Abnormal enhancement of separated turbulent air flow and heat transfer in inclined single-row oval-trench dimples at the narrow channel wall

Abstract

Abstract New shapes of surface vortex generators are proposed which allow improving the energy performance of channels of propulsion devices and contribute towards the safety of space flights. Abnormal enhancement of heat transfer and separated turbulent air flow in oval-trench dimples of depth 0.3 inclined at an angle of 45о to the incoming flow and located in-line at the heated wall of the narrow channel is accompanied by a four-fold growth of relative negative friction and an almost five-fold increase of relative heat transfer in the separation zone. At the same time, a maximum secondary flow velocity in the vicinity of the dimple reaches a maximum flow velocity in the plane-parallel channel. A reason for the onset of this phenomenon (ultra intensification of transport processes) caused by the formation of a high pressure drop between closely spaced stagnation zones on the windward side of the dimple and a low pressure on the entrance spherical portion of the dimple is disclosed.