Design method for monitoring lake and reservoir water body flow field floating objects

Abstract

The invention relates to a design method for monitoring lake and reservoir water flow field floaters. The method comprises the following steps: selecting a control equation; selecting an analysis mode; modeling and grid division are carried out; setting boundary conditions and parameters; and carrying out numerical simulation and comparative analysis on the multi-type drifts. Through physical experiment and computer simulation of the seven elaborately selected drifts, the flowing characteristics of the seven drifts and the pressure difference between the left side and the right side in the water flow are calculated, and according to the characteristic that the objects tend to move towards the side with the small pressure difference, through comparison and simulation, the drifts with the small pressure difference can be obtained. And determining that the ball shape is the shape most easily drifting in the water flow with the maximum flow speed, so that the shape of the ball-shaped object serving as the drifting buoy is obtained, and the movement track of the ball-shaped drifting object can accurately represent the flowing track of the water flow in the lake and reservoir.

Description

Technical Field

[0001] The invention relates to a design method for monitoring the flow field of lake water bodies, which is an auxiliary method for hydraulic research and a method for designing floating objects that drift in rivers to study the flow field of water bodies in lakes or reservoirs. Background Art

[0002] Lakes and reservoirs with a wide surface area appear calm and peaceful on the surface, but in fact, due to various factors such as the inflow and outflow of water or wind disturbance, there is a natural flow of water on the surface of the lake. This natural flow mainly exists in the surface layer of the water body. Of course, in some cases, there is also flow in the depths of the water body, but the surface flow of the water body is more direct and has a greater impact on human life. For a long time, the observation of the water flow on the surface of wide water bodies such as lakes and reservoirs has always been carried out by throwing simple buoys and observing with the naked eye, and hand-drawing the flow field. The shape of the buoy used is mainly designed for manufacturing convenience rather than according to the principles of hydraulics. What kind of buoy meets the requirements of hydrodynamics, and how to design a floating object that meets the requirements of water flow and can accurately display the water flow of lakes and reservoirs is a problem that needs to be solved. Summary of the invention

[0003] In order to overcome the problems of the prior art, the present invention proposes a design method for monitoring floating objects in the flow field of lakes and reservoirs. The method sets seven representative simulated floating objects, conducts physical model experiments and simulates the simulation model of virtual space, and finally draws the conclusion that the spherical shape can represent the flow trajectory of water.

[0004] The object of the present invention is achieved by: a design method for monitoring floating objects in the flow field of lake water bodies, the steps of the method are as follows:

[0005] Step 1, select the control equation:

[0006] Control equation: Expressed in x, y two-dimensional rectangular coordinate system:

[0007]

[0008] Where: ρ is the fluid density; t is the time; p is the pressure; u is the x-component of the velocity; v is the y-component of the velocity; μ is the dynamic viscosity of the fluid;

[0009] Step 2, select the analysis method:

[0010] Select the finite element method as the discretization method: The finite element method discretization process is:

[0011] 1) Discretize the fluid solution calculation area into multiple independent units, and then generate discrete equations in each unit based on the variational method or weighted residual method, so that the error function is reduced to the minimum value and a stable solution appears;

[0012] 2) Combine the discrete equations in each unit to obtain the overall equation system in the entire basin, and then obtain the numerical solution in the entire basin through the given initial values ​​and boundary conditions;

[0013] Step 3, modeling and meshing: establish a physical model in the laboratory and a simulation model in the simulation space of the computer; physical model: set up a water trough with left and right side walls on both sides, and the water flows along the left and right side walls; simulation model: the numerical simulation model uses an unstructured triangular grid to discretize the fluid domain. In order to obtain more accurate results, the surface of the sphere is locally meshed. The physical model, numerical simulation model and mesh of the numerical simulation model include:

[0014] (1) Complete sphere: A complete sphere is fixed on one side of the water tank as a floating object. The corresponding water tank and sphere are constructed in the simulation space, and a grid is established around the sphere. The grid around the sphere is dense and then gradually increases.

[0015] (2) Linear penetrating sphere: A sphere with a cylindrical hole penetrating the center of the sphere is fixed on one side of the water flow trough as a floating object. The central axis of the cylindrical hole is perpendicular to the water flow direction. A grid is established around the sphere with a cylindrical hole penetrating the center of the sphere in the simulation space. The grid around the sphere with a cylindrical hole penetrating the center of the sphere is dense, and then the grid is gradually increased;

[0016] (3) Cross-penetrated sphere: A sphere with orthogonal cylindrical holes is fixed on one side of the water flow trough as a floating object. One of the two cylindrical holes is perpendicular to the water flow direction, and the other is along the water flow direction. A grid is established around the sphere in the simulation space. The grid around the sphere and the side wall close to the sphere is dense, and then the grid is gradually increased.

[0017] (4) Double spheres of equal diameter: Two spheres of the same diameter that are tightly fixed together are fixed on one side of the water flow channel as drift objects. The two spheres are arranged along the direction of the water flow. A grid is established around the spheres in the simulation space. The grid around the spheres and the side walls close to the spheres is dense, and then the grid is gradually increased.

[0018] (5) Two spheres, one large and one small: Two tightly fixed spheres with different diameters are fixed on one side of the water flow channel as floating objects. The two spheres are arranged along the direction of the water flow, with a diameter difference of one time. A grid is established around the spheres in the simulation space. The grid around the spheres and the side walls close to the spheres are dense, and then the grid is gradually enlarged.

[0019] (6) Ellipsoid: A water trough with left and right side walls is set up, and the water flows along the left and right side walls. An ellipsoid with a major and minor axis that differs by one time is fixed on one side of the water trough. The major axis of the ellipsoid is along the direction of the water flow. A grid is established around the sphere in the simulation space. The grids around the sphere and between the side walls close to the sphere are dense, and then the grids are gradually increased.

[0020] (7) Sphere with protrusions: A water trough with left and right side walls is set up, and the water flows along the left and right side walls. A plurality of small spheres are evenly distributed on an outer circumference and fixed on one side of the water trough. The diameter of the large sphere is more than twice the diameter of the small sphere. A grid is established around the sphere in the simulation space. The grid around the sphere and the side walls close to the sphere are dense, and then the grid is gradually increased.

[0021] Step 4, boundary conditions and parameter settings: The boundary conditions are set as follows:

[0022] (1) The inlet boundary condition type is uniform flow boundary condition:

[0023] U 中 =U max ,

[0024] Where: Flow velocity U at the middle of the inlet 中 is the maximum speed U max , the flow velocity gradually decreases toward the side walls;

[0025] (2) The outlet boundary condition type is set to free outflow boundary condition:

[0026] P = 0;

[0027] Where: P is the outlet pressure;

[0028] (3) Boundary conditions of the side wall parallel to the water flow direction:

[0029] v=0

[0030] (4) According to the basic assumptions of fluid mechanics, the surface of the drift object is set to a no-slip boundary condition:

[0031] u=0,v=0;

[0032] Step 5, numerical simulation and comparative analysis of multiple types of drifting objects: start the water flow in the flow trough, with the maximum flow rate in the middle, and the flow rate gradually decreases toward the side walls on both sides, and the flow rate is 0 at the side walls; measure the pressure on both sides of each drifting object, and calculate the pressure difference of the water flow on the left and right sides of each drifting object; at the same time, start the numerical model simulation in the computer, simulate the water flow through the simulated drifting object in the simulated flow trough, and generate the pressure distribution on both sides of each simulated drifting object; the left side of the drifting object is an area with a larger water flow rate and a smaller pressure, while the right side is an area with a smaller water flow rate and a larger pressure; accordingly, the drifting object tends to move to the side with a smaller pressure in the water flow, that is, it tends to move to the middle position with a larger water flow rate; from the pressure simulation of the physical model experiment and the numerical simulation model, it can be seen that among the seven types of drifting objects, the sphere is subjected to the largest pressure difference, indicating that among the seven types of drifting objects, the sphere is most conducive to moving with the mainstream.

[0033] The advantages and beneficial effects of the present invention are as follows: the present invention conducts physical experiments and computer simulations on seven carefully selected drifting objects, calculates the flow characteristics of the seven drifting objects and the pressure difference on the left and right sides in the water flow, and according to the characteristic that objects tend to move to the side with a smaller pressure difference, after comparison and simulation, determines that the spherical shape is the shape that is easiest to drift in the water flow with the fastest flow rate, thereby obtaining the shape of the spherical object as a drifting buoy, and the movement trajectory of the spherical drifting object can accurately represent the flow trajectory of the water flow in the lake reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0035] Figure 1 is a flow chart of the method described in an embodiment of the present invention;

[0036] Figure 2 is a schematic diagram of a complete spherical drift object and a grid according to an embodiment of the present invention;

[0037] Figure 3 Schematic diagram of a linear through-type spherical drift object and a grid according to an embodiment of the present invention;

[0038] Figure 4 Schematic diagram of a cross-penetrating spherical drift object and a grid according to an embodiment of the present invention;

[0039] Figure 5 Schematic diagram of a double spherical floating object of equal diameter and a grid according to an embodiment of the present invention;

[0040] Figure 6 Schematic diagram of a large and a small double spherical floating object and a grid according to an embodiment of the present invention;

[0041] Figure 7 is a schematic diagram of an ellipsoidal drift object and a grid according to an embodiment of the present invention;

[0042] Figure 8 It is a schematic diagram of a spherical floating object with protrusions and a grid according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] Example:

[0044] This embodiment is a design method for monitoring floating objects in the flow field of lake water bodies. The steps of the method are as follows (process as shown in FIG. Figure 1 shown):

[0045] Step 1, select the control equation:

[0046] The control equations of the fluid domain can use the Navier-Stokes equations under the assumption of homogeneous and incompressible viscous fluid, and set the fluid density and viscosity unchanged. Control equations: Expressed in the x, y two-dimensional rectangular coordinate system: The flow field of water flow in lakes and reservoirs is mainly reflected in the surface layer of water, so it is sufficient to use two-dimensional hydrodynamic control equations without the need for three-dimensional research.

[0047]

[0048] Wherein: ρ is the fluid density; t is the time; p is the pressure; u is the x-component of the velocity; v is the y-component of the velocity; μ is the fluid dynamic viscosity; all studies in this embodiment are numerically simulated using COMSOL Multiphysics software.

[0049] Step 2, select the analysis method: Computational Fluid Dynamics (CFD) is an interdisciplinary subject between mathematics, fluid mechanics and computers that emerged with the development of computers. Its main research content is to solve the control equations of fluid mechanics through computers and numerical methods, simulate and analyze fluid mechanics problems that are difficult to set physical conditions during the experiment, save a lot of manpower and material resources, and provide reference for subsequent experiments.

[0050] According to different discretization methods, computational fluid dynamics solution methods can be roughly divided into three types: finite volume method, finite difference method and finite element method, etc., among which the finite element method is adopted in this embodiment.

[0051] The basic discretization process of this method is: first, the fluid solution calculation area is discretized into multiple independent units, and then the discrete equations in each unit are generated based on the variational method or the weighted residual method, so that the error function is reduced to the minimum and a stable solution appears. The entire fluid domain is composed of multiple small finite element interconnected sub-regions, so an approximate solution can be found for each unit solution. Then, the discrete equations in each unit are combined together to obtain the overall equation set in the entire flow domain, and then the numerical solution in the entire flow domain is obtained by giving the initial value and boundary conditions. For the use of unstructured grids at various resolutions, the finite element method often increases the number of grids to improve accuracy, but the memory requirements and calculation time will increase. In the current work, a triangular mesh type is used. The triangular mesh is attractive for its simplicity. Compared with general polygonal meshes, many operations are easier for triangular meshes, especially in the area near the boundary wall and the outer boundary wall of the object. High-precision mesh quality can be produced when the fluid flow is anisotropic.

[0052] Select the finite element method as the discretization method: The finite element method discretization process is:

[0053] 1) Discretize the fluid solution calculation area into multiple independent units, and then generate discrete equations in each unit based on the variational method or weighted residual method, so that the error function is reduced to the minimum value and a stable solution appears;

[0054] 2) Combine the discrete equations in each unit to obtain the overall equation system in the entire basin, and then obtain the numerical solution in the entire basin through the given initial values ​​and boundary conditions;

[0055] Step 3, modeling and meshing: establish a physical model in the laboratory and a simulation model in the simulation space of the computer; Physical model: set up a flow channel with left and right side walls (left and right determined by the direction of water flow), and the water flows along the left and right side walls ( Figure 2-Figure 8 Flows from left to right in the water channel); cut a section in the water channel as the length of the watershed, such as using a rectangular box with a length of 4.4m and a width of 1m, with water entering one side of the two short sides of the box ( Figure 2-Figure 8 Left side), water outflow on the other side ( Figure 2-Figure 8 The long side of the box is the direction of water flow. The box is used to simulate the water flow basin formed by the lake water area. Experiments have proved that this method of simulating lakes and reservoirs is feasible. Figure 2-Figure 8 for the lower side), fix the drifting objects, such as Figure 2-Figure 8As shown, simulation model: In order to obtain more accurate results for the numerical simulation model, it is necessary to perform local mesh encryption on the surface area; COMSOL Multiphysics software can be used to mesh the fluid domain within the established model, and the fluid domain is discretized using unstructured triangular meshes, and local mesh encryption is performed on the surface of the sphere. The seven simulated drifting objects are carefully selected, and the shape of each simulated drifting object represents the shape of at least two or more real drifting objects. Although only seven simulated drifting objects were used for simulation experiments, they represent hundreds of object shapes. The physical model, numerical simulation model, and mesh of the numerical simulation model include:

[0056] (1) Complete sphere: A complete sphere is fixed as a floating object on one side of the water tank. The corresponding water tank and sphere are constructed in the simulation space, and a grid is established around the sphere. The grid around the sphere is dense and then gradually increased. Figure 2 shown.

[0057] A complete sphere is used as a floating object, with the center of the sphere located in the middle right of the box, 0.1m away from the right side wall, and the radius of the sphere is 0.06m. A simulated water flow trough, sphere and its grid are established in the computer simulation space, that is, the model is established in the physical space and the computer simulation space at the same time, the same below. The complete sphere is used to study the state of isotropic objects drifting in the water.

[0058] (2) Linear penetrating sphere: A sphere with a cylindrical hole penetrating the center of the sphere is fixed on one side of the water flow trough as a floating object. The central axis of the cylindrical hole is perpendicular to the water flow direction. A grid is established around the sphere with a cylindrical hole penetrating the center of the sphere in the simulation space. The grids around the sphere with a cylindrical hole penetrating the center of the sphere are densely packed between the side walls close to the sphere, and then the grids are gradually enlarged; Figure 3 shown.

[0059] Using the rectangular box water flow trough mentioned above, the drifting object is located in the middle right position of the box, the center of the circle is 0.1m away from the side wall, the radius of the sphere is 0.06m, and there is a cylindrical hole with a radius of 0.02m running through the center of the sphere. It is used to study the drifting state of objects with straight holes in the water flow. The model diagram and grid diagram are shown as follows Figure 3 shown.

[0060] (3) Cross-penetrated sphere: A sphere with orthogonal cylindrical holes is fixed on one side of the water flow trough as a floating object. One of the two cylindrical holes is perpendicular to the water flow direction, and the other is along the water flow direction. A grid is established around the sphere in the simulation space. The grid around the sphere and the side wall close to the sphere is dense, and then the grid is gradually increased; Figure 4 shown.

[0061] The above rectangular box is used, in which the drifting object is located in the middle right position of the box, the center of the sphere is 0.1 away from the right side wall, the radius of the sphere is 0.06m, and there are two mutually perpendicular cylindrical holes with a radius of 0.02m passing through the sphere, which is used to study the state of objects with cross-through holes drifting in the water flow. The model diagram and grid diagram are shown as follows Figure 4 shown.

[0062] (4) Double spheres of equal diameter: Two spheres of the same diameter that are tightly fixed together are fixed on one side of the water flow channel as drift objects. The two spheres are arranged along the direction of the water flow. A grid is established around the spheres in the simulation space. The grids around the spheres and the walls close to the spheres are dense, and then the grids are gradually increased. Figure 5 shown.

[0063] The above rectangular box is used. The two combined spheres as drift objects are located in the middle of the box on the right side. The center of the circle is 0.1 away from the side wall. The radius of the two spheres is 0.03m. It is used to study the state of an object with a length-to-width ratio of about one drifting in the water. The model diagram and grid diagram are shown in the figure below. Figure 5 shown.

[0064] (5) Two spheres, one large and one small: Two spheres of different diameters are fixed tightly together as floating objects on one side of the water tank. The two spheres are arranged along the direction of the water flow, with a diameter difference of one time. A grid is established around the spheres in the simulation space. The grid around the spheres and the wall close to the spheres is dense, and then the grid is gradually increased; Figure 6 shown.

[0065] The above rectangular box, as the drifting object, has two spheres located in the middle right of the box, with the center of the sphere 0.1 away from the side wall, the radius of the large sphere is 0.02m, and the radius of the small sphere is 0.01m. It is used to study the state of the object with protrusions drifting in the water flow, and the state of the object drifting in the water flow when the cross section of the upstream and downstream water flow suddenly changes. The model diagram and grid diagram are shown as follows Figure 6 As shown in the figure, since the two combined spheres have different front and back terms, it is the only simulated floating object among the seven models that has requirements on the direction of water flow.

[0066] (6) Ellipsoid: Set up a water trough with left and right side walls on both sides. The water flows along the left and right side walls. Fix an ellipsoid with a major axis and a minor axis that differ by one time on one side of the water trough. The major axis of the ellipsoid is along the direction of the water flow. Build a grid around the sphere in the simulation space. The grids around the sphere and the side walls close to the sphere are dense, and then gradually increase in size. Figure 7 shown.

[0067] The above rectangular box, in which the ellipsoid is located in the middle right of the box, the center of the circle is 0.1 from the right side wall, the major axis a is 0.06m, and the minor axis b is 0.03m. It is used to study the state of an object drifting in the water flow when the cross-section of the upstream and downstream flow changes slowly. The model diagram and grid diagram are shown in the figure below. Figure 7 shown.

[0068] (7) Sphere with protrusions: A water trough with left and right side walls is set up, and the water flows along the left and right side walls. A plurality of small spheres are evenly distributed on an outer circumference and fixed on one side of the water trough. The diameter of the large sphere is more than twice the diameter of the small sphere. A grid is established around the sphere in the simulation space. The grid around the sphere and the side walls close to the sphere are dense, and then the grid is gradually increased; Figure 8 shown.

[0069] The above rectangular box, in which the drifting object is located in the middle right position of the box, the center of the circle is 0.1 away from the side wall, the radius of the large sphere is 0.045m, and the diameter of the small sphere around the large sphere is 0.0075m. It is used to study the state of an isotropic object with a protrusion on the surface drifting in the water flow. The model diagram and grid diagram are shown as follows Figure 8 shown.

[0070] Except for (5), the water flow in the above-mentioned water flow channel can flow in both positive and negative directions, that is, Figure 2-Figure 8 , that is, it can be from left to right or from right to left, and the research effect is the same. However, the water flow effect of (5) is inconsistent in the two directions, and research can be carried out on drifting objects of different shapes.

[0071] It should be noted that the “two sides” described in this embodiment are determined according to the conventional direction of water flow, and the “left” and “right” are both the left and right of the normal downstream flow. Figure 2-Figure 8 The water flow direction set in is from left to right, so Figure 2-Figure 8 The upper part in the figure is left, and the lower part is right.

[0072] Step 4, boundary conditions and parameter settings: The boundary conditions are set as follows:

[0073] (1) The inlet boundary condition type is uniform flow boundary condition:

[0074] U 中 =U max ,

[0075] Where: Flow velocity U at the middle of the inlet 中 is the maximum speed U max , the flow velocity gradually decreases toward the side walls;

[0076] At the entrance of the sink ( Figure 2-Figure 8The flow velocity in the middle of the horizontal direction (on the left side) is the maximum flow velocity, and it is assumed that the water flow is uniform over the entire flow surface.

[0077] (2) The outlet boundary condition type is set to free outflow boundary condition:

[0078] P = 0;

[0079] Where: P is the outlet pressure;

[0080] At the outlet of the sink ( Figure 2-Figure 8 The water flow at the outlet is free, so the outlet water pressure is set to 0.

[0081] 3) Wall boundary conditions parallel to the water flow direction:

[0082] v=0

[0083] (4) According to the basic assumptions of fluid mechanics, the surface of the drift object is set to a no-slip boundary condition:

[0084] u=0,v=0;

[0085] Step 5, numerical simulation and comparative analysis of multiple types of drift objects: Open the water flow in the flow channel (in Figure 2-Figure 8 The water flows from left to right), the middle is the maximum flow rate (can be set to 1.5m / s), the flow rate gradually decreases towards the side walls, and the flow rate is 0 at the side walls; measure the pressure on both sides of each drifting object, and use the measuring instrument to select the measuring point on both sides of the drifting object ( Figure 2-Figure 8 The pressure is measured at the corresponding points on the upper and lower sides of the drift, and at the points on the left and right sides of the drift according to the direction of the water flow. The measurement point can be firstly at the place where the diameter of the drift is the largest, and then several points upstream and downstream are selected for measurement, and the pressure difference of the water flow on the left and right sides of each drift is calculated ( Figure 2-Figure 8 The pressure at the corresponding points in the upper and lower parts of the image is subtracted), and the maximum pressure difference is recorded in a table; at the same time, the numerical model simulation is started in the computer to simulate the water flow through the simulated drifting objects in the simulated flow trough, and the pressure distribution on both sides of each simulated drifting object is generated; the left side of the drifting object is an area with a larger water flow velocity and a smaller pressure, while the right side is an area with a smaller water flow velocity and a larger pressure; accordingly, the drifting object tends to move to the side with a smaller pressure in the water flow, that is, it tends to move to the middle position with a larger water flow velocity. The specific parameters of the pressure difference on both sides of each drifting object in the physical experiment are shown in Table 1.

[0086] Table 1 Pressure difference on both sides of drifting objects

[0087]

[0088] From the pressure simulation of the physical model experiment and the numerical simulation model, it can be seen that among the seven types of drifting objects, the sphere is subject to the largest pressure difference, indicating that among the seven types of drifting objects, the sphere is most conducive to moving with the mainstream.

[0089] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred arrangement scheme, a person skilled in the art should understand that the technical solution of the present invention (such as the form of the rope, the state of the river, the sequence of steps, etc.) can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A design method for monitoring floating objects in the flow field of lakes and reservoirs, characterized in that: The steps of the method are as follows: Step 1: Select the control equation and analysis method: Control equation: Expressed in x, y two-dimensional rectangular coordinate system: Where: ρ is the fluid density; t is the time; p is the pressure; u is the x-component of the velocity; v is the y-component of the velocity; μ is the dynamic viscosity of the fluid; Step 2, select the analysis method: Select the finite element method as the discretization method: The finite element method discretization process is: 1) Discretize the fluid solution calculation area into multiple independent units, and then generate discrete equations in each unit based on the variational method or weighted residual method, so that the error function is reduced to the minimum value and a stable solution appears; 2) Combine the discrete equations in each unit to obtain the overall equation system in the entire basin, and then obtain the numerical solution in the entire basin through the given initial values ​​and boundary conditions; Step 3, modeling and meshing: establish a physical model in the laboratory and a simulation model in the simulation space of the computer; physical model: set up a water trough with left and right side walls on both sides, and the water flows along the left and right side walls; simulation model: the numerical simulation model uses an unstructured triangular grid to discretize the fluid domain. In order to obtain more accurate results, the surface of the sphere is locally meshed. The physical model, numerical simulation model and mesh of the numerical simulation model include: (1) Complete sphere: A complete sphere is fixed on one side of the water tank as a floating object. The corresponding water tank and sphere are constructed in the simulation space, and a grid is established around the sphere. The grid around the sphere is dense and then gradually increases. (2) Linear penetrating sphere: A sphere with a cylindrical hole penetrating the center of the sphere is fixed on one side of the water flow trough as a floating object. The central axis of the cylindrical hole is perpendicular to the water flow direction. A grid is established around the sphere with a cylindrical hole penetrating the center of the sphere in the simulation space. The grid around the sphere with a cylindrical hole penetrating the center of the sphere is dense, and then the grid is gradually increased; (3) Cross-penetrated sphere: A sphere with orthogonal cylindrical holes is fixed on one side of the water flow trough as a floating object. One of the two cylindrical holes is perpendicular to the water flow direction, and the other is along the water flow direction. A grid is established around the sphere in the simulation space. The grid around the sphere and the side wall close to the sphere is dense, and then the grid is gradually increased. (4) Double spheres of equal diameter: Two spheres of the same diameter that are tightly fixed together are fixed on one side of the water flow channel as drift objects. The two spheres are arranged along the direction of the water flow. A grid is established around the spheres in the simulation space. The grid around the spheres and the side walls close to the spheres is dense, and then the grid is gradually increased. (5) Two spheres, one large and one small: Two tightly fixed spheres with different diameters are fixed on one side of the water flow channel as floating objects. The two spheres are arranged along the direction of the water flow, with a diameter difference of one time. A grid is established around the spheres in the simulation space. The grid around the spheres and the side walls close to the spheres are dense, and then the grid is gradually enlarged. (6) Ellipsoid: A water trough with left and right side walls is set up, and the water flows along the left and right side walls. An ellipsoid with a major and minor axis that differs by one time is fixed on one side of the water trough. The major axis of the ellipsoid is along the direction of the water flow. A grid is established around the sphere in the simulation space. The grids around the sphere and between the side walls close to the sphere are dense, and then the grids are gradually increased. (7) Sphere with protrusions: A water trough with left and right side walls is set up, and the water flows along the left and right side walls. A plurality of small spheres are evenly distributed on an outer circumference and fixed on one side of the water trough. The diameter of the large sphere is more than twice the diameter of the small sphere. A grid is established around the sphere in the simulation space. The grid around the sphere and the side walls close to the sphere are dense, and then the grid is gradually increased. Step 4, boundary conditions and parameter settings: The boundary conditions are set as follows: (1) The inlet boundary condition type is uniform flow boundary condition: IN 中 =U max , Where: Flow velocity U at the middle of the inlet 中 is the maximum speed U max , the flow velocity gradually decreases toward the side walls; (2) The outlet boundary condition type is set to free outflow boundary condition: P＝0； Where: P is the outlet pressure; (3) Boundary conditions of the side wall parallel to the water flow direction: v＝0 (4) According to the basic assumptions of fluid mechanics, the surface of the drift object is set to a no-slip boundary condition: u=0,v=0; Step 5, numerical simulation and comparative analysis of multiple types of drifting objects: start the water flow in the flow trough, with the maximum flow rate in the middle, and the flow rate gradually decreases toward the side walls on both sides, and the flow rate is 0 at the side walls; measure the pressure on both sides of each drifting object, and calculate the pressure difference of the water flow on the left and right sides of each drifting object; at the same time, start the numerical model simulation in the computer, simulate the water flow through the simulated drifting object in the simulated flow trough, and generate the pressure distribution on both sides of each simulated drifting object; the left side of the drifting object is the area with a larger water flow rate and a smaller pressure, while the right side is the area with a smaller water flow rate and a larger pressure; accordingly, the drifting object tends to move to the side with a smaller pressure in the water flow, that is, it tends to move to the middle position with a larger water flow rate; from the pressure simulation of the physical model experiment and the numerical simulation model, it can be seen that among the seven types of drifting objects, the sphere is subjected to the largest pressure difference, indicating that among the seven types of drifting objects, the sphere is most conducive to moving with the mainstream.

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