Moving particle semi-implicit simulation method for dam break-floating body interaction

Abstract

The invention relates to a mobile particle semi-implicit simulation method for dam break-floating body interaction. The method comprises the following steps: establishing a computational domain model, dividing a computational domain through particles, defining a plurality of particle types, and setting initial conditions and motion attributes of a floating body; establishing a neighbor particle set, and calculating the particle number density of each particle; constructing a secondary free surface, and judging the free surface by using the judgment model; establishing threshold type particles, and standardizing the distribution of fluid particles far away from a free surface by using a migration model; estimating the middle movement speed and the middle displacement of the fluid particles, and calculating the displacement of gate particles; constructing a calculation model for solving the pressure of the flow field, and solving the total pressure by adopting a Gaussian iteration method; fluid force and torque borne by the floating body are calculated, and the speed and displacement of the floating body are calculated; and calculating the gradient of the flow field pressure, and updating and exporting the speed and displacement of the fluid particles to obtain the updated speed and updated displacement of the fluid particles.

Description

Technical Field

[0001] The invention relates to the technical field of computer simulation, and in particular to a moving particle semi-implicit simulation method of dam-break-floating body interaction. Background Art

[0002] Dam break flow can not only cause flooding and submergence, but also produce strong impact and destructive force on downstream objects, leading to coastal invasion, structural damage and dangerous movement of objects. Severe dam break flow may even cause major disasters, resulting in huge property losses and casualties. Secondly, the waves generated by dam break flow are very similar to the tsunami process, so it is often widely used to study the interaction between tsunamis and structures or ships. In addition, because it is more economical to use the dam break process to study the wave problem than the traditional wave making process, the dam break flow slamming process on the horizontal deck is often used to approximate the deck wave process. In ship and ocean engineering, the interaction between dam break and floating body is a very important topic, especially the violent interaction problem when there are waves on the deck and large-scale swaying of the floating body under severe sea conditions, which is of great importance to ship safety. Therefore, it is necessary to study and analyze the phenomenon of violent interaction between dam break and floating body.

[0003] At present, the research and analysis of dam break-floating body interaction is mainly carried out through experiments or computational fluid dynamics methods. The results obtained by the experimental method can usually objectively reflect the process of dam break-floating body interaction. However, the experimental method not only consumes a long time and has a high economic cost, but also has difficulty in obtaining comprehensive flow field information. The computational fluid dynamics method can realize the research and analysis of dam break-floating body interaction with relatively low time and economic cost, and can obtain comprehensive flow field information. Computational fluid dynamics methods can be divided into grid method and meshless method. So far, some researchers have used the grid method to study the dam break-floating body interaction process. However, due to the difficulties of the grid method in simulating drastic free surface changes, there are few simulation studies on the dam break-floating body drastic interaction with deck waves and large-scale swaying of the floating body.

[0004] In computational fluid dynamics, the moving particle semi-implicit method is an important meshless method based on Lagrangian description. Compared with the mesh method, it can capture free surfaces more easily, and can easily show the separation and fusion of fluids. It has certain advantages in simulating drastic changes in free surfaces. Therefore, it is widely used in the simulation of various dam break problems, including dam break processes in dry and wet bottom waterways, dam break processes in movable rivers, dam break processes with rigid obstacles set downstream, dam break processes with flexible obstacles set downstream, and the process of interaction between destructible structures and dam break flows. However, there are relatively few studies on the use of the moving particle semi-implicit method to simulate the violent interaction between dam break flows and floating bodies. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, according to the present invention, a moving particle semi-implicit simulation method for dam break-floating body interaction is provided, which comprises the following steps:

[0006] Establishing a computational domain model, dividing the computational domain by particles, defining a number of particle types, and setting initial conditions and motion properties of floating bodies;

[0007] Establish a neighbor particle set and calculate the particle number density of each particle;

[0008] Construct a secondary free surface and use the judgment model to judge the free surface;

[0009] Threshold-type particles are established to regulate the distribution of fluid particles far away from the free surface using a migration model;

[0010] estimating the intermediate movement speed and intermediate displacement of the fluid particles, and calculating the displacement of the gate particles;

[0011] A computational model for solving flow field pressure is constructed, and the total pressure is solved using Gaussian iteration method;

[0012] Calculating the fluid force and torque on the floating body, and calculating the velocity and displacement of the floating body;

[0013] The gradient of the flow field pressure is calculated, and the velocity and displacement of the fluid particles are updated and derived to obtain the updated velocity and updated displacement of the fluid particles.

[0014] In one embodiment, the computational domain model is composed of a numerical pool wall, an upstream fluid, a downstream fluid, a gate, and a floating body.

[0015] In another embodiment, the step of dividing the computational domain by particles further comprises:

[0016] Setting the initial spacing of particles to define several of the particle types;

[0017] Using particles to discretize the regions of the upstream fluid, the downstream fluid, the gate, and the floating body;

[0018] The discrete pool wall is constructed in the form of three layers of particles, wherein the three layers of particles are wall pressure particles, Newman boundary particles and ghost particles from the inside to the outside;

[0019] The position of the discrete particles at the initial moment is assigned according to their position information.

[0020] In yet another embodiment, the step of establishing a neighbor particle set and calculating the particle number density of each particle further comprises:

[0021] Searching for neighbor particles of each pressure wall particle and the fluid particle, thereby establishing a neighbor particle set, wherein the radius of the search domain is 2.1l0;

[0022] Calculate the particle number density for each particle:

[0023]

[0024] Where n(i) represents the particle number density of particle number i, r ij represents the distance between particle i and particle j, w(r ij ) represents the kernel function.

[0025] In yet another embodiment, the step of constructing a secondary free surface and using a judgment model to judge the free surface further comprises:

[0026] Initially judging, according to the particle number density, the particles are divided into internal particles, free surface particles and undetermined particles;

[0027] When the initial judgment indicates that the undetermined particle exists, the undetermined particle is further judged, and in the neighbor particle domain of the undetermined particle, the area between 1.010 and 2.110 away from the undetermined particle is divided into 8 parts;

[0028] In the case that there is no neighbor particle in the eight parts, the undetermined particle is determined to be the free surface particle; or

[0029] In the case where there is at least one neighbor particle in the eight parts, the undetermined particle is determined to be the internal particle.

[0030] In yet another embodiment, the step of establishing threshold-type particles to regulate the distribution of fluid particles away from the free surface using a migration model further comprises:

[0031] Make sure that the fluid particles away from the free surface satisfy the symmetry equation:

[0032]

[0033] in, represents the particle migration amount, FS particles represent particles far away from the free surface, represents the displacement vector from particle i to particle j; w ij represents the weight,

[0034]

[0035] r ij,min represents the minimum distance between particle i and its neighbor particles, α shift represents the migration threshold parameter, Cshift Represents a constant greater than 0 and less than 1.

[0036] In yet another embodiment, the step of estimating the intermediate motion speed and intermediate displacement of the fluid particles further comprises:

[0037]

[0038] in, and represent the intermediate speed and intermediate displacement of particle i respectively; and They represent the velocity and displacement of particle i at the nth time step respectively; ν and Δt represent the gravitational acceleration, fluid dynamic viscosity coefficient and time step, respectively.

[0039] In yet another embodiment, the step of calculating the displacement of the gate particle further comprises:

[0040]

[0041] In yet another embodiment, the step of constructing a calculation model for solving the flow field pressure further comprises:

[0042] For the free surface particles, Dirichlet boundary conditions are used and the pressure is set to 0.

[0043] P i =0,i∈free surface particle

[0044] For non-free surface particles, make them satisfy:

[0045]

[0046] Where d represents the calculation dimension, n0 represents the initial particle number density, and γ represents the empirical parameter;

[0047] For Newman boundary particles, it satisfies:

[0048]

[0049] The pressure equations corresponding to all pressure particles are combined to construct a large linear equation system, and the total pressure of the flow field is solved by the Gaussian iteration method.

[0050] In yet another embodiment, the simulation method further comprises calculating the fluid force F acting on the floating body. fy and torque L f :

[0051]

[0052] Among them, F fyIt represents the vertical component of the fluid force acting on the floating body, L f is the torque acting on the floating body, n bw represents the total number of particles on the floating body wall, P k represents the pressure on the kth wall particle, S k represents the wall area corresponding to the kth wall particle, represents the unit external normal vector of the kth wall particle,

[0053] represents the unit vector in the vertical direction, represents the position vector of the kth wall particle, The position vector representing the center of rotation of the float. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, wherein:

[0055] Figure 1 A flow chart of a moving particle semi-implicit simulation method for dam break-floating body interaction according to an embodiment of the present invention is shown.

[0056] Figure 2 A schematic diagram of arranging three layers (wall surface) of particles according to an embodiment of the present invention is shown.

[0057] Figure 3 A schematic diagram showing the determination of a free surface in a secondary free surface according to an embodiment of the present invention

[0058] Figure 4 A schematic diagram of a dam-break-floating body interaction model according to an embodiment of the present invention is shown;

[0059] Figure 5 A flow chart of a moving particle semi-implicit simulation method for dam-break-floating body interaction according to another embodiment of the present invention is shown.

[0060] Figure 6 A comparison diagram of the fluid profile in the dam-break-floating body interaction simulation at different times and the experiment according to an embodiment of the present invention is shown.

[0061] Figure 7 A comparison diagram of a wavefront rise simulation time history curve according to an embodiment of the present invention and an experimental result is shown.

[0062] Figure 8 A comparison diagram of a simulated time history curve of the heave motion of a floating body according to an embodiment of the present invention and an experimental result is shown.

[0063] Fig. 9 A comparison diagram of a simulated time history curve of the pitching motion of a floating body according to an embodiment of the present invention and an experimental result is shown.

[0064] Fig.10 Shows Figure 4 The comparison diagram of the pressure simulation time history curve at point M is shown with the experimental results. DETAILED DESCRIPTION

[0065] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0066] like Figure 1 As shown, it shows a flow chart of a moving particle semi-implicit simulation method for dam break-floating body interaction according to an embodiment of the present invention. The present invention proposes a moving particle semi-implicit simulation method for dam break-floating body interaction, which includes:

[0067] S1: Establish a computational domain model, divide the computational domain by particles, define several particle types, and set initial conditions and motion properties of the floating body;

[0068] In particular, the computational domain model is composed of a numerical pool wall, an upstream fluid, a downstream fluid, a gate, and a floating body. A spatial coordinate system Oxz is set for the computational domain model, wherein the x-axis direction is equivalent to the dam-break flow direction, and the z-axis direction is the vertical direction.

[0069] Furthermore, the computational domain is divided by particles, that is, the computational domain is discretized by using particles. The specific steps include:

[0070] -Set the initial particle spacing to define several particle types;

[0071] -Use particles to discretize the upstream fluid, downstream fluid, gate and floating body areas;

[0072] -Use three layers of particles to construct the discrete pool wall. The three layers of particles are wall pressure particles, Newman boundary particles and ghost particles from the inside to the outside.

[0073] -Give the initial position of discrete particles according to their position information;

[0074] - Optionally, initial velocities are assigned to the pool wall particles, fluid particles, gate particles, and floating body particles, and mass and moment of inertia are assigned to the floating body.

[0075] S2: Establish a neighbor particle set and calculate the particle number density of each particle;

[0076] In order to implement step S2, the specific operations may include:

[0077] -Search for neighbor particles of each pressure wall particle and fluid particle, thereby establishing a neighbor particle set, where the radius of the search domain is 2.1l0;

[0078] Calculate the particle number density for each particle:

[0079]

[0080] Where n(i) represents the particle number density of particle number i, r ij represents the distance between particle i and particle j, w(r ij ) represents the kernel function. In particular, an exponential kernel function is used here:

[0081]

[0082] Among them, r e represents the search radius, and in general, r e The value range is 2.1l0, where l0 is the average distance between particles.

[0083] S3: construct the secondary free surface and use the judgment model to judge the free surface;

[0084] In order to implement step S3, the specific operations may include:

[0085] The first judgment is to classify particles into three types according to the particle number density, namely internal particles, free surface particles and undetermined particles, as follows:

[0086]

[0087] Wherein, β1 and β2 are two adjustment parameters. According to experience, β1 and β2 are preferably 0.98 and 0.2 respectively.

[0088] When a particle is determined to be a pending particle, a second / further judgment is required to further determine whether it is an internal particle or a free surface particle. Figure 3 As shown, in the neighbor particle domain of the (target) particle, the area between 1.0l0 and 2.1l0 away from the target particle is divided into 8 parts. If two adjacent parts of these 8 parts do not have any neighbor particles, the target particle should be judged as a free surface particle; otherwise, the target particle should be judged as an internal particle.

[0089] S4: Establish threshold-type particles to regulate the distribution of fluid particles far away from the free surface using a migration model;

[0090] In order to ensure that the particles can satisfy the symmetry equation, the migration amount is calculated according to the following formula:

[0091]

[0092] in, represents the particle migration amount; FS particles represent particles far away from the free surface, specifically defined as particles without any free surface particles in the neighborhood; represents the displacement vector from particle i to particle j; w ij represents weight; Δr i Satisfies the following equation:

[0093]

[0094] Among them, r ij,min represents the minimum distance between particle i and its neighbor particles; α shift represents the migration threshold parameter; C shift is a constant greater than 0 and less than 1, preferably C shift =0.5.

[0095] S5: Estimate the intermediate movement speed and intermediate displacement of the fluid particles and calculate the displacement of the gate particles;

[0096] Among them, in order to estimate the intermediate movement speed and intermediate displacement of fluid particles, the following formula can be used for estimation:

[0097]

[0098] in, and represent the intermediate speed and intermediate displacement of particle i respectively; and They represent the velocity and displacement of particle i at the nth time step respectively; ν and Δt represent the gravitational acceleration, fluid dynamic viscosity coefficient and time step, respectively.

[0099] Furthermore, the displacement of the gate particles is calculated according to the lifting speed of the gate, using the following formula:

[0100]

[0101] The subscript "gate" indicates that it is a gate particle.

[0102] S6: Construct a computational model for solving the flow field pressure and use the Gaussian iteration method to solve the total pressure;

[0103] In order to implement step S6, the specific operations may include:

[0104] First, for the free surface particles, the Dirichlet boundary condition is used and the pressure is set to 0, as shown below:

[0105] P i = 0, i∈ free surface particle (9)

[0106] For the fluid particles on non-free surfaces, the following discrete pressure Poisson equation is satisfied:

[0107]

[0108] Where d represents the calculation dimension; n0 represents the initial particle number density; γ represents the empirical parameter;

[0109] For Newman boundary particles, the following boundary conditions are satisfied:

[0110]

[0111] The pressure equations corresponding to all pressure particles are combined to construct a large linear equation system, and the total pressure of the flow field is further solved by the Gaussian iteration method;

[0112] S7: Calculate the fluid force and torque on the floating body, and calculate the velocity and displacement of the floating body;

[0113] In order to implement step S7, the following formula can be used for calculation:

[0114]

[0115] Among them, F fy It represents the vertical component of the fluid force acting on the floating body, L f is the torque acting on the floating body, n bw represents the total number of particles on the floating body wall, P k represents the pressure on the kth wall particle, S k represents the wall area corresponding to the kth wall particle, represents the unit external normal vector of the kth wall particle, represents the unit vector in the vertical direction, represents the position vector of the kth wall particle, The position vector representing the center of rotation of the float.

[0116] Furthermore, the rigid body motion equation is used to calculate the floating body motion, which is specifically calculated by the following formula:

[0117]

[0118] Among them, M f Indicates the mass of the floating body; a fy Represents the component of the acceleration of the floating body in the vertical direction; ω fIt represents the angular velocity of the floating body's pitch; I represents the moment of inertia of the floating body.

[0119] S8: Calculate the gradient of the flow field pressure, update and derive the velocity and displacement of the fluid particles to obtain the updated velocity and updated displacement of the fluid particles.

[0120] In order to implement step S8, the flow field pressure gradient, the updated velocity and the updated displacement of the fluid particles can be calculated using the following formulas:

[0121]

[0122] Among them, NS particles refer to near-free-surface particles, i.e., free-surface particles or fluid particles whose neighboring particles contain free-surface particles; represents the minimum pressure in the neighborhood of particle i.

[0123] Further, the velocity and displacement of the fluid particles are updated according to the following formulas, that is, the updated velocity and updated displacement of the fluid particles:

[0124]

[0125] After the updated velocity and displacement of the fluid particles are exported, they are used as calculation data for subsequent processing to determine whether the time step has reached the stop criterion. If not, proceed to the next time step calculation; if so, end the calculation.

[0126] Embodiment 1

[0127] According to the present invention, it can be carried out in a two-dimensional experimental pool including a water reservoir, a downstream section and a floating body. The total length of the pool is 2000mm, the total width is 600mm, and the total height is 800mm. A gate is set at 500mm from the right wall, dividing the entire pool into two sections, wherein the upstream section is a water reservoir with a length of 500mm and a water level recorded as Hr; the downstream section has a total length of 1500mm and a water depth of 150mm. In order to monitor the free surface lift, a liquid level gauge is set at 1300mm from the left wall. A rectangular floating body is placed on the downstream section. The distance between the center of the floating body and the left wall is 300mm. The length, width and height of the floating body are 300mm, 595mm and 100mm respectively. At the initial moment, the floating body is stationary on the water surface, and the initial draft is 30mm. The weight of the floating body is 5.35kg, and the moment of inertia is 0.0045kg·m 2 A pressure monitoring point M is set on the right side of the floating body, 30 mm above the bottom of the floating body, to monitor the impact of the dam break wave on the floating body.

[0128] like Figure 1As shown, the present invention provides a simulation method of dam break-floating body violent interaction based on Fortran language, comprising the following steps:

[0129] S1', establish a computational domain model for the violent interaction between dam break and floating body, divide the computational domain by particles, define different particle types, and set initial conditions and motion properties of floating body.

[0130] Specifically, the above step S1' may further include:

[0131] S11', set up a spatial coordinate system Oxz, where the x-axis direction is the same as the dam-break flow direction, and the z-axis direction is the vertical direction;

[0132] S12', establishing a computational domain model of dam-break-floating body violent interaction, wherein the computational domain model is composed of a numerical pool wall, an upstream fluid, a downstream fluid, a gate, and a floating body;

[0133] S13', using particles to discretize / divide the computational domain and define different particle types;

[0134] Among them, combined Figure 2 The pool wall adopts a three-layer particle layout. The solid particles are the inner wall particles of the pool, which have pressure properties and are therefore defined as pressure wall particles. The other two layers of particles are auxiliary particles, which are used to ensure the neighborhood completeness of the wall particles. They do not participate in the pressure calculation and are therefore defined as non-pressure wall particles.

[0135] The floating body wall is processed by particle discretization and defined as pressure wall particles; the particles inside are also divided and defined as non-pressure wall particles.

[0136] The gate is also discretized using particles, and the gate particles are set / defined as pressure wall particles.

[0137] The upstream / downstream fluid is also discretized using particles, and the particle type is defined as fluid particles, which participate in the pressure calculation. In this embodiment, the particles are discretized using uniform particles, and the initial particle spacing l0 is 0.010m.

[0138] S14', set the initial velocity of the pool wall particles, fluid particles and floating particles to 0; the horizontal component of the gate initial velocity is 0, and the vertical component is 1.46m / s;

[0139] S15', set the floating body mass to 5.35kg and the moment of inertia to 0.0045kg·m 2 ;

[0140] S2', construct the secondary free surface and use the judgment model to judge the free surface;

[0141] Specifically, the above step S2' may also include:

[0142] S21', search for neighbor particles of each pressure wall particle and fluid particle, thereby establishing a neighbor particle set, and the radius of the search domain is 2.1l0;

[0143] S22', using the above formulas (1) and (2) to calculate the particle number density of each pressure wall particle and fluid particle, and then according to the above formulas (3) and Figure 3 To determine whether the particle is a free surface particle;

[0144] S23', judging whether the target particle is far away from the free surface particle, the specific judgment logic is: if a particle is a free surface particle, then the target particle is a near free surface particle; if the target particle is a non-free surface particle, and its neighbor particles include free surface particles, then the target particle is defined as a near free surface particle; if there is no free surface particle among the neighbor particles of a non-free surface particle, then the target particle is defined as a far away free surface particle.

[0145] S24', using the above formula (4) to migrate the particle far away from the free surface, and correct its position so that it satisfies the symmetry equation;

[0146] S3', estimate the intermediate movement speed and intermediate displacement of the fluid particles, and calculate the displacement of the gate particles;

[0147] Specifically, the above step S3' may also include:

[0148] S31', first set the time step Δt, in this embodiment, Δt is 0.0001s;

[0149] S32', estimating the intermediate velocity and intermediate displacement of the fluid particles according to the above formulas (6) and (7);

[0150] S33', continue to set the speed of the gate particle to 1.46 m / s, and then calculate the displacement of the gate particle according to the above formula (8);

[0151] S4', constructing a calculation model for solving the flow field pressure to solve the total pressure, and calculating the velocity and displacement of the floating body;

[0152] Specifically, the above step S4' may also include:

[0153] S41', for free surface particles, Dirichlet boundary conditions are used and the pressure is set to 0;

[0154] S42', for the pressure particles on the non-free surface, the discrete pressure Poisson equation as shown in formula (10) is satisfied;

[0155] S43', combine the equations satisfied by these particles to construct a symmetrical large linear equation system;

[0156] S44', using Gaussian iteration method to solve this large linear equation system, the flow field pressure is obtained;

[0157] S45', according to the above formulas (12) and (13), the fluid force and torque acting on the floating body are calculated, and the linear acceleration and angular acceleration of the floating body can be obtained from the rigid body motion equation, thereby further calculating the velocity and displacement of the floating body at the next moment, and updating the velocity and displacement information of the floating body particles;

[0158] S5', calculate the gradient of the flow field pressure, update the velocity and displacement of the fluid particles, and export the calculated data for post-processing.

[0159] Specifically, the above step S5' may further include:

[0160] S51', using formula (16) to calculate the pressure gradient of the fluid particles, and obtaining the velocity and displacement of the fluid particles in the next time step through formulas (17) and (18);

[0161] S52', export post-processing data, which can be divided into two parts. The first part includes the wave surface lift curve obtained by the numerical level gauge, the pressure duration curve at the pressure monitoring point, and the heave and pitch motion curves of the floating body. This part of the data is plotted as the corresponding characteristic curve and compared with the experimental results; the second part is the simulation field data, which is plotted as the shape and pressure cloud diagram of the flow field at each time step.

[0162] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A moving particle semi-implicit simulation method for dam-break-floating body interaction, characterized in that: The following steps are involved: Establishing a computational domain model, dividing the computational domain by particles, defining a number of particle types, and setting initial conditions and motion properties of floating bodies; Establish a neighbor particle set and calculate the particle number density of each particle; Construct a secondary free surface and use the judgment model to judge the free surface; Threshold-type particles are established to regulate the distribution of fluid particles far away from the free surface using a migration model; estimating the intermediate movement speed and intermediate displacement of the fluid particles, and calculating the displacement of the gate particles; A computational model for solving flow field pressure is constructed, and the total pressure is solved using Gaussian iteration method; Calculating the fluid force and torque on the floating body, and calculating the velocity and displacement of the floating body; The gradient of the flow field pressure is calculated, and the velocity and displacement of the fluid particles are updated and derived to obtain the updated velocity and updated displacement of the fluid particles.

2. The moving particle semi-implicit simulation method of dam-break-floating body interaction according to claim 1 is characterized in that: The computational domain model is composed of a numerical pool wall, an upstream fluid, a downstream fluid, a gate and a floating body.

3. The moving particle semi-implicit simulation method of dam-break-floating body interaction according to claim 2 is characterized in that: The step of dividing the computational domain by particles further comprises: Setting the initial spacing of particles to define several of the particle types; Using particles to discretize the regions of the upstream fluid, the downstream fluid, the gate, and the floating body; The discrete pool wall is constructed in the form of three layers of particles, wherein the three layers of particles are wall pressure particles, Newman boundary particles and ghost particles from the inside to the outside; The position of the discrete particles at the initial moment is assigned according to their position information.

4. The moving particle semi-implicit simulation method of dam-break-floating body interaction according to claim 1 is characterized in that: The step of establishing a neighbor particle set and calculating the particle number density of each particle further includes: Search the neighbor particles of each pressure wall particle and the fluid particle, thereby establishing a neighbor particle set, where the radius of the search domain is Calculate the particle number density for each particle: Where n(i) represents the particle number density of particle number i, r ij represents the distance between particle i and particle j, w(r ij ) represents the kernel function.

5. The moving particle semi-implicit simulation method of dam-break-floating body interaction according to claim 4 is characterized in that: The step of constructing a secondary free surface and using a judgment model to judge the free surface further includes: Initially judging, according to the particle number density, the particles are divided into internal particles, free surface particles and undetermined particles; When the initial judgment indicates that the undetermined particle exists, the undetermined particle is further judged, and in the neighbor particle domain of the undetermined particle, the area between 1.010 and 2.110 away from the undetermined particle is divided into 8 parts; In the case that there is no neighbor particle in the eight parts, the undetermined particle is determined to be the free surface particle; or In the case where there is at least one neighbor particle in the eight parts, the undetermined particle is determined to be the internal particle.

6. The moving particle semi-implicit simulation method of dam-break-floating body interaction according to claim 5 is characterized in that: The step of establishing threshold type particles and regulating the distribution of fluid particles away from the free surface by using a migration model further includes: Make sure that the fluid particles away from the free surface satisfy the symmetry equation: i∈FS particle in, represents the particle migration amount, FS particles represent particles far away from the free surface, represents the displacement vector from particle i to particle j; w ij represents the weight, r ij,min represents the minimum distance between particle i and its neighbor particles, α shift represents the migration threshold parameter, C shift Represents a constant greater than 0 and less than 1.

7. The moving particle semi-implicit simulation method of dam-break-floating body interaction according to claim 6 is characterized in that: The step of estimating the intermediate movement speed and intermediate displacement of the fluid particles further comprises: in, and represent the intermediate speed and intermediate displacement of particle i respectively; and They represent the velocity and displacement of particle i at the nth time step respectively; ν and Δt represent the gravitational acceleration, fluid dynamic viscosity coefficient and time step, respectively.

8. The moving particle semi-implicit simulation method of dam-break-floating body interaction according to claim 7 is characterized in that: The step of calculating the displacement of the gate particle further comprises:

9. The moving particle semi-implicit simulation method of dam-break-floating body interaction according to claim 8 is characterized in that: The step of constructing a calculation model for solving the flow field pressure further includes: For the free surface particles, Dirichlet boundary conditions are used and the pressure is set to 0. P i =0,i∈free surface particle For non-free surface particles, make them satisfy: i∈non-free surface particle Where d represents the calculation dimension, n0 represents the initial particle number density, and γ represents the empirical parameter; For Newman boundary particles, it satisfies: i∈Newman boundary particle The pressure equations corresponding to all pressure particles are combined to construct a large linear equation system, and the total pressure of the flow field is solved by the Gaussian iteration method.

10. The moving particle semi-implicit simulation method of dam-break-floating body interaction according to claim 9, characterized in that: It also includes the calculation of the fluid force F acting on the floating body fy and torque L f : Among them, F fy It represents the vertical component of the fluid force acting on the floating body, L f is the torque acting on the floating body, n bw represents the total number of particles on the floating body wall, P k represents the pressure on the kth wall particle, S k represents the wall area corresponding to the kth wall particle, represents the unit external normal vector of the kth wall particle, represents the unit vector in the vertical direction, represents the position vector of the kth wall particle, The position vector representing the center of rotation of the float.

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