Experimental Investigation on the Near-ground Flow Structure of Buoyancy Induced Vortices

Abstract

This research focuses on the lower near-ground flow structure of buoyancy-induced vortices at laboratory scale for various swirl vane angles. The time-averaged velocity components are measured from both horizontal cross-sections and vertical planes above the ground plane using Particle Image Velocimetry (PIV) for one-cell, one to two-cell transition, and two-cell type vortices. The vortex wandering effect and a force balance analysis are also carried out based on the timeaveraged Navier-Stokes equations for different types of vortex structures. The results show that centripetal acceleration and radial pressure gradient are the primary contributors to the force balance near the ground. The results also reveal that vortices developed with 45° vane angle have the minimum wandering, corresponding to the minimum unsteady forces in both the radial and vertical directions.