Fluid Dynamic Seminar

Abstract:

The accurate prediction of laminar-turbulent transition in the boundary layer is a critical step in the design of hypersonic flight vehicles. Depending on the type of vehicle and its mission, the temperature inside the boundary layer on the vehicle surface may be very high owing to a conversion of kinetic energy into thermal energy. In comparison to laminar flows, turbulent flows induce much higher thermal load on the surface of vehicles moving through a planetary atmosphere at high speed. As a result of the high temperature, chemical reactions may occur and change the composition of the gas, leading to non-ideal gas effects. Moreover, the surface of hypersonic flight vehicles may not be smooth but contain localized roughness, which alters the transition process. Several fundamental physical processes related to laminar–turbulent transition and hydrodynamic instability in high-speed boundary layers are not yet understood. Both roughness effects and effects related to chemical reactions on laminar-turbulent transition will be discussed.