Research On Numerical Simulation Method Of Debris-soil Landslide Generated Impulse Waves In Reservoir Based On Equivalent Fluid

Landslides,rockfalls,and debris flows can cause secondary disasters such as surge wave when they occur in reservoirs,lakes,rivers,and oceans,threatening the safety of ship navigation and coastal infrastructure.Debris soil landslides are one of the main types of reservoir landslides in mountainous areas,characterized by large volume and fast sliding speed,which are prone to instability after heavy rainfall.The surge wave disasters caused by these landslides are common and typical,which require widespread attention.Seeking a highly efficient and accurate numerical simulation method to predict the formation process of debris soil landslide surge waves is a prerequisite for disaster early warning.This paper conducts a study on the numerical simulation method of landslide surge waves based on continuum mechanics theory,analyzing the motion characteristics of landslides,the morphological changes of surge waves,and flow field information,providing a scientific basis for landslide surge wave disaster early warning.The main results are as follows:(1)Treating the debris soil landslide as a special continuous fluid medium,the Herschel-Bulkley rheological model and bottom resistance model are loaded using C language programming,combined with the VOF multiphase flow model and Realizable turbulence model.The numerical simulation method of landslide surge is established by solving N-S equation.(2)The influence of the resistance model on the rheological characteristics of the landslide is analyzed.The results show that increasing the sliding friction coefficient f value or decreasing the turbulence parameter ζ value will both lead to an increase in bottom resistance,thereby making the deformation of the landslide more noticeable.As the length of the landslide increases,the influence of these changes weakens.When the landslide moves at high speed,the influence of the f value on the landslide morphology decreases,while the influence of the ζ value on the landslide morphology increases.In addition,increasing the internal friction coefficient K value will reduce the deformation rate of the landslide,making the thickness distribution of the landslide more uniform.(3)The distribution law of particle size was studied during the movement of granular landslides.During the motion process,the granular flow experiences inverse particle ordering and self-channeling phenomena.When the granular landslide moves in water,the fluid does not hinder the upward migration of larger particles during the inverse ordering process,but the viscous resistance of the water leads to a decrease in the difference in movement distance between coarse and fine particles,and the distance of landslide movement becomes shorter.The variation law of landslides under different fractal dimensions was analyzed,and the process of landslide surge wave action was elucidated by using numerical simulation to invert experimental results,and the variation law of velocity field and pressure field in the basin was obtained.The influence of fractal dimension on the parameter values of the resistance model was studied,and the results showed that after increasing the fractal dimension,the friction coefficient f value at the bottom of the waterborne landslide increased,and the friction coefficient K value inside the underwater landslide increased.(4)Through three-dimensional numerical simulation of potential landslide surge waves in the actual reservoir area,the motion information of surge waves in the entire reservoir area at different times is obtained.It is found that the water body fluctuates violently within a range of about 0.3 km downstream of the landslide,forming the strongest disaster-causing surge waves,which belong to the red warning zone.The surge wave propagation stage in the straight river channel belongs to the orange warning zone.As the surge wave passes through the bend terrain,the surge wave warning standard gradually changes from the orange warning to the yellow warning,and the wave height decreases significantly.The study also found that when the surge wave propagates in the narrow straight river channel,the wave height attenuates slowly,and the wave shape is more similar to a solitary wave,with a strong disaster-causing ability.The winding and tortuous river channel terrain plays an important role in reducing the energy of surge waves.