed in space and time, and the underwater topography suitable for the hydrodynamic force is shaped. The coastal zone contains precious natural resources, is a main place for coastal biochemical circulation and organic carbon storage, and provides a place for human beings and a plurality of animals and plants to live in rest. Therefore, prediction of coastal terrain evolution is of great significance for protecting and developing coastal zone resources, preventing and reducing disasters and managing coastal spaces.
Storm surge is one of common marine disasters in coastal zones of China, and the process of storm surge is usually accompanied by storm water increase, strong tide and huge wave action. Storm water increase can cause coastal inundation and flood washing, and threatens life and property safety of coastal people. The wave current and strong water body turbulence caused by continuous breaking of huge waves in the near-shore water area and the superposition of the enhanced current cause the violent movement of silt, so that the coastal topography is greatly changed on the time scale of several days. At the moment, if a channel exists on the coast, silt flushed from the beach is often accumulated in the channel to cause a sudden silt phenomenon, great pressure is brought to dredging work, and the safe navigation of a ship is even influenced in serious cases. The strong wave flow interaction in the storm surge process and the sediment movement mechanism under the action of the strong wave flow interaction are not well understood, and the accurate prediction of the coast topography evolution and the channel sedimentation under the storm surge action still has great difficulty at present.
The integral physical model test can intuitively and completely reproduce the coastal water power and sediment process, and provides a feasible method for predicting the coastal terrain evolution and channel sedimentation under the action of storm surge. However, the movement mechanism of the silt under the action of the storm surge is different from that of the silt under the action of a single tidal current or wave, and the existing common tidal current silt physical model test method and wave physical model test method cannot be simply transplanted to be used for the silt physical model test under the action of the storm surge. In addition, the grain sizes of the silt inside and outside the normally-wavy broken wave band of many sandy coasts and silty silt coasts are greatly different, and the physical processes such as starting, suspending, settling and the like have large differences, so that the evolution process of the underwater terrain cannot be simulated simply by adopting uniform sand with a single grain size in the coast physical model test, and the existing silt physical model test is lack of a sand selection and similar scale determination method of the silt with different grain sizes under the combined action of wave current.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a physical model test method for coast evolution and channel siltation under the action of storm surge.
In order to achieve the above object, the present invention provides a physical model test method for coast evolution and channel siltation under storm surge, which is characterized by comprising:
(1) Determining a test range and a moving bed range of the model based on the evolution range of the historical storm surge terrain of the prototype coast;
(2) Determining the plane geometric scale lambda of the model based on the test range, the test site size, the tidal generation system current generation capacity and the wave generation capacity of the wave generator l And vertical geometric scale lambda h ；
Wave height ratio rule lambda H Sum wavelength scale lambda L Is equal to the vertical geometric scale lambda h According to the formula λ T ＝λ h 1/2 Calculating to obtain wave period scale lambda T According to the formula λ V ＝λ h 1/2 Calculating to obtain a flow velocity scale lambda V ；
(3) Determining the median diameter of the prototype sand, the particle density of the prototype sand and the apparent dry density of the prototype sand;
(4) Determining the median particle diameter of the model sand, the particle density of the model sand and the apparent dry density of the model sand:
(4.1) calculating a particle size ratio rule meeting similar starting requirements according to the silt starting similarity rule, the wave height ratio rule, the wavelength ratio rule, the flow velocity ratio rule, the median particle size of the prototype sand, the particle density of the prototype sand and the particle density of the model sand to be selected;
(4.2) calculating a particle size scale meeting the convection transport similarity and a particle size scale meeting the sedimentation similarity according to a sedimentation velocity scale formula meeting the convection transport similarity, a particle size scale formula meeting the sedimentation velocity similarity, a plane geometric scale, a vertical geometric scale, the median particle size of the prototype sand, the particle density of the prototype sand and the particle density of the model sand to be selected;
(4.3) determining a final particle size ratio based on the particle size ratio satisfying similar starting and the particle size ratio satisfying similar convection transport and similar sedimentation;
(4.4) determining the median particle diameter of the model sand, the particle density of the model sand and the apparent dry density of the model sand;
(5) Calculating a sand content scale and a slushing time scale;
(6) Determining a storm surge level process, a storm surge tide process and a storm surge wave process at the boundary of the model;
(7) Manufacturing a fixed bed terrain and a moving bed terrain in a test pool;
if wading buildings and artificial terrains are arranged on the fixed bed terrains or the moving bed terrains, the wading building terrains and the artificial terrains are manufactured in the test pool;
arranging tide generating systems at the upstream boundary and the downstream boundary of the fixed-bed terrain of the model;
arranging a wave making machine at the open sea boundary of the model fixed bed terrain according to the wave direction of storm surge;
arranging wave guide plates on two sides of the wave making machine;
sand adding devices are respectively arranged on the upstream of the moving bed terrain and the downstream of the moving bed terrain;
(8) Adding water into a test pool to reach a model water level corresponding to the average water level of the prototype coastal wind before the storm surge, wherein the model water level corresponding to the average water level of the prototype coastal wind before the storm surge = the average water level of the prototype coastal wind before the storm surge ÷ vertical geometric scale;
setting a wave which does not start silt through the wave making machine, operating for a period of time to compact the model sand, closing the wave making machine after the model sand is compact, and waiting for the water surface of the test pool to be calm;
(9) Setting a tide generating system according to a storm tide level process and a storm tide flow process, setting a wave making machine according to a storm tide wave process, starting the tide generating system and the wave making machine, starting a sand adding device for adding sand, and starting a test;
(10) Calculating the test operation time t according to the scale of the action time of storm tide of the prototype coastal wind and the erosion time;
and when the test operation is finished, closing the sand adding device, the wave making machine and the tide generating system, draining water in the test water tank, measuring the terrain after the test operation is finished, and subtracting the moving bed terrain before the test from the terrain after the test operation is finished to obtain the silt scouring distribution under the action of storm surge.
Preferentially, the test range and the moving bed range of the model are determined based on the historical storm surge terrain evolution range of the prototype coast, and the method is realized by the following steps:
setting the open sea boundary of the moving bed according to the collected historical storm surge landform evolution data of similar scale or storm surge sediment mathematical model resultsIs arranged outside the landform evolution range caused by storm surge, and the open sea boundary water depth of the moving bed is more than or equal to the starting water depth h under the action of storm surge cr Starting water depth h under storm surge cr Calculated according to the following formula:
wherein arcsinh is the inverse of sinh; l is s The wave wavelength during the wind tide, and H is the wave height during the wind tide; d is the prototype Sha Zhongzhi particle size; g is the acceleration of gravity; rho s Is the prototype sand particle density, ρ is the density of water;
u b in order to research the water flow velocity at the bottom of the sea area water depth, the water flow velocity is determined by the actual measurement data of the tidal current of the prototype coast or the result of a storm surge mathematical model; epsilon is a set coefficient;
the distance between the open sea boundary of the test range and the open sea boundary of the moving bed is more than or equal to 3-5 times of the model wavelength.
Preferably, the median particle diameter, particle density and apparent dry density of the prototype sand are determined by:
if the internal and external silt of the normal wave broken wave band of the prototype coast is not the same type of the following three types of silt, sampling the prototype sand on the prototype coast, and measuring to obtain the median particle diameter, the particle density and the apparent dry density of the prototype sand;
the three types of silt are:
1. the median particle size is greater than 0.1mm;
2. a median particle diameter of greater than or equal to 0.03mm but less than or equal to 0.1mm and a clay content of less than 25%;
3. a median particle size of less than 0.03mm and a clay content of greater than or equal to 25%;
if the sediment inside and outside the original coast normally-wavy broken band is the same sediment of the three types, taking the average value of the median particle sizes of the sediment inside and outside the original coast normally-wavy broken band as the median particle size of the original sand, taking the average value of the particle densities of the sediment inside and outside the original coast normally-wavy broken band as the particle density of the original sand, and taking the average value of the apparent dry densities of the sediment inside and outside the original coast normally-wavy broken band as the apparent dry density of the original sand.
Preferentially, the model sands inside and outside the normal wave broken wave band adopt the model sands with the same grain size or the model sands with two grain sizes;
if the model sands inside and outside the normal wave broken wave band adopt the model sands with two grain diameters, the difference of the apparent dry densities of the model sands with the two grain diameters is less than 100kg/m 3 。
Preferably, step (4.1) calculates a particle size ratio satisfying similar start-up rule according to silt start-up similarity rule, wave height ratio, wavelength ratio, flow rate ratio, median particle size of prototype sand, particle density of prototype sand and particle density of model sand to be selected:
in the formula: lambda [ alpha ] d Is a particle size scale; lambda [ alpha ] L Is a wavelength scale, λ H Is a wave height scale;
is a function of
Ratio of values in prototype coast to model, in prototype coast ρ s Taking the value as the particle density of the prototype sand, taking the value of d as the median diameter of the prototype sand in the prototype coast, and taking the value of u as the median diameter of the prototype sand in the prototype coast b Taking the value as the water flow velocity at the bottom of the depth of the prototype coast, and in the model, rho s Taking the value as the particle density of the model sand, taking the value of d as the median diameter of the model sand in the model, and taking the value of u as the median diameter of the model sand in the model b Taking the value as the flow velocity of the water flow at the bottom of the model water depth;
ρ is the density of water; g is gravity acceleration; epsilon is a set coefficient;
L s the wave length during a tide.
Preferentially, (4.2) calculating a particle size scale satisfying the similar convection transport and the similar sedimentation according to a sedimentation velocity scale formula satisfying the similar convection transport, a particle size scale formula satisfying the similar sedimentation velocity, a plane geometric scale, a vertical geometric scale, the median particle size of the prototype sand, the particle density of the prototype sand and the particle density of the model sand to be selected, and realizing the following steps:
the formula of the sinking velocity scale satisfying the similarity of convection transport is as follows:
in the formula, λ ω A silt sinking speed scale; lambda [ alpha ] l Is a plane geometric scale, lambda h Is a vertical geometric scale;
according to the formula (3) and the Wuhan's water conservancy electric power college sinking speed formula, determining a particle size scale formula meeting the condition that the convection transportation is similar to the sinking speed, wherein the particle size scale formula meeting the condition that the convection transportation is similar to the sinking speed is as follows:
in the formula: Δ = (ρ) s /ρ)-1，
Representing a function
In the ratio of the values in the prototype coast and the model coast, d in the prototype coast is the median particle size of the prototype sand, and d in the model is the median particle size of the model sand; upsilon is the motion viscosity coefficient of water;
(4.3) determining a final particle size ratio based on the particle size ratio which meets similar starting and the particle size ratio which meets similar convection transportation and similar sedimentation, and realizing the following steps:
and (4) determining the value of a final particle size ratio according to the selectable model sand resources, wherein the value of the final particle size ratio is between the particle size ratio which is obtained by calculation in the step (4.1) and meets the requirements of starting similarity and the particle size ratio which is obtained by calculation in the step (4.2) and meets the requirements of convection transport similarity and sedimentation similarity.
Preferentially, (4.4) determining the median particle size of the model sand, the particle density of the model sand and the apparent dry density of the model sand by:
obtaining a model sand sample;
drying the model sand sample by using an oven;
measuring the volume and the mass of the dried model sand sample;
measuring the median particle diameter of the model sand sample and the particle density of the model sand sample;
dividing the measured mass by the measured volume to obtain the apparent dry density of the model sand sample;
if the model sand sample cannot be obtained or the oven does not exist, calculating the apparent dry density of the model sand according to the following formula:
in the formula: rho d Apparent dry density, ρ, of model sand s And d is the median particle diameter of the model sand.
Preferentially, (5) calculating a sand content ratio scale and a sluicing time ratio scale, and realizing the steps as follows:
sand content scale lambda S Calculated as follows:
in the formula (I), the compound is shown in the specification,
is a silt particle density scale which is formed by prototype silt particlesDividing the particle density by the particle density of the model sand;
is rho s -the ratio of the value of ρ in the prototype sand to the value in the model sand;
slide rule lambda for slushing time t Calculated as follows:
in the formula, λ ρd The ratio of the mean value of the apparent dry density of the sediment inside and outside the original normal wave broken wave band to the mean value of the apparent dry density of the sediment inside and outside the model normal wave broken wave band.
Preferably, the sand adding device is respectively arranged at the upstream of the moving bed terrain and the downstream of the moving bed terrain, and the sand adding device is realized by the following steps:
if the model sand with the same particle size is adopted inside and outside the normal wave broken wave band in the model, arranging a sand adding device on the upstream boundary and the downstream boundary of the moving bed respectively, wherein the length of the sand adding device is equal to the width of the moving bed terrain;
if model sands with different particle sizes are adopted inside and outside the normal wave breaking wave band, two sand adding devices are respectively arranged on the upstream boundary and the downstream boundary of the moving bed terrain, the length of the sand adding device close to a shoreline is the width of the wave breaking band under the action of normal waves, and the length of the sand adding device close to the open sea is the distance between a wave breaking point and the open sea boundary of the moving bed terrain;
the single width sand adding rate P when the sand adding device works is as follows:
in the formula: h is a total of p Is the depth of water, S, of the prototype coast corresponding to the location of sand addition p The sand content of the prototype coast corresponding to the sand addition location, V p The water depth average flow velocity of the prototype coast corresponding to the sand adding position is obtained; lambda [ alpha ] h Is a vertical geometric scale; lambda [ alpha ] V To a flow rate scale, λ S Is a sand content scale;
determining the sand content of the prototype coast according to the actually measured sand content of the prototype coast; if the sand content is not measured on the prototype coast, the sand content is determined by the following formula:
in the formula, V c The average flow velocity of storm surge tidal current is obtained; v w The flow velocity of the broken wave of the storm surge is shown, and F is a sediment factor; rho s Is the prototype sand particle density, ρ is the density of water; g is the acceleration of gravity; h is the depth of the prototype coast water;
silt factor F is determined by the following formula:
in the formula: d is a radical of 0 Is the characteristic particle size, a is the characteristic area, d is the median particle size of the prototype sand;
storm surge velocity of flow V w Calculated as follows:
in the formula: gamma ray b Is an index of wave breaking; h b To break the wave height.
Preferentially, (10) calculating the test running time t according to the scale of the action time and the erosion and deposition time of the prototype coastal storm tide:
t＝t p /λ t (24)
in the formula: t is t p Is the time of storm surge of coastal wind, lambda t Is a scale for measuring the erosion and deposition time.
The invention achieves the following beneficial effects:
the invention provides a method for determining a test range and a moving bed range under the combined action of wave currents, a method for selecting sand by model sand, a method for calculating sand content and sand adding rate, and the method can reasonably consider the separation condition of the sand inside and outside a normally-wavy broken wave band;
the method comprises the steps of (3) and (4), and provides a method for determining the median particle size, the particle density and the apparent dry density of the prototype sand and the model sand, compared with the existing single-particle-size test method, the method disclosed by the invention can reasonably consider the common action of the separation condition of the sediment inside and outside the normal wave broken wave band and the wave flow;
the steps (6), (7), (8) and (9) in the method provide a setting method suitable for the boundary, the terrain, the initial water level and the sand adding method of a physical model test of seashore evolution and channel siltation under the action of storm surge, the method considers the sediment movement mechanism under the combined action of the storm surge level process and wave flow, and can more accurately simulate the evolution process of the seashore beach under the action of storm surge.
The test method provided by the invention is not only suitable for sandy coasts, but also suitable for silty and muddy coasts; the method is not only suitable for natural coasts, but also suitable for artificial repair coasts; the method has wide application prospect in the fields of port and waterway construction, coast restoration and the like;
the test method disclosed by the invention adopts a calculation method of the starting water depth, the sediment starting threshold value, the sand content and the sand adding rate under the combined action of the wave current, so that the movement process of the sediment under the action of storm surge can be simulated more reasonably;
the test method disclosed by the invention can consider two model sands with different grain sizes, and can more accurately simulate some coast terrain evolution processes with obvious horizontal sediment separation.
Drawings
FIG. 1 is a schematic representation of a model of the present invention;
FIG. 2 is a schematic representation of a model of the present invention;
FIG. 3 is a graph of course mileage versus fouling thickness obtained from the model test of the present invention.
Detailed Description
The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Example one
A physical model test method for seashore evolution and channel siltation under the action of storm surge comprises the following steps:
(1) Determining a test range and a moving bed range of the model based on the evolution range of the historical storm surge terrain of the prototype coast;
(2) Determining the plane geometric scale lambda of the model based on the test range, the test site size, the tidal generation system current generation capacity and the wave generation capacity of the wave generator l And a vertical geometric scale λ h ；
Wave height ratio rule lambda H Sum wavelength scale lambda L Equal to the vertical geometric scale lambda h According to the formula λ T ＝λ h 1/2 Calculating to obtain wave period scale lambda T According to the formula λ V ＝λ h 1/2 Calculating to obtain a flow rate scale lambda V ；
(3) Determining the median diameter, particle density and apparent dry density of the prototype sand;
(4) Determining the median particle diameter, particle density and apparent dry density of the model sand:
(4.1) calculating a particle size scale meeting similar starting requirements according to a silt starting similarity law, a wave height scale, a wavelength scale, a flow rate scale, the median particle size of prototype sand, the particle density of prototype sand and the particle density of a model sand to be selected;
(4.2) calculating a particle size scale meeting the convection transportation similarity and a particle size scale meeting the sedimentation similarity according to a sinking speed scale formula meeting the convection transportation similarity, a particle size scale formula meeting the sinking speed similarity, a plane geometric scale, a vertical geometric scale, a prototype Sha Lijing, a prototype sand particle density and a model sand particle density to be selected;
(4.3) determining a final particle size scale based on the particle size scale meeting the starting similarity and the particle size scale meeting the convection transport similarity and the sedimentation similarity;
(4.4) determining the median particle diameter of the model sand, the particle density of the model sand and the apparent dry density of the model sand;
(5) Calculating a sand content scale and a slushing time scale;
(6) Determining a storm surge tide level process, a storm surge tide process and a storm surge wave process at the boundary of the model according to the actually measured tide level, the actually measured tide, the actually measured wave or the existing storm surge and wave mathematical model results of the prototype coast corresponding to the boundary of the model;
(7) Manufacturing a fixed bed terrain and a moving bed terrain in a test pool;
if wading buildings and artificial terrains are arranged on the fixed-bed terrains or the moving-bed terrains, the wading building terrains and the artificial terrains are manufactured in the test pool;
arranging tide generating systems at the upstream boundary and the downstream boundary of the fixed-bed terrain of the model;
arranging a wave making machine at the outer sea boundary of the model fixed bed terrain according to the storm surge wave direction of the prototype coast;
arranging wave guide plates on two sides of the wave making machine;
sand adding devices are respectively arranged on the upstream of the moving bed terrain and the downstream of the moving bed terrain;
(8) Adding water into a test pool to reach a model water level corresponding to the average water level of the prototype coastal wind before the storm surge, wherein the model water level corresponding to the average water level of the prototype coastal wind before the storm surge = the average water level of the prototype coastal wind before the storm surge ÷ vertical geometric scale;
setting a wave which does not start silt through the wave making machine, operating for a period of time to compact the model sand, closing the wave making machine after the model sand is compact, and waiting for the water surface of the test pool to be calm;
(9) Setting a tide generating system according to a storm tide level process and a storm tide flow process, setting a wave making machine according to a storm tide wave process, starting the tide generating system and the wave making machine, starting a sand adding device for adding sand, and starting a test;
(10) Calculating the test operation time t according to the scale of the action time of storm tide of the prototype coastal wind and the erosion time;
and when the test operation is finished, closing the sand adding device, the wave making machine and the tide generating system, draining water in the test water tank, measuring the terrain after the test operation is finished, and subtracting the moving bed terrain before the test from the terrain after the test operation is finished to obtain the silt scouring distribution under the action of storm surge.
Further, in this embodiment, the test range and the moving bed range of the model are determined based on the historical storm surge terrain evolution range of the prototype coast, and the method includes the following steps:
according to the collected historical geomorphic evolution data of storm surge of similar scale or the mathematical model result of the sediment of storm surge, the open sea boundary of the moving bed is arranged outside the geomorphic evolution range caused by storm surge, and the depth of the open sea boundary water of the moving bed is greater than or equal to the starting depth h under the action of storm surge cr Starting water depth h under storm surge cr Calculated according to the following formula:
wherein arcsinh is the inverse of sinh; l is a radical of an alcohol s Wave wavelength during a wind tide, and H is wave height during the wind tide; d is the prototype Sha Zhongzhi particle size; g is the acceleration of gravity; ρ is a unit of a gradient s Is the prototype sand particle density, and rho is the density of water;
u b in order to research the water flow velocity at the bottom of the sea area water depth, the water flow velocity is determined by the actual measurement data of the tidal current of the prototype coast or the result of a storm surge mathematical model; epsilon is a set coefficient;
the distance between the open sea boundary of the test range and the open sea boundary of the moving bed is more than or equal to 3-5 times of the model wavelength.
Further, in this example, the median particle diameter, particle density and apparent dry density of the prototype sand were determined by the following steps:
if the sediment inside and outside the original coast normally-wavy broken wave band is not the same type of the following three types of sediment, sampling the original sediment on the original coast, and measuring to obtain the median particle size, particle density and apparent dry density of the sediment inside and outside the original coast normally-wavy broken wave band;
the three types of silt are:
1. the median particle size is greater than 0.1mm;
2. a median particle diameter of greater than or equal to 0.03mm but less than or equal to 0.1mm and a clay content of less than 25%;
3. median particle diameter of less than 0.03mm and clay content of greater than or equal to 25%;
if the sediment inside and outside the original coast normally-wavy broken band is the same sediment of the three types, taking the average value of the median particle sizes of the sediment inside and outside the original coast normally-wavy broken band as the median particle size of the original sand, taking the average value of the particle densities of the sediment inside and outside the original coast normally-wavy broken band as the particle density of the original sand, and taking the average value of the apparent dry densities of the sediment inside and outside the original coast normally-wavy broken band as the apparent dry density of the original sand.
Further, in the embodiment, the model sands inside and outside the normal wave broken wave band adopt the model sands with the same grain size or the model sands with two grain sizes;
if the model sands inside and outside the normal wave broken wave band adopt the model sands with two grain diameters, the difference of the apparent dry densities of the model sands with the two grain diameters is less than 100kg/m 3 。
Further, in this embodiment, in step (4.1), a particle size ratio that satisfies similar start-up rules is calculated according to the silt start-up similarity law, the wave height ratio, the wavelength ratio, the flow rate ratio, the median particle size of the prototype sand, the particle density of the prototype sand, and the density of the model sand to be selected:
in the formula: lambda [ alpha ] d Is a particle size scale; lambda L Is a wavelength scale, λ H Is a wave height scale;
is a function of
Ratio of values in prototype coast to model, in prototype coast ρ s Taking the value as the particle density of the prototype sand, taking the value of d as the median diameter of the prototype sand in the prototype coast, and taking the value of u as the median diameter of the prototype sand in the prototype coast b The value is the water flow velocity at the bottom of the depth of the prototype coast, and rho is measured in the model s Take a value ofThe particle density of the model sand, d in the model is the median particle diameter of the model sand, and u in the model b Taking the value as the flow velocity of the water flow at the bottom of the model water depth; ρ is the density of water; g is the acceleration of gravity; epsilon is a set coefficient;
prototype coastal water depth bottom water flow velocity u b Determined by the actual measurement data of the tidal current of the prototype coast or the result of a storm surge mathematical model, and the flow velocity u of the water flow at the bottom of the model water depth b The flow rate of the bottom water flow of the prototype is divided by a flow rate scale.
Further, in this embodiment (4.2), a particle size scale satisfying the similar convection transport and similar sedimentation is calculated according to a sinking velocity scale formula satisfying the similar convection transport, a particle size scale formula satisfying the similar sinking velocity, a plane geometry scale, a vertical geometry scale, a median particle size of the prototype sand, a particle density of the prototype sand, and a density of the model sand particles to be selected, and the method is implemented by the following steps:
the sinking rate scale formula meeting the similarity of convection transport is as follows:
in the formula, λ ω A silt sinking speed scale; lambda [ alpha ] l Is a plane geometric scale, lambda h Is a vertical geometric scale;
according to the formula (3) and the sinking speed formula of the Wuhan's water conservancy and electric power college, determining a particle size scale formula which meets the condition that the convection transport is similar to the sinking speed, wherein the particle size scale formula which meets the condition that the convection transport is similar to the sinking speed is as follows:
in the formula: Δ = (ρ) s /ρ)-1，
Representing a function
In the ratio of the values in the prototype coast and the model coast, d in the prototype coast is the median particle size of the prototype sand, and d in the model is the median particle size of the model sand;
(4.3) determining a final particle size ratio based on the particle size ratio which meets similar starting and the particle size ratio which meets similar convection transportation and similar sedimentation, and realizing the following steps:
and (3) determining the value of a final particle size scale according to the optional model sand resource, wherein the value of the final particle size scale is between the particle size scale which is obtained by calculation in the step (4.1) and meets the requirements of starting similar particle size scales and the particle size scale which is obtained by calculation in the step (4.2) and meets the requirements of convection transport similar particle size scales and sedimentation similar particle size scales.
Further, in the present embodiment
(4.4) determining the median particle diameter of the model sand, the particle density of the model sand and the apparent dry density of the model sand by:
obtaining a model sand sample;
drying the model sand sample by using an oven;
measuring the volume and mass of the dried model sand sample;
measuring the median particle diameter of the model sand sample and the particle density of the model sand sample;
dividing the measured mass by the measured volume to obtain the apparent dry density of the model sand sample;
if the model sand sample cannot be obtained or the oven does not exist, calculating the apparent dry density of the model sand according to the following formula:
in the formula: rho d Apparent dry density, ρ, of model sand s Is the particle density of the model sand and d is the median particle size of the model sand.
The median particle diameter, particle density and apparent dry density of the prototype sand can also be obtained by:
obtaining a prototype Sha Yangpin;
drying the prototype Sha Yangpin by an oven;
measuring the volume and the mass of the dried prototype sand sample;
dividing the measured mass by the measured volume to obtain the apparent dry density of the prototype sand;
if the prototype sand sample cannot be obtained or the oven is not available, calculating the apparent dry density of the prototype sand by the following formula:
in the formula: rho d Apparent dry density, ρ, of the prototype sand s Is the particle density of the prototype sand and d is the median particle diameter of the prototype sand.
Further, in this embodiment (5), the sand content scale and the erosion time scale are calculated by the following steps:
sand content scale lambda S Calculated as follows:
in the formula (I), the compound is shown in the specification,
the silt particle density scale is obtained by dividing the original sand particle density by the model sand particle density;
is rho s -the ratio of the value of ρ in the prototype sand to the value in the model sand;
slide rule lambda for slushing time t Calculated as follows:
in the formula, λ ρd The ratio of the mean value of the apparent dry density of the sediment inside and outside the original normal wave broken wave band to the mean value of the apparent dry density of the sediment inside and outside the model normal wave broken wave band.
Further, in the present embodiment, the sand adding device is respectively disposed upstream of the moving bed terrain and downstream of the moving bed terrain, and the sand adding device is realized by the following steps:
if the model sand with the same particle size is adopted inside and outside the normal wave broken wave band in the model, arranging a sand adding device on the upstream boundary and the downstream boundary of the moving bed respectively, wherein the length of the sand adding device is equal to the width of the moving bed terrain;
if model sands with different particle sizes are adopted inside and outside the broken wave band of the constant wave, two sand adding devices are respectively arranged on the upstream boundary and the downstream boundary of the moving bed terrain, the length of the sand adding device close to the shore line is the width of the broken wave band under the action of the constant wave, and the length of the sand adding device close to the open sea is the distance between the broken wave point and the open sea boundary of the moving bed terrain;
the single width sand adding rate P when the sand adding device works is as follows:
in the formula: h is p Is the depth of water, S, of the prototype coast corresponding to the location of sand addition p The sand content, V, of the prototype coast corresponding to the sand addition p The water depth average flow velocity of the prototype coast corresponding to the sand adding position is obtained; lambda [ alpha ] h Is a vertical geometric scale; lambda V To a flow rate scale, lambda S Is a sand content scale;
determining the sand content of the prototype coast according to the actually measured sand content of the prototype coast; if the sand content is not measured on the prototype coast, the sand content is determined by the following formula:
in the formula, V c The average flow velocity of storm surge tidal current is obtained; v w The flow velocity of the broken wave of the storm surge is shown, and F is a sediment factor; rho s Is the prototype sand particle density, and rho is the density of water; g is the acceleration of gravity; h is the depth of the prototype coast water;
silt factor F is determined by the following formula:
in the formula: d 0 Is a characteristic particle diameter, a is a characteristic area, d 0 ＝0.11mm；a＝0.0024mm 2 (ii) a d is the median particle size of the prototype sand; storm surge velocity of flow V w Calculated as follows:
in the formula: gamma ray b Is an index of wave breaking; h b To break the wave height.
Further, in this embodiment (10), the test operation time t is calculated according to the scale of the action time of storm surge of the prototype coastal wind and the erosion time:
t＝t p /λ t (37)
in the formula: t is t p Is the time of storm surge of coastal wind, lambda t Is a scale for measuring the erosion and deposition time.
And if a channel exists on the moving bed terrain before the test, acquiring the sediment accumulation condition in the channel.
Determining the plane geometric scale lambda of the model based on the test range, the test site size, the tidal generation system current generation capacity and the wave generation capacity of the wave generator l And vertical geometric scale lambda h The present embodiment is not described in detail, which belongs to the prior art.
ε is a set coefficient, and is 0.486 × 10 -6 ；
The sand adding device, the model sand, the wave maker and the wave guide plate can adopt a plurality of types in the prior art, and the skilled person can select a proper type according to the actual requirement, so that the embodiment is not illustrated.
The tidal generation system flow generation capacity refers to the flow rate generated by the tidal generation system, and the flow rate can be generated, and the parameters mainly comprise the flow rate;
the wave making machine wave making capability refers to how high and how long a period of waves can be made, and the parameters include: wave height and wave period.
Determining the plane geometric scale lambda of the model based on the test range, the test site size, the tidal generation system current generation capacity and the wave generation capacity of the wave generator l And a vertical geometric scale λ h This step is prior art and will not be described in detail in this embodiment.
Example two
As shown in FIG. 1, the shoreline of a fine sand silty coast is approximately NE to SW. Within the wave zone of the standing wave (within about 4 meters of water depth and within 1km range near the shore) the coast transverse gradient is 1/60, and the transverse gradient outside the wave zone of the standing wave is about 1:500. the sand grain diameter within the normal wave broken wave band is thicker, and the median grain diameter is about 0.12mm; the silt particle size outside the normal wave broken wave band is finer, and the median particle size is about 0.06mm. Where ports and channels are constructed on the coast.
After the construction of ports and channels, it is found that under the action of storm surge, the profile of a coastal beach is greatly adjusted, and rapid silt is easily generated at a specific position of a channel. Therefore, the process of the evolution of the coastal terrain and the sedimentation of the channel under the action of storm surge is inverted, the silt transport mechanism under the action of storm surge is understood, and the phenomenon of channel rapid sedimentation under the action of storm surge is prevented from becoming the heaviest of the port channel management unit.
The following describes how to predict the coast terrain evolution and the channel siltation under the action of a storm surge by using the physical model test method for the coast terrain evolution and the channel siltation under the action of storm surge provided by the invention with reference to the embodiment and the drawings, and the basic implementation steps are as follows.
(1) The experiment aims to predict the sea land topography evolution situation and the sediment accumulation situation in the channel within a range of several kilometers near the port channel under the action of a certain storm surge. The historical storm surge landform evolution data with similar scale at the place shows that under the action of the storm surge, the adjustment of the horizontal section of the beach is obvious. Compared with the landforms of the coast before and after the storm surge process of similar scale, the landform evolution influenced by the storm surge mainly occurs within 10m of water depth. According to the formula (1), the starting water depth under the action of storm surge is calculated to be 11.5m, the particle size in calculation is 0.06mm, the wave height is 3.3m, the wavelength is 75m, and the bottom tidal flow velocity is 0.40m/s according to the result of a mathematical model.
From the above analysis, the experimental range of the model and the moving bed range of the model were determined as follows:
the moving bed range takes the port channel as a center and comprises 9km of a shore line in the northeast direction (upstream of storm surge), 4km of the shore line in the southwest direction (downstream of storm surge), a boundary of the outer sea of the moving bed is defined near a 12m deep line and is 6km offshore on average. The test range of the model takes the port channel as the center and comprises 14km of a northeast direction shore line and 7km of a southwest direction shore line of the port, the boundary of the outer sea of the model is near a 17m deep line, the average distance of the outer sea is 11km, and the test range and the moving bed range are shown in figure 1.
The sea boundary of the test range in the model is estimated to be 6.25-12.5m away from the sea boundary of the moving bed range by a plane scale of 400-800. The vertical scale is 60-120, the wavelength is 80-120m, and the model wavelength is about 0.67-2.0m. The distance between the outer sea boundary of the model in the test range and the outer sea boundary of the moving bed range meets the requirement that the distance is more than or equal to 3-5 times of the wavelength of the model.
(2) Comprehensively considering the test range, the size of a test site, the current generation capacity of a tidal generation system and the capacity of a wave generator, and determining that the plane geometric scale and the vertical geometric scale of the model are respectively 500 and 80; the wave height scale and the wavelength scale are equal to the vertical geometric scale 80, and the flow rate scale is according to the formula lambda V ＝λ h 1/2 Calculated to be 8.94, where h Is a vertical geometric scale.
(3) The original coast normal-wave broken wave band is approximately positioned near a 4m isophotic line, the difference of the grain sizes of the silt inside and outside the normal-wave broken wave band is obvious, the grain size of the original Sha Zhongzhi in the broken wave band is 0.12mm, the grain size of the original Sha Zhongzhi outside the broken wave band is 0.06mm, and the content of the silt and the clay at two positions is less than 25%. And (3) determining the median particle size of the prototype sand, the particle density of the prototype sand and the apparent dry density of the prototype sand inside and outside the normal wave broken wave band respectively if the properties of the sand and sand inside and outside the normal wave broken wave band have great difference. According to the measured data of coast, the normal waves break the sediment in the wave bandThe median particle diameter, the particle density and the apparent dry density were 0.12mm,2650kg/m, respectively 3 And 1400kg/m 3 (ii) a The median diameter, the particle density and the apparent dry density of the sediment outside the normal wave breaking zone are respectively 0.06mm,2650kg/m 3 And 1450kg/m 3 。
(4) The median particle size, particle density and apparent dry density of the model sand within the normally-wavy waveband were first determined according to the following procedures.
Firstly, according to the formula (3) which is the formula of the particle size ratio satisfying the similar start of silt, the particle size ratio satisfying the similar start is 0.38. Trial calculation is carried out, wherein the wavelength ratio scale and the wave height ratio scale are 80; the flow rate scale is 8.94; according to the result of the mathematical model, the bottom tidal current flow rate is 0.40m/s; the particle size and density of the silt in the prototype coastal break wave zone are respectively 0.12mm and 2650kg/m 3 (ii) a The model sand is prepared by selecting refined coal powder, and the particle density is about 1350kg/m 3 。
Secondly, the sediment sedimentation rate scale meeting the similarity of convection transport is 1.43 according to the formula (4). Substituting the formula (1.43) into the formula (5), and obtaining a particle size scale of 0.55 meeting the requirements of similar convection transport and similar sedimentation through trial calculation. Trial calculation of the motion viscosity coefficient upsilon of the reclaimed water is 1 multiplied by 10 -6 m 2 S; the particle size and density of the silt in the prototype coastal break wave zone are respectively 0.12mm and 2650kg/m 3 (ii) a The model sand is prepared by selecting refined coal powder, and the particle density is about 1350kg/m 3 。
Thirdly, according to the trial calculation results, the particle size ratio should be between 0.38 and 0.55, and the final particle size ratio is taken to be 0.50. Thus, the median particle size of the model sand should be 0.24mm and the particle density 1350kg/m 3 . The apparent dry density of the model sand is 750kg/m by measuring the volume and density of the dried model sand 3 。
Then, the refined coal powder is also selected to prepare the model sand outside the broken wave band. Similarly, the median particle diameter, particle density and apparent dry density of the model sand outside the broken band can be obtained as follows: 0.12mm,2650kg/m 3 And 700kg/m 3 。
(5) Calculating the sand content scale lambda according to the formula (7) S Equal to 0.42; calculating the erosion-deposition time ratio according to the formula (8)Ruler lambda t Equal to 262, i.e. 3 days on the prototype coast, corresponding to model 16.5 minutes.
(6) And extracting a storm surge level process, a tide process and a wave process at the boundary of the model from the result of the storm surge mathematical model.
(7) The physical model layout is shown in fig. 1. The method comprises the steps of manufacturing a fixed bed terrain and a moving bed terrain in a test water tank 1, manufacturing a harbor basin 2, a sand blocking embankment 3 and a navigation channel 4 on the test terrain at the same time, arranging a tide generating system 5 according to the upstream and downstream boundaries of a model fixed bed, arranging a wave generator 6 near the outer sea boundary of the model fixed bed according to the wave direction of storm surge, arranging wave guide plates 7 on two sides of the wave generator, arranging a first sand adding device 8 and a second sand adding device 9 on the upstream of the moving bed, and arranging a third sand adding device 10 and a fourth sand adding device 11 on the downstream of the moving bed. The first and second sand adding devices 8 and 9 and the third and fourth sand adding devices 10 and 11 are respectively arranged side by side. The lengths of the third sand adding device 10 and the first sand adding device 8 are equal to a boundary between a shoreline and the model initial terrain model Sha Zhongzhi with the grain diameter of 0.24mm and 0.12mm; the lengths of the second sand adding device 9 and the fourth sand adding device 11 are equal to the boundary between the model initial terrain model Sha Zhongzhi particle size of 0.24mm and 0.12mm and the outer sea boundary of the moving bed.
(8) Adding water into a test pool to the average water level before storm surge, setting a small wave which does not start silt through a wave making machine, running for 6 hours to fully compact model sand, and closing the wave making machine after the model sand is compact to wait for the water surface to be calm.
(9) The tide generating system is arranged according to the storm tide level and the tide process, the wave making machine is arranged according to the storm tide wave process, the tide generating system and the wave making machine are started, the sand adding device is started, and the test is started.
In the test, the sand adding rate of two sets of sand adding devices at the upstream and downstream of the moving bed at different depths of water is calculated according to a formula (9), wherein the sand content is calculated according to a formula (10). In the calculation, the average flow speed of the wind, tide and tide is determined according to the result of a mathematical model; determining the storm surge flow rate according to a formula (12); the crushing index is determined according to the sea harbor hydrological Specification (JTS 145-2-2013); the wave breaking wave height is obtained by calculation according to the wave breaking index and the water depth; the storm tide flow velocity is basically parallel to the wave breaking flow velocity, and the prototype water depth average flow velocity is obtained by adding the storm tide flow velocity and the wave breaking flow velocity. The results of the calculation of the breaking index, the breaking wave height, the storm tidal velocity, the breaking wave velocity, the sand content and the sand addition rate are shown in Table 1.
(10) At this time, the duration of storm surge was 3 days, and the test run time was 16.5 minutes as calculated according to the formula (13). After the operation is carried out for 16.5 minutes, the sand adding system, the wave making machine and the tide generating system are closed, water in the water tank is drained, the terrain is measured, the terrain is the terrain after the storm surge action, the initially set terrain is subtracted from the terrain, and the silt scouring distribution under the storm surge action including the silt sedimentation condition in the channel can be obtained. Figure 2 shows a photograph of the terrain in the vicinity of the basin channel after the storm surge. Fig. 3 shows the distribution of silt accumulation along the course in the channel. It can be found that strong silt deposition occurs at the 2.0-4.5km of the mileage of the flight, and the maximum deposition thickness exceeds 5m.
TABLE 1 calculation results of fragmentation index, fragmentation wave height, storm tidal velocity, fragmentation wave velocity, sand content and sand addition rate
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A physical model test method for seashore evolution and channel siltation under the action of storm surge is characterized by comprising the following steps:
(1) Determining a test range and a moving bed range of the model based on the evolution range of the historical storm surge terrain of the prototype coast;
(2) Based on the test range, the test site size and the tide generation systemDetermining the plane geometric scale lambda of the model based on the flow capacity and the wave-making capacity of the wave-making machine l And a vertical geometric scale λ h ；
Wave height ratio rule lambda H And wavelength scale lambda L Equal to the vertical geometric scale lambda h According to the formula λ T ＝λ h 1/2 Calculating to obtain wave period scale lambda T According to the formula λ V ＝λ h 1/2 Calculating to obtain a flow velocity scale lambda V ；
(3) Determining the median diameter of the prototype sand, the particle density of the prototype sand and the apparent dry density of the prototype sand;
(4) Determining the median particle diameter of the model sand, the particle density of the model sand and the apparent dry density of the model sand:
(4.1) calculating a particle size ratio rule meeting similar starting requirements according to the silt starting similarity rule, the wave height ratio rule, the wavelength ratio rule, the flow velocity ratio rule, the median particle size of the prototype sand, the particle density of the prototype sand and the particle density of the model sand to be selected;
(4.2) calculating a particle size scale meeting the convection transport similarity and a particle size scale meeting the sedimentation similarity according to a sinking speed scale formula meeting the convection transport similarity, a particle size scale formula meeting the sinking speed similarity, a plane geometric scale, a vertical geometric scale, the median particle size of the prototype sand, the particle density of the prototype sand and the particle density of the model sand to be selected;
(4.3) determining a final particle size ratio based on the particle size ratio satisfying similar starting and the particle size ratio satisfying similar convection transport and similar sedimentation;
(4.4) determining the median particle diameter of the model sand, the particle density of the model sand and the apparent dry density of the model sand;
(5) Calculating a sand content scale and a slushing time scale;
(6) Determining a storm surge level process, a storm surge tide process and a storm surge wave process at the boundary of the model;
(7) Manufacturing a fixed bed terrain and a moving bed terrain in a test pool;
if wading buildings and artificial terrains are arranged on the fixed-bed terrains or the moving-bed terrains, the wading building terrains and the artificial terrains are manufactured in the test pool;
arranging tide generating systems at the upstream boundary and the downstream boundary of the fixed-bed terrain of the model;
arranging a wave making machine at the open sea boundary of the model fixed bed terrain according to the wave direction of storm surge;
arranging wave guide plates on two sides of the wave making machine;
sand adding devices are respectively arranged at the upstream of the moving bed terrain and the downstream of the moving bed terrain;
(8) Adding water into a test pool to reach a model water level corresponding to the average water level of the prototype coastal wind before the storm surge, wherein the model water level corresponding to the average water level of the prototype coastal wind before the storm surge = the average water level of the prototype coastal wind before the storm surge ÷ vertical geometric scale;
setting a wave which does not start silt through the wave making machine, operating for a period of time to compact the model sand, closing the wave making machine after the model sand is compact, and waiting for the water surface of the test pool to be calm;
(9) Setting a tide generating system according to a storm tide level process and a storm tide flow process, setting a wave making machine according to a storm tide wave process, starting the tide generating system and the wave making machine, starting a sand adding device for adding sand, and starting a test;
(10) Calculating the test operation time t according to the scale of the action time of storm tide of the prototype coastal wind and the erosion time;
and when the test operation is finished, closing the sand adding device, the wave making machine and the tide generating system, draining water in the test pool, measuring the terrain after the test operation is finished, and subtracting the moving bed terrain before the test from the terrain after the test operation is finished to obtain silt scouring distribution under the action of storm tide.
2. The physical model test method for seashore evolution and channel siltation under storm surge action according to claim 1, characterized in that, based on the terrain evolution range of the historical storm surge of the prototype seashore, the test range and the moving bed range of the model are determined, and the method is realized by the following steps:
setting the open sea boundary of the moving bed at the place where storm surge can cause according to the collected historical storm surge landform evolution data with similar scale or storm surge sediment mathematical model resultOutside the landform evolution range, the open sea boundary water depth of the moving bed is more than or equal to the starting water depth h under the action of storm surge cr Starting water depth h under storm surge cr Calculated according to the following formula:
wherein arcsinh is the inverse of sinh; l is s The wave wavelength during the wind tide, and H is the wave height during the wind tide; d is the prototype Sha Zhongzhi particle size; g is the acceleration of gravity; rho s Is the prototype sand particle density, and rho is the density of water;
u b in order to research the flow velocity of water flow at the bottom of the sea water depth, the flow velocity is determined by the actual measurement data of the tide of the prototype coast or the result of a storm surge mathematical model; epsilon is a set coefficient;
the distance between the open sea boundary of the test range and the open sea boundary of the moving bed is more than or equal to 3-5 times of the model wavelength.
3. The physical model test method for the coastal evolution and channel siltation under the action of storm surge according to claim 1, wherein the median particle size, the particle density and the apparent dry density of the prototype sand are determined by the following steps:
if the internal and external silt of the normal wave broken wave band of the prototype coast is not the same type of the following three types of silt, sampling the prototype sand on the prototype coast, and measuring to obtain the median particle diameter, the particle density and the apparent dry density of the prototype sand;
the three types of silt are:
1. the median particle size is greater than 0.1mm;
2. a median particle diameter of greater than or equal to 0.03mm but less than or equal to 0.1mm and a clay content of less than 25%;
3. a median particle size of less than 0.03mm and a clay content of greater than or equal to 25%;
if the sediment inside and outside the original coast normally-wavy broken band is the same sediment of the three types, taking the average value of the median particle sizes of the sediment inside and outside the original coast normally-wavy broken band as the median particle size of the original sand, taking the average value of the particle densities of the sediment inside and outside the original coast normally-wavy broken band as the particle density of the original sand, and taking the average value of the apparent dry densities of the sediment inside and outside the original coast normally-wavy broken band as the apparent dry density of the original sand.
4. The physical model test method for coast evolution and channel siltation under storm surge according to claim 3, wherein the model sands inside and outside the normal wave breaking wave band adopt the same grain size model sands or two grain sizes model sands;
if the model sands inside and outside the normal wave broken wave band adopt the model sands with two grain diameters, the difference of the apparent dry densities of the model sands with the two grain diameters is less than 100kg/m 3 。
5. The physical model test method for the coastal evolution and the channel siltation under the storm surge action according to claim 1, wherein the step (4.1) is to calculate the particle size ratio rule meeting the similar starting rule according to the silt starting similarity rule, the wave height ratio rule, the wavelength ratio rule, the flow velocity ratio rule, the median particle size of the prototype sand, the particle density of the prototype sand and the particle density of the model sand to be selected:
in the formula: lambda [ alpha ] d Is a particle size scale; lambda [ alpha ] L Is a wavelength scale, lambda H Is a wave height scale;
is a function of
Ratio of values in prototype coast to model, in prototype coast ρ s Taking the value as the particle density of the prototype sand on the prototype coastD is the median diameter of the prototype sand, u is the median diameter of the prototype sand in the coast of the prototype b Taking the value as the water flow velocity at the bottom of the depth of the prototype coast, and in the model, rho s Taking the value as the particle density of the model sand, taking the value of d as the median diameter of the model sand in the model, and taking the value of u as the median diameter of the model sand in the model b Taking the value as the flow velocity of the water flow at the bottom of the model water depth;
ρ is the density of water; g is the acceleration of gravity; epsilon is a set coefficient;
L s the wave length during a tide.
6. The physical model test method for coastal evolution and channel siltation under storm surge action of claim 1, wherein (4.2) the particle size scale satisfying similar convection transport and similar sedimentation is calculated according to a sinking velocity scale formula satisfying similar convection transport, a particle size scale formula satisfying similar sinking velocity, a plane geometric scale, a vertical geometric scale, a median particle size of prototype sand, a particle density of prototype sand and a particle density of model sand to be selected, and the method is realized by the following steps:
the sinking rate scale formula meeting the similarity of convection transport is as follows:
in the formula, λ ω A silt sinking speed scale; lambda [ alpha ] l Is a plane geometric scale, λ h Is a vertical geometric scale;
according to the formula (3) and the Wuhan's water conservancy electric power college sinking speed formula, determining a particle size scale formula meeting the condition that the convection transportation is similar to the sinking speed, wherein the particle size scale formula meeting the condition that the convection transportation is similar to the sinking speed is as follows:
in the formula: Δ = (ρ) s /ρ)-1，
Representing a function
In the ratio of the values in the prototype coast and the model coast, d in the prototype coast is the median particle size of the prototype sand, and d in the model is the median particle size of the model sand; upsilon is the motion viscosity coefficient of water;
(4.3) determining a final particle size scale based on the particle size scale meeting the starting similarity and the particle size scale meeting the convection transport similarity and the sedimentation similarity, and realizing the method by the following steps:
and (4) determining the value of a final particle size ratio according to the selectable model sand resources, wherein the value of the final particle size ratio is between the particle size ratio which is obtained by calculation in the step (4.1) and meets the requirements of starting similarity and the particle size ratio which is obtained by calculation in the step (4.2) and meets the requirements of convection transport similarity and sedimentation similarity.
7. The physical model test method for the coastal evolution and channel siltation under storm surge action of claim 1, wherein (4.4) the median particle size of the model sand, the particle density of the model sand and the apparent dry density of the model sand are determined by the following steps:
obtaining a model sand sample;
drying the model sand sample by using an oven;
measuring the volume and the mass of the dried model sand sample;
measuring the median particle diameter of the model sand sample and the particle density of the model sand sample;
dividing the measured mass by the measured volume to obtain the apparent dry density of the model sand sample;
if the model sand sample cannot be obtained or the oven does not exist, calculating the apparent dry density of the model sand according to the following formula:
in the formula: rho d Apparent dry density, ρ, of model sand s Is the particle density of the model sand and d is the median particle size of the model sand.
8. The physical model test method for the coastal evolution and channel siltation under the action of storm surge according to claim 1, wherein (5) a sand content scale and a silt flushing time scale are calculated, and the method is realized by the following steps:
sand content scale lambda S Calculated as follows:
in the formula (I), the compound is shown in the specification,
the silt particle density scale is obtained by dividing the original sand particle density by the model sand particle density;
is rho s -the ratio of the value of ρ in the prototype sand to the value in the model sand;
slide rule lambda of scouring time t Calculated as follows:
in the formula (I), the compound is shown in the specification,
the ratio of the mean value of the apparent dry density of the sediment inside and outside the original normal wave broken wave band to the mean value of the apparent dry density of the sediment inside and outside the model normal wave broken wave band.
9. The physical model test method for seashore evolution and channel siltation under storm surge action according to claim 1, characterized in that sand adding devices are respectively arranged at the upstream of the moving bed terrain and the downstream of the moving bed terrain, and the method is realized by the following steps:
if the model sand with the same particle size is adopted inside and outside the normal wave broken wave band in the model, arranging a sand adding device on the upstream boundary and the downstream boundary of the moving bed respectively, wherein the length of the sand adding device is equal to the width of the moving bed terrain;
if model sands with different particle sizes are adopted inside and outside the broken wave band of the constant wave, two sand adding devices are respectively arranged on the upstream boundary and the downstream boundary of the moving bed terrain, the length of the sand adding device close to the shore line is the width of the broken wave band under the action of the constant wave, and the length of the sand adding device close to the open sea is the distance between the broken wave point and the open sea boundary of the moving bed terrain;
the single width sand adding rate P when the sand adding device works is as follows:
in the formula: h is p Is the depth of water, S, of the prototype coast corresponding to the location of sand addition p The sand content, V, of the prototype coast corresponding to the sand addition p The water depth average flow velocity of the prototype coast corresponding to the sand adding position is obtained; lambda h Is a vertical geometric scale; lambda [ alpha ] V To a flow rate scale, lambda S Is a sand content scale;
determining the sand content of the prototype coast according to the actually measured sand content of the prototype coast; if no prototype coast has measured sand content, then it is determined by the following formula:
in the formula, V c The average flow velocity of storm surge tidal current is obtained; v w The flow velocity of the broken wave of the storm surge is shown, and F is a sediment factor; rho s Is the prototype sand particle density, and rho is the density of water; g is gravity acceleration; h is the depth of the prototype coast water;
silt factor F is determined by the following formula:
in the formula: d 0 Is the characteristic particle size, a is the characteristic area, d is the median particle size of the prototype sand;
storm surge velocity of flow V w Calculated as follows:
in the formula: gamma ray b Is an index of wave breaking; h b To break the wave height.
10. The physical model test method for seashore evolution and channel siltation under storm surge according to claim 1, wherein (10) the test running time t is calculated according to the scale of action time and erosion time of the prototype coastal storm surge:
t＝t p /λ t (12)
in the formula: t is t p Is the time of storm surge of the original coastal wind, lambda t Is a scale for measuring the erosion and deposition time.
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