CFD to VorTECH Pressure-Field Comparison and Roughness Effect on Flow

Abstract

A numerical simulator that very closely resembles the experimental tornado simulator facility called VorTECH at Texas Tech University (TTU) is modeled using three-dimensional simulation. Details of an efficient, simplified computational fluid dynamics (CFD) model without vanes are presented. The pressure field is compared with experimental observations with an emphasis on the vortex breakdown, touchdown, and post-touchdown phase of a tornado. The simulation results indicate that the time-averaged radial ground pressure profile follows a similar trend with the experiment in terms of pressure field distribution. The tornado vortex core is found to be in a transient state in both space and time. The flow at higher swirl ratios has also been observed to lead to greater unsteadiness in flow. Moreover, the effect of roughness on the critical touchdown swirl ratio was also investigated, and increasing roughness length was found to increase the critical touchdown swirl ratio and vice-versa.