Numerical simulation method of water flow impact force on ship piers under high-speed water flow

Abstract

The present invention relates to the field of canal design and testing, and specifically discloses a numerical simulation method for the impact force of water flow on mooring piers under high-speed water flow, comprising: establishing a three-dimensional hub model based on the existing oblique intersection of the overflow weir outlet channel and the navigation channel under the ship lock; using three-dimensional simulation software to establish a water flow mathematical model based on the established three-dimensional hub model; using water level and flow velocity distribution data measured from the physical model of the hub where the mooring pier is located to identify and verify the water flow mathematical model, thereby obtaining an identified and verified water flow mathematical model; based on a fluid-solid coupling mathematical model, using the verified water flow mathematical model to perform fluid-solid coupling simulation under high-speed water flow, thereby obtaining a result of the water flow impact force on the mooring pier. The water flow impact force result obtained by the method of the present invention can improve the efficiency and accuracy of the water flow impact force simulation, can evaluate the structural stability of the mooring pier based on the water flow impact force on the mooring pier, and guide the design of the mooring pier, thereby ensuring the safety performance of the mooring pier during flood diversion.

Description

Technical Field

[0001] The invention relates to the technical field of canal design tests, and in particular to a numerical simulation method for the impact force of water flow on a pier under high-speed water flow. Background Art

[0002] Freight demand is rapidly increasing, and with significant room for economic and social development for a long time to come, the demand for water-friendly material transportation will further increase, placing an increasingly urgent demand on Haikou's development. The construction of the canal is crucial to the long-term development of the region. During the canal's design, cascaded hubs will be constructed to control water levels and ensure the safety of ships.

[0003] A hub is usually composed of a ship lock, a spillway and a connecting dam. The hub plays the role of flood diversion. The hub flood diversion project includes a retaining dam and a spillway structure. The spillway structure is composed of three parts in the longitudinal direction: the upstream inlet channel section, the middle channel section and the downstream outlet channel section. The spillway structure is located on the left side of the ship lock. An overflow weir is set downstream of the spillway to ensure the water depth of the middle connecting channel when the flood is discharged, so as to reduce the flow rate and prevent scouring. The downstream of the overflow weir is connected to the excavated stilling pool, followed by a concrete tank, and is obliquely connected to the lower navigation channel of the ship lock. Since the overflow weir outlet channel and the lower navigation channel of the ship lock intersect obliquely, the discharged water flows obliquely to the middle and lower sections of the berthing section, resulting in a high flow rate in this berthing section. For larger ships, corresponding docking facilities are usually set up in the berthing section, such as mooring piers. The mooring piers are designed to prevent the ship from colliding with the canal dam after moving sideways. The mooring piers are mostly made of reinforced concrete and are usually set up in a horizontal row at the foundation of the berthing section.

[0004] During flood diversion at the hub, high-speed water flows form a hydraulic jump in the overflow weir's stilling basin, creating intense turbulence. This turbulent flow is filled with countless vortices of varying sizes and rotational directions. The strong mixing effect of the stilling basin's water flow can lead to pulsation in flow velocity and pressure. Because the overflow weir's outflow channel intersects obliquely with the ship lock's lower navigation channel and the river curves, the downstream water diffuses through the stilling basin and exits the lock's berthing section, located at the outlet of the outflow channel. This causes the downstream water to rush obliquely toward the berthing section. Some mooring piers are located in the mainstream, subjecting them to significant lateral impact from the current, adversely affecting the structural safety of the mooring pier columns. Furthermore, under the impact of the turbulent flow from the overflow weir, the viscosity of the water flowing through the column structure causes boundary layer separation, forming vortices. The periodic shedding of vortices causes fluctuating pressure, which in turn induces structural vibration. This can further destabilize the mooring pier structure, compromising its safe operation.

[0005] In order to cooperate with the design of the hub project and demonstrate and optimize the structure and layout of the mooring piers, it is necessary to simulate the impact force of the water flow on the mooring piers under high-speed water flow during flood diversion, so as to verify the stability of the mooring piers, study the hub's energy dissipation and anti-impact effects, and whether the navigation flow conditions of the lock meet the regulatory requirements, and provide technical support for the engineering design. The numerical simulation of water flow impact force in the existing technology generally adopts fluid-solid coupling numerical simulation, but the existing method takes into account the oblique intersection of the overflow weir outlet channel and the navigation channel under the lock, and cannot establish a numerical simulation for the actual terrain of the hub, resulting in the simulated water flow impact force under high-speed water flow during flood diversion. The results are inaccurate. Therefore, there is an urgent need for a numerical simulation method for the impact force of water flow on the mooring piers under high-speed water flow. Summary of the Invention

[0006] The purpose of the present invention is to provide a numerical simulation method for the water flow impact force on piers under high-speed water flow to address the problem that the numerical simulation method of water flow impact force in the existing technology cannot be applied to the actual terrain of the hub and does not take into account the water flow impact force under high-speed water flow during flood diversion, resulting in inaccurate simulated water flow impact force results.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The numerical simulation method of the water flow impact force on the pier under high-speed water flow includes the following contents:

[0009] A three-dimensional model of the hub was established based on the oblique intersection of the overflow weir outlet channel and the navigation channel under the lock at the hub where the pier is located;

[0010] Using three-dimensional simulation software, a water flow mathematical model is established based on the established three-dimensional model of the hub;

[0011] Using the water level and flow velocity distribution data measured by the physical model of the hub where the pier is located, the water flow mathematical model is identified and verified to obtain the identified and verified water flow mathematical model;

[0012] Based on the fluid-solid coupling mathematical model, the verified water flow mathematical model is used to perform fluid-solid coupling simulation under high-speed water flow, and the water flow impact force results of the mooring pier are obtained.

[0013] In the technical solution of the present invention, a three-dimensional model of the hub is first established based on the oblique intersection of the overflow weir outlet channel and the lower navigation channel of the ship lock at the hub where the ship mooring pier is located. Then, a water flow mathematical model is established. By combining the hub physical model with the water flow mathematical model, the measured and simulated water level and flow velocity distribution data are compared. The two complement each other and verify each other to obtain a verified water flow mathematical model. Then, a fluid-solid coupling mathematical model is added to perform a fluid-solid coupling simulation of the downstream water flow impacting the ship mooring pier to obtain the water flow impact force data of the ship mooring pier. The method of the present invention can simulate the lateral impact force of the water flow on the ship mooring pier based on the oblique intersection of the overflow weir outlet channel and the lower navigation channel of the ship lock at the hub where the ship mooring pier is located. The water flow impact force result obtained after the numerical simulation is accurate and can be used to evaluate the structural stability of the ship mooring pier and guide the design of the ship mooring pier.

[0014] As a preferred solution of the present invention, in order to completely simulate the entire discharge process of the diversion gate and accurately simulate the impact force of the water flow on the pier under high-speed water flow, the simulation range of the hub three-dimensional model includes the upstream inflow flow adjustment section, the upper approach channel section, the diversion gate and ship lock section, the overflow weir and energy dissipation pool section, the lower approach channel section, and the downstream outflow flow adjustment section. The simulation length of the hub three-dimensional model is determined according to the flow velocity distribution data measured by the hub physical model. Based on the flow velocity distribution data, the simulation length of the hub physical model is shortened to obtain the simulation length of the hub three-dimensional model.

[0015] As a preferred embodiment of the present invention, establishing the water flow mathematical model specifically includes:

[0016] S11, performing grid division on the hub three-dimensional model to divide the three-dimensional space into unit volumes;

[0017] S12, determining the boundary range of the three-dimensional model of the hub; the inlet boundary adopts the flow boundary during flood diversion, and the outlet boundary adopts the pressure boundary condition, the pressure boundary condition includes the water level during flood diversion, and the flow boundary and pressure boundary conditions are obtained by simulation calculation based on a one-dimensional water flow mathematical model;

[0018] S13, establishing the water flow mathematical model based on the processed three-dimensional model of the hub.

[0019] As a preferred solution of the present invention, when meshing the three-dimensional model of the hub, a hexahedral structured grid is used, and the flood diversion inlet and outlet berthing sections, flood diversion gate sections and overflow weir sections in the key research areas are locally encrypted using a gradient grid processing method.

[0020] As a preferred embodiment of the present invention, the established water flow mathematical model includes a continuity equation and a momentum equation. The continuity equation is expressed as follows:

[0021]

[0022] The momentum equation states that the rate of change of the momentum of the fluid in the microelement with respect to time is equal to the sum of the various forces acting on the microelement from the outside (Newton's second law). The equation is expressed as:

[0023]

[0024]

[0025] Where x, y, and z are the coordinate components in the three directions, with units of m; u, v, and w are the velocity components in the three directions, with units of m / s; Ax, Ay, and Az are the area fractions corresponding to the fluid passing through the three directions; t is time; V F is the volume fraction of the area within the grid where fluid can flow; ρ is the fluid density, in kg / m 3 ; p is pressure, unit is Pa; Gx, Gy, Gz are body force accelerations in three directions, unit is m / s 2 ; fx, fy, and fz are the viscous accelerations in the three directions, in m / s 2 ; μ is the dynamic viscosity, unit is Pa·s; τ is the solid stress.

[0026] As a preferred embodiment of the present invention, the calculation of the water flow mathematical model adopts a pressure-velocity coupling algorithm, including:

[0027] S200, set the time step and assume an intermediate velocity field;

[0028] S201, using the intermediate velocity field to solve the momentum equation to obtain a relationship between the pressure correction value and the intermediate velocity field;

[0029] S202, substituting the relationship between the pressure correction value and the intermediate velocity field into the continuity equation to obtain the Poisson equation with the pressure correction value;

[0030] S203, solving the Poisson equation to obtain the pressure correction value and pressure field, substituting it back into the momentum equation to solve the velocity field at the new moment;

[0031] S204, determine whether the calculation at the current time step has converged; if not, return to S201, adjust the time step, and continue iteration; if converged, calculate the transport equation of the volume ratio function, update the free surface information, and then enter the iteration of the physical quantity of the next time step.

[0032] As a preferred embodiment of the present invention, the transport equation of the volume ratio function is expressed as follows:

[0033]

[0034] Where F is the volume ratio function, which represents the ratio of the volume occupied by each unit fluid in the computational domain to the volume of the fluid that the unit can accommodate; F DIF is the effective volume fraction diffusion term; S c is the turbulent Schmidt constant.

[0035] As a preferred embodiment of the present invention, the hub physical model is a normal model made according to the hub structure at a geometric scale of 1:60. The water level and flow velocity distribution data of different positions of the hub physical model are obtained by measurement. Then, the water level and flow velocity distribution data measured by the hub physical model are compared with the water level and flow velocity distribution data of the water flow mathematical model to observe whether the error meets the requirements. Otherwise, the parameters of the water flow mathematical model are repeatedly adjusted until the simulation results of the water flow mathematical model and the measured results of the water flow mathematical model have a good fitting effect, so as to realize the identification and verification of the water flow mathematical model.

[0036] As a preferred embodiment of the present invention, the standard motion equation expression for the solid region solved by the fluid-solid coupling mathematical model is:

[0037]

[0038] Where ρ is the density of the solid material, t is the time, and x is a coordinate point in the solid material. is the Hamiltonian operator, σ is the Cauchy stress tensor, and b is the body force.

[0039] As a preferred embodiment of the present invention, the Cauchy stress tensor is a measure of the stress state in the material and is calculated by the linear Hookean model for each time step increment. The calculation formula is:

[0040]

[0041] where the superscripts n and n+1 denote the previous and current time periods, K and G are the bulk modulus and shear modulus, respectively, E is the strain increment, and tr(E) is the trajectory of the strain increment E.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The present invention provides a numerical simulation method for the impact force of water flow on mooring piers under high-speed water flow. First, a three-dimensional model of the hub is established, and then a water flow mathematical model is established. The physical model of the hub and the water flow mathematical model are combined to compare the measured and simulated water level and flow velocity distribution data. The two cooperate with each other and complement each other to obtain a verified water flow mathematical model. Then, a fluid-solid coupling mathematical model is added to perform a fluid-solid coupling simulation of the impact of the downstream water flow on the mooring pier to obtain the water flow impact force data of the mooring pier. The method of the present invention can simulate the lateral impact force of the water flow on the mooring pier based on the oblique intersection of the overflow weir outlet channel and the lower navigation channel of the ship lock at the hub where the mooring pier is located. The water flow impact force result obtained after the numerical simulation is accurate and can be used to evaluate the structural stability of the mooring pier based on the water flow impact force of the mooring pier and guide the design of the mooring pier, thereby ensuring the safety performance of the mooring pier during flood diversion.

[0044] 2. The numerical simulation method of the present invention takes into account the real viscous fluid and the fluid-solid coupling between the pier and the water. It has few additional assumptions and the results obtained are more realistic in theory. The water flow impact force data of the moored pier under high-speed water flow simulated by this method is of the same magnitude as the results calculated in port regulations, which verifies that the calculation results of this method are credible. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a plan layout diagram of the three-dimensional model of the horse trail hub in Example 1;

[0046] Figure 2 This is the overall rendering of the three-dimensional model of the horse trail hub in Example 1;

[0047] Figure 3 A three-dimensional view of the grid division of the horse track hub in Example 1;

[0048] Figure 4 Flowchart for solving mathematical models of water flow;

[0049] Figure 5 This is a comparison and verification diagram of the upstream water level of the hub physical model (a) and the water flow mathematical model (b) in Example 1;

[0050] Figure 6 Graphs comparing the upstream flow field of the hub physical model (a) and the water flow mathematical model (b) in Example 1;

[0051] Figure 7 This is a comparison and verification diagram of the downstream flow field of the hub physical model (a) and the water flow mathematical model (b) in Example 1;

[0052] Figure 8 This is a plan view of the overall flow field of the horse track hub in Example 1;

[0053] Figure 9This is the flow field cloud map of the Madao hub dam in Example 1;

[0054] Figure 10 This is the flow field cloud diagram of the overflow weir of Madao Hub in Example 1;

[0055] Figure 11 This is the flow field cloud map of the flood diversion inlet of Madao Hub in Example 1;

[0056] Figure 12 This is the flow field cloud map of the flood diversion outlet of Madao hub in Example 1;

[0057] Figure 13 This is a cloud diagram of the local flow field at the downstream pier of Example 1;

[0058] Figure 14 This is a vector cloud diagram of the local flow field at the downstream berth in Example 1;

[0059] Figure 15 This is a comparison diagram of the high-speed water flow impact force on the pier at the horse track hub in Example 1;

[0060] Markings in the picture: 1- docking pier. DETAILED DESCRIPTION

[0061] In order to more clearly describe the invention purpose, technical solutions and technical effect advantages in the specific implementation cases of the present invention, the solutions in the specific embodiments will be described in detail in conjunction with the drawings of the specification of the present invention. The specific technical solutions involved in the following specific embodiments are only for the purpose of clearly and completely describing the innovative technical solutions of the present invention. They themselves are only part of the specific implementation plans that can be adopted by the present invention, not all embodiments, and should not be understood as limiting the innovative solutions of the present invention. Any solution that adopts the same inventive concept of the present invention should be included in the scope of protection of the present invention.

[0062] Secondly, the descriptions of the drawings in the specific embodiments of the present invention are only for the purpose of facilitating technical personnel's understanding of the present invention. The details in the drawings are for the purpose of clearly presenting the technical solution. It should not be assumed that all technical features in the drawings must be included in the specific implementation cases, nor should the details in the drawings be considered as additional limitations on the innovative technical solution of the present invention. The components in the various embodiments described and shown in the drawings can be combined and arranged in different configurations. These changes in combination and arrangement should be considered as part of the entire embodiment of the innovative solution of the present invention and included in the scope of protection of the present invention.

[0063] In summary, the solutions or descriptions presented in the specific embodiments and drawings of the present invention are not intended to limit the scope of protection claimed, but merely represent selected embodiments / cases to help technicians understand the relevant innovative solutions. Based on these embodiments, all other equivalent or parallel embodiments obtained by those skilled in the art without inventive effort are also within the scope of protection claimed by the present invention.

[0064] Example 1

[0065] This embodiment provides the Western Land-Sea New Corridor (Pinglu) Canal (hereinafter referred to as the "Pinglu Canal"). The Pinglu Canal starts from the Pingtangjiangkou of Hengzhou City, Nanning, in the Xijin Reservoir area of ​​the Xijiang River. The Pinglu Canal cascade hub will successively build three hubs: Madao, Qishi and Qingnian. The Pinglu Canal is built according to the standards of a Class I inland waterway, navigable by 5,000-ton ships, and each hub will have a double-line 5,000-ton ship lock built at one time. This embodiment takes the mooring piers in the Madao hub as the research object. The Madao hub is usually composed of a double-line ship lock, a flood discharge gate and a connecting dam. The Madao hub flood diversion project includes a left-bank retaining dam and a flood discharge structure. The plan layout of the Madao hub is shown in the figure below. Figure 1 As shown, the mooring section is equipped with a mooring pier 1 for larger ships. Due to the terrain of the Madao hub, the overflow weir outlet channel in the hub and the lower navigation channel of the ship lock intersect obliquely, causing the downstream water to rush obliquely toward the middle and lower sections of the mooring section, resulting in a high flow velocity in the mooring section. The mooring pier is located in the mainstream and is subject to a large lateral impact force from the water flow. High-speed water flow has a significant impact on the stability of the mooring pier structure. This embodiment provides a numerical simulation method for the water flow impact force on the mooring pier under high-speed water flow, including the following contents:

[0066] A three-dimensional model of the hub was established based on the oblique intersection of the overflow weir outlet channel and the navigation channel under the lock at the hub where the pier is located;

[0067] Using three-dimensional simulation software, a water flow mathematical model is established based on the established three-dimensional model of the hub;

[0068] Using the water level and flow velocity distribution data measured by the physical model of the hub where the pier is located, the water flow mathematical model is identified and verified to obtain the identified and verified water flow mathematical model;

[0069] Based on the fluid-solid coupling mathematical model, the verified water flow mathematical model is used to perform fluid-solid coupling simulation under high-speed water flow, and the water flow impact force results of the mooring pier are obtained.

[0070] To fully simulate the entire flood diversion gate discharge process, the physical model of the hub was constructed using a normal model with a geometric scale of 1:60, taking into account the river flow characteristics of the project section, the test mission requirements, and factors such as the test site size and water supply capacity. The simulation range of the physical model was approximately 4.0 km, from approximately 2.0 km upstream of the Madao hub dam axis to approximately 2.0 km downstream of the dam axis (including approximately 400 m of the hub section). The roughness of the physical model was selected to be between 0.011 and 0.015. The riverbed of the physical model was surfaced with cement mortar, with a roughness value that met the resistance similarity requirements. The physical model was constructed using the section panel method, with appropriate increase in the number of section panels in the sections where the channel bends, hub flood gates, and ship locks are located. The contour method was also used to accurately control the riverbed topography.

[0071] The simulation scope of the hub's three-dimensional model includes the upstream inflow flow pattern adjustment section, the upper approach channel section, the diversion gate and ship lock section, the overflow weir and energy stilling basin section, the lower approach channel section, and the downstream outflow flow pattern adjustment section. In order to improve calculation efficiency, the simulation length of the hub's three-dimensional model is determined according to the velocity distribution data measured by the hub's physical model. Based on the velocity distribution data, the simulation length of the hub's physical model is shortened to obtain the simulation length of the hub's three-dimensional model, that is, the total longitudinal length is 3000m, of which 1420m is above the upper lock head and 1580m is below the upper lock head. The plan layout of the Madao hub is as follows: Figure 1 In the simulation, the oblique intersection angle between the overflow weir outlet channel and the navigation channel under the lock is 45°.

[0072] According to the plane layout, the 3D model of the hub is established using the 3D modeling software CATIA. Figure 2 As shown, it outputs the stl format required by the three-dimensional numerical simulation software.

[0073] The three-dimensional simulation software used in this embodiment uses the commercial CFD software FLOW-3D (free-surface flows-3Dimensions) to simulate complex flows ranging from incompressible to highly compressible. Its functions include importing geometric models, generating grids, defining boundary conditions, performing calculations, and post-processing the results. Establishing the mathematical model of the water flow specifically includes:

[0074] S11, performing grid division on the hub three-dimensional model to divide the three-dimensional space into unit volumes;

[0075] S12, determining the boundary range of the three-dimensional model of the hub; the inlet boundary adopts the flow boundary during flood diversion, and the outlet boundary adopts the pressure boundary condition, which includes the water level elevation during flood diversion and is obtained by simulation calculation based on a one-dimensional water flow mathematical model;

[0076] S13, establishing the water flow mathematical model based on the processed three-dimensional model of the hub.

[0077] In terms of grid generation, FLOW-3D uses rectangular grid blocks with self-defined fixed grid points to generate grids. It is not only easy to generate grids, but also the established grids have no correlation with geometric drawings. Therefore, the grids are not restricted by changes in geometric structures. In addition, for local grid encryption in the calculation area, multiple grid blocks can be established using linked or nested grid blocks. At the same time, FLOW-3D uses FAVORTM technology, which allows rectangular grids to describe complex geometric shapes, thereby enabling efficient and accurate definition of geometric shapes. In the entire simulation calculation area, the calculation grid type uses a hexahedral structured grid. For the key research areas of the flood diversion inlet and outlet berthing section, flood diversion gate section and overflow weir section, a gradient grid processing method is used for local encryption, such as Figure 3 The minimum grid size is 1m, the maximum grid size is 5m, and the total number of grids is approximately 8.6 million.

[0078] The inlet boundary adopts the flow boundary condition, and the diversion flow Q is given as 1600m3 / s. The outlet boundary adopts the pressure boundary condition, and the control water level elevation Hout=38.06m and the water surface pressure p=p are given when diverting the flood. a (atmospheric pressure) based on a one-dimensional flow mathematical model. The water level elevation is calculated using a one-dimensional flow mathematical model for the long river section. The calculation considers only the conditions after the Madao hub flood diversion discharge stabilizes (not considering the unstable conditions between Madao and Qishi during the initial flood discharge). At the upper surface boundary of the computational area grid, since the free surface represents the interface between the water and the atmosphere, the boundary condition is set as a pressure boundary condition, with a given water surface pressure of p = 1.013 × 10⁵ Pa and F = 0 (filled with air).

[0079] The wall roughness of the solid wall boundary within the flow channel is set to 0.012, corresponding to a concrete roughness of 0.020. At the initial moment of calculation, the initial hydrostatic fluid is given based on the upstream and downstream water levels, and the initial hydrostatic fluid obeys the static pressure distribution law.

[0080] To solve fluid flow problems, it's first important to understand that any fluid flow is governed by physical conservation laws. The basic conservation laws include the law of conservation of mass, the law of conservation of momentum, and the law of conservation of energy. Describing these conservation laws using mathematical equations forms the governing equations for the fluid. There are two methods for describing fluid motion when establishing and deriving governing equations: the Lagrangian method and the Euler method. The Lagrangian method studies the motion of individual fluid particles and determines the motion of the entire fluid by studying the motion laws of each fluid particle. This method is also known as the particle system method. The Euler method, also known as the flow field method, studies the motion of different fluid particles at a fixed point in space to understand the flow conditions within the entire flow space. This study will use the Euler method to study the flow field, treating the fluid as incompressible. The mathematical model of water flow established includes the continuity equation and the momentum equation.

[0081] The law of conservation of mass of a fluid is described by the continuity equation, which means that the change in mass of a fluid element per unit time is equal to the net mass flowing into the element during the corresponding time interval. The continuity equation is expressed as:

[0082]

[0083] The law of conservation of fluid momentum is described by the momentum equation (NS equation), which means that the rate of change of the momentum of the fluid in the microelement with time is equal to the sum of the various forces acting on the microelement from the outside (Newton's second law). The expression of the NS equation is:

[0084]

[0085] Where x, y, and z are the coordinate components in the three directions, with units of m; u, v, and w are the velocity components in the three directions, with units of m / s; Ax, Ay, and Az are the area fractions corresponding to the three directions of the fluid; V F is the volume fraction of the area within the grid where fluid can flow; ρ is the fluid density, in kg / m 3 ; p is pressure, unit is Pa; Gx, Gy, Gz are body force accelerations in three directions, unit is m / s 2 ; fx, fy, and fz are the viscous accelerations in the three directions, in m / s 2 , satisfying formulas (5) to (13); μ is the dynamic viscosity, in Pa·s; τ is the solid stress.

[0086] (1) Turbulence equation

[0087] Predicting any turbulent flow can be achieved by solving the NS equations, a method known as Direct Numerical Simulation (DNS). However, even for the simplest turbulent flow, describing the smallest vortices requires a very short time interval and a large number of grid nodes. Therefore, directly solving the NS equations consumes enormous computational time and computer memory, which are beyond the reach of current computing power.

[0088] For practical water flow problems, it's often unnecessary to understand the full details of the flow field at any given moment; rather, the average flow field changes caused by turbulence are of greater interest. Following this principle, the most widely used approach is the Reynolds averaging method. This method, building on the transient continuity and momentum equations, expresses turbulent motion as a superposition of time-averaged and instantaneous pulsating flows, resulting in the time-averaged (Reynolds) equations for turbulence. However, during this time-averaging process, six new Reynolds stress terms are added to the time-averaged turbulence equations, resulting in a larger number of unknowns than the number of equations, making the equations non-closed and unsolvable. Therefore, an assumption regarding the Reynolds stress is necessary to link the pulsating and time-averaged values ​​of turbulence. Currently, the most commonly used assumption is the eddy viscosity hypothesis proposed by Boussinesq, which introduces the turbulent viscosity μt and establishes a functional relationship between the Reynolds stress and the average velocity gradient and the turbulent viscosity μt. With the introduction of the Boussinesq eddy viscosity assumption, the key to numerical simulation of turbulence becomes determining μt. Here it is necessary to introduce the turbulence model again to establish the relationship between μt and the time-averaged parameters of turbulence, so that the time-averaged equations of turbulence are closed. According to the number of differential equations that determine μt, the turbulence model can be divided into a zero-equation model, a one-equation model and a two-equation model. At present, the most widely used in engineering is the standard k-ε two-equation model, that is, the transport equations for turbulent energy k and turbulent energy dissipation rate ε are introduced respectively. In the standard k-ε model, for each component of Reynolds stress, the assumed turbulent viscosity μt is the same, that is, μt is an isotropic scalar. In strong vortex, curved wall flow or curved streamline flow, the turbulent flow is anisotropic, and μt should also be an anisotropic tensor. In order to make up for the defects of the standard k-ε model, it is necessary to make corrections and improvements. Among them, the more widely used correction schemes are the RNG k-ε model and the Realizable k-ε model. This embodiment adopts the RNG k-ε turbulence model, and the k-ε turbulence model equation is expressed as follows:

[0089] k equation expression:

[0090]

[0091] ε equation expression:

[0092]

[0093] μ eff =μ+μ t (19)

[0094]

[0095] Where k is the turbulent kinetic energy, unit is m 2 / s 2 ; ε is the turbulent energy dissipation rate, unit is m 2 / s 2 ;Diff k is the turbulent energy diffusion term, satisfying formula (16); Diff ε is the diffusion term of turbulent energy dissipation rate, satisfying formula (17); P T is the generation term of turbulent energy k caused by the average velocity gradient, satisfying formula (18); C s is the turbulence parameter, the default value is 1; μ eff is the corrected turbulent viscosity, in Pa·s, satisfying formula (19); μ t is the turbulent viscosity, in Pa·s, satisfying formula (20); is the model constant after the mainstream time-averaged strain is introduced, which satisfies formula (21); η is the ratio of the turbulence time scale to the average flow time scale, which satisfies formula (22); E xy 、E xz 、E yz are the time-averaged strain rates of the main stream in three directions, satisfying formulas (23) to (25); α k , α ε are the reciprocals of the effective Prandtl numbers of k and ε, respectively, and are set to 1.3; C μ 、C 1ε 、C 2ε is an empirical constant with values ​​of 0.0845, 1.42, and 1.68 respectively; η0 is the typical value of η, with a value of 4.377, and β is 0.012.

[0096] (2) Free surface model

[0097] The VOF model (the Fraction Volume of Fluid Method) is used to solve flow problems involving a free surface. In the VOF model, all fluids share a common set of momentum equations, which are calculated for each unit cell within the flow field and record the volume fraction occupied by each fluid component within each unit cell. The basic principle of the VOF model is to determine the free surface by studying the volume ratio function F of the fluid and grid within the grid cell, tracking the changes in the fluid rather than the motion changes of particles within the free surface. The direction of the maximum gradient of the fluid and grid volume ratio function F is the normal direction of the free surface. By solving the value of F and the normal direction of the free surface, the shape of the free surface can be determined. The advantages of using the VOF model are high computational efficiency, short computation time, and low computer resource usage. However, handling changes in the volume ratio function F is more complex, and uncertainties can affect the simulation results, making them inaccurate. The VOF method uses P, U, and V as independent primitive variables. Due to its simple and easy-to-handle boundaries, it has significant advantages in studying the motion of multiphase fluid interfaces. In the TruVOF model adopted in this embodiment, the transport equation of the volume ratio function F is expressed as follows:

[0098]

[0099] Where F is the volume ratio function, which represents the ratio of the volume occupied by each unit fluid in the computational domain to the volume of fluid that the unit can accommodate. F = 1 means that the computational grid unit is filled with water, F = 0 means that the computational grid unit is filled with gas, and 0 < F < 1 means that the computational grid unit contains both water and gas. DIF is the effective volume fraction diffusion term; S c is the turbulent Schmidt constant.

[0100] The TruVOF model used in this embodiment is a significant improvement on the original VOF model, which improves the accuracy of boundary conditions and interface tracking. It uses a single-phase fluid VOF volume method for calculation, which can accurately track free liquid surface problems and solve them very quickly.

[0101] Before using a mathematical model of water flow for computational fluid dynamics calculations, the computational domain must be discretized. This involves dividing the spatially continuous computational domain into numerous subdomains, identifying the nodes within each domain, and generating a grid. The governing equations must then be discretized on the grid, essentially converting the governing equations in partial differential format into a system of algebraic equations at each node. Grid discretization has a significant impact on numerical computations. Different discretization methods, grids, and nodes have different meanings and functions, and also differ in their requirements and usage. Due to different assumptions about the distribution of dependent variables between nodes and the methods used to derive discrete equations, equation discretization methods include numerical solutions such as the finite difference method, the finite element method, and the finite volume method. The finite difference method (FDM) is used to discretize the equations of the three-dimensional mathematical model in this embodiment. This method divides the solution domain into a rectangular or orthogonal curve differential grid, stores pressure, velocity, volume ratio functions, and other unknown scalars at the gridline nodes, and replaces the derivatives of the partial differential equations for these unknowns with difference quotients, thereby discretizing the differential equations of continuous functions into differential equations for a finite number of unknowns at the grid nodes. Each equation contains the dependent variable values ​​of the function to be determined at the node and some nearby nodes. By solving these algebraic equations, the numerical solution of the differential equation can be obtained. The discretization format uses a first-order upwind format that takes into account the flow direction.

[0102] The calculation of the water flow mathematical model adopts the pressure-velocity coupling algorithm, such as Figure 4 Shown, including:

[0103] S200, set the time step and assume an intermediate velocity field;

[0104] S201, using the intermediate velocity field to solve the momentum equation to obtain a relationship between the pressure correction value and the intermediate velocity field;

[0105] S202, substituting the relationship between the pressure correction value and the intermediate velocity field into the continuity equation to obtain the Poisson equation with the pressure correction value;

[0106] S203, solving the Poisson equation to obtain the pressure correction value and pressure field, substituting it back into the momentum equation to solve the velocity field at the new moment;

[0107] S204, determine whether the calculation at the current time step has converged; if not, return to S201, adjust the time step, and continue iteration; if converged, calculate the transport equation of the volume ratio function, update the free surface information, and then enter the iteration of the physical quantity of the next time step.

[0108] During the calculation process, it is determined whether the preset convergence conditions are met. The convergence condition is the pressure convergence condition, which is the convergence condition provided by FLOW-3D.

[0109] The physical model of the hub was constructed using a normal model with a geometric scale of 1:60, based on the river flow characteristics of the project section, the test mission requirements, and factors such as the test site size and water supply capacity. The simulation range of the physical model was from approximately 2.0 km upstream of the Madao hub dam axis to approximately 2.0 km downstream of the dam axis (including approximately 400 m of the hub section), for a total simulated river section length of approximately 4.0 km. The roughness of the physical model was to be between 0.011 and 0.015. The riverbed of the physical model was plastered with cement mortar, with a roughness value that met resistance similarity requirements. The physical model was constructed using the section panel method, with appropriate intensification of the section panels at the channel bends, hub spillway, and ship lock sections. This was supplemented by the contour method to accurately control the riverbed topography. The planar position of the physical model was controlled using a triangulated mesh and primary and secondary traverses, and elevations were measured using a level.

[0110] Flood diversion at Madao Hub: When the Yujiang River encounters a 20-year flood, the flood diversion capacity of Madao Hub is 1000m 3 / s, when the Yujiang River encounters a 50-year flood, the flood diversion capacity of the Madao hub is 1600m 3 / s. Therefore, the test flow of the flood diversion of Madao Hub is 1000m 3 / s and 1600m 3 / s. The water flow mathematical model was verified using the results of the hub physical model, and the verification condition was a flood diversion flow of 1600m 3 / s, downstream water level 38.06m working conditions, mainly for water level and flow velocity distribution comparison verification, such as Figures 5 to 7 The verification results show that the upstream water level error is about 5 cm, the flow velocity error is about 0.2 m / s, and the downstream flow velocity error is relatively large. Analysis shows that the main reason for the large error in the downstream flow velocity distribution is the high flow velocity and violent turbulence of the water outflowing the pool, which is a turbulent flow with a high Reynolds number. Affected by the pulsation of the water flow, the direction and velocity of the water flow are constantly changing during the physical model measurement, and the measurement results are slightly smaller. The mathematical model of water flow assumes the inner mean of the NS equation, and compared with the physical model results, the flow velocity value is larger. Overall, the accuracy of the mathematical model of water flow can meet the research needs.

[0111] The Fluid-Structure Interaction (FSI) mathematical model solves fully coupled solid dynamics and fluid flow, primarily resolving elastic stresses within solid components. The FSI model does not utilize the original structured finite difference mesh used for fluid and heat transfer calculations. Instead, it utilizes a conforming, unstructured finite element (FE) mesh that deforms with the solid. FLOW-3D Meshing is used to generate a new finite element (FE) mesh for solid components (FSI) or for entire solid regions. The standard hexahedral mesh is used unmodified (when the Hexahedral option is selected) and is generated by splitting the standard mesh into five tetrahedrons (when the Tetrahedral option is selected). At the boundaries of the solid region, the nearest nodes are moved to the surface of the solid region along the surface normal. For the Hexahedral option, neighboring nodes can be eliminated or merged with neighboring nodes. Therefore, FE mesh creation is fully automatic and requires no additional user input. Elements far from interfaces always have eight nodes. Due to the merging of nodes near solid interfaces, elements on surfaces can have seven, six, five, or even four nodes.

[0112] (1) Equations of motion and stress equations

[0113] The fluid-solid coupling mathematical model solves the standard equation of motion in the solid region:

[0114]

[0115] Where ρ is the density of the solid material, t is the time, and x is a coordinate point in the solid material. is the Hamiltonian, σ is the Cauchy stress tensor, and b is the body force. The Cauchy stress tensor is a measure of the stress state in a material. For elastic solids, it is related to the material's strain, as well as thermal and other internal stresses. Strain is the amount of physical deformation experienced by the material and is also a tensor. The method used is based on small incremental deformations, that is, the strain increment is calculated from one time step to the next:

[0116]

[0117] Here E is the strain increment, subscripts i and j are rectangular coordinates (x, y, z), T represents the device, n is the time node, e i are the unit normal vectors in x, y, and z respectively. δx is the displacement vector, and its calculation formula is:

[0118] δx=x n+1 -x n (30)

[0119] Where: Xn is the position of the material point in the previously calculated time period, and Xn+1 is the position of the same point in the current time period.

[0120] Current time level σ n+1 The Cauchy stress tensor of is calculated from the linear Hookean model at each time step increment as:

[0121]

[0122] Here, the superscripts n and n+1 denote the previous and current time periods. K and G are the bulk modulus and shear modulus, respectively, and tr(E) is the trajectory of the strain increment E, which is the sum of its diagonal components. The bulk modulus K is a user-defined parameter that describes the material's resistance to isotropic expansion or contraction. The shear modulus G describes the material's resistance to shear.

[0123] The bulk and shear moduli, K and G, can be specified directly or derived by specifying Young's modulus (E) and Poisson's ratio (v1). The model is applicable to any combination of two of the four elastic properties. These relationships are:

[0124]

[0125] As Poisson's ratio approaches 0.5, K approaches infinity, which means the material approaches its incompressible limit. All of these properties can be defined as functions of temperature.

[0126] The acceleration term in formula (28) is obtained from the position at different time points. Therefore:

[0127]

[0128] (2) Finite Element Method (FEM)

[0129] Equation (28) contains a three-dimensional partial differential equation that is solved at each time step, and its unknown quantity is x n-1 (σ n+1 Directly from x n-1 and the earlier time level value of σ in formula (31). The finite element method (FEM) uses the weighted residual method to solve formula (28). The weighted residual form of formula (28) is:

[0130]

[0131] Here, Ψ represents the weighting function and Ω represents the domain. In order to minimize the order of the derivative in the formula, the following identity is used:

[0132]

[0133] From formula (34), formula (35) and Green's theorem, we can get:

[0134]

[0135] Here n is the outward-pointing normal on the surface of the domain Ω. dΓ is the area of ​​the smallest fraction of the solid domain interface. The superscripts "n-1," "n," and "n+1" denote the time horizon of each variable. The last term on the right-hand side is nonzero only at the interface of the domain. The weight function Ψ consists of a set of basis functions that are defined as nonzero only around the nodes to which they correspond and zero at all other nodes. Therefore:

[0136]

[0137] Where nnodes is the total number of nodes in the grid, x is the position in physical coordinates, and ψ i is the local basis function defined near node number i. Basis functions are continuous, and their first-order derivatives exist but are discontinuous.

[0138] The concept of elements is considered in the basis function ψ i This is helpful when plotting the vertices of a domain. An element is a small portion of the domain whose vertices correspond to nodes. There are 8 nodes in a standard hexahedral element. For a tetrahedral element, the graph is similar, but there are 4 nodes, with vertices at (0,0,0), (1,0,0), (0,1,0), and (0,0,1). The basis functions corresponding to these nodes are i In this space, all are non-zero. The basis functions of nodes that do not belong to the current element are all zero. Therefore, considering formula (37), formula (36) becomes:

[0139]

[0140] The above formula is a set of terms, where only a few terms are non-zero in a particular element. Then, we assemble the formula (38) element by element. Because ψ in formula (38) k is nonzero only in the elements shared by node k, so Equation (38) is actually a set of nnodes equations, one for each node. Furthermore, because there are three Cartesian directions, there are a total of 3 × nnodes scalar equations. This integral is solved numerically using the Gaussian quadrature method, and the resulting linear system of equations is solved iteratively using the generalized minimum residual (GMRES) solver, similar to the method for solving the coupled momentum and continuity equations in fluids. The standard equations of motion are solved using the finite element method (FEM).

[0141] (3) Boundary conditions of solid regions

[0142] Fluid-structure interaction automatically determines the boundary conditions of each unit surface of the solid component. When these surfaces contact the fluid area, the local fluid pressure determines the traction force (n·σ) in formula (38) n+1 ).therefore:

[0143] n·σ n+1 =-nρ fluid (39)

[0144] Where ρ fluid is the fluid density, and the negative sign appears because compression is negative in the convention for solid stresses. When a boundary surface is adjacent to a (fluid) domain boundary, the boundary type determines the conditions imposed on the solid. Adjacent wall boundaries, the solid domain is fixed; that is, the nodes are attached to the boundary and cannot move. At symmetry boundaries, the nodes can slide freely along the boundary but can neither penetrate nor be extracted. At other boundaries, the traction force is calculated using the pressure in the adjacent boundary elements according to equation (39). For FSI components, when the default coupling option (No coupling) is selected, when an FSI component is in contact with another component (standard or FSI), the interface is always assumed to be fixed; that is, the nodes at the interface do not move during the simulation.

[0145] The impact of water flow on mooring piers is a typical bidirectional fluid-solid coupling problem, that is, the mooring piers deform under the impact of high-speed water flow, and the flow field characteristics change due to the movement of the piers, and the flow field and pressure field distribution acting on the piers also change accordingly. 3 / s, and the downstream water level was 38.06m, and the three-dimensional flow field characteristics near the Madao hub pier were simulated in detail; on this basis, the fluid-solid coupling mathematical model was added to carry out a fluid-solid coupling simulation of the high-speed water flow impacting the pier.

[0146] like Figures 8-14The calculated flow field results show that, in the downstream direction, the water flow is obstructed by the mooring pier, and the water velocity gradually decreases to zero. At this point, the water's kinetic energy is completely converted into pressure energy, acting on the mooring pier (deceleration and pressure increase). The subsequent liquid particles in the water convert some of this pressure energy into kinetic energy, changing their original flow direction and continuing to flow forward along both sides of the mooring pier (increase in speed and decrease in pressure). Due to the viscosity of the water flow, a certain amount of energy is dissipated after flowing around the mooring pier. The water flow separates behind the pier, forming backflow vortices (typical Karman vortex streets). These vortices gradually dissipate with the movement of the water. Overall, a high-pressure area forms on the upstream side of the mooring pier, while a low-pressure area forms on the downstream side. This pressure difference between the front and rear constitutes the impact pressure exerted by the downstream water flow on the mooring pier. In the cross-flow direction, the water accelerates toward the sides of the docking piers. Influenced by boundary conditions, the flow or pressure field on both sides of the docking piers becomes asymmetrically distributed, resulting in a cross-flow pressure differential, which is the impact pressure of the cross-flow on the docking piers. Integrating all stresses acting on the load-bearing sections of the docking piers yields the total impact force of the water on the docking piers. In terms of velocity distribution, the flood diversion inlet has a relatively low overall flow velocity due to its large cross-section, with the mainstream velocity ranging from 0.8m / s to 1.6m / s. After dissipating energy through the stilling basin below the overflow weir, the flow pattern becomes more turbulent, with an uneven velocity distribution across the entire cross-section. High-speed water flows primarily along the left bank and down to the flood diversion outlet, with mainstream velocities ranging from 1.8m / s to 3.8m / s. The high-speed water primarily impacts docking piers 7# to 10#.

[0147] Because the impact of water flow on mooring pier columns is a typical bidirectional fluid-solid coupling problem, it is difficult to analyze using purely theoretical methods. In actual engineering, the empirical formulas recommended by the "Port Engineering Load Code" (JTS144-1-2010) and the "General Code for Design of Highway Bridges and Culverts" (JTG D60-1-2015) are currently mainly used for calculation. The empirical formulas recommended by the two codes differ only slightly in form. Taking the port code as an example:

[0148] F w =C w ρV 2 A / 2

[0149] Where: F w is the standard value of water flow force (kN); C w is the water flow resistance coefficient, which is 1.5 according to the specification; ρ is the water density (t / m); V is the design flow velocity (m / s); A is the projected area of ​​the calculation component on the plane perpendicular to the flow direction (m 2 ), which can be calculated based on the pier size and water level. The fluid-structure interaction simulation results and the standard calculated values ​​are summarized in Table 1.

[0150] Table 1 Calculation results of the impact force of high-speed water flow on the piers of Xiamadao hub

[0151]

[0152]

[0153] Note: X7 indicates the seventh mooring pier from top to bottom downstream.

[0154] The data in the table shows that the high-speed water flow primarily impacts the downstream piers 7# to 10#. The fluid-solid coupling simulation yields a corresponding high-speed water flow impact force of 195 to 890 kN, while the standard calculation yields a high-speed water flow impact force of 102 to 787 kN. The results of the two methods differ somewhat, primarily due to the fact that the empirical formula recommended by the standard makes numerous assumptions during derivation, involves empirical coefficients, and makes it difficult to accurately determine the calculation boundary conditions. Numerical simulation, on the other hand, considers the actual viscous fluid and the fluid-solid coupling between the piers and the water, making fewer additional assumptions and yielding theoretically more realistic results. Overall, however, the two methods achieve comparable results, mutually validating each other and verifying the reliability of the results of this method.

[0155] For those skilled in the art, when understanding the solutions described in the specific embodiments of the present invention, they can refer to conventional technical manuals in the field. At the same time, for the places where the above-mentioned terms appear, they can make appropriate understanding or adjustments for reference, and deduce the implementation of the same or similar technical solutions without paying any creative work.

[0156] The above embodiments describe only the basic principles, main features and / or advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and the invention content of the specification only describe the principles or specific cases of the present invention. Without departing from the essence of the innovative ideas of the present invention, the innovative solutions of the present invention may be subject to various changes and improvements, and these changes and improvements all fall within the scope of protection claimed by the present invention.

Claims

1. A numerical simulation method for the impact force of water flow on a pier under high-speed water flow, characterized in that: Includes the following: Based on the oblique intersection of the overflow weir outlet channel and the navigation channel under the lock at the hub where the pier is located, a three-dimensional model of the hub was established; Using three-dimensional simulation software, a water flow mathematical model is established based on the three-dimensional model of the hub; establishing the water flow mathematical model specifically includes: S11, performing grid division on the hub three-dimensional model to divide the three-dimensional space into unit volumes; S12, determining the boundary range of the three-dimensional model of the hub; the inlet boundary adopts the flow boundary during flood diversion, and the outlet boundary adopts the pressure boundary condition, the pressure boundary condition includes the water level during flood diversion, and the flow boundary and pressure boundary conditions are obtained by simulation calculation based on a one-dimensional water flow mathematical model; S13, establishing the water flow mathematical model based on the processed three-dimensional model of the hub; The water level and flow velocity distribution data measured by the physical model of the hub where the pier is located are used to identify and verify the water flow mathematical model, thereby obtaining the identified and verified water flow mathematical model; the hub physical model is a normal model produced according to the hub structure in accordance with a geometric scale, and the water level and flow velocity distribution data at different positions of the hub physical model are obtained by measurement. The water level and flow velocity distribution data measured by the hub physical model are then compared with the water level and flow velocity distribution data of the water flow mathematical model to observe whether the error meets the requirements. Otherwise, the parameters of the water flow mathematical model are repeatedly adjusted until the simulation results of the water flow mathematical model and the measured results of the water flow mathematical model have a good fitting effect, thereby achieving the identification and verification of the water flow mathematical model; Based on the fluid-solid coupling mathematical model, the verified water flow mathematical model is used to simulate the fluid-solid coupling under high-speed water flow to obtain the water flow impact force results of the pier; the established water flow mathematical model includes the continuity equation and the momentum equation; The calculation of the water flow mathematical model adopts a pressure-velocity coupling algorithm, including: S200, set the time step and assume an intermediate velocity field; S201, using the intermediate velocity field to solve the momentum equation to obtain a relationship between the pressure correction value and the intermediate velocity field; S202, substituting the relationship between the pressure correction value and the intermediate velocity field into the continuity equation to obtain the Poisson equation with the pressure correction value; S203, solving the Poisson equation to obtain the pressure correction value and pressure field, substituting it back into the momentum equation to solve the velocity field at the new moment; S204, determine whether the calculation at the current time step has converged; if not, return to S201, adjust the time step, and continue iteration; if converged, calculate the transport equation of the volume ratio function, update the free surface information, and then enter the iteration of the physical quantity of the next time step.

2. The numerical simulation method for the impact force of water flow on a pier under high-speed water flow according to claim 1 is characterized in that: The simulation range of the hub three-dimensional model includes the upstream inflow flow adjustment section, the upper navigation channel section, the diversion gate and ship lock section, the overflow weir and energy stilling pool section, the lower navigation channel section, and the downstream outflow flow adjustment section. The simulation length of the hub three-dimensional model is determined according to the flow velocity distribution data measured by the hub physical model. Based on the flow velocity distribution data, the simulation length of the hub physical model is shortened to obtain the simulation length of the hub three-dimensional model.

3. The numerical simulation method of the water flow impact force on a pier under high-speed water flow according to claim 1 is characterized in that: When meshing the three-dimensional model of the hub, a hexahedral structured grid is used, and the gradient grid processing method is used to perform local encryption on the flood diversion inlet and outlet berthing sections, flood diversion gate sections, and overflow weir sections in the key research areas.

4. The numerical simulation method of the water flow impact force on a pier under high-speed water flow according to claim 1 is characterized in that: The continuity equation is expressed as: The momentum equation is expressed as: Where x, y, and z are the coordinate components in the three directions, with units of m; u, v, and w are the velocity components in the three directions, with units of m / s; Ax, Ay, and Az are the area fractions corresponding to the fluid passing through the three directions; t is time; V F is the volume fraction of the area within the grid available for fluid flow; is the fluid density in kg / m 3 ; p is pressure, unit is Pa; Gx, Gy, Gz are body force accelerations in three directions, unit is m / s 2 ; fx, fy, and fz are the viscous accelerations in the three directions, in m / s 2 ; μ is the dynamic viscosity, unit is Pa·s; τ is the solid stress.

5. The numerical simulation method of the water flow impact force on a pier under high-speed water flow according to claim 4 is characterized in that: The transport equation expression of the volume ratio function is as follows: Where F is the volume ratio function, which represents the ratio of the volume occupied by each unit fluid in the computational domain to the volume of the fluid that the unit can accommodate; F DIF is the effective volume fraction diffusion term; S c is the turbulent Schmidt constant.

6. The numerical simulation method for the impact force of water flow on a pier under high-speed water flow according to any one of claims 1 to 5, characterized in that: The standard motion equation expression for the solid region solved by the fluid-solid coupling mathematical model is: in is the density of the solid material, t is the time, x is a coordinate point in the solid material, is the Hamiltonian operator, is the Cauchy stress tensor, and b is the body force.

7. The numerical simulation method of the water flow impact force on a pier under high-speed water flow according to claim 6 is characterized in that: The Cauchy stress tensor calculation formula is: Where n and n+1 superscripts represent the previous and current time periods, K and G are the bulk modulus and shear modulus respectively, and E is the strain increment. is the trajectory of the strain increment E.

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