Spectral Measurements of the Wall Shear Stress and Wall Pressure in a Turbulent Boundary Layer: Theory.

摘要

Two derivations are presented which are pertinent to the experimental measurement of turbulent wall shear stress, using flush mounted hot film sensors. The first, a steady state heat transfer analysis, is necessary in order to determine the thickness of the thermal boundary layer that developed over the hot film. The fundamental validity of the use of hot film sensors to measure the wall shear stress depends on the thickness of the thermal boundary layer relative to the thickness of the viscous sublayer in the turbulent boundary layer. The second derivation involves an unsteady heat transfer analysis, which is necessary in order to determine the frequency range over which the fluctuating wall shear stress may be accurately resolved. Keywords: Turbulent boundary layer; Wall pressure fluctuations; Wall shear stress fluctuations. (jhd)