The effect of transverse plate vibration on the mean laminar convective boundary layer heat transfer rate

Abstract

Heat transfer experiments were conducted to ascertain the effects of transverse plate vibration on the local heat transfer rate, that is, the local Nusselt number. The nominal mean free-stream velocity for the main results presented in this paper is 4 m/s, giving a Reynolds number range up to 2.5 × 10 5. The plate vibration frequency is 60 Hz, and the typical plate vibration level at the excitation point of the heat transfer test plate ranges from 1.7 to 12 mm/s (peak). The effect of the plate vibration on the heat transfer is attributed to the stability characteristics of the induced boundary layer velocity oscillations. A detailed flow-field investigation indicates that the induced velocity oscillations in the laminar boundary layer are unstable. It is the nonlinear development of these unstable velocity oscillations and the resulting laminar-turbulent transition that produces an increase in the local heat transfer rate. The local heat transfer augmentation is in some cases as large as 290%. It is observed that at low levels of plate vibration the rate at which the local heat transfer increases with respect to the downstream direction is large and that the local heat transfer augmentation occurs mainly in the downstream region of the test plate. As the level of plate vibration is increased, the rate at which heat transfer increases with respect to the downstream direction is reduced, but the starting point at which heat transfer augmentation begins is moved upstream.