Simulation Research On Movement Process Of Viscous Debris Flow Based On SPH Method

Debris flows usually form under extreme weather conditions,and have characteristics such as large initial potential energies,short duration times,fast running speeds and unpredictability.In recent years,human activities have become more frequent,and extreme weather conditions have increased significantly,leading to the frequent occurrence of debris flow disasters around the world.In addition,the scale of debris flow has been increasing.Therefore,studying the movement process of debris flow is significant for its scientific prediction and reasonable prevention.As is known,the dynamic characteristics of debris flow are very complex.Furthermore,the motion of debris flow also involves complex large deformation problems.However,it is easy to distort the mesh with the application of the traditional grid-based method when solving large deformation problems.The existing numerical models of debris flow motion generally analyse the motion characteristics of the debris flow under the longitudinal profile.In addition,the 3D problem is simplified to a 2D scenario according to the depth-integrated(averaged)theory;therefore,the velocity and depth of debris flow can be featured on a 2D horizontal section,which can obviously improve the computational efficiency.However,it cannot accurately characterize the 3D motion process of a real debris flow.In this paper,the smooth particle Hydrodynamics(SPH)method is introduced in the study of fluid deformation,and the natural advantage of dealing with the free surface is brought into play.Based on the NavierStokes equation,the SPH motion control equations of two-dimensional viscous fluid is extended to the simulation of three-dimensional viscous dam-break fluid motion.Based on that,the governing equations of three-dimensional viscous debris flow are derived.The main results are as follows:(1)Based on the Navier-Stokes equation,the motion control equations of the non-viscous fluid,viscous fluid and viscous debris flow are derived with the SPH method.It is more suitable to solve the boundary problem of complex geometry to prevent fluid particles from penetrating the boundary under real terrain by improving the method of boundary processing.(2)Combined with the rheology theory,the calculation method of shear stress term and effective viscosity coefficient of viscous debris flow is given,which avoids the failure of program calculation when the effective viscosity coefficient approaches infinity.The effectiveness of the method is verified with some examples,which lays a foundation for describing the motion process of viscous debris flow in complex topography.(3)Using Python language,simulation programs of fluid movement process are formed.Three kinds of fluid(non-viscous fluid,viscous fluid and viscous debris flow)are simulated.The effectiveness of the program is verified with the corresponding examples,which provides technical support for the simulation of the motion process of different types of fluid.(4)The numerical model of the Wenjia Gully under the real terrain condition is constructed,and the motion process of the viscous debris flow in the “8.13” Wenjia Gully is simulated.It is verified that the SPH method is feasible in the problem of 3D viscous debris flow motion,and it provides a theoretical basis for predicting the migration path and the disaster area of viscous debris flow.