The effects of freestream turbulence on airfoil boundary layer behavior at low Reynolds numbers.

Abstract

An experimental study was conducted to determine the effects of freestream turbulence on airfoil boundary layer behavior. Freestream turbulence intensity levels up to approximately 4% and length scales up to approximately two inches were generated using turbulence-generating grids. Data were collected using a single-wire hot-wire probe in conjunction with a three-dimensional traversing system. Increased levels of freestream turbulence were found to cause correspondingly earlier transition to a turbulent boundary layer. Boundary layer growth was found to be unaffected by freestream turbulence levels up to 4% at length scales an order of magnitude greater than the boundary layer thickness. For length scales on the order of boundary layer thickness, a 12% increase in the turbulent boundary layer thickness was found with an increase in turbulence intensity from 0.23% to 0.5%.