Turbulent modeling of a vortex boundary layer flow

The boundary layer flow of an atmospheric vortex was analyzed by utilizing a two-equation model of turbulence together with the conventional boundary layer equations. Steady-state solutions were obtained from the time-dependent solutions by using a predictor-corrector, multiple iteration method. Surprisingly complicated flow patterns with four circulating regions (4-cell vortex) were predicted in a meridional plane of the boundary layer. The intrinsic nature of sharp-turning, large-shear, and high-swirl flow characteristics may provide explanations for the tremendous roars and extremely intensive damage to ground structures associated with tornadoes. The present results are in good agreement with the tornado dust clouds simulated in our laboratory as well as those observed in natural cases.