Enhanced energy dissipation rates in laminar boundary layers subjected to elevated levels of freestrearn turbulence

Enhanced energy dissipation rates in laminar boundary layers subjected to elevated levels of freestream turbulence are investigated for zero pressure gradient flow with freestream turbulence intensities ranging from 0.2% to 7%. The freestream turbulence markedly changes both the mean and fluctuating velocity distributions resulting in increased energy dissipation rates per unit area by up to 34%. A shortcoming of current numerical and analytical techniques is the inability to accurately predict this increased energy dissipation. A new correlation, based upon experimental measurements using the hotwire technique, has been developed to account for this increased rate of energy dissipation. The correlation developed implements the momentum thickness Reynolds number and turbulence intensity at the leading edge to capture the enhanced energy dissipation rates due to elevated freestream turbulence intensity in the laminar boundary layers investigated. The correlation is then applied to well-known flat plate test cases and good agreement is found. (c) 2006 The Japan Society of Fluid Mechanics and Elsevier B.V. All rights reserved.