CN108398377B - Simulation device for measuring friction coefficient of bottom of shallow lake and using method thereof - Google Patents
Simulation device for measuring friction coefficient of bottom of shallow lake and using method thereof Download PDFInfo
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- CN108398377B CN108398377B CN201810166607.5A CN201810166607A CN108398377B CN 108398377 B CN108398377 B CN 108398377B CN 201810166607 A CN201810166607 A CN 201810166607A CN 108398377 B CN108398377 B CN 108398377B
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Abstract
The invention discloses a simulation device for measuring the friction coefficient of a shallow lake bottom and a using method thereof.A water enters an experimental water tank from a water inlet pipe of the device through a constant-flow water tank, then flows through the lake bottom simulated by filling with submerged plants, gravels and sludge after being stabilized by a stabilizing cover in the experimental water tank, and finally flows out from a non-pressure water outlet pipe; a sliding support and a trolley are erected above the experimental water tank, and a speed measuring device connected with a telescopic rod of the trolley can measure the water flow speed of any position above the submerged plant; and finally, calculating the bottom friction coefficients of the submerged plants and the emergent plants according to a newly derived bottom friction coefficient formula. The device simulates the underwater environment of an actual water area, the water flow rate is artificially controllable, and the application range is very wide; the flow velocity fluctuation of the whole device is small, and the influence on the measurement result caused by uneven flow velocity distribution in the water body is reduced to the maximum extent; the method can measure a plurality of groups of data in the three-dimensional water area, adopts an optimized mathematical formula to calculate, greatly reduces errors and obviously improves the precision.
Description
Technical Field
The invention belongs to the technical field of water body ecological environment simulation, and particularly relates to a simulation device for measuring the friction coefficient of a shallow lake bottom and a using method thereof.
Background
The vicinity with shallow lakes is a densely populated area and is the area where human activities are most frequent. With the reduction of the water quality of lakes, the eutrophication of lakes and the cyanobacterial blooms caused by the eutrophication of lakes become the main water environment problem of shallow lakes, and the research on the migration and diffusion rules of lake pollutants becomes the current research focus. Hydrodynamics research related to pollutant migration and diffusion mainly uses mathematical model simulation for a long time, and the model construction and the research on the model can effectively and intuitively simulate and predict the pollutant migration and diffusion rule. Although a great deal of work is done on the lake water power numerical simulation at present, most of parameters are obtained through analysis or calibration and are limited by data, and the parameters are unreasonable or inaccurate.
In the numerical simulation work of lake water power, the bottom friction coefficient is an important parameter in the model. The water bottom roughness varies depending on the silt and vegetation type. In natural watercourses, submerged and emergent vegetation can be considered one of the sources of energy dissipation, and vegetation is therefore considered an additional current resistance to coarseness. The conditions of the bottoms of different lake regions are not similar, the types and the densities of plants at the bottoms are different, and in order to accurately simulate the hydrodynamic force and the flow field conditions of the lake, the values of the Mannich coefficient (namely the bottom friction coefficient) at the bottom of the lake under different underlying surface conditions and different vegetation conditions need to be determined through experiments.
In recent years, lake model research is often set according to common parameters, and research experiments on actual bottom friction coefficients of lakes are very few. In the prior art, for example, the publication No. CN104535295B provides a multifunctional experimental apparatus for simulating hydraulic elements of a slope flow and an experimental method thereof, although the flow velocity of the water flow is measured by simulating the plants at the bottom of a lake and the roughness of the slope is measured according to a specific formula, there are many problems: firstly, the device can only calculate the roughness of the slope by measuring the water flow rate close to the top of the underwater float grass, the measurement range is limited, and if the water flow rate at a certain position fluctuates greatly, the final calculation result is greatly influenced; secondly, the flow velocity of water flow cannot be controlled manually, and the simulation device has great limitation on the actual environment of different shallow lakes; thirdly, due to external interference and device structure reasons, the flow velocity of water flow is unstable, and the precision of the bottom friction coefficient result is greatly influenced; fourthly, the adopted Manning roughness formula is not suitable for shallow lakes containing vegetation due to the self limitation, so that the result error is large and the accuracy cannot be guaranteed.
Therefore, the invention needs to design a simulation device for measuring the bottom friction coefficient of a shallow lake, effectively ensures the stability of water flow, and obtains an optimized Manning roughness formula for calculation by using a more reasonable derivation mode so as to obtain the bottom friction coefficient with higher precision and more in line with the reality.
Disclosure of Invention
In order to solve the problems of the prior art, the invention provides a simulation device for measuring the friction coefficient of the bottom of a shallow lake, which is realized by the following technical scheme.
A simulation device for measuring the friction coefficient of the bottom of a shallow lake comprises a constant-flow water tank and an experimental water tank which are connected through a water pipe from left to right; the constant-current water tank and the experimental water tank are both of box-type structures with upper covers, the upper cover of the constant-current water tank is connected with a water inlet pipe, the rightmost end of the experimental water tank is connected with a non-pressure water outlet pipe, and a constant-current valve is arranged on the non-pressure water outlet pipe;
a flow stabilizing cover is vertically arranged in the experiment water tank, the flow stabilizing cover divides the experiment water tank into a left flow stabilizing part and a right experiment part, water flows into the constant flow water tank from the water inlet pipe, then flows into the flow stabilizing part of the experiment water tank, flows through the experiment part and flows out from the non-pressure water outlet pipe;
the bottom of the experimental part is uniformly divided into an upstream section, a midstream section and a downstream section from left to right in sequence, the upper surfaces of the upstream section and the downstream section are positioned on the same plane, the upper surface of the midstream section is downwards concave, and the lower surfaces of the upstream section, the midstream section and the downstream section are positioned on the same horizontal plane; the upstream section and the downstream section are made of smooth PVC plates, the midstream section is made of perforated PVC plates uniformly provided with concave holes, and the thickness of each perforated PVC plate is half of that of each smooth PVC plate; the concave hole of the perforated PVC plate is used for embedding a float grass model according to the actual vegetation condition of the water bottom of the water area to be simulated;
the experiment part is characterized in that sliding supports capable of sliding back and forth are arranged above two opposite sides of the experiment part in a stretching mode, sliding trolleys are arranged on the sliding supports, telescopic rods stretching downwards are arranged on the trolleys, and speed measuring devices are arranged at the tail ends of the lower portions of the telescopic rods.
When the device is used, firstly, according to the actual vegetation condition of the river bottom of a water area to be simulated, a submerged plant model is embedded on the perforated PVC plate according to a scale, and gravels or sludge are paved; and then the water inlet pipe and the constant flow valve are opened and adjusted to control the flow rate of water flow, the sliding support, the trolley and the telescopic rod are adjusted to fix the position of the speed measuring device, and then the flow rate of water flow at the position can be measured. The constant-flow water tank is communicated with the experimental water tank, so that the water levels of the constant-flow water tank and the experimental water tank are kept at the same height through the principle of the communicating vessel, the height of the water level can be controlled by adjusting the water flow speed of the water inlet pipe, and the influence on the measurement precision due to the fact that the water flow speed entering the experimental water tank is too high can be prevented through the delaying effect of the constant-flow water tank; the water flowing into the experimental water tank can further keep the flow velocity of the water on the upper layer and the lower layer of the experimental water tank stable under the action of the flow stabilizing cover on the flow stabilizing part, so that the local uneven distribution of the water flow on the upper layer and the lower layer is avoided, and the measurement error is reduced; the constant-flow water tank and the constant-flow cover of the constant-flow part cooperate to ensure that the water flow velocity flowing into the experimental water tank is stable and keeps a fixed proportional relation with the water flow velocity of the actual water area to be simulated. The device can measure the water flow velocity of any point in the three-dimensional water area, forms a plurality of groups of data, avoids the influence of certain error data on the whole experimental result, can artificially control the water flow velocity, and greatly improves the application range of the device.
Preferably, the constant-flow water tank is divided into an overflow part and a water inlet part which are communicated with each other at the upper part by a limit baffle plate with the liftable middle part, and the water inlet part is close to the experimental water tank; the inlet tube corresponds the portion of intaking, overflow pipe is connected to overflow portion below. The purpose is that as a second guarantee for maintaining the water level heights of the constant-flow water tank and the experimental water tank and the water flow stability, when the water flow speed cannot be accurately controlled due to faults of the water inlet pipe, and if the water level of the water inlet part exceeds the height of the limit baffle, redundant water can flow into the overflow part through the limit baffle and is discharged; in addition, the water inlet part of the constant-flow water tank and the water level of the experimental water tank can be controlled by adjusting the height of the limiting baffle, so that the water depth environment of various actual shallow lakes can be simulated.
Preferably, a downstream water level control water tank is arranged between the experimental part of the experimental water tank and the non-pressure water outlet pipe, a water retaining gate is arranged between the experimental part and the downstream water level control water tank, a gate of the water retaining gate is opened and closed along the vertical direction, and the gate height of the water retaining gate is the same as the experimental water tank height. When the gate of the water retaining gate is opened along the vertical direction, the same flow of water flows out of the upper layer and the lower layer of the experimental water tank, so that the difference of the water flow rates of the upper layer and the lower layer is further reduced; if the gate is opened and closed in the horizontal direction, the water flow at the opening part of the gate is fast, and the water flow of other water layers is slow, so that the stability of the whole water flow speed in the experimental water tank is not facilitated.
Preferably, the device is also provided with a drainage pump, an underground water pool and a backflow water pump which are sequentially connected through a water pipe, wherein the drainage pump is connected with a non-pressure water outlet pipe, and the backflow water pump is connected with the water inlet pipe. The aim is to recover the water flowing out of the non-pressure water outlet pipe for recycling.
Preferably, the sliding support, the trolley and the telescopic rod move in an electric mode. This aim at improves the control accuracy and the degree of automation of sliding support, dolly and telescopic link.
The invention also provides a using method of the simulation device, which comprises the following steps:
s1, burying a submerged plant model on the perforated PVC plate according to the actual river bottom condition and a fixed scale, and paving sand stones or sludge;
s2, opening and adjusting the water inlet pipe and the constant flow valve to control the flow rate of water flow, adjusting the sliding support, the trolley and the telescopic rod to fix the position of the speed measuring device, and measuring a plurality of groups of h, u and h after the flow rate of water flow is stablevAnd uv(ii) a Wherein h is the vertical distance from a certain position of the speed measuring device in water to the water bottom, u is the flow velocity of water measured at the position, and hvIs the vertical distance from the top of the model of submerged plant to the bottom of the water, uvThe flow velocity of the water flow measured at the top of the submerged plant model;
s3, substituting the groups h and u obtained in the step S2 into a formula
Fitting an equation curve in orgin software and calculating to obtain related parameters A, B and u*A value of (b), wherein u*A, B is the normal relation to the material and arrangement of the water bottom for the purpose of friction and flow speedCounting;
s4, converting u obtained in the step S2 into uvAnd u obtained in step S3*Substitution formula
Calculating to obtain the drag force coefficient C of a certain position in waterSinking die；
S5, and then according to the formula
Calculated to obtain M, nSinking dieAnd nSinking and consolidatingWherein h is0For measuring the total depth of water surface at the section, g is gravity acceleration, M is Manning number, nSinking dieManning roughness coefficient, lambda, for submerged plant models1Is the ratio of the actual height of the submerged plant to the model, nSinking and consolidatingThe actual Manning roughness coefficient of the submerged plant is obtained;
s6, according to the formula
Calculate nErecting formwork(ii) a Wherein c is a conversion coefficient, nErecting formworkThe Mannich roughness coefficient of the emergent aquatic plant model, kappa is the Karman constant and usually takes a value of 0.4, and b is the width of the experimental part;
s7, according to the formula
Calculate nWell-balanced and strongI.e. the actual Manning roughness coefficient of emergent aquatic plants, where lambda2The ratio of the actual height of the emergent aquatic plant to the model.
In the above measurement method, the formula
A new drag force calculation mode which is derived by self optimization of the inventor enables the finally calculated submerged plant bottom friction coefficient and emergent plant bottom friction coefficient to have higher precision.
Compared with the prior art, the invention has the beneficial effects that:
1. the device can simulate the three-dimensional underwater environment of an actual water area, is convenient to measure the water flow rates of a plurality of groups of different positions, reduces the influence of wrong measurement data at one or more positions on a final result to the maximum extent, can artificially control the water flow rate, can simulate the environment of various shallow lakes, and has wide application range;
2. through the synergistic effect of the constant-flow water tank, the constant-flow cover of the steady-flow part of the experimental water tank and the water retaining gate, the flow velocity of water flow of the whole experimental water tank is very stable, and the influence of uneven distribution of the flow velocity of water at the upper layer and the lower layer of a water body on the measurement precision is reduced to the greatest extent;
3. the calculation is carried out by adopting the self-optimized mathematical formula, the adopted mathematical formula is more scientific and reasonable, various shallow lakes containing vegetation can be perfectly simulated, and the result error caused by the self limitation of the selected formula is reduced.
Drawings
FIG. 1 is a schematic structural diagram of a simulation apparatus for measuring a friction coefficient of a shallow lake bottom according to an embodiment;
FIG. 2 is a top view of an experimental tank and a sliding support of the simulation apparatus for measuring the friction coefficient of the bottom of a shallow lake according to one embodiment;
FIG. 3 is a cross-sectional view of a sliding support and a trolley of the simulation apparatus for measuring the friction coefficient of the bottom of a shallow lake according to one embodiment;
FIG. 4 is a schematic structural diagram of a simulation apparatus for measuring the friction coefficient of a shallow lake bottom according to the second embodiment.
In the figure: 1. a water inlet pipe; 2. a constant flow water tank; 201. an overflow section; 202. a water inlet part; 203. a limit baffle; 204. an overflow pipe; 3. an experimental water tank; 301. a flow stabilizing part; 302. an experimental part; 4. a flow stabilizing cover; 5. a smooth PVC sheet; 6. punching a PVC plate; 7. a sliding support; 8. a trolley; 9. a telescopic rod; 10. a speed measuring device; 11. a water retaining gate; 12. a downstream water level control tank; 13. a non-pressure water outlet pipe; 14. a constant flow valve; 15. an underground water pool; 16. draining pump; 17. and (4) refluxing to a water pump.
Detailed Description
The technical solutions of the embodiments in this patent will be described clearly and completely with reference to the accompanying drawings, and it is obvious that the described embodiments are only some embodiments, not all embodiments, of this patent. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the patent without making creative efforts, shall fall within the protection scope of the patent.
In the description of this patent, it is noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", "top", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience in describing the patent and for simplicity in description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the patent. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of this patent, it is noted that, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "communicating" are to be construed broadly, e.g., as meaning fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. It is to be noted that all the figures are exemplary representations. The meaning of the above terms in this patent may be specifically understood by those of ordinary skill in the art.
The patent is described in further detail below with reference to specific embodiments and with reference to the attached drawings.
Example one
The simulation device for measuring the friction coefficient of the bottom of the shallow lake as shown in the figures 1-3 comprises a constant-flow water tank 2 and an experimental water tank 3 which are connected through a water pipe from left to right; the constant-current water tank 2 and the experimental water tank 3 are both box-type structures with upper covers, the upper cover of the constant-current water tank 2 is connected with a water inlet pipe 1, the rightmost end of the experimental water tank 3 is connected with a non-pressure water outlet pipe 13, and a constant-current valve 14 is arranged on the non-pressure water outlet pipe 13; a flow stabilizing cover 4 is vertically arranged in the experimental water tank 3, the flow stabilizing cover 4 divides the experimental water tank 3 into a left flow stabilizing part 301 and a right experimental part 302, water flows into the constant-flow water tank 2 from the water inlet pipe 1, then flows into the flow stabilizing part 301 of the experimental water tank 3, flows through the experimental part 302, and finally flows out from the non-pressure water outlet pipe 13; the bottom of the experimental part 302 is uniformly divided into an upstream section, a midstream section and a downstream section from left to right in sequence, the upper surfaces of the upstream section and the downstream section are positioned on the same plane, the upper surface of the midstream section is downwards concave, and the lower surfaces of the upstream section, the midstream section and the downstream section are positioned on the same horizontal plane; the upstream section and the downstream section are made of smooth PVC plates 5, the midstream section is made of perforated PVC plates 6 uniformly provided with concave holes, and the thickness of the perforated PVC plates 6 is half of that of the smooth PVC plates 5; the concave holes of the perforated PVC plate 6 are used for embedding aquatic weed models according to the actual vegetation condition of the water bottom of the water area to be simulated; the upper portion of the two opposite sides of the experimental part 302 is provided with a sliding support 7 capable of sliding back and forth in a stretching mode, the sliding support 7 is provided with a sliding trolley 8, the trolley 8 is provided with a telescopic rod 9 capable of stretching downwards, and the tail end of the lower portion of the telescopic rod 9 is provided with a speed measuring device 10.
The method for measuring and calculating the bottom friction coefficients of submerged plants and emergent plants comprises the following steps:
s1, burying a submerged plant model on the perforated PVC plate according to the actual river bottom condition and a fixed scale, and paving sand stones or sludge;
s2, opening and adjusting the water inlet pipe and the constant flow valve to control the flow rate of water flow, adjusting the sliding support, the trolley and the telescopic rod to fix the position of the speed measuring device, and measuring a plurality of groups of h, u and h after the flow rate of water flow is stablevAnd uv(ii) a Wherein h is the vertical distance from a certain position of the speed measuring device in water to the water bottom, u is the flow velocity of water measured at the position, and hvIs the vertical distance from the top of the model of submerged plant to the bottom of the water, uvThe flow velocity of the water flow measured at the top of the submerged plant model;
s3, substituting the groups h and u obtained in the step S2 into a formula
Fitting an equation curve in orgin software and calculating to obtain related parameters A, B and u*A value of (b), wherein u*A, B is a constant related to the material and arrangement of the water bottom for the friction flow velocity;
s4, converting u obtained in the step S2 into uvAnd u obtained in step S3*Substitution formula
Calculating to obtain the drag force coefficient C of a certain position in waterSinking die；
S5, and then according to the formula
Calculated to obtain M, nSinking dieAnd nSinking and consolidatingWherein h is0For measuring the total depth of water surface at the section, g is gravity acceleration, M is Manning number, nSinking dieManning roughness coefficient, lambda, for submerged plant models1Is the ratio of the actual height of the submerged plant to the model, nSinking and consolidatingThe actual Manning roughness coefficient of the submerged plant is obtained;
s6, according to the formula
Calculate nErecting formwork(ii) a Wherein c is a conversion coefficient, nErecting formworkThe Mannich roughness coefficient of the emergent aquatic plant model, kappa is the Karman constant and usually takes a value of 0.4, and b is the width of the experimental part;
s7, according to the formula
Calculate nWell-balanced and strongI.e. fruits of emergent aquatic plantsCoefficient of interplanetary roughness, wherein2The ratio of the actual height of the emergent aquatic plant to the model.
When the device is used, firstly, according to the actual vegetation condition of the river bottom of a water area to be simulated, a submerged plant model is embedded on the perforated PVC plate according to a scale, and gravels or sludge are paved; and then the water inlet pipe and the constant flow valve are opened and adjusted to control the flow rate of water flow, the sliding support, the trolley and the telescopic rod are adjusted to fix the position of the speed measuring device, and then the flow rate of water flow at the position can be measured. The constant-flow water tank is communicated with the experimental water tank, so that the water levels of the constant-flow water tank and the experimental water tank are kept at the same height through the principle of the communicating vessel, the height of the water level can be controlled by adjusting the water flow speed of the water inlet pipe, and the influence on the measurement precision due to the fact that the water flow speed entering the experimental water tank is too high can be prevented through the delaying effect of the constant-flow water tank; the water flowing into the experimental water tank can further keep the flow velocity of the water on the upper layer and the lower layer of the experimental water tank stable under the action of the flow stabilizing cover on the flow stabilizing part, so that the local uneven distribution of the water flow on the upper layer and the lower layer is avoided, and the measurement error is reduced; the constant-flow water tank and the constant-flow cover of the constant-flow part cooperate to ensure that the water flow velocity flowing into the experimental water tank is stable and keeps a fixed proportional relation with the water flow velocity of the actual water area to be simulated. The device can measure the water flow velocity of any point in the three-dimensional water area, forms a plurality of groups of data, avoids the influence of certain error data on the whole experimental result, can artificially control the water flow velocity, and greatly improves the application range of the device.
Example two
The simulation device for measuring the friction coefficient of the bottom of the shallow lake as shown in FIG. 4 comprises a constant flow water tank 2 and an experimental water tank 3 which are connected through a water pipe from left to right; the constant-current water tank 2 and the experimental water tank 3 are both box-shaped structures with upper covers, the upper cover of the constant-current water tank 2 is connected with a water inlet pipe 1, the constant-current water tank 2 is divided into an overflow part 201 and a water inlet part 202 which are communicated with each other at the upper part by a limit baffle 203 with the liftable middle part, and the water inlet part 202 is close to the experimental water tank 3; the water inlet pipe 1 corresponds to the water inlet part 202, and an overflow pipe 204 is connected below the overflow part 201; the rightmost end of the experimental water tank 3 is connected with a downstream water level control water tank 12, a water retaining gate 11 is arranged between the experimental part 302 and the downstream water level control water tank 12, a gate of the water retaining gate 11 is opened and closed along the vertical direction, and the gate height of the water retaining gate 11 is the same as that of the experimental water tank 3; the right end of the downstream water level control water tank 12 is connected with a non-pressure water outlet pipe 13, and the non-pressure water outlet pipe 13 is provided with a constant flow valve 14; a flow stabilizing cover 4 is vertically arranged inside the experimental water tank 3, and the flow stabilizing cover 4 divides the experimental water tank 3 into a left flow stabilizing part 301 and a right experimental part 302; the bottom of the experimental part 302 is uniformly divided into an upstream section, a midstream section and a downstream section from left to right in sequence, the upper surfaces of the upstream section and the downstream section are positioned on the same plane, the upper surface of the midstream section is downwards concave, and the lower surfaces of the upstream section, the midstream section and the downstream section are positioned on the same horizontal plane; the upstream section and the downstream section are made of smooth PVC plates 5, the midstream section is made of perforated PVC plates 6 uniformly provided with concave holes, and the thickness of the perforated PVC plates 6 is half of that of the smooth PVC plates 5; the concave holes of the perforated PVC plate 6 are used for embedding aquatic weed models according to the actual vegetation condition of the water bottom of the water area to be simulated; a sliding support 7 capable of sliding back and forth is arranged above two opposite sides of the experimental part 302 in a crossing manner, a sliding trolley 8 is arranged on the sliding support 7, a telescopic rod 9 capable of stretching downwards is arranged on the trolley 8, and a speed measuring device 10 is arranged at the tail end below the telescopic rod 9; the device is also provided with a draining pump 16, an underground water pool 15 and a backflow water pump 17 which are sequentially connected through a water pipe, wherein the draining pump 16 is connected with the non-pressure water outlet pipe 13, and the backflow water pump 17 is connected with the water inlet pipe 1.
The water flows into the constant-flow water tank 2 from the water inlet pipe 1, then flows into the flow stabilizing part 301 of the experimental water tank 3, flows through the experimental part 302 and the downstream water level control water tank 12, finally flows out from the non-pressure water outlet pipe 13, and then flows into the constant-flow water tank 2 from the water inlet pipe 1 again through the action of the drainage pump 16, the underground water tank 15 and the return water pump 17.
The device calculates the bottom friction coefficient of the submerged plant and the emerged plant according to the measuring and calculating method described in the first embodiment. On the basis of the device provided by the first embodiment, the stability of the flow velocity of water flow in the experimental water tank is further improved, and the water flow at any position in the experimental water tank is ensured not to fluctuate in a large range; especially, when the water level of the experimental water tank needs to be adjusted when water areas with different depths are measured, the rising or falling of the water level is very stable. This improves the accuracy of the measurement results and indirectly reduces the error of the calculation results.
Application example
Taking a certain water area of the Taihu lake as an example, the state of submerged plants in the water area is simulated, and the area is known to be completely submerged plants, lambda 12, submerged plant hvThe initial velocity of the water tank was 0.05m/s at 0.15m, and the velocity u of the water stream was measured at a vertical distance h from the bottom of the water using the apparatus of examples 1 and 2, respectively, as follows:
the Manning roughness coefficient n of the corresponding submerged plant model calculated in the example 1 and the example 2 is obtained through fitting calculationSinking die30.68 and 27.27, respectively, corresponding to the actual Mannich roughness coefficient n of submerged plants in the water area of the Taihu lakeSinking and consolidating34.43 and 30.61.
The data are verified by MIKE21 water quality model softwareSinking and consolidatingThe accuracy of (2). Mike21 is a two-dimensional dynamic model software among a series of hydrodynamic water quality model software developed by the danish hydrodynamic research institute (DHI), and is mostly used to treat lakes, estuaries, and coastal areas where vertical changes may be ignored in water quality prediction. The numerical calculation method adopted by the Flow Model FM of the hydrodynamic Model in Mike21 is a finite volume method, the algorithm has good conservation property and can accurately process torrent and discontinuous solution, and the Model adopts a non-structural grid, can simultaneously use a mixed grid aiming at the topographic features of a prediction area, is convenient to process complex boundary conditions, has better calculation precision and saves time relatively.
Establishing a two-dimensional water quality hydrodynamic response relation of the Taihu lake in MIKE21 water quality model software, and measuring the actual Manning roughness coefficient n according to the experiments of example 1 and example 2Sinking and consolidatingIs taken as a parameter and is put into a model according to the actually measured water level flow of the hydrological stationThe model was run for boundary conditions, and the Taihu lake flow field was simulated. And selecting a plurality of point positions on the Taihu lake to actually measure the flow rate water level, and carrying out calibration verification on the point positions and the flow rate water level simulating the point in the MIKE model. The actual Mannich coefficient n experimentally measured according to examples 1 and 2 was subjected to error analysisSinking and consolidatingThe absolute errors of the simulated water level value and the actually measured water level value are both less than 20cm, and the absolute error of the embodiment 2 is obviously less than that of the embodiment 1. Therefore, the model can be used, the side surface reflects that the measurement precision of the devices of the embodiment 1 and the embodiment 2 is higher and more accurate, and the precision of the embodiment 2 is the highest and most accurate.
Claims (5)
1. A use method of a simulation device for measuring the friction coefficient of the bottom of a shallow lake is characterized by comprising a constant-flow water tank and an experimental water tank which are connected through a water pipe from left to right; the constant-current water tank and the experimental water tank are both of box-type structures with upper covers, the upper cover of the constant-current water tank is connected with a water inlet pipe, the rightmost end of the experimental water tank is connected with a non-pressure water outlet pipe, and a constant-current valve is arranged on the non-pressure water outlet pipe;
a flow stabilizing cover is vertically arranged in the experiment water tank, the flow stabilizing cover divides the experiment water tank into a left flow stabilizing part and a right experiment part, water flows into the constant flow water tank from the water inlet pipe, then flows into the flow stabilizing part of the experiment water tank, flows through the experiment part and finally flows out from the non-pressure water outlet pipe;
the bottom of the experimental part is uniformly divided into an upstream section, a midstream section and a downstream section from left to right in sequence, the upper surfaces of the upstream section and the downstream section are positioned on the same plane, the upper surface of the midstream section is downwards concave, and the lower surfaces of the upstream section, the midstream section and the downstream section are positioned on the same horizontal plane; the upstream section and the downstream section are made of smooth PVC plates, the midstream section is made of perforated PVC plates uniformly provided with concave holes, and the thickness of each perforated PVC plate is half of that of each smooth PVC plate; the concave hole of the perforated PVC plate is used for embedding a float grass model according to the actual vegetation condition of the water bottom of the water area to be simulated;
sliding supports capable of sliding back and forth are arranged above two opposite sides of the experimental part in a crossing mode, sliding trolleys are arranged on the sliding supports, telescopic rods capable of stretching downwards are arranged on the trolleys, and speed measuring devices are arranged at the tail ends of the lower portions of the telescopic rods;
the use method of the simulation device comprises the following steps:
s1, burying a submerged plant model on the perforated PVC plate according to the actual river bottom condition and a fixed scale, and paving sand stones or sludge;
s2, opening and adjusting the water inlet pipe and the constant flow valve to control the flow rate of water flow, adjusting the sliding support, the trolley and the telescopic rod to fix the position of the speed measuring device, and measuring a plurality of groups of h, u and h after the flow rate of water flow is stablevAnd uv(ii) a Wherein h is the vertical distance from a certain position of the speed measuring device in water to the water bottom, u is the flow velocity of water measured at the position, and hvIs the vertical distance from the top of the model of submerged plant to the bottom of the water, uvThe flow velocity of the water flow measured at the top of the submerged plant model;
s3, substituting the groups h and u obtained in the step S2 into a formula
Fitting an equation curve in orgin software and calculating to obtain related parameters A, B and u*A value of (b), wherein u*A, B is a constant related to the material and arrangement of the water bottom for the friction flow velocity;
s4, converting u obtained in the step S2 into uvAnd u obtained in step S3*Substitution formula
Calculating to obtain the drag force coefficient C of a certain position in waterSinking die；
S5, and then according to the formula
Calculated to obtain M, nSinking dieAnd nSinking and consolidatingWherein h is0For measuring the total depth of water surface at the section, g is gravity acceleration, M is Manning number, nSinking dieManning roughness coefficient, lambda, for submerged plant models1Is the ratio of the actual height of the submerged plant to the model, nSinking and consolidatingThe actual Manning roughness coefficient of the submerged plant is obtained;
s6, according to the formula
And
calculate nErecting formwork(ii) a Wherein c is a conversion coefficient, nErecting formworkThe Manning roughness coefficient of the emergent aquatic plant model, k is the Karman constant and usually takes a value of 0.4, and b is the width of the experimental part;
s7, according to the formula
Calculate nWell-balanced and strongI.e. the actual Manning roughness coefficient of emergent aquatic plants, where lambda2The ratio of the actual height of the emergent aquatic plant to the model.
2. The use method of the simulation device for measuring the friction coefficient of the bottom of the shallow lake as claimed in claim 1, wherein the constant flow water tank is divided into an overflow part and a water inlet part which are communicated with each other at the upper part by a limit baffle plate with a liftable middle part, and the water inlet part is close to the experimental water tank; the inlet tube corresponds the portion of intaking, overflow pipe is connected to overflow portion below.
3. The use method of the simulation device for measuring the friction coefficient of the bottom of the shallow lake as claimed in claim 1, wherein a downstream water level control water tank is arranged between the experimental part of the experimental water tank and the non-pressure water outlet pipe, a water retaining gate is arranged between the experimental part and the downstream water level control water tank, a gate of the water retaining gate is opened and closed along a vertical direction, and the gate height of the water retaining gate is the same as the experimental water tank height.
4. The use method of the simulation device for measuring the friction coefficient of the bottom of the shallow lake as claimed in claim 1, further comprising a drainage pump, an underground water pool and a return water pump which are connected in sequence through a water pipe, wherein the drainage pump is connected with a non-pressure water outlet pipe, and the return water pump is connected with the water inlet pipe.
5. The use method of the simulation device for measuring the friction coefficient of the bottom of the shallow lake as claimed in claim 1, wherein the sliding support, the trolley and the telescopic rod are electrically moved.
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