Indirect measurement of free-stream turbulence level in wind tunnels

Abstract

In this study we investigate the possibility of predicting the free stream turbulence levels by an indirect measurement. The main motivation for this is that in some wind tunnels direct hot wire measurements are not possible and there is a need to measure the turbulence levels in these wind tunnels. We constructed a flat-plate model with a 6:1 ellipse as a leading edge and place it inside a wind tunnel. Inside the wind tunnel the turbulence was produced by one of three different perforated grids, with different holes and mesh sizes. The free-stream turbulence conditions were documented for the three grids in terms of the total r.m.s. and spectra of stream wise velocity fluctuations. The response of the boundary layer near the leading edge was then measured through wall-normal profiles of the mean and r.m.s. velocity fluctuations. We find a linear input-output response of the Klebanoff mode amplitude with the free-stream turbulence level. © 2019 Elsevier B.V., All rights reserved.