Flying-Hot-wire Study of Flow Past an NACA 4412 Airfoil at Maximum Lift

Abstract

Hot-wire measurements have been made in the boundary layer, the separated region, and the near wake for \nflow past an NACA 4412 airfoil at mad mum lift. The Reynolds number based on chord was about 1,500,000. \nSpecial care was taken to achieve a two-dimensional mean flow. The main instrumentation was a flying hot wire; \nthat is, a hot-wire probe mounted on the end of a rotating arm. The probe velocity was sufficiently high to avoid \nthe usual rectification problem by keeping the relative flow direction always within a range of ± 30 deg from the \nprobe ads. A digital computer was used to control synchronized sampling of hot-wire data at closely spaced \npoints along the probe arc. Ensembles of data were obtained at several thousand locations in the flowfield. The \ndata include Intermittency, two components of mean velocity, and twelve mean values for double, triple, and \nquadruple products of two velocity fluctuations. No Information was obtained about the third (spanwise) \nvelocity component. An unexpected effect of rotor interference was identified and brought under reasonable \ncontrol. The data are available on punched cards in raw form and also after use of smoothing and interpolation \nroutines to obtain values on a fine rectangular grid aligned with the airfoil chord. The data are displayed In the \npaper as contour plots.