Numerical Simulation of Tornado like Vortices in Two and Three Dimensions around Complex Geometries

We present here results from two and three dimensional numerical simulations of a tornado like vortex. The simulations study the transport of generated vortices through a complex geometry of buildings as present in an urban area. The path of the tornado is driven by the surrounding winds as well as the interaction with buildings, which are assumed to be indestructible. The turbulent flow around several complex shaped buildings is governed by the Navier stokes equations and the numerical simulations are performed using the RANS equations and a k-ɛ model. The two critical points of this study are the generation of the vortex and the treatment of the boundary conditions, especially on the buildings. Different approaches are considered in order to generate the vortices in two and then in three dimensions, and the boundary condition are carefully discussed. The results obtained are physically reasonable.