A study of tornado induced mean aerodynamic forces on a gable-roofed building by the large eddy simulations

•Tornado induced forces on a building have been successfully reproduced by LES.•Volume averaged velocity (VAV) is proposed to normalized the aerodynamic forces.•VAV is the link between tornado and straight-line wind induced forces.

A tornado simulator was built and tornado-induced mean aerodynamic forces on a gable-roofed building were numerically studied. Simulated mean flow fields and mean forces acting on a building model showed satisfactory agreement with those from experiments verifying the accuracy of the tornado simulator. Around the world experimental tornado simulators are very limited which makes estimating tornado induced forces much difficult. Therefore, examining whether or not there are any relationships between tornado induced forces and straight-line wind induced forces is the target of this study. After checking mean wind profiles below the height of building in tornado flow fields, a kind of spiral was found. This spiral is unique compared with profiles in traditional wind tunnel. Therefore a concept of volume averaged velocity was proposed and found to be the linkage between tornado induced mean forces and straight-line wind induced mean forces, i.e. removing tornado induced atmospheric pressures, the building in tornado experiences similar responses with those in wind tunnel if the direction of volume averaged velocity is same. Based on this finding, a method estimating the tornado-induced mean aerodynamic forces using the straight-line wind tunnel is proposed and the results transformed from the data base of the straight-line wind tunnel show satisfactory agreement with those directly calculated in the tornado simulator.