Research

Research Agenda

Reliable predictions of complex physical systems of course requires mathematical models of the physical phenomena involved and the ability to generate accurate numerical solutions of the model equations. Perhaps more important, however is a systematic, comprehensive treatment of the calibration and validation of the models, as well as the quantification of their uncertainties. The PECOS center is dedicated to the development and deployment of advanced methods for calibration, validation and uncertainty quantification in complex multi-physics models. Furthermore, validation is the central issue because when uncertainty is considered, validation also involves the processes of calibration and prediction.  Therefore, the research and development at the PECOS center is directed at the “validation cycle,” in which validation failures are used to drive model development and the acquisition of new data.  All research activities at the center directly support the development, deployment or application of the validation cycle.

Overarching Application

A space capsule reentering the atmosphere, with relevant physical phenomena labeled.

The development of methods and tools for validation and uncertainty quantification is best pursued in the context of a complex multi-physics application, since this ensures that many of the challenges inherent in real applications will be addressed.  Furthermore, by addressing a problem of scientific and national interest, we have an opportunity to make meaningful advances in science by pursuing the application of validation and uncertainty quantification.

At the PECOS center, we have chosen reentry vehicles as the overarching target application for our efforts. A vehicle entering the atmosphere from space experiences an extreme thermal environment due to the very large velocities involved. The extremely high kinetic energy of the on-coming air (up to about 100MW/m²) is suddenly converted into thermal energy as the air passes through the bow shock. This raises the temperature of the air to as high as 20,000K, resulting in dissociation and possibly ionization of the air molecules. When this super-heated air flows over the vehicle, it results in very high heat transfer to the surface, requiring a thermal protection system (TPS) to ensure the survival of the vehicle, and we consider vehicles with an ablative TPS. Our interest is in the survival of the vehicle, so we consider the prediction of the consumption rate of the ablative TPS, and the peak heat flux to the vehicle. To predict these quantities, models of ablation, aerochemistry, hypersonic flow, thermal radiation and turbulence are needed.