Analysis of Air Vortex Interaction with Porous Screens

This work studies a model of air vortex flow propagation through porous screens. In experimental investigation, a new and unique apparatus is constructed and used for velocity measurements and visualization of the interaction of air vortex with porous screens. A custom-made, high-precision vortex generator provides a variety of velocity profiles for vortex flow generated with an unprecedented level of precision. The flow fields are captured by using a fog generator and a high-speed CCD camera. The porous screens are constructed out of acrylic rods with various orientations and porosity from rod separation. A variety of parameters are set to be control groups, including porosity of porous screens ($\varphi =0.3-0.8$) and Reynolds number of vortex ring ($Re=700-3000$). The results in experimental tests show the effect of porosity and air injection velocity on the behavior of air flow (separation, accumulation), and the transport phenomena of vortex flow while interacting with porous screens.

In numerical study, two models of free vortex ring generator are designed and compared. Experimental setup and conditions are reproduced in two-dimensional numerical model. The goal to develop the numerical model is for obtaining variation of kinetic energy and vorticity of flow which are hard to measure experimentally. Besides porosity of porous screen and injection Reynolds number of vortex ring, more parameters are compared and analyzed, including the distance between vortex ring generator and porous screens ($L=50-150mm$) and diameter of vortex ring generator ($Dp=20-50mm$). The results from simulation model is validated by comparing its vortex ring features to those produced in experiments.