الفهرس 
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Abstract
To obtain a better understanding of the interaction of a tornado with the ground the present work considers a numerical model of the central region of an axisymmetrical vortex near the ground. With the object of obtaining a detailed description of mean values of wind velocity and pressures , two transport equations for the kinetic energy of turbulence k and its rate of dissipation & are solved simultaneously with the set of basic equations of continuity , momentum and energy. A staggered mesh on a stretched coordinate system is used . The momentum equations are solved in their primitive form and an iterative solution for the pressure is obtained such that the velocity divergence vanishes everywhere. To verify the model , experimental measurements by Savino and Keshok (1965) in a vortex chamber are considered. The two-equation turbulence model results are compared with the experimental values. The comparison tends to verify the fundamental soundness of the model. For the tornado-like flow a cylindrical domain of radius R0 is assumed to consist of a converging zone of height h with a prescribed inward flow at the side boundary and an upper zone that extends up to a height H where the radial velocity approaches zero at the boundary.
Typical low-level mean mind mean wind velocity and pressure distributions for tornado-like flows are predicted . The effect of swirl ratio S on the flow field is discussed . An estimate of the nondimensional pressure DROP is made for different values of swirl ratio. The dependence of the flow parameters on Reynolds number is analyzed and the effect of ground roughness on the velocity profiles is discussed .