Effect of free-stream turbulence characteristics on boundary layer transition

Abstract

The present measurement campaign on the free-stream turbulence induced boundary layer transition scenario has provided a unique set of experimental data. This new set of data has the potential to enhance the understanding of the effect of the free-stream turbulence characteristic length scales on the transition location and not only the turbulence intensity, which has been the focus in most previous studies. Recent investigations where the turbulence intensity has been kept essentially constant, while the integral length scale has been changed, show that the transition location is advanced for increasing length scale. The present data confirms previous results for low turbulence intensities, but shows the opposite behavior for high turbulence intensities, i.e. that the transition location is advanced for decreasing integral length scales. Important to underline here is that the integral length scale has a relatively small influence on the transition location as compared to the turbulence intensity and data analyses are now directed towards enhanced understanding of how the different parts of the incoming energy spectrum affects the energy growth inside the boundary layer.