A design method for monitoring floating objects in the water flow field of lakes and reservoirs

Abstract

The present invention relates to a design method for monitoring floating objects in the water flow field of lakes and reservoirs, including: selecting control equations; selecting analysis methods; modeling and mesh generation; boundary condition and parameter settings; numerical simulation and comparative analysis of multiple types of floating objects. Through physical experiments and computer simulations on seven carefully selected floating objects, the present invention calculates the flow characteristics of the seven floating objects and the pressure difference between the left and right sides in the water flow. According to the characteristic that an object tends to move towards the side with a smaller pressure difference, through comparison and simulation, it is determined that the spherical shape is the most likely to drift in the water flow with the maximum velocity, thereby obtaining the spherical shape as the shape of the floating buoy. The movement trajectory of the spherical floating object can accurately represent the flow trajectory of the water in the lake and reservoir.

Description

Technical Field

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

[0002] Lakes and reservoirs with broad water surfaces appear calm and serene on the surface. However, in fact, due to various factors such as the inflow and outflow of water or the disturbance of the wind, there is a natural flow of water on the surface of the lake water. This natural flow mainly exists in the surface layer of the water body. Of course, in some cases, there is also water flow in the deep part 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 broad water bodies such as lakes and reservoirs has been carried out by throwing simple buoys and observing them with the naked eye, and hand-drawing the flow field. The shapes of the buoys used are mainly designed for convenience of manufacture, rather than based on hydraulic principles. What kind of buoy meets the requirements of hydrodynamics and how to design a floating object that meets the water flow requirements and can accurately display the water flow in 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 water flow field of lakes and reservoirs. The method conducts physical model experiments and simulations of a virtual space simulation model on seven representative simulated floating objects, and finally draws the conclusion that the spherical shape can represent the water flow trajectory.

[0004] The object of the present invention is achieved as follows: A design method for monitoring floating objects in the water flow field of lakes and reservoirs, and the steps of the method are as follows:

[0005] Step 1, select the control equation:

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

[0007]

[0008] In the formula: 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;

[0009] Step 2, select the analysis method:

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

[0011] 1) Discretize the fluid solution calculation region into multiple independent units, and then generate discrete equations in each unit based on the variational method or the 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 set within the entire river basin, and then obtain the numerical solution within the entire river basin through the given initial values and boundary conditions;

[0013] Step 3, modeling and mesh generation: 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 flow flows along the left and right side walls. Simulation model: The numerical simulation model discretizes the fluid domain using unstructured triangular meshes. To obtain more accurate results, local mesh refinement is performed on the surface of the sphere. The physical model, the numerical simulation model, and the mesh of the numerical simulation model include:

[0014] (1) Complete sphere: Fix a complete sphere as a floating object on one side of the water trough, construct the corresponding water trough and sphere in the simulation space, and establish a mesh around the sphere. The mesh around the sphere is dense and then gradually increases;

[0015] (2) Straight-through sphere: Fix a sphere with a cylindrical hole passing through the center of the sphere as a floating object on one side of the water trough. The central axis of the cylindrical hole is perpendicular to the water flow direction. Establish a mesh around the sphere with a cylindrical hole passing through the center of the sphere in the simulation space. The mesh between the sphere with a cylindrical hole passing through the center of the sphere and the side wall close to the sphere is dense and then gradually increases;

[0016] (3) Cross-through sphere: Fix a sphere with orthogonal cylindrical holes passing through it as a floating object on one side of the water trough. One of the two cylindrical holes is perpendicular to the water flow direction and the other is along the water flow direction. Establish a mesh around the sphere in the simulation space. The mesh between the sphere and the side wall close to the sphere is dense and then gradually increases;

[0017] (4) Equal-diameter double spheres: Fix two spheres with the same diameter tightly fixed together as a floating object on one side of the water trough. The two spheres are arranged along the water flow direction. Establish a mesh around the spheres in the simulation space. The mesh between the spheres and the side wall close to the spheres is dense and then gradually increases;

[0018] (5) One large and one small double spheres: Fix two spheres with different diameters tightly fixed together as a floating object on one side of the water trough. The two spheres are arranged along the water flow direction and the diameter difference is one time. Establish a mesh around the spheres in the simulation space. The mesh between the spheres and the side wall close to the spheres is dense and then gradually increases;

[0019] (6) Ellipsoid: Set a water channel 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 twice as long as the minor axis on one side of the water channel. The major axis of the ellipsoid is in the direction of the water flow. Establish a grid around the sphere in the simulation space. The grid between the sphere and the side walls close to the sphere is dense, and then the grid gradually increases;

[0020] (7) Sphere with protrusions: Set a water channel with left and right side walls on both sides. The water flows along the left and right side walls. Fix a sphere with multiple small spheres evenly distributed on its outer circumference on one side of the water channel. The diameter of the large sphere is more than twice the diameter of the small sphere. Establish a grid around the sphere in the simulation space. The grid between the sphere and the side walls close to the sphere is dense, and then the grid gradually increases;

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

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

[0023] U 中 = U max ,

[0024] where: The flow velocity U 中 in the middle of the inlet is the maximum velocity U max , and the flow velocity gradually decreases towards the side walls on both sides;

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

[0026] P = 0;

[0027] where: P is the outlet pressure;

[0028] (3) The boundary condition of the side wall parallel to the water flow direction:

[0029] v = 0

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

[0031] u = 0, v = 0;

[0032] Step 5, Numerical Simulation and Comparative Analysis of Multiple Types of Drift Objects: Turn on the water flow in the flume, with the maximum flow velocity in the middle, and the flow velocity gradually decreasing towards the side walls, where the flow velocity is 0 at the side walls; measure the pressures on both sides of each drift object and calculate the pressure difference of the water flow on the left and right sides of each drift object; at the same time, turn on the numerical model simulation in the computer to simulate the water flow passing through the simulated drift objects in the simulated flume, and generate the pressure distribution on both sides of each simulated drift object; the left side of the drift object is the area with a larger water flow velocity and a smaller pressure, while the right side is the area with a smaller water flow velocity and a larger pressure; accordingly, the drift object tends to move towards the side with a smaller pressure in the water flow, that is, it tends to move towards the middle position with a larger water flow velocity; from the pressure simulation of the physical model experiment and the numerical simulation model, among the seven types of drift objects, the spherical ball has the largest pressure difference, indicating that the sphere is the most conducive to moving with the mainstream among the seven types of drift objects.

[0033] The advantages and beneficial effects of the present invention are as follows: Through physical experiments and computer simulations on seven carefully selected drift objects, the present invention calculates the flow characteristics of the seven drift objects and the pressure difference on the left and right sides in the water flow. According to the characteristic that an object tends to move towards the side with a smaller pressure difference, through comparison and simulation, it is determined that the spherical shape is the most likely shape to drift in the water flow with the largest flow velocity, thereby obtaining the spherical object as the shape of the drift buoy. The movement trajectory of the spherical drift 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 drawings and embodiments.

[0035] Figure 1 is the flowchart of the method described in the embodiment of the present invention;

[0036] Figure 2 is the schematic diagram of the complete spherical drift object and the grid described in the embodiment of the present invention;

[0037] Figure 3 is the schematic diagram of the linear penetration type spherical drift object and the grid described in the embodiment of the present invention;

[0038] Figure 4 is the schematic diagram of the cross penetration type spherical drift object and the grid described in the embodiment of the present invention;

[0039] Figure 5 is the schematic diagram of the equal diameter double spherical drift object and the grid described in the embodiment of the present invention;

[0040] Figure 6 is the schematic diagram of the large and small double spherical drift object and the grid described in the embodiment of the present invention;

[0041] Figure 7 is the schematic diagram of the ellipsoidal drift object and the grid described in the embodiment of the present invention;

[0042] Figure 8 It is a schematic diagram of the spherical floating object with protrusions and the grid described in the embodiments of the present invention. Detailed implementation manners

[0043] Embodiment:

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

[0045] Step 1, select the control equation:

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

[0047]

[0048] In the formula: 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; all researches in this embodiment use the COMSOL Multiphysics software for numerical simulation.

[0049] Step 2, select the analysis method: Computational Fluid Dynamics (CFD) is an interdisciplinary subject between mathematics, fluid mechanics and computer 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 experiments, save a large amount of manpower and material resources, and provide references for subsequent experiments.

[0050] According to different discretization methods, the solution methods of computational fluid dynamics can be roughly divided into three types: the Finite Volume Method, the Finite Difference Method, and the Finite Element Method, etc. Among them, 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 ( Figures 2 - 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 ( Figures 2 - 8 Left side), water outflow on the other side ( Figures 2 - 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. Figures 2 - 8 for the lower side), fix the drifting objects, such as Figures 2 - 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] Using the above rectangular box, where the drift object is located slightly to the right of the middle of the box, the center of the sphere is 0.1 away from the right side wall, and the radius of the spherical ball is 0.06 m. There are two cylindrical holes with a radius of 0.02 m and perpendicular to each other passing through the spherical ball, which are used to study the floating state of an object with intersecting straight through-holes in the water flow. The model diagram and mesh diagram are as Figure 4 shown.

[0062] (4) Equal-diameter double spheres: Two spheres with the same diameter tightly fixed together are used as the drift object and fixed on one side of the flume. The two spheres are arranged in the direction of the water flow. A mesh is established around the spheres in the simulation space. The mesh between the spheres and the side walls close to the spheres is dense, and then the mesh is gradually increased; as Figure 5 shown.

[0063] Using the above rectangular box, the two combined spheres used as the drift object are located slightly to the right of the middle of the box, the center of the circle is 0.1 away from the side wall, and the radius of both spherical balls is 0.03 m, which is used to study the floating state of an object with an aspect ratio of about one in the water flow. The model diagram and mesh diagram are as Figure 5 shown.

[0064] (5) One large and one small double spheres: Two spheres with different diameters tightly fixed together are used as the drift object and fixed on one side of the flume. The two spheres are arranged along the water flow direction, and the diameter difference is one time. A mesh is established around the spheres in the simulation space. The mesh between the spheres and the side walls close to the spheres is dense, and then the mesh is gradually increased; as Figure 6 shown.

[0065] In the above rectangular box, the two spherical balls used as the drift object are located slightly to the right of the middle of the box, the center of the circle is 0.1 away from the side wall, the radius of the large spherical ball is 0.02 m, and the radius of the small spherical ball is 0.01 m, which is used to study the floating state of an object with a protrusion and the floating state of an object when the cross-section changes suddenly in the oncoming water flow and the backwater flow. The model diagram and mesh diagram are as Figure 6 shown. Since the front and back items of the two combined spheres are different, it is the only simulated drift object with requirements for the water flow direction among the seven models.

[0066] (6) Ellipsoid: Set up a flume with left and right side walls on both sides, the water flow flows along the left and right side walls, fix an ellipsoid with a major axis and minor axis difference of one time on one side of the flume, the major axis of the ellipsoid is in the direction of the water flow, establish a mesh around the sphere in the simulation space, the mesh between the sphere and the side walls close to the sphere is dense, and then the mesh is gradually increased; as Figure 7 shown.

[0067] The above rectangular box, where the ellipsoid is located at a position slightly to the right of the middle of the box, and the center of the circle is 0.1 away from the right side wall. The major axis a is 0.06 m and the minor axis b is 0.03 m. It is used to study the drifting state of an object in water when the cross-sections of the water flow facing and against the current change slowly. Its model diagram and mesh diagram are as shown in Figure 7 shown.

[0068] (7) Sphere with protrusions: Set a water trough with left and right side walls on both sides. The water flows along the left and right side walls. Fix a large sphere with a number of small spheres evenly distributed on its outer circumference on one side of the water trough. The diameter of the large sphere is more than twice the diameter of the small sphere. Establish a mesh around the sphere in the simulation space. The mesh between the sphere and the side walls close to the sphere is dense, and then the mesh gradually increases; as shown in Figure 8 shown.

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

[0070] Except for (5), the water flow in the above water trough can flow in both forward and reverse directions, that is, as shown in Figures 2 - 8 , that is, it can flow from left to right or from right to left, and the research effects generated are the same. However, the water flow effects in the two directions of (5) are inconsistent, and different-shaped floating objects can be studied.

[0071] It should be noted that the "both sides" mentioned in this embodiment are determined according to the conventional water flow direction, and its "left" and "right" are the left and right in the normal downstream flow. Figures 2 - 8 The set water flow direction in is from the left to the right, so Figures 2 - 8 the upper part in is the left and the lower part is the right.

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

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

[0074] U 中 = U max ,

[0075] where: the flow velocity U 中 in the middle of the inlet is the maximum velocity U max , and the flow velocity gradually decreases towards the side walls on both sides;

[0076] At the inlet of the water trough ( Figures 2 - 8The flow velocity in the middle horizontally on the left side is the maximum flow velocity, and it is assumed that the water flow is uniform across the entire flow surface.

[0077] (2) Set the outlet boundary condition type to a free outflow boundary condition:

[0078] P = 0;

[0079] where: P is the outlet pressure;

[0080] At the outlet of the water tank ( Figures 2 - 8 on the right side), the water flow is freely outflowing, so the outlet water flow pressure is set to 0.

[0081] 3) The sidewall boundary condition in the direction parallel to the water flow:

[0082] v = 0

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

[0084] u = 0, v = 0;

[0085] Step 5, Numerical simulation and comparative analysis of multiple types of floating objects: Turn on the water flow in the flume ( Figures 2 - 8 the water flow moves from left to right), the middle has the maximum flow velocity (which can be set to 1.5 m / s), the flow velocity gradually decreases towards the sidewalls on both sides, and the flow velocity is 0 at the sidewalls; Measure the pressures on both sides of each floating object, and use a measuring instrument to select measurement points to measure the pressures on both sides of the floating object ( Figures 2 - 8 the corresponding points on the upper and lower sides of the floating object during drifting, and in the direction of the water flow, they are the points on the left and right sides of the floating object), the measurement points can preferably be at the maximum diameter of the floating object, and then select several points upstream and downstream for measurement respectively, and calculate the pressure difference of the water flow on the left and right sides of each floating object ( Figures 2 - 8 subtract the pressures of the upper and lower corresponding points), record the maximum pressure difference in a table; At the same time, turn on the numerical model simulation in the computer to simulate the water flow flowing through the simulated floating objects in the simulated flume, and generate the pressure distributions on both sides of each simulated floating object; The left side of the floating object is the area with a relatively large water flow velocity and a relatively small pressure, while the right side is the area with a relatively small water flow velocity and a relatively large pressure; Accordingly, the floating object tends to move towards the side with a smaller pressure in the water flow, that is, it tends to move towards the middle position with a larger water flow velocity. The specific parameters of the pressure difference on both sides of each floating object in the physical experiment are shown in Table 1.

[0086] Table 1 Pressure difference on both sides of the floating object

[0087]

[0088] From the pressure simulation of physical model experiments and numerical simulation models, it can be seen that among the seven types of floating objects, the spherical ball has the largest pressure difference, indicating that the sphere is the most conducive to moving with the mainstream among the seven types of floating objects.

[0089] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred arrangement, those of ordinary skill 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 equivalently replaced 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: Control equation: Expressed in x, y two-dimensional rectangular coordinate system: Where: ρ is the fluid density; t is the time; 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 numerical 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; numerical simulation model: the numerical simulation model uses unstructured triangular meshes to discretize the fluid domain, and in order to obtain 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 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 enlarged. (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 channel 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 as floats on one side of the water flow tank. 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 spheres with different diameters that are tightly fixed together are fixed as floats on one side of the water flow 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 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 floating object is set to a no-slip boundary condition: u=0,v=0; Step 5, numerical simulation and comparative analysis of multiple types of floating objects: start the water flow in the water 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 floating object, and calculate the pressure difference of the water flow on the left and right sides of each floating object; at the same time, start the numerical model simulation in the computer, simulate the water flow through the simulated floating object in the simulated water trough, and generate the pressure distribution on both sides of each simulated floating object; the left side of the floating 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 floating 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 floating objects, the sphere is subjected to the largest pressure difference, indicating that among the seven types of floating objects, the sphere is most conducive to moving with the mainstream.

Images