Flow field properties local to near-wall shear layers in a low Reynolds number turbulent boundary layer

Abstract

Combined hot-wire anemometry and flow visualizations are used to explore the properties of near-wall shear layers in a low Reynolds number turbulent boundary layer (Rθ= U∞ θ/ ν ≅ 1200). The experiments employed two four-element probes positioned in the buffer layer. Data from these sensors were acquired synchronously with high speed, dual view, 35 mm movies of vaporized mineral oil fog illuminated via two orthogonal laser sheets. Near-wall shear layers were identified as satisfying the visual criterion of a narrow fissure of passive marker moving upward through the buffer layer in concert with a strong deceleration in the axial velocity trace. The present results reveal that the local flow f..