Wind Tunnel Test And Numerical Simulation Of Snow Drifting Effect On Low-rise Buildings With Stepped Flat Roofs

The snowstorm is one of the top ten disasters facing the world since the twentieth century.The snow drifting is an important part of the snowstorm.In recent years,with the development of the economy and high-latitude regions,low-rise buildings around the world have been reported in the event of collapse,damage and failure under wind-snow conditions,directly causing huge loss of life and property.The study of snow drifting involving fluid dynamics,particle dynamics and structure dynamics is an interdisciplinary issue,and theoretical research is very difficult.However,there are few studies on the phenomenon of snow drifting on lowrise buildings at home and abroad,which exist many shortcomings at present.Taking the stepped flat roof as he research object,this dissertation systematically studies the snow distribution characteristics of roofs,the flow field distribution with or without snow cover boundary,and numerical simulation technology of snow drifting.The main contents are as follows:1.The main similarity parameters for the wind tunnel test of snow drifting were reviewed,and the characteristics of flow field and the material properties of silica sand were measured.Under the condition of different nominal wind velocities,the wind tunnel test of snow drifting on stepped flat roofs with different windward width was carried out.The distributions of snow on roofs were measured.The effects of width-height ratio and wind velocity on the total amount of snow erosion and the mean mass transport rate on roofs were analyzed.2.Four groups of stepped flat roofs with different width-height ratio were designed,and snow cover boundary on roofs was made by 3D printing based on the results of wind tunnel test for snow drifting.The characteristics of flow field for stepped flat roofs were studied by PIV technology.The wind velocity profile was measured firstly,and then the effect of width-height ratio on the distribution of flow field was studied under the condition of 0° and 180° wind direction;the changes of flow field with or without snow cover boundary were compared;the relationship between the flow field pattern and the snow pattern were analyzed based on results of the PIV test and wind tunnel test of snow drifting.3.The grid type,data storage and common dynamic mesh methods were briefly introduced.Then,the general flow process and shortcomings of applying the dynamic mesh method in numerical simulation of snow drifting were summarized.The common interpolation methods were reviewed,and the interpolation process on the snow cover boundary was constructed and derived based on the radial basis function.Combined with the mesh law,the mesh adaptation was implemented for the computational domain.This method was suitable for both 2D and 3D mesh adjustment.4.Based on the time scale similarity criterion,the equivalent wind duration was determined,and based on the relative residual of the average mass transport rate of snow phase,the optimum iteration method was adopted to determine the optimal subsection of duration.Combined with adaptive-mesh method using RBF interpolation,a quasi-dynamic and time-marching method was proposed for numerical simulations of snow drifting,which could effectively reduce the computation cost.Finally,the snow distribution on 2D and 3D stepped flat roofs were simulated,and the differences between two-dimensional and three-dimensional numerical simulation were compared.