In-Flight Measurements of Freestream Atmospheric Turbulence Intensities

Abstract

The last key to implementing laminar flow control on swept-wings is controlling the crossflow instability. One promising technology is spanwise-periodic discrete roughness elements (DREs). Previous work has shown success with applique DREs and extending the region of laminar flow. This work seeks to extend the DRE technology to include dielectric barrier discharge plasma actuators as well as recreate past experiments with applique DREs.

One major need in implementing DREs and controlling crossflow is attaining an accurate measurement of the freestream atmospheric turbulence intensities. Knowing the atmospheric turbulence intensity will allow for comparing wind tunnel experiments to the flight environment and help produce better wind tunnel experiments by allowing them to better match the flight environment. Also, knowledge of the turbulence intensity at the specific instance of an experimental data point will allow for determining if differences in experimental results are the result of a difference in turbulence intensity. It has been determined through this work that the levels of freestream turbulence range from 0.023% - 0.047% with an average of 0.035%. These levels were reached through the use of temporal correlations to remove electronic noise as well as acoustic sound from the hotwire measurements and hence are lower than previously calculated.