Numerical Study on Effect of Secondary Surface on Rectangular Vortex Generator

One way of achieving higher efficiency in electro-mechanical is by inducing vortices over the heated surface with the help of a vortex generator (VG). The strength of these vortices is proportionate to the amount of heat transported. In this paper, the evolution and propagation of the produced primary vortex behind a VG with the attached secondary surface (SS) are studied experimentally and numerically. The addition of SS is found to augment heat transfer significantly with an additional drag. The obtained experimental results complement the numerical predictions for the modified VG. Linear regression analysis is performed to optimize the geometry of SS for a higher heat extraction rate and lower drag. The SS placed at an optimum location increases the Nusselt number on the heated plate by 8.9%, with a decrement in the drag by 3.2%, compared to the reference case. The addition of SS produces a vortex of higher strength and propagates downstream at a slower rate. Moreover, it exposes the vortex to higher shear in the flow, which in turn enhances the heat transfer rate.