candlerg

Hypersonic flight in the atmosphere is starting to become a reality. One of the key outstanding issues in the development of hypersonic flight systems is the lack of understanding of the process of how the flow field transitions from a smooth laminar state to a turbulent state. This process is critical, because the aerodynamic heating and drag increase significantly when the boundary layer becomes turbulent. Over the past several years, the Candler research group has been developing the capability to simulate the transition process using stability theory, methods from linear systems analysis, and large-scale direct numerical simulations. The work has now progressed to the state that they can run very large simulations on the MSI supercomputers to support several funded research projects. The focus of the work being performed at MSI is direct numerical simulations; these require large grids and must be integrated for an extended time period. These simulations provide a complete picture of the transition process, and can be applied to realistic flight configurations. For example, the simulations have identified for the first time a leading-edge instability process that is driven by strong cross flow effects on swept leading edges. The envisioned simulations will be used to help support an AFOSR-funded sounding rocket flight experiment and to provide exact data for comparison with novel linear stability analysis approaches.