The HyperCAT (Hypersonics) Lab

Welcome to the HyperCAT Lab

HyperCAT stands for Hypersonic Computational AeroThermodynamics.  The main goal is to develop computational methods that provide consistently accurate results for aerothermodynamic loading (i.e., surface pressure, heat transfer, and skin friction) at hypersonic speeds. 

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About the Lab

The recent reinterest in developing hypersonic vehicles around the world for both air and space purposes brings back attention to the prediction of aerothermodynamics loads.  The accurate prediction of the loads especially in the regions of shock wave boundary layer interactions is very important.  A sharp increase in surface pressure and heat transfer in a small region over the surface may occur due to the interaction of shock waves and boundary layer interaction.  Accurate prediction of the sudden rise is necessary to avoid structural failure.  One sample of a such disaster is the structural failure of X-15 (see figure).   

Despite several decades of work in this area, the consistently accurate prediction of the loads has not been achieved yet.  In this lab, our main goal is to find computational methods/models that provide consistently accurate predictions of aerothermodynamic loadings.  The physics involved in such a problem is so complicated that there is a need to divide the problem into several categories including laminar/transitional/turbulent and perfect gas/thermally perfect gas/non-equilibrium gas/reactive gas.  In this lab, we mainly work in the following categories to separate the problems associated with turbulent flow from the non-equilibrium modeling of the flow:

• Laminar Non-equilibrium Shock Wave Boundary Layer Interaction: In this category, we try to achieve the most appropriate modeling of the non-equilibrium properties of the gas including vibrational-translational energy transfer, vibrational-vibrational energy transfer, thermochemical reactions, etc.  The main point is that we do not need to include the most sophisticated model possible.  We need models accurate enough to be able to achieve the required accuracy of the aerothermodynamic loading in the shortest possible time.
  
• Perfect Gas Turbulent Shock Wave Boundary Layer Interaction:  In this category, the main goal is to find the appropriate method to solve the turbulent flow near the cold wall.  Cold walls are typical of hypersonic flows.  Due to the cold wall, there is a large temperature gradient near the wall.  This large temperature gradient prevents most of the current methods from achieving accurate results in hypersonic flows.  For example, RANS models cannot provide consistently accurate results for aerothermodynamic loadings of hypersonic shock wave boundary layer interactions. Other possible methods are Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS).  Due to the computationally expensive nature of DNS, we are working to make an LES method that is capable of consistently accurate prediction of aerothermodynamic loading in hypersonic flows.  We have developed a recycling-rescaling method named Ht&p that is capable of providing correct turbulent properties for such a large temperature gradient.  Our current work is to examine and perfect this model to be able to achieve the consistently accurate prediction of aerothermodynamic loadings.