A likely mechanism for the little-understood tornado genesis is proposed and its numerical implementation is presented. The Burgers-Rott vortex with its axis in the vertical direction is introduced as an instability mechanism, and the flow field then evolves under the influence of the atmospheric pressure, temperature and density variations with altitude. Buoyancy effects are implemented using the Boussinesq model. Results are presented and discussed for a set of conditions including mesh type and size, different turbulence models, and a few different boundary conditions. Post-processed results of the transient simulations including animations contain a wealth of information to help analyze tornado behavior. Velocity contours, pressure contours, vorticity contours, streamlines, and iso-surfaces show the evolution of a complex flow field possessing many characteristics of a tornado. At longer times from the start, the flow field becomes more asymmetric with the vortex core becoming more twisted, and the eye of the vortex drifting away from the axis of the computational domain. The single initial vortex then transitions into multiple vortices of varying size and orientation. These high Reynolds number (Re ~109) simulation results show flow fields that resemble highly unsteady, massively separated turbulent flows with eddies at a wide range of spatial scales.
K. M. Issac, "Simulation of Natural Tornado Genesis and Evolution from an Initial Instability Profile,", Feb 2023.
Mechanical and Aerospace Engineering
Keywords and Phrases
Tornado CFD simulation, Mars dust devils, tornado genesis, evolution, decay.
Article - Journal
© 2023, K. M. Isaac