Transient Thermal Response of Turbulent Compressible Boundary Layers

A general numerical method is developed with the capability to predict the transient thermal boundary layer response under various flow and thermal conditions. The transient thermal boundary layer variation due to a moving compressible turbulent fluid of varying temperature was numerically studied on a 2-D semi-infinite flat plate. The Reynolds-averaged boundary-layer equations are solved based on the compressible Falkner-Skan transformation. Turbulence is modeled using a two-layer eddy-viscosity model developed by Cebeci and Smith, and the turbulent Prandtl number formulation originally developed by Kays and Crawford. The governing differential equations are discretized with the Keller-box method. The numerical accuracy is validated through grid independence studies and comparison with the steady state solution. In turbulent flow as in laminar, heat transfer coefficient is initially very different from that obtained from quasi-steady analysis. It is found that, both the transient time scale and the magnitude of the transient heat transfer coefficients differ significantly between turbulent and laminar flow. The more complex variation of transient heat transfer rate in turbulent flow is evident, and needs further study.