Numerical study of microjet and heat flux effects on flow separation and heat transfer over a ramp

Abstract

The control of flow and heat transfer has recently been of great interest to engineering researchers in light of computational technology advances. Microjets are used as control solutions to avoid flow separation and increase heat transfer. The present study evaluates a microjet over a ramp at microjet velocity ratios (jet to inflow velocity) of V jet / U 0 = 1, 2, and 4 and heat flux ratios (heat flux to based heat flux) of q s / q 0 = 1, 2, and 3 to examine the flow separation area and heat transfer improvement numerically. The numerical velocity and temperature gradients were compared to earlier numerical and experimental works. Then, the flow over the ramp was analyzed at the aforementioned microjet velocity and heat flux ratios. Moreover, streamlines, bed pressure, fluid temperature, and bed Nusselt number were evaluated. It was found that a microjet with the optimal velocity could not only diminish the separation bubble but also improve heat transfer. A rise in the velocity ratio from 2 to 4 led to a nearly 33% decrease in the separation bubble and an approximately 20% rise in the Nusselt number. In addition, the microjets enhanced heat transfer by up to 50%.