Practical Experience With the Discrete Green’s Function Approach to Convective Heat Transfer

Abstract

The heat transfer from a short uniform heat flux strip beneath a turbulent boundary layer with and without freestream turbulence was measured using a liquid crystal imaging technique. Freestream turbulence intensities were on the order of 12 percent. Data were taken at momentum thickness Reynolds numbers on the order of 1000 and 2000 for the turbulent and steady freestreams, respectively. Heat transfer enhancement due to the presence of freestream turbulence was quantified in terms of the ratio of the average St’s on the strip: turbulent freestream divided by steady freestream. Compared to the baseline case of a uniformly heated surface upstream of the strip, the heat transfer enhancement decreased by 20 percent. The temperature distribution measured on and downstream of the heated strip represented one column of a discrete Greens function that was used to predict the heat transfer for any arbitrarily specified thermal boundary condition given the same flowfield. Predictions are compared against correlations and numerical predictions as well as data from the literature. The details and practical applications of this approach to handling heat transfer with non-uniform thermal boundary conditions are presented.