Fundamental Studies of Surface Roughness and Ablating Flows
Start Date
2-3-2011 1:55 PM
Description
National interest in hypersonic flight provides the motivation to develop closure models for high-speed turbulent boundary layer flows with mechanical, thermal and chemical non-equilibrium effects. Our approach toward developing the required models is based on algebraic truncations to the second-order turbulent transport equations, which include non-equilibrium effects. One of the major challenges associated with developing these models is a lack of experimental information to verify assumptions and validate performance. In this presentation, we will describe (1) the results from a series of experimental studies focused on providing improved understanding of the effects of roughness on the structure of the turbulent boundary layer and (2) plans for upcoming experiments characterizing heat transfer and surface ablation. For the roughness studies, high-fidelity experimental characterizations of the turbulence response to both global and local non-equilibrium were performed at Mach 3.0 and 5.0 using particle image velocimetry. These studies are providing new insights into the fundamental differences between supersonic and subsonic mechanical non-equilibrium flows, as well as guidance for assessing turbulence model applicability. A large part of our recent efforts have focused on developing new laser based diagnostics and hypersonic facilities to extend our experimental methods to include flows with ablation. Specifically, we have developed a new diagnostic to enable temperature, velocimetry and concentration measurements. In this presentation, we will discuss our approach and show representative results.
Fundamental Studies of Surface Roughness and Ablating Flows
National interest in hypersonic flight provides the motivation to develop closure models for high-speed turbulent boundary layer flows with mechanical, thermal and chemical non-equilibrium effects. Our approach toward developing the required models is based on algebraic truncations to the second-order turbulent transport equations, which include non-equilibrium effects. One of the major challenges associated with developing these models is a lack of experimental information to verify assumptions and validate performance. In this presentation, we will describe (1) the results from a series of experimental studies focused on providing improved understanding of the effects of roughness on the structure of the turbulent boundary layer and (2) plans for upcoming experiments characterizing heat transfer and surface ablation. For the roughness studies, high-fidelity experimental characterizations of the turbulence response to both global and local non-equilibrium were performed at Mach 3.0 and 5.0 using particle image velocimetry. These studies are providing new insights into the fundamental differences between supersonic and subsonic mechanical non-equilibrium flows, as well as guidance for assessing turbulence model applicability. A large part of our recent efforts have focused on developing new laser based diagnostics and hypersonic facilities to extend our experimental methods to include flows with ablation. Specifically, we have developed a new diagnostic to enable temperature, velocimetry and concentration measurements. In this presentation, we will discuss our approach and show representative results.