CASCADE TECHNOLOGIES INC — Department of Defense STTR Phase II: ABSTRACT: Predicting the wall heat loading experienced by hypersonic vehicles during the

Description

ABSTRACT: Predicting the wall heat loading experienced by hypersonic vehicles during the transition from laminar to turbulent boundary layer flow is the grand-challenge tackled by the present proposal. Previous studies have not focused completely on this phenomenon. In this work we adopt high-fidelity numerical simulations (Direct Numerical Simulation, DNS) to shed some light on the problem, with the objective of obtaining a detailed statistical description of the physical phenomena relevant to the transitional region. The focus is on the dynamics of large-scale structures and the turbulence characteristics in this highly intermittent region. In Phase I we demonstrated, the existence of a potential flow mechanism for the local overshoot behavior. The overall goal of the project is to develop a physics-based engineering model that correctly represents the heating profile during transition. This model aims at directly representing the modified turbulent energy redistribution process that is active in the transitional region due to highly non-equilibrium effects. DNS computations will provide insight into the transition region, by identifying the connection between wall heating peaks, localized Reynolds stresses and coherent vortical structures. preliminary engineering model developed for the flow over a flat plate will further be tested, and extended. BENEFIT: The outcome of the project is an add-on tool that will be implemented seamlessly within commercial CFD environments and can , therefore, directly be used by designers and analysis. The effort of establishing cause/effect relationships that lead to the heat-transfer overshoot within the transition region, and the subsequent validation of the predictive capabilities, will also offer confidence regarding design choices.