Experimental study of fluid flow and heat transfer of jet impingement in cross-flow with a vortex generator pair

Abstract The present paper investigates the fluid flow and heat transfer behaviors of jet impingement in cross-flow modified by a vortex generator pair (VGP). The velocity of the jet is kept at 12 m/s and that of the cross-flow is varied between 5 m/s and 8 m/s. The spacing between the jet and target surface is 4 times the jet diameter. Particle Image Velocimetry (PIV) and Liquid Crystal Thermography (LCT) are used to measure the flow field and heat transfer, respectively. The interaction of the cross-flow and jet produces various vortices, and the jet is shown to be deflected downstream by the cross-flow. The streamwise velocity of the jet increases with the cross-flow while the wall-normal velocity and turbulent kinetic energy are reduced close to the target wall. The overall effect is to decrease the impingement heat transfer. The presence of the vortex generator pair decreases the cross-flow momentum and induces the downwash flow upstream, which is favorable for the jet penetration. Thus the jet has higher impinging velocity towards the wall with elevated turbulent kinetic energy. This explains the heat transfer enhancement of the jet impingement in cross-flow due to the VGP. When the height of the VGP increases, the positive influence on the impingement becomes more evident. It demonstrates that the heat transfer on the target wall is dominated by the wall-normal velocity of the impingement and the turbulent kinetic energy, rather than the streamwise velocity along the cross-flow direction. The combined experimental results of the fluid flow and heat transfer can also be used for validating and improving numerical simulation methods.