Wall Image Velocimetry through deviation of temperature disturbances transport from Taylor hypothesis

Abstract

In this paper the feasibility of a strategy to retrieve quantitative estimations of the skin friction t is reported. The strategy grounds on the measurement of the propagation speed UT of temperature disturbances Tw very close to the surface of a slender body, as obtained by means of a Temperature Sensitive Paint. Here we shortly report about relationships between speed of convection of disturbances of different fluid dynamic quantities, as retrieved from literature and about a Taylor-Hypothesis-based, physically motivated way to extract an average convection velocity from time histories of Tw maps. Then, results in terms of streamwise component of friction velocity and friction coefficient are presented for the suction side of a NACA 0015 hydrofoil model at a Reynolds number Re = 1:8 × 105 and Angles of Attack AoA = [1◦;3◦;5◦;7◦;10◦]. The profiles of time and spanwise averaged friction coefficient Cf(x) are proposed and commented. Time averaged maps (i.e. streamwise and spanwise averaged distributions) of ut are reported and commented as well.