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Topographic effects on tornado-like vortex

  • Nasir, Zoheb (Civil and Environmental Engineering/WindEEE Institute, Western University (formerly The University of Western Ontario)) ;
  • Bitsuamlak, Girma T. (Civil and Environmental Engineering/WindEEE Institute, Western University (formerly The University of Western Ontario))
  • Received : 2018.04.04
  • Accepted : 2018.07.03
  • Published : 2018.08.25

Abstract

The effects of steep and shallow hills on a stationary tornado-like vortex with a swirl ratio of 0.4 are simulated and quantified as Fractional Speed Up Ratios (FSUR) at three different locations of the vortex with respect to the crests of the hills. Steady state Reynolds Averaged Naiver Stokes (RANS) equations closed using Reynolds Stress Turbulence model are used to simulate stationary tornadoes. The tornado wind field obtained from the numerical simulations is first validated with previous experimental and numerical studies by comparing radial and tangential velocities, and ground static pressure. A modified fractional speed-up ratio (FSUR) evaluation technique, appropriate to the complexity of the tornadic flow, is then developed. The effects of the hill on the radial, tangential and vertical flow components are assessed. It is observed that the effect of the hill on the radial and vertical component of the flow is more pronounced, compared to the tangential component. Besides, the presence of the hill is also seen to relocate the center of tornadic flow. New FSUR values are produced for shallow and steep hills.

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