A coupled method and system for the near-field and far-field propagation and evolution of landslide-generated tsunamis

Abstract

The present invention discloses a coupled method and system for the near-field and far-field propagation and evolution of landslide-induced surges. The method steps include: using the particle discrete element method and the smoothed particle hydrodynamics method to simulate the near-field movement of granular landslides; taking the simulated near-field movement as the initial boundary condition to calculate the far-field movement of granular landslides; and based on the drag force and buoyancy force, completing the near-field and far-field propagation and evolution of granular landslides during the movement and the process of entering water. Through the fine numerical simulation of key areas, the present invention can more accurately predict the propagation path, speed, and influence range of landslide-induced surges. This is crucial for disaster warning and risk assessment. At the same time, the model of the present invention can consider the terrain, geology, hydrological conditions, etc. in more detail, improving the authenticity of the simulation of landslide-induced surges. In addition, by simulating different scenarios, the present invention can evaluate the potential impacts of landslide-induced surges on coastal structures, residential areas, and critical infrastructure, providing hazard analysis for rescue and planning.

Description

Technical Field

[0001] The present invention relates to the fields of water conservancy engineering, geotechnical mechanics, and geological disaster prevention and control, and particularly relates to a coupling method and system for the near and far-field propagation and evolution of landslide-generated waves. Background Art

[0002] Under the action of external disaster-causing factors, such as rainfall, earthquake, reservoir water level regulation, etc., an unstable landslide body will generate landslide-generated wave disasters, threatening river channel buildings and structures. Landslide-generated wave disasters have now become an important threat to personnel, property, and engineering safety. In order to analyze the hazards of landslide-generated waves caused by the landslide body squeezing water into the water, numerical methods can be used for simulation and analysis.

[0003] However, the existing simulation and analysis methods have great defects:

[0004] 1. Slow calculation speed: Especially for complex fluid dynamics problems, traditional calculation methods require a large amount of computing resources and time, which is particularly obvious in real-time simulation or large-scale simulation.

[0005] 2. Limited calculation accuracy: When dealing with complex fluid interfaces, highly turbulent flows, etc., it may be difficult for traditional methods to achieve high accuracy. In addition, for irregular or free-surface fluids, accuracy is also a challenge.

[0006] 3. Numerical stability problems: Some fluid calculation methods may encounter numerical stability problems under specific conditions, such as when dealing with high-speed flows or large-gradient flow fields. Summary of the Invention

[0007] To solve the technical problems in the above background, the present invention aims to propose a coupling method that can expand the research scope as much as possible while ensuring accuracy, taking into account the waves generated by the volume of the landslide body and the waves generated by the speed of the landslide body, as well as the buoyancy, drag force, and lubrication effect of water between the landslide body and the water. The present invention completes the division of computational particles in the far-field region by simulating the influence between the upstream and downstream during the wave propagation process, effectively improving the calculation accuracy and efficiency.

[0008] To achieve the above object, the present invention provides a coupling method for the near and far-field propagation and evolution of landslide-generated waves, and the steps include:

[0009] Using the particle discrete element method and the smoothed particle hydrodynamics to simulate the near-field motion of the granular landslide;

[0010] Taking the simulated near-field motion as the initial boundary condition to calculate the far-field motion of the granular landslide;

[0011] Based on the drag force and buoyancy, complete the near and far-field propagation and evolution of the granular landslide during the movement and water entry process.

[0012] Preferably, the method for simulating the near-field motion includes: using the particle discrete element method to simulate the near-field motion of the granular landslide, and simultaneously using the smoothed particle hydrodynamics method to simulate the generation of the surge after the landslide enters the water and its propagation characteristics in the near field; when calculating the near-field motion, the coupling effect between the fluid and the solid is realized through the buoyancy and drag forces during the coupling of the solid and the liquid, so as to simulate the landslide body motion and the landslide surge during the process of entering the water.

[0013] Preferably, the method for calculating the position, velocity and pressure of the near-field particles includes:

[0014]

[0015] where a external is the acceleration caused by the external force; a pressure is the acceleration caused by the pressure difference inside the fluid; a viscosity is the acceleration caused by the velocity difference inside the fluid; g represents the external force; p represents the pressure; ρ represents the density; μ represents the dynamic viscosity of the fluid; u represents the particle velocity inside the fluid.

[0016] Preferably, the calculation method of the near-field motion includes: determining the spatial coordinates and masses of the particles at the initial moment; according to the distances between the particles, each particle determines its adjacent particles, and by integrating the forces acting on the adjacent particles, each particle is expressed by other particles.

[0017] Preferably, the method for calculating the far-field motion includes: using the position, velocity and pressure of the near-field particles as the initial boundary conditions in the far-field calculation and checking the calculation results; during the calculation process, referring to the existence of the water body in the solid voids, considering the porosity and immersion area between the solids, and calculating the drag force and buoyancy force acting on the solids.

[0018] Preferably, the method for completing the near-far field propagation and evolution includes: using the drag force and buoyancy force as the bridge between the particle discrete element model and the smoothed particle hydrodynamics model, so that these two meshless methods are solved in the same framework:

[0019]

[0020]

[0021]

[0022] where B represents the solid particles; ζ k represents the momentum transfer coefficient; ε k and v flow,k respectively represent the porosity and average flow velocity of the particle near field; W ikdenotes the Wendland smooth kernel function; m i denotes the mass of fluid particle i; denotes the drag force exerted by the fluid particle on the centroid of the particle; v k denotes the particle velocity, v i denotes the particle velocity; V k denotes the volume of the block particle.

[0023] The present invention also provides a coupled system for the near - and far - field propagation and evolution of landslide surge waves, which is used to implement the above - mentioned method, and includes: a near - field motion calculation module, a far - field motion calculation module, and an evolution module;

[0024] The near - field motion calculation module is used to simulate the near - field motion of granular landslides by using the particle discrete element method and the smoothed particle hydrodynamics;

[0025] The far - field motion calculation module is used to take the simulated near - field motion as the initial boundary condition and calculate the far - field motion of the granular landslide;

[0026] The evolution module is used to complete the near - and far - field propagation and evolution of the granular landslide during the movement and water - entry process based on the drag force and buoyancy.

[0027] Preferably, the working process of the near - field motion calculation module includes: using the particle discrete element method to simulate the near - field motion of the granular landslide, and at the same time using the smoothed particle hydrodynamics to simulate the generation of the surge wave after the landslide enters the water and its propagation characteristics in the near - field; when calculating the near - field motion, the coupling effect between the fluid and the solid is realized through the buoyancy and drag force during the coupling of the solid and the liquid, so as to simulate the landslide surge wave during the movement and water - entry process of the landslide body.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] Through the fine numerical simulation of key areas, the present invention can more accurately predict the propagation path, speed, and influence range of landslide surge waves. This is crucial for disaster warning and risk assessment. At the same time, the model of the present invention can consider the terrain, geology, hydrological conditions, etc. in more detail, improving the authenticity of the landslide surge wave simulation. In addition, by simulating different scenarios, the present invention can also evaluate the potential impact of landslide surge waves on coastal structures, residential areas, and critical infrastructure, providing hazard analysis for rescue and planning. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 Schematic diagram of the method flow of the embodiment of the present invention. Specific implementation manner

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0034] Embodiment 1

[0035] As Figure 1 shown, it is a schematic diagram of the method flow of this embodiment, and the steps include:

[0036] S1. Use particle discrete element and smoothed particle hydrodynamics to simulate the near-field movement of granular landslides.

[0037] For near-field calculation, the movement of granular landslides is simulated using particle discrete element (DEM), and at the same time, smoothed particle hydrodynamics (SPH) is used to simulate the generation of surges after the landslide enters the water and their propagation characteristics in the near field. When calculating the coupling effect between solids and liquids, buoyancy and drag forces are used to achieve the coupling effect between fluids and solids. Thus, the movement of the landslide body and the landslide surge during the process of entering the water are simulated. Record the positions, velocities, and pressures of the near-field particles, and use them as the initial boundary conditions for the far-field calculation; the specific calculation methods for the positions, velocities, and pressures of the near-field particles include:

[0038]

[0039] where a external is the acceleration caused by external forces; a pressure is the acceleration caused by the pressure difference inside the fluid; a viscosity is the acceleration caused by the velocity difference inside the fluid; g represents external forces; p represents pressure; ρ represents density; μ represents the dynamic viscosity of the fluid; u represents the particle velocity inside the fluid.

[0040] The calculation process of the near-field movement of granular landslides can be divided into the following aspects.

[0041] Particle initialization configuration: that is, determine the spatial coordinates and masses of the particles at the initial moment. In subsequent calculations, the coordinates of the particles change with time, but the mass remains unchanged.

[0042] Search for neighboring particles: Each particle's adjacent particles are determined according to the distance between particles. By integrating the forces acting on the adjacent particles, each particle needs to be expressed in terms of other particles;

[0043] Among them, the density expression is:

[0044]

[0045] Among them, W(||x - x j ||2, h) is the smoothing kernel function. The kernel function is used to describe the influence of a particle's interaction with the particles within a radius of 2h around it. h is the calculation radius, r is the distance between two particles, and m j is the mass of particle j. Among them,

[0046]

[0047] In the 3D case

[0048] Calculate the pressure based on density and relative position. In the calculation, generally, the arithmetic mean of the pressures of both particles is used to replace the pressure of a single particle, r i The force generated by pressure at the point of

[0049]

[0050] In the 3D case, substituting the above formula into the kernel function gives:

[0051]

[0052]

[0053] Among them, h is the kernel function calculation radius, p i and p j are the pressures of particles i and j respectively, and p j is the pressure of the particles near the calculation point. r is the distance between them, m is the mass of the particle at point i, ρ i is the density at point i, and ρ j is the density at point j.

[0054] Control of particle motion: Three conservation equations in the SPH format, together with the equation of state of the medium and the equation of the particle's motion position, result in a system of equations that can be solved explicitly to calculate and control the particle motion; The specific steps include:

[0055] For each particle i, the density ρ i can be calculated using the following formula:

[0056] ρ i = Σ j mj W(r ij ,h)

[0057] where ∑ j denotes the summation over all neighboring particles j; m j is the mass of particle j; W(ri j ,h) is the kernel function; h is the smoothing length.

[0058] For each particle i, the change in velocity can be obtained by solving the momentum equation:

[0059]

[0060] where is the acceleration of particle i; p i and p j are the pressures of particle i and j respectively; Π ij is the artificial viscosity term used to simulate the viscous effect of the fluid; is the gradient of the kernel function with respect to particle i; g is the external force such as gravity; F d，i is the drag force acting on fluid particle i:

[0061]

[0062] where φ is the porosity of the solid, representing the available space for fluid flow inside the solid; v i is the velocity of the fluid particle; v solid is the velocity of the solid particle or solid region; C d is the drag coefficient:

[0063]

[0064] where μ f represents the dynamic viscosity of fluid particle f; d k represents the diameter of the discrete element particle k.

[0065] The position of the particle is updated after each time step Δt by Δx i (t+Δt) = x i (t) + v i Δt, where x i (t) and v i are the position and velocity of the particle at time t respectively.

[0066] S2. Use the simulated near-field motion as the initial boundary condition to calculate the far-field motion of the granular landslide.

[0067] At the far field, the smoothed particle hydrodynamics (SPH) calculation method is adopted, and the minimum particle radius is enlarged, which is beneficial to the calculation of fluid propagation. Thus, the problem of excessive calculation scale and low calculation efficiency during far-field propagation is solved. SPH is based on a system of partial differential equations with variables such as density, velocity, and energy. It approximately expresses the function describing the field as the integral of the product of an arbitrary function and a kernel function using "kernel function approximation", and discretizes the flow field by using the method of discrete particles. The continuous fluid is discretized into multiple interacting particles, and the basic physical properties of the particles, such as position, velocity, mass, gravity, pressure, and viscous force, need to be repeatedly calculated. Each particle follows Newton's second law. Between the near field and the far field, the function of the field is approximately expressed as the integral of the product of an arbitrary function and a kernel function using "kernel function approximation".

[0068] During the calculation process, the existence of water in the solid voids is considered, and the porosity and immersion area between solids are considered to calculate the drag force and buoyancy force on the solids. Record the position, velocity, and pressure of the near-field particles, and use them as the initial boundary conditions for the far-field calculation, and check the calculation results to ensure the continuity and accuracy in the near-field and far-field calculations. When using the virtual particle method as the coupling method for near-field and far-field calculations in SPH, it is first necessary to create one or more layers of virtual particles around the near-field boundary. The positions of these virtual particles should correspond to the actual boundary, and their properties (such as density, pressure) are initialized according to the boundary conditions or the properties of the fluid particles.

[0069] The specific steps for recording and updating the properties of virtual particles include:

[0070] 1. Recording of velocity and acceleration: The velocity and acceleration of virtual particles can be determined according to the motion of the solid boundary or according to the properties of the fluid particles. For example, if the boundary is stationary, the velocity and acceleration of the virtual particles can be set to zero. If the boundary is in motion, then the velocity and acceleration of the virtual particles should reflect this motion.

[0071] 2. Reflection principle: In some cases, the velocity of virtual particles can be determined by the reflection principle. For example, if a fluid particle moves towards a solid wall, the velocity of the virtual particle can be set to the reverse of the fluid particle's velocity, so as to simulate the collision and rebound of the fluid particle with the solid wall.

[0072] 3. Influence of boundary conditions: The properties of virtual particles can also be adjusted according to the boundary conditions. For example, if the boundary is impenetrable, then virtual particles can be used to ensure that fluid particles do not pass through the boundary.

[0073] Once the properties of virtual particles (such as velocity, acceleration, pressure, etc.) are determined, they can be used as initial boundary conditions in SPH calculations. At each time step of the simulation, fluid particles interact with these virtual particles, thus correctly simulating the interaction between the fluid and the boundary.

[0074] In the far-field calculation, the function of the field is approximated as the integral of the product of an arbitrary function and a kernel function using "kernel function approximation". The calculation method is the same as that of the near-field. Only the particle size values are different. The.vtk format is used to record solid objects, and solid objects can be divided into floating solid objects and fixed solid objects according to their constraint conditions. The.bi4 format is used to record particle position, velocity, and pressure information.

[0075] S3. Based on the drag force and buoyancy force, complete the near-far field propagation and evolution of granular landslides during movement and entry into water.

[0076] The drag force and buoyancy force are used as the bridge between the particle discrete element model and the smoothed particle hydrodynamics model, enabling these two meshless methods to be solved within the same framework:

[0077]

[0078]

[0079]

[0080] Among them, B represents solid particles; ζ k represents the momentum transfer coefficient; ε k and v flow,k respectively represent the porosity and average flow velocity of the particle near-field; W ik represents the Wendland smoothing kernel function; m i represents the mass of fluid particle i; represents the drag force exerted by the fluid particle on the particle centroid; v k represents the particle velocity, v i represents the particle velocity; V k represents the volume of the block particle.

[0081] Embodiment 2

[0082] This embodiment also provides a landslide surge near-far field propagation and evolution coupling system, including: a near-field motion calculation module, a far-field motion calculation module, and an evolution module; the near-field motion calculation module is used to simulate the near-field motion of granular landslides using particle discrete element and smoothed particle hydrodynamics; the far-field motion calculation module is used to calculate the far-field motion of granular landslides with the simulated near-field motion as the initial boundary condition; the evolution module is used to complete the near-far field propagation and evolution of granular landslides during movement and entry into water based on the drag force and buoyancy force.

[0083] Among them, the workflow of the near-field motion calculation module includes: using the particle discrete element method to simulate the near-field motion of granular landslides, and simultaneously using the smoothed particle hydrodynamics method to simulate the generation of the surge after the landslide enters the water and its propagation characteristics in the near field; when calculating the near-field motion, the coupling effect between the fluid and the solid is realized through the buoyancy and drag forces during the coupling of the solid and the liquid, so as to simulate the landslide body motion and the landslide surge during the process of entering the water.

[0084] The workflow for calculating the position, velocity, and pressure of near-field particles includes:

[0085]

[0086] Among them, a external is the acceleration caused by the external force; a pressure is the acceleration caused by the internal pressure difference of the fluid; a viscosity is the acceleration caused by the internal velocity difference of the fluid; g represents the external force; p represents the pressure; ρ represents the density; μ represents the dynamic viscosity of the fluid; u represents the particle velocity inside the fluid.

[0087] The calculation process of the near-field motion includes: determining the spatial coordinates and mass of the particles at the initial moment; according to the distance between the particles, each particle determines its adjacent particles, and by integrating the forces acting on the adjacent particles, each particle is expressed by other particles.

[0088] The workflow of the far-field motion calculation module includes: using the position, velocity, and pressure of the near-field particles as the initial boundary conditions for the far-field calculation and checking the calculation results; during the calculation process, referring to the presence of water in the voids of the solid, considering the porosity and immersion area between the solids, and calculating the drag force and buoyancy force acting on the solid.

[0089] The workflow of the evolution module includes: using the drag force and buoyancy force as the bridge between the particle discrete element model and the smoothed particle hydrodynamics model, so that these two meshless methods are solved under the same framework:

[0090]

[0091]

[0092]

[0093] Among them, B represents the solid particles; ζ k represents the momentum transfer coefficient; ε k and v flow,k respectively represent the porosity and average flow velocity of the particle near-field; W ik represents the Wendland smoothing kernel function; mi Represents the mass of fluid particle i; Represents the drag force exerted by the fluid particle on the particle centroid; v k Represents the particle velocity, v i Represents the particle velocity; V k Represents the volume of the bulk particle.

[0094] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A landslide surge near-field and far-field propagation evolution coupling method, characterized in that the steps include: The near-field motion of granular landslide is simulated by using particle discrete element method and smoothed particle hydrodynamics. The simulated near-field motion is used as an initial boundary condition to calculate the far-field motion of the granular landslide; Based on the drag force and buoyancy, the near-field and far-field propagation evolution of the granular landslide during movement and water entry is completed; the method for completing the near-field and far-field propagation evolution includes: using the drag force and buoyancy as a bridge between the particle discrete element model and the smooth particle fluid dynamics model, so that these two meshless methods are solved in the same framework: Wherein, B represents a solid particle; ζ k represents the momentum transfer coefficient; ε k and v flow,k represent the porosity and average flow velocity in the particle near field respectively; W ik represents the Wendland smooth kernel function; m i represents the mass of fluid particle i; represents the drag force of the fluid particles on the particle mass center; v k represents the particle velocity, v i represents the particle velocity; V k Represents the volume of bulk particles.

2. The landslide surge near-field and far-field propagation evolution coupling method according to claim 1 is characterized in that: The method for simulating the near-field motion includes: using particle discrete elements to simulate the near-field motion of a granular landslide, and using smooth particle fluid dynamics to simulate the generation of surges after the landslide enters the water and its propagation characteristics in the near field; when calculating the near-field motion, the coupling between the fluid and the solid is achieved through the buoyancy and drag force during the coupling of the solid and the liquid, thereby simulating the movement of the landslide body and the landslide surge during the water entry process.

3. The landslide surge near-field and far-field propagation evolution coupling method according to claim 2 is characterized in that: Methods for calculating the position, velocity, and pressure of near-field particles include: Among them, a external is the acceleration caused by external force; a pressure is the acceleration caused by the pressure difference inside the fluid; a viscosity is the acceleration caused by the flow velocity difference inside the fluid; g represents the external force; p represents the pressure; ρ represents the density; μ represents the dynamic viscosity of the fluid; and u represents the particle velocity inside the fluid.

4. The landslide surge near-field and far-field propagation evolution coupling method according to claim 2 is characterized in that: The calculation method of the near-field motion includes: determining the spatial coordinates and mass of the particles at the initial moment; calculating the forces acting on the adjacent particles of each particle according to the distance between the particles, and each particle is expressed by other particles.

5. The landslide surge near-field and far-field propagation evolution coupling method according to claim 3 is characterized in that: The method for calculating the far-field motion includes: applying the position, velocity and pressure of the near-field particles as initial boundary conditions to the far-field calculation, and verifying the calculation results; during the calculation process, referring to the existence of water in the solid voids, considering the porosity and immersion area between the solids, and calculating the drag force and buoyancy of the solid.

6. A landslide surge near-field and far-field propagation evolution coupling system, the system is used to implement the method according to any one of claims 1 to 5, characterized in that: include: Near-field motion calculation module, far-field motion calculation module and evolution module; The near-field motion calculation module is used to simulate the near-field motion of granular landslide by using particle discrete element and smooth particle fluid dynamics; The far-field motion calculation module is used to calculate the far-field motion of the granular landslide by taking the simulated near-field motion as the initial boundary condition; The evolution module is used to complete the near-field and far-field propagation evolution of granular landslide during movement and entry into water based on drag force and buoyancy.

7. The landslide surge near-field and far-field propagation evolution coupling system according to claim 6 is characterized in that: The workflow of the near-field motion calculation module includes: using particle discrete elements to simulate the near-field motion of a granular landslide, and using smooth particle fluid dynamics to simulate the generation of surges after the landslide enters the water and its propagation characteristics in the near field; when calculating the near-field motion, the coupling between the fluid and the solid is achieved through the buoyancy and drag force during the coupling of the solid and the liquid, thereby simulating the movement of the landslide body and the landslide surge during the water entry process.

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