Continuing Challenges in Physico-Chemical Modelling for Hypersonic CFD

The rapid and significant advances in computational power both in terms of hardware and software in recent years and the resurgence in 1980's of interest in future concepts for hypersonic transportation systems have identified CFD as an important and indispensable tool for R & D in the field. To take advantage of this valuable tool for reliable simulations and predictions one must pay careful attention to the quality and validity of the modelling inputs that go into the development of the CFD codes while striving to improve their numerical accuracy and algorithmic efficiency. Whereas the CFD has made significant progress in speed and scope for numerical analysis of the larger and more complex PDE systems needed for treating relevant hypersonic flows, the earlier state-of-the art conventional physico-chemical models and input data have shown the need for further improvements. Some of the 'rate-limiting' steps in achieving predictive capability via CFD are related to inadequacies in the physico-chemical models and associated data used in describing the multi-species high-temperature chemically reacting gas flows occurring in and around hypersonic vehicles. Some of these continuing modelling challenges are briefly reviewed here with typical examples from current literatur