The Study On Downburst Wind Rain Field Characteristics And Its Load Effects On Low-rise Building Under Downburst

The downburst is a type of short-term strong wind near the ground,which is resulted from the downdraft impacting ground violently in the thunderstorm weather.According to whether rainfall happens in the process of downbursts or not,downbursts can be divided into two categories,wet downburst and dry downburst respectively.Wind-driven-rain?WDR?occurs in the process of wet downburst.Recently,some relevant researches have shown that WDR will produce obvious rain loads on the windward side of buildings,which can not be ignored.However,most of existing researches focus on the WDR under the common Atmospheric Boundary Layer?ABL?wind and the researches on the WDR of downbursts are lack.Besides,the wind speed profiles of downbursts are completely different with the common ABL wind so that raindrops have more complex trajectories and distributions under downbursts.Therefore,it is necessary to study the characteristics of wind and rain field of downbursts and the load effects on buildings.In this paper,based on the impinging jet model,the domain of downburst was built.The Computational Fluid Dynamics?CFD?method was used to study the characteristics of wind and rain field of downburst and its load effects on low-rise buildings.The main contents are as follows:1)According to physical experiments,the numerical simulations of scaling downbursts were carried out,and the distributions of wind pressure coefficients on various surfaces of buildings with different geometrical shapes were obtained.Compare the effects of different turbulence models and near-wall treatment methods on the simulation results of downburst impacting on buildings and an effective parameter setting was given.2)A full-scale downburst wind field model was established.The different terrain roughness was achieved by compiling program to adjust the uniform roughness element height and distribution density.Then,the downburst wind fields with different terrain roughness were numerically simulated.The characteristics of downburst wind profile under different roughness length were discussed.3)The TTU?Texas Tech University?standard low-rise building model was put into the downburst domain and the distributions of wind pressure coefficient on each surface of the building model were simulated at different radial distances.The numerical results atr=1D_jet were compared with the experimental results under the Atmospheric Boundary Layer wind.4)In the calculated domain,the Discrete Phase Model was used to insert raindrops to study the characteristics of wind and rain field of downbursts.By dealing with the statistical information of raindrops impacting on the windward side and roof at different radial distances,the ratio of rain loads and wind loads would be compared.