The Numerical Simulation Of Wind And Sand Flow Fields On Building By Lattice Boltzmann Method

The northwest area of China is seriously affected by the wind and sand,and the force of the wind and sand on the buildings is greater than the net wind load.At present,the main research in the field of building win d resistance in our country is the net wind load on the building,and the research on the wind sand load on the building,especially the impact force of sand particles is relatively less.It is of great engineering significance to carry out the research on the wind sand flow field and the impact force of sand particles on the building.Lattice Boltzmann method(LBM)is a complete discretization model,which discretizes the fluid into fluid particles,discretizes the computational flow field into a series of grids,discretizes the time into time steps,and describes the flow process of the fluid by the collision and migration process of the particle density distribution function on the specified grid line.The real macro density and velocity of the fluid are directly determined by the particle density distribution function It is calculated.In this paper,the LBM method is used to simulate the elevation and level of low buildings in the sand flow field.Firstly,the wind sand flow field of two-dimensional facade building is simulated.The wind profile,turbulence,sand velocity and sand concentration gradient in front of the building,and the impact force of sand on the windward side of the building are studied under four conditions: two kinds of wind speed and two kinds of sediment falling.The results show that: The presence of sand particles in the wind field will reduce the wind speed of the wind field and increase the turbulence of the wind field.The speed of the sand particles is less than the wind speed at the same height.From the average value,the three particle sizes are 0.3mm,0.375 mm,and 0.45 mm.The speed of the sand particles is about 95%,92%,and 89.5% of the wind speed,respectively;the sand particle size,the amount of falling sand,and the w ind speed have significant effects on the sand concentration and the impact force of the sand particles;The sand concentration and impact force decrease,and the sand concentration and impact force below it increase;above 0.1m,the sand concentration increases with the increase of wind speed,and below 0.1m,the sand concentration decreases with the increase of wind speed.Second,through the wind tunnel test,the flow field characteristics and sand impact force under two wind speeds and two sediment loa ds are studied.The data measured in the wind tunnel test and the data obtained in the third chapter are compared and analyzed.The analysis results show that: The simulated wind field and the wind tunnel test wind field have maintained a relatively high c onsistency;the average difference between the simulated sand concentration and the test sand concentration under the four working conditions is less than 15%;the simulated impact force agrees with the test results in the trend Good.From a numerical poin t of view,the average difference between the simulated impact force and the test results of the four working conditions is less than 20%.Finally,taking the plane of 1/2 building height,the two-dimensional wind sand flow field of horizontal building is simulated.The sand velocity,impact force and flow around the sand were studied under two different conditions.The results show that: Sand velocity and sand impact force are distributed evenly along the cross wind direction.Periodic vortices will form b ehind the building model.After the sand particles bypass the building model,they are mainly distributed around the vortex.