Velocity and turbulence characteristics of a semiconfined orthogonally impinging slot jet

An experimental investigation to determine velocity and turbulence characteristics of a semiconfined (where the nozzle is integral to a confinement plate) impinging slot jet has been undertaken. Jet nozzle to impingement plate spacings of 4 and 9.2 jet widths, at a Reynolds number of 20,000, were considered in detail. Measurements parallel to the impingement plate were made by using hot-wire anemometry, up to 9 jet widths from the axis and across the jet plane, to document the jet exit conditions and jet development. Measurements show that the potential core of the jet is longer for the semiconfined configuration when compared with the unconfined, owing to limited entrainment and spreading of the jet. In the impinging jet, velocity and turbulence data were related directly to heat transfer. Low levels of turbulence observed in the stagnation region and its subsequent development in the wall jet suggest that transition to a turbulent wall jet occurs when the impingement plate is placed within the potential core of the jet. This coincides with the development of secondary maxima in heat transfer. When the impingement plate is placed in the developing jet, heat transfer decreases monotonically along the plate, and the data show that the jet is effectively turbulent at the stagnation point. (C) Elsevier Science Inc., 1997.