Large eddy simulations of translation and surface roughness effects on tornado-like vortices

The effects of translation and surface roughness on tornado-like vortices were studied using Large Eddy Simulation (LES) of a laboratory scale tornado. The translation was simulated by employing a moving-wall boundary condition and surface roughness was introduced by physical modeling of roughness element blocks. For lower swirl ratios the translation reduces the maximum mean tangential velocity whereas for high swirl ratios it causes a slight increase in the maximum mean tangential velocity. The introduction of surface roughness causes an overall effect similar to reducing the swirl ratio.