Numerical and Experimental Study of Microvortex Generators

Abstract

A series of experimental and computational studies was conducted on vane-type microvortex generators (MVG) with the aim of better understanding the behavior and to improve the design of such devices. The traditional rectangular and triangular vanes along with unique NACA0012 and E423 airfoil-shaped vanes were studied with a height of while being embedded in a turbulent boundary layer of a flat plate. To assess the reliability of the numerical prediction of the drag forces acting on an MVG, a wind tunnel experiment was conducted. The experiment was conducted at a Reynolds number of 155, based on the friction velocity and the MVG height. A very good agreement was found between the experimental and numerical drag predictions for the MVGs with strong vortices. Fair agreement was found for the two MVGs with weak vortices. From the four specified vane-type MVGs, the best performing MVG configuration was sought by looking at the ratio of the vortex’s circulation strength to the drag of the MVG vanes. It was found that triangular vanes had the best ratio and NACA0012-shaped vanes had the second best ratio. With alternation of the vane angle, vanes placed at angles of 18–20 deg had the best ratio. To supplement the performance study, the effect of the Reynolds number on the MVGs was also considered. A rectangular MVG vane was modeled at Reynolds numbers of 90 to 1150. A logarithmic relation was found between the Reynolds number of the MVG and the generated vortex’s circulation and the drag of the MVG.