抄録
Heat transfer performance is investigated in a channel with a delta wing-type vortex generator (VG) installed in laminar and turbulent flows. It was shown from numerical results that the turbulence promoted by VG enhances the heat transfer more effectively than the Reynolds stress in the laminar flow. In the separation region of VG wing, negative velocity fluctuation is transferred by the downwash, which causes negative Reynolds stress. On the other hand, the temperature fluctuation is still positive because of the difference between vector and scalar quantities. The dissimilarity between momentum and heat transfers observed in the rear side of VG influences the high heat transfer performance with low drag penalty in the laminar flow. While in the turbulent flow, the Reynolds stress overcomes the turbulent heat flux in the downstream of VG, because the negative velocity fluctuation in the core of longitudinal vortex is swirled up by the induced vortex motion. This negative dissimilarity leads to a poor performance compared with the laminar flow. The effect of a punch hole beneath the wing is discussed numerically. The results showed a little poor heat transfer performance as compared with the channel with a punch hole, since the swirling up of negative velocity fluctuation mentioned above is intensified by stronger longitudinal vortices.
