The temperature field above a concentrated heat source on a vertical adiabatic surface

This investigation presents detailed measurements of the laminar temperature field above a highly localized heat source on an instrumented, transparent, vertical adiabatic surface in water. This flow situation is particularly complicated because it is three-dimensional. Small diameter thermocouples were used to measure both the surface temperature variation and the temperature profile in the fluid above the heat source for a range of heat flux. In addition, a Schlieren system was used to visualize the spanwise and normal thermal boundary layers. The downstream growth of the spanwise boundary layer was found to be relatively weak (proportional to x ^{1 5}), while the boundary-layer thickness normal to the surface above the source was found to increase linearly with downstream distance, x. By comparing these results to those of the well-known point and line source plumes, we conclude that this preferential growth is attributed to the effect of the surface on the entrainment of ambient fluid. Our measurements indicate that the surface temperature above the source decays proportional to x^-0.77. This is between the x-independence found for a point source plume (x^-1) and a line source of heat on an adiabatic surface (x^{- 3 5}). Appropriate scaling functions were also determined which collapse measured temperature data for various heat flux and location to a single curve.