Dissimilar heat transfer enhancement by a vortex tube introduced in plane Couette flow and its realization mechanism

Abstract

The purpose of this study is to find what kind of vortices should be introduced in order to enhance dissimilar heat transfer and to interpret its physical mechanism. We carry out a direct numerical simulation on heat and momentum transfer by a vortex introduced into plane Couette flow. The parameters in this system are the Reynolds number, the initial circumferential velocity, the position, the radius and the inclination angle of the vortex. For dissimilar heat transfer enhancement, if a strong vortex can be generated, a spanwise-oriented anti-cyclonic vortex should be introduced, otherwise, a spanwiseoriented cyclonic vortex should be introduced. The reason why the cyclonic (or anticyclonic) vortex realizes dissimilarity is that the streamwise pressure gradient and the streaklines intensify the difference between the temperature and the streamwise velocity in the upper and lower (or downstream and upstream) regions of the vortex, which makes the Reynolds stress dominate over the turbulent heat flux.