International Journal of Heat and Mass Transfer, Vol.47, No.8-9, 1827-1845, 2004
An experimental study of fluid in an impinging mechanics and heat transfer slot jet flow
An experimental study of flow field, surface pressure, and heat transfer rates of a submerged, turbulent, slot jet impinging normally on a flat plate is presented. Two nozzle-to-surface spacings of 3.5 and 0.5 nozzle exit hydraulic diameters, which correspond to transitional and potential-core jet impingement, respectively, are considered. Fluid mechanical data include measurements of mean flow field and variance of normal and cross velocity fluctuations, mean surface pressure, and RMS surface pressure fluctuations along the nozzle minor axis. Local heat transfer coefficients are calculated from detailed surface temperature measurements. The heat transfer data follow a trend similar to previous studies, exhibiting high heat transfer rates in the impingement region for transitional jet impingement, and a non-monotonic decay in heat transfer coefficient for potential-core jet impingement. The fluid flow results indicate that past impingement, locations of high streamwise fluctuating velocity variance occur in the wall jet flow for both nozzle spacings. The RMS surface pressure fluctuation profile exhibits a maximum at the impingement line for the transitional jet impingement, and corresponds well with the rise in near-wall velocity fluctuation variance in the free jet prior to impingement. For potential-core jet impingement, the streamwise location of peak RMS pressure fluctuations corresponds to the highly correlated turbulence in the outer region of the wall-bounded flow. Further, there is a good correspondence between the locations of secondary peak in heat transfer and near-wall streamwise fluctuating velocity variance. The occurrence of the outer peak prior to the near-wall peak in streamwise velocity variance for the potential-core jet impingement suggests that the interaction between correlated motion in the outer region and near-wall turbulence causes the rise in heat transfer coefficient towards a secondary peak. (C) 2003 Elsevier Ltd. All rights reserved.