Measurements of skin friction and heat transfer beneath an impinging slot jet

Abstract

An experimental study was performed to measure skin friction and surface heat transfer for an orthogonal slot jet impinging on a flat plate. Surface pressure, total pressure, velocity profiles, skin friction and temperature distributions were obtained within twenty nozzle widths of jet centerline at a range of 20,000<Rej<36,000. Stanton gauge, and oil film methods were used to measure skin friction. Multiple micro-thermocouples attached to an iso-flux surface were utilized to acquire the target plate temperature distribution. The majority of the experimental data was taken at a nozzle-to-plate spacing of four nozzle widths where the jet was still within its potential core length. The local surface heat transfer and skin friction distributions showed local extrema that were not coincident, and whose behavior do not appear to be entirely consistent with hypotheses that attribute the secondary peak to laminar-to-turbulent transition of the surface layer. It is believed that these off center peaks occur as a consequence of enhanced turbulent momentum and heat transport in the wall-normal direction.