CN111236132B - Method and device for determining single-width sand conveying rate of pump station approach channel and front pool - Google Patents

Method and device for determining single-width sand conveying rate of pump station approach channel and front pool Download PDF

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CN111236132B
CN111236132B CN201811433374.7A CN201811433374A CN111236132B CN 111236132 B CN111236132 B CN 111236132B CN 201811433374 A CN201811433374 A CN 201811433374A CN 111236132 B CN111236132 B CN 111236132B
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sand
rate
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CN111236132A (en
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陈鑫
朱启祥
王福军
汤远
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China Agricultural University
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China Agricultural University
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B1/00—Equipment or apparatus for, or methods of, general hydraulic engineering, e.g. protection of constructions against ice-strains
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B3/00—Engineering works in connection with control or use of streams, rivers, coasts, or other marine sites; Sealings or joints for engineering works in general
    • E02B3/02—Stream regulation, e.g. breaking up subaqueous rock, cleaning the beds of waterways, directing the water flow
    • E02B3/023—Removing sediments

Abstract

The embodiment of the invention provides a method and a device for determining a pump station approach channel and a single-width sand conveying rate of a front pool, wherein the method comprises the following steps: acquiring the flow velocity, the flow period, the sediment particle size, the ratio of sediment to water density and the motion viscosity coefficient of water of an outer boundary layer of a pump station approach channel and a front pool water body; acquiring the Siertz number and friction factors of the sand-containing moving bed surface of the reciprocating flow; based on all the parameters, boundary layer asymmetry analysis of the movable bed surface is carried out, erosion depth and boundary layer thickness are obtained, and instantaneous single-width sand conveying rate of the volume meter under the reciprocating flow condition is obtained. The embodiment of the invention carries out design calculation through the determined thickness of the boundary layer of the relevant movable bed surface and the phase difference parameter, and reflects the negative net sand transportation generated by the large phase difference effect in asymmetric flow by setting the relation between the instantaneous sand transportation rate and the flow rate frequency and the phase residue of the sand transportation rate after the flow rate is reduced and the phase drift of the relative flow rate.

Description

Method and device for determining single-width sand conveying rate of pump station approach channel and front pool
Technical Field
The embodiment of the invention relates to the technical field of hydraulic engineering, in particular to a method and a device for determining single-width sand conveying rate of a pump station approach and a front pool.
Background
During the reciprocating flow of the sand-containing bed surface of the pump station approach channel and the front pool, the single-width sand conveying rate is dynamically changed. The instantaneous single-width sand conveying rate widely used in engineering is deduced based on a constant flow theory, and the asymmetric development and the phase difference effect of a reciprocating flow boundary layer cannot be reflected.
This leads to the disadvantages: the method can not reflect the phase drift and phase residue of the sand conveying rate relative to the flow velocity, can not give the relation between the instantaneous sand conveying rate and the flow velocity frequency, and is not suitable for the negative net sand conveying situation generated by the large phase difference effect in the asymmetric flow.
The determination of the sand transport rate under the action of the asymmetric development and the phase difference of the boundary layer is an important basis for judging the net sand transport rate of the sand-containing movable bed surface under the condition of reciprocating flow and is also a basis for judging the conditions of pumping sand into a pump station and the abrasion of the water pump. However, so far, there is no achievement or method for reference to give the instantaneous single-width sand conveying rate of the pump station approach channel and the front pool sand-containing movable bed surface under the reciprocating flow condition.
Disclosure of Invention
In order to solve the above problems, embodiments of the present invention provide a method and an apparatus for determining a single-width sand transporting rate of a pump station approach channel and a front pool.
In a first aspect, an embodiment of the present invention provides a method for determining a pump station approach channel and a front pool single-width sand conveying rate, including:
acquiring the flow velocity, the flow period, the sediment particle size, the ratio of the sediment to the water density, the gravity acceleration and the water movement viscosity coefficient of an outer boundary layer of a pump station approach channel and a front pool water body;
acquiring the Sierpiz number and the friction factor of a reciprocating flow sand-containing movable bed surface according to the flow velocity of the outer boundary layer of the pump station approach channel and the front pool water body, the flow period, the sediment particle size, the ratio of the sediment to the water density and the gravitational acceleration;
based on all the parameters, boundary layer asymmetry analysis of the movable bed surface is carried out, erosion depth and boundary layer thickness are obtained, and instantaneous single-width sand conveying rate of the volume meter under the reciprocating flow condition is obtained.
In a second aspect, an embodiment of the present invention provides a device for determining a single-width sand transporting rate of a pump station approach channel and a front pool, including:
the first module is used for acquiring the flow velocity, the flow period, the sediment particle size, the ratio of sediment to water density, the gravitational acceleration and the water movement viscosity coefficient of an outer boundary layer of a pump station approach and a front pool water body;
the second module is used for acquiring the Sierpiz number and the friction factor of the reciprocating flow sand-containing moving bed surface according to the flow velocity of the outer boundary layer of the pump station approach channel and the front pool water body, the flow period, the sediment particle size, the ratio of the sediment to the water density and the gravitational acceleration;
and the third module is used for analyzing the boundary layer asymmetry of the movable bed surface based on all the parameters to obtain the erosion depth and the boundary layer thickness so as to obtain the instantaneous single-width sand conveying rate of the volume meter under the reciprocating flow condition.
According to the method and the device for determining the single-width sand conveying rate of the pump station approach channel and the front pool, the design calculation is carried out through the determined thickness of the boundary layer of the relevant movable bed surface and the phase difference parameter, the time response required by the single-width sand conveying rate in the unsteady flow relative to the hydrodynamic condition can be reflected, the phase residue of the sand conveying rate after the flow speed is reduced, the phase drift of the relative flow speed, the relation between the given instantaneous sand conveying rate and the flow speed frequency and the negative net sand conveying rate generated by the action of the large phase difference in the asymmetric flow are reflected.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
Fig. 1 is a flow chart of a method for determining a pump station approach channel and a front pool single-width sand conveying rate according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the flow velocity, erosion depth and boundary layer thickness of the outer boundary layer of the asymmetric reciprocating flow in accordance with an embodiment of the present invention;
FIG. 3 is a schematic diagram showing the relationship between the instantaneous single-width sand conveying rate and the flow rate times of the asymmetric reciprocating flow in the case of 0.1mm in the embodiment of the present invention;
FIG. 4 is a diagram showing the relationship between the net single-width sand-transporting rate of the asymmetric reciprocating flow and the maximum flow rate when the diameter D is 0.1mm in the embodiment of the present invention;
FIG. 5 is a schematic diagram showing the relationship between the instantaneous single-width sand conveying rate and the flow rate of the asymmetric reciprocating flow when the diameter D is 0.25mm in the embodiment of the present invention;
FIG. 6 is a schematic diagram showing the relationship between the instantaneous single-width sand conveying rate and the flow rate of the asymmetric reciprocating flow when the diameter D is 0.4mm in the embodiment of the present invention;
fig. 7 is a schematic structural diagram of a device for determining a pump station approach channel and a front pool single-width sand conveying rate according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a flowchart of a method for determining a pump station approach channel and a front pool single-width sand transportation rate according to an embodiment of the present invention, as shown in fig. 1, the method includes:
s1, acquiring the flow velocity, the flow period, the sediment particle size, the ratio of sediment to water density, the gravity acceleration and the water movement viscosity coefficient of the outer boundary layer of the pump station approach and the forebay water body;
s2, acquiring the Sierpiz number and the friction factor of the reciprocating flow sand-containing moving bed surface according to the flow velocity of the outer boundary layer of the pump station approach channel and the forebay water body, the flow period, the sediment particle size, the ratio of the sediment to the water density and the gravity acceleration;
and S3, based on all the parameters, performing boundary layer asymmetry analysis on the movable bed surface to obtain the erosion depth and the boundary layer thickness so as to obtain the instantaneous single-width sand conveying rate of the volume meter under the reciprocating flow condition.
The method comprises the steps of firstly obtaining the flow velocity, the flow period, the sediment particle size, the ratio of the sediment to the water density, the gravity acceleration and the water movement viscosity coefficient of an outer boundary layer of a pump station approach channel and a forebay water body, obtaining the Sierpiz number and the friction factor of a reciprocating flow sand-containing moving bed surface, carrying out asymmetric analysis on the moving bed surface to obtain the erosion depth and the boundary layer thickness, and calculating to obtain the instantaneous single-width sand conveying rate of a volume meter under the reciprocating flow condition.
According to the method for determining the single-width sand conveying rate of the pump station approach channel and the front pool, the design calculation is carried out through the determined thickness of the boundary layer of the relevant movable bed surface and the phase difference parameter, the time response required by the single-width sand conveying rate in the unsteady flow relative to the hydrodynamic condition can be reflected, the phase residue of the sand conveying rate after the flow speed is reduced, the phase drift of the relative flow speed, the relation between the given instantaneous sand conveying rate and the flow speed frequency and the negative net sand conveying rate generated by the action of the large phase difference in the asymmetric flow are reflected.
On the basis of the above embodiment, the obtaining of the erosion depth and the boundary layer thickness based on all the above parameters and the boundary layer asymmetry analysis of the mobile bed surface to obtain the instantaneous single-width sand transporting rate of the volumeter under the reciprocating flow condition specifically includes:
obtaining the ratio of the settling time of the silt in the sand conveying layer to the flow period and the settling velocity of the silt according to the flow velocity of the outer boundary layer, the Sherz number, the flow period, the particle size of the silt, the ratio of the silt to the density of water, the motion viscosity coefficient of water and the gravitational acceleration;
obtaining the phase drift of the erosion depth to the flow velocity and the residue of the phase according to the ratio of the settling time of the sediment in the sediment transport layer to the flow period;
acquiring the erosion depth and the boundary layer thickness according to the outer boundary layer flow velocity, the maximum value of the outer boundary layer flow velocity, the flow period, the sediment particle size, the friction factor of the reciprocating flow sand-containing moving bed surface, the phase residue, the critical Sierpis number, the ratio of the sediment to the water density, the sediment sedimentation velocity and the Sierpis number;
and acquiring the instantaneous single-width sand conveying rate of the volume meter under the reciprocating flow condition according to the erosion depth, the thickness of the boundary layer, the maximum sediment volume concentration and the flow velocity of the outer boundary layer.
Specifically, the embodiment of the present invention can derive an analytic solution of the flow velocity distribution of the sand-containing moving bed surface by using 6 known quantities u (T), T, D, s, g, and v. Wherein U (t) is the outer boundary layer flow velocity, which varies with time; t is the period of the fluctuation; d is the grain size of the silt; s is the ratio of silt to water density; g is the acceleration of gravity; v is the kinematic viscosity coefficient of water.
Fig. 2 is a schematic diagram of the flow velocity, erosion depth and boundary layer thickness of the outer boundary layer of the asymmetric reciprocating flow in the embodiment of the present invention, and as shown in fig. 2, the flow velocity of the outer boundary layer of the representative asymmetric reciprocating flow, which embodies the skewness of velocity and acceleration, can be expanded by using the series as follows:
Figure BDA0001883172160000051
wherein U (t) represents the outer boundary layer flow velocity, t represents time, k represents the order of harmonics, and N represents the order of harmonics, which may be ∞, WkRepresenting the amplitude of the harmonic of order k, omega representing the frequency of the harmonic, and taking the values 2 pi/T, phikLag representing the k harmonic, t0Denotes an initial time, which is a parameter for setting U (0) to 0.
Since U (t) is known, N, W thereink、ω、t0、φkAre all known values.
In order to embody the phase difference effect, the technical scheme of the invention adopts three parameters psi, psi and alpha:
Figure BDA0001883172160000052
Figure BDA0001883172160000053
α＝exp(-0.2/Ψ)， (4)
wherein psi is the ratio of the settling time of the silt in the sand transporting layer to the flow period; psi represents the phase drift of the erosion depth versus flow velocity; alpha represents the residual of the phase, i.e. the ratio of the amount of sand still in motion at the moment of flow diversion to the maximum amount of sand entrainment.
The relevant parameters satisfy:
Figure BDA0001883172160000054
Figure BDA0001883172160000055
Figure BDA0001883172160000056
wherein Θ is the Sherz number; the subscript m represents the maximum value; thetamIs the maximum Sherz number; u shapemIs the maximum value of the outer boundary layer flow velocity; f is the friction factor of the reciprocating flow sand-containing moving bed surface; w is the silt settling velocity.
In order to embody the asymmetry of the boundary layer of the movable bed surface, the erosion depth delta and the boundary layer thickness delta adopted by the inventionBThe following formula:
Figure BDA0001883172160000061
Figure BDA0001883172160000062
wherein Θ iscrIs the critical Sherz number, generally 0.05, and the erosion depth is the distance from the surface of the saturated sand-containing layer to the initial bed surface.
The instantaneous single-width sand transport rate of the volumeter under reciprocating flow conditions can be derived as follows:
Figure BDA0001883172160000063
wherein SmThe maximum silt volume concentration is generally 0.6.
Sgn (U) U/U is needed in the engineeringm|nApproximation phi/phimThe existing observation shows that the index is 1-5. Taking the infinite limit of phase residue, wherein delta of the formula (8) is a constant; neglecting deltaBIs then phi/phi of the present inventionmAnd Sgn (U) U |UmAnd | coincide.
Taking the limit that the phase residue is infinitesimally small, the delta of the formula (8) is proportional to the power of 2 of U, and neglecting 4.61 delta + deltaBCan make the phi/phi of the inventionmApproximately Sgn (U) U/Um|5。
On the basis of the above embodiment, the obtaining of the instantaneous single-width sand transporting rate of the volumeter in the reciprocating flow condition further comprises:
acquiring the order of harmonic waves, the amplitude of each order of harmonic waves, the frequency of the harmonic waves, the initial time and the lag angle of each order of harmonic waves in the flow rate expansion series of the asymmetric reciprocating flow outer boundary layer according to the flow rates of the outer boundary layers of the pump station approach channel and the front pool water body;
and acquiring the instantaneous single-width bed load sand conveying rate of the volume meter under the reciprocating flow condition according to the erosion depth, the thickness of the boundary layer, the maximum sediment volume concentration and the flow velocity of the outer boundary layer.
In particular, the instant single-wide bed load sand transport rate phi of the volumeter under the reciprocating flow condition of the inventionbComprises the following steps:
Figure BDA0001883172160000071
after calculating the values of the parameters from the expressions (1) to (7) according to U, T, D, s, g and v, the erosion depths Delta and the boundary layer thicknesses Delta of the expressions (8) to (9) can be determinedBTogether with SmAnd the instantaneous single-width sand conveying rate of U substituted by the volume meters of the formulas (10) to (11).
In this embodiment, the method described above is verified.
One standard atmospheric pressure and 20 ℃ water temperature are known. U shapem＝1.2m/s、T＝5.0s、D＝1.0×10-4m、s＝2.65、g＝9.8m/s2、v＝1.0×10-6m2And s. The asymmetric 2-step Stokes reciprocating flow velocity process is adopted as follows: u (T) ═ 0.96cos [2 pi (T/T-0.214)]+0.24cos[4π(t/T-0.214)]See the broken line in fig. 2, where N is 2 and W corresponds to formula (1)k＝0.96×0.25k-1、ω＝0.4πs-1、t0＝-0.18s、φk＝-0.5(k-1)π。
(II) calculating theta and f, and adopting the formulas (5) to (6) provided by the invention.
(1) First, let's assume thetam< 1, f obtained from formula (6) is 6.6X 10-3(ii) a Substituting formula (5) to obtain thetam2.94 > 1. Assuming this is not true, proceed to step (2)
(2) According to the formula thetamGreater than 1, add UmSubstituting formula (5) with thetamSubstituted by formula (6) to obtain
Figure BDA0001883172160000072
From formula (12) to yield f ═ 1.0X 10-2Substituting formula (5) to obtain thetam4.45, wherein:
Θ(t)＝3.09U2， (13)
and (III) calculating w and psi, and adopting the formula (2) and the formula (7) provided by the invention.
From formula (7) w is 8.4 × 10-3m/s, substituting formula (2) to obtain psi ═ 1.1.
And fourthly, calculating psi and alpha, and adopting the formulas (3) and (4) provided by the invention.
Obtaining ψ of 8.7 × 10 from formula (3)-1s, α is 8.3 × 10 from formula (4)-1。
(V) calculating the erosion depth delta and the boundary layer thickness deltaBThe formulas (8) and (9) provided by the invention are adopted.
G, D, T and UmAnd 2-4, obtaining all parameters thetam、ΘcrF, ψ, α, w and formula (13) are obtained by substituting formulae (8) to (9):
D(t+0.87)＝(30.54+4.26U2)×10-4， (14)
δB(t)＝0.022×[max(1,3.09U2)]0.18， (15)
and (VI) calculating the instantaneous single-width sand conveying rate and the bed load sand conveying rate by adopting the formula (10) and the formula (11).
Retardation of Delta of equation (14) by 0.87S, SmSubstitution of formula (15) for formula (10) 0.6The single-width sand conveying rate in volume under the reciprocating flow condition of the invention is as follows:
Figure BDA0001883172160000081
the result of FIG. 3 is obtained by substituting U (t) for formula (16).
FIG. 3 is a schematic diagram showing the relationship between the instantaneous single-width sand conveying rate and the flow rate times of the asymmetric reciprocating flow when D is 0.1mm, as shown in FIG. 3, D is 0.1mm, phi/phimIs a dimensionless single-width sand conveying rate; T/T is dimensionless time; n represents the function Sgn (U) | U/Um|n(ii) a U is the outer boundary layer flow rate; u shapemIs the maximum value of the outer boundary layer flow velocity; d is the sand grain size.
The period average value of the formula (16)<φ>Is net single wide sand transport rate; changing UmRepeating the steps 1-6 to obtain<φ>In fig. 4. FIG. 4 is a diagram showing the relationship between the net single-width sand-transporting rate of the asymmetric reciprocating flow and the maximum flow rate when D is 0.1mm in the embodiment of the present invention,<φ>is the net sand transport rate per unit m2/s；UmIs the maximum value of the outer boundary layer flow velocity in m/s.
Retardation of Delta of equation (14) by 0.87S, SmWhen the formula (15) is 0.6, the single-width sand conveying rate of the bed load mass in the volume under the reciprocating flow condition can be obtained by substituting the formula (11).
Increasing the particle size to D0.25 mm, repeating the above steps 1-6, and decreasing the corresponding phase difference parameter to psi 1.5 × 10-1、ψ＝1.2×10-1s、α＝2.6×10-1Corresponding to FIG. 5, FIG. 5 is a schematic diagram showing the relationship between the instantaneous single-width sand transporting rate and the number of flow rates of the asymmetric reciprocating flow when the embodiment D of the present invention is 0.25mm, and in FIG. 5, phi/phimIs a dimensionless single-width sand conveying rate; T/T is dimensionless time; n represents the function Sgn (U) | U/Um|n(ii) a U is the outer boundary layer flow rate; u shapemIs the maximum value of the outer boundary layer flow velocity; d is the sand grain size.
Further increasing the particle diameter to D0.4 mm, and reducing the corresponding phase difference parameter to psi 8.6 × 10-2、ψ＝6.8×10-2s、α＝1.0×10-1Corresponding to fig. 6, the single width sand transporting rate of the present invention.
FIG. 6 is a schematic diagram showing the relationship between the instantaneous single-width sand-transporting rate and the flow rate of the asymmetric reciprocating flow when D is 0.4mm in the embodiment of the present invention, phi/phimIs dimensionless single width sand transporting rate, T/T is dimensionless time, n represents function Sgn (U) U/Um|nU is the outer boundary layer flow velocity, UmIs the maximum value of the flow velocity of the outer boundary layer, and D is the grain size of the silt.
By adopting the technical scheme, the invention has the following 3 advantages that the instantaneous sand conveying rate changes along with time, wherein the advantages are brought by the development of a boundary layer and the action of phase difference:
1. the phase difference of the sand conveying rate relative to the flow speed can be reflected.
FIG. 2 shows that the erosion depth Δ of the solid line of the present invention lags behind the phase of the broken line flow rate U at T/T-0.17 due to phase shift, resulting in the sand transport rate φ/φ of FIG. 3mThe maximum value in the positive flow phase (T/T0.00-0.42) lags behind the peak point in time (T/T0.21), and likewise the maximum value in the negative flow phase (T/T0.42-1.00) lags behind the valley point in time (T/T0.71). Due to the large phase residual, as shown in fig. 2, the erosion depth is not reduced to 0, and a large amount of silt in the positive flow stage (T/T ═ 0.00-0.42) is brought into the negative flow stage (T/T ═ 0.42-1.00), so that the erosion depth of the stage is close to that in the positive flow stage (T/T ═ 0.00-0.42); the sand transport rate is increased in the negative flow phase (T/T ═ 0.42-1.00), so that phi/phi in FIG. 3mCan approach Sgn (U) U/Um|nThe lower theoretical limit of exponent of (1).
2. Can be suitable for the negative net sand transportation generated by the action of large phase difference in asymmetric flow.
The 2-step Stokes flow of the discontinuous line of fig. 2 is a typical asymmetric reciprocating flow, and the thickness variation of the boundary layer is also asymmetric. As shown in the dotted line of fig. 2, the boundary layer thickness in the negative flow stage (T/T ═ 0.42-1.00) is relatively thin, and the sand conveying rate in the negative flow stage (T/T ═ 0.42-1.00) is relatively enhanced corresponding to the relatively strong boundary layer flow velocity; combined with large phase difference effect, phi/phi of figure 3mOver Sgn (U) | U/Um|nIndex of (1)The lower limit n is 1, resulting in the large U of FIG. 4mThe negative direction of (1) net sand transportation.
3. The relation between the instantaneous sand conveying rate and the flowing speed times is unified.
The invention can make phi/phi get infinite limit of phase residuemApproximately Sgn (U) U/Um|nThe lower index limit n of (1); the phase remains at an infinitesimal limit, which can be made phi/phimApproximately Sgn (U) U/Um|nThe upper index limit n of (2) is 5. As the particle diameter D increases from 0.1mm to 0.25mm to 0.4mm, the retardation effect decreases. Correspondingly, the sand transport rate for the negative flow phase (T/T ═ 0.42-1.00) is relatively reduced, so that φ/φ of FIG. 5mCan approach Sgn (U) U/Um|nThe index n of fig. 6 is 3, and the index n of fig. 6 is further closer to 5.
Fig. 7 is a schematic structural diagram of a device for determining a pump station approach channel and a front pool single-width sand transporting rate according to an embodiment of the present invention, as shown in fig. 7, the device includes a first module 701, a second module 702, and a third module 703, where:
the first module 701 is used for acquiring the flow velocity, the flow period, the sediment particle size, the ratio of sediment to water density, the gravity acceleration and the motion viscosity coefficient of water of the outer boundary layer of the water body of the pump station approach and the forebay;
the second module 702 is configured to obtain the siertz number and the friction factor of the reciprocating flow sand-containing bed surface according to the flow velocity of the outer boundary layer of the pump station approach and the front pool water body, the flow period, the grain size of the silt, the ratio of the silt to the water density, and the gravitational acceleration;
the third module 703 is used for obtaining erosion depth and boundary layer thickness based on all the above parameters and performing boundary layer asymmetry analysis of the mobile bed surface to obtain instantaneous single-width sand conveying rate of the volume meter under reciprocating flow condition.
The device for determining the single-width sand conveying rate of the pump station approach channel and the front pool provided by the embodiment of the invention can reflect the time response required by the single-width sand conveying rate relative to hydrodynamic conditions in non-constant flow by performing design calculation through the determined thickness of the boundary layer of the relevant movable bed surface and phase difference parameters, reflect the phase residue of the sand conveying rate after the flow speed is reduced, the phase drift of the relative flow speed, and the given relation between the instantaneous sand conveying rate and the flow speed times, and judge the negative net sand conveying generated by the action of large phase difference in asymmetric flow.
The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (6)

1. A method for determining the single-width sand conveying rate of a pump station approach channel and a front pool is characterized by comprising the following steps:
acquiring the flow velocity, the flow period, the sediment particle size, the ratio of the sediment to the water density, the gravity acceleration and the water movement viscosity coefficient of an outer boundary layer of a pump station approach channel and a front pool water body;
according to the outer boundary layer flow velocity, the flow period, the sediment particle size, the ratio of the sediment to the water density and the gravitational acceleration of the pump station approach channel and the forebay water body, the friction factor of the Sierpitz number and the reciprocating flow sediment-bearing bed surface is obtained, and the method specifically comprises the following steps:
Figure FDA0002783656910000011
Figure FDA0002783656910000012
wherein theta represents the Siertz number, f represents the friction factor of the reciprocating flow sand-containing moving bed surface, U represents the flow velocity of the outer boundary layer, and theta representsmDenotes the maximum Sherz number, UmRepresenting the maximum value of the flow velocity of the outer boundary layer, s representing the ratio of the silt to the density of water, g representing the gravitational acceleration, D representing the particle size of the silt, and T representing the flow period;
based on all the parameters, the specific value of the settling time and the flow period of the sediment in the sediment transport layer and the sediment settling velocity are obtained, and the method specifically comprises the following steps:
Figure FDA0002783656910000013
Figure FDA0002783656910000014
wherein Ψ represents the ratio of the settling time of the sediment in the sediment transport layer to the flow period, w represents the sediment settling velocity, and ν represents the kinetic viscosity coefficient of the water;
according to the specific value of the settling time and the flowing period of the sediment in the sediment transport layer, the phase drift of the erosion depth to the flow velocity and the residue of the phase are obtained, and the method specifically comprises the following steps:
Figure FDA0002783656910000021
α＝exp(-0.2/Ψ)，
wherein ψ represents a phase drift of the erosion depth to a flow velocity, and α represents a residual of the phase;
based on all the parameters, and performing boundary layer asymmetry analysis of the mobile bed surface to obtain the erosion depth and the boundary layer thickness, specifically:
Figure FDA0002783656910000022
Figure FDA0002783656910000023
wherein Δ represents the erosion depth, δBRepresenting the boundary layer thickness;
based on all the parameters, the instantaneous single-width sand conveying rate of the volume meter under the reciprocating flow condition is obtained.
2. The method of claim 1, wherein said obtaining an instantaneous single-width sand transport rate of the volumeter under reciprocating flow conditions further comprises:
acquiring the order of harmonic waves, the amplitude of each harmonic wave, the frequency of the harmonic wave, the initial time and the lag angle of each harmonic wave in the flow velocity expansion series of the asymmetric reciprocating flow outer boundary layer according to the flow velocity and the flow period of the outer boundary layer of the pump station approach channel and the front pool water body;
and acquiring the instantaneous single-width bed load sand conveying rate of the volume meter under the reciprocating flow condition according to the erosion depth, the thickness of the boundary layer, the maximum sediment volume concentration and the flow velocity of the outer boundary layer.
3. The method of claim 2, wherein the obtaining of the erosion depth and the boundary layer thickness based on all the above parameters and the boundary layer asymmetry analysis of the mobile bed surface to obtain the instantaneous single-width sand transporting rate of the volumeter under the reciprocating flow condition comprises:
obtaining the ratio of the settling time of the silt in the sand conveying layer to the flow period and the settling velocity of the silt according to the flow velocity of the outer boundary layer, the Sherz number, the flow period, the particle size of the silt, the ratio of the silt to the density of water, the motion viscosity coefficient of the water and the gravitational acceleration;
obtaining the phase drift of the erosion depth to the flow velocity and the residue of the phase according to the ratio of the settling time of the sediment in the sediment transport layer to the flow period;
acquiring the erosion depth and the boundary layer thickness according to the outer boundary layer flow velocity, the maximum value of the outer boundary layer flow velocity, the flow period, the sediment particle size, the friction factor of the reciprocating flow sand-containing moving bed surface, the phase residue, the critical Sierpis number, the ratio of the sediment to the water density, the sediment sedimentation velocity and the Sierpis number;
and acquiring the instantaneous single-width sand conveying rate of the volume meter under the reciprocating flow condition according to the erosion depth, the thickness of the boundary layer, the maximum sediment volume concentration and the flow velocity of the outer boundary layer.
4. The method according to claim 1, wherein the obtaining of the instantaneous single-width sand transporting rate of the volumeter under reciprocating flow conditions from the erosion depth, the boundary layer thickness, the maximum silt volume concentration and the outer boundary layer flow rate comprises:
Figure FDA0002783656910000031
wherein φ (t) represents the instantaneous single-width sand transport rate of the volumeter under said reciprocating flow conditions.
5. The method according to claim 4, wherein the obtaining of the instantaneous single-wide bed load sediment transport rate of the volumeter under reciprocating flow conditions from the erosion depth, the boundary layer thickness, the maximum sediment volume concentration and the outer boundary layer flow rate comprises:
Figure FDA0002783656910000041
wherein phi isb(t) represents the instantaneous single-width bed load sand transport rate of the volumeter under said reciprocating flow conditions.
6. The utility model provides a pump station approach and determination device of preceding pond list width sand conveying rate which characterized in that includes:
the first module is used for acquiring the flow velocity, the flow period, the sediment particle size, the ratio of sediment to water density, the gravitational acceleration and the water movement viscosity coefficient of an outer boundary layer of a pump station approach and a front pool water body;
the second module is used for acquiring the Sierpiz number and the friction factor of the reciprocating flow sand-containing moving bed surface according to the flow velocity of the outer boundary layer of the pump station approach channel and the front pool water body, the flow period, the sand particle size, the ratio of the sand to the water density and the gravity acceleration, and specifically comprises the following steps:
Figure FDA0002783656910000042
Figure FDA0002783656910000043
wherein theta represents the Siertz number, f represents the friction factor of the reciprocating flow sand-containing moving bed surface, U represents the flow velocity of the outer boundary layer, and theta representsmDenotes the maximum Sherz number, UmRepresenting the maximum value of the flow velocity of the outer boundary layer, s representing the ratio of the silt to the density of water, g representing the gravitational acceleration, D representing the particle size of the silt, and T representing the flow period;
based on all the parameters, the specific value of the settling time and the flow period of the sediment in the sediment transport layer and the sediment settling velocity are obtained, and the method specifically comprises the following steps:
Figure FDA0002783656910000044
Figure FDA0002783656910000045
wherein Ψ represents the ratio of the settling time of the sediment in the sediment transport layer to the flow period, w represents the sediment settling velocity, and ν represents the kinetic viscosity coefficient of the water;
according to the specific value of the settling time and the flowing period of the sediment in the sediment transport layer, the phase drift of the erosion depth to the flow velocity and the residue of the phase are obtained, and the method specifically comprises the following steps:
Figure FDA0002783656910000051
α＝exp(-0.2/Ψ)，
wherein ψ represents a phase drift of the erosion depth to a flow velocity, and α represents a residual of the phase;
a third module, configured to perform boundary layer asymmetry analysis on the bed surface based on all the parameters, and obtain an erosion depth and a boundary layer thickness, specifically:
Figure FDA0002783656910000052
Figure FDA0002783656910000053
wherein Δ represents the erosion depth, δBRepresenting the boundary layer thickness;
based on all the parameters, the instantaneous single-width sand conveying rate of the volume meter under the reciprocating flow condition is obtained.
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