Motion and heat transfer in the Blasius flow containing a pulsating component

Abstract

Studies are made of the unsteady flow and heat transfer characteristics in the laminar boundary layer about a flat plate when the oncoming free stream contains a pulsating component. The complete, unsteady, boundary layer equations are solved by using a recently-developed numerical solution procedure. A wide range of the two key external parameters in the free stream, i.e., the applitude of pulsation, A, and the frequency parameter α [ ωx ∗/U e ], is dealt with in the present numerical computations. Comprehensive and systematically organized numerical computational results have been acquired, providing descriptions of the details of unsteady flow and thermal fields. The present numerical results indicate consistently with the available data based on the previous linearized analytical predictions in the limits of α ⪡ 1 and α ⪡ 1. When the frequency parameter α is small, the flow in the entire depth of the boundary layer exhibits a phase lead over the oncoming free stream. The present computational results supply the details of the behavior of flow and skin friction in the range of intermediate values of α and for finite values of A. The thermal structure is scrutinized by using the computed results. The mean temperature field is found to be substantially unaffected by the presence of the pulsating component. For small values of α, both the skin friction and heat transfer are in phase with each other. However, as α increases, the conventional Reynolds analogy is shown to be inapplicable.