Experiments on the Combined Effects of Roughness and Momentum Injection on Turbulence over an Ablative Thermal Protection System

With the retirement of the shuttle program, and the subsequent development of the commercial space industry, research in space technology is experiencing resurgence. Newly designed crew capsules, such as Orion CEV, require the use of Thermal Protection Systems and with the aid of computer simulations and advances in material sciences it is now possible to drastically reduce the weight and increase the lifecycle of these vehicles. But, due to the inherent complexity of modeling the flow physics of a re-entry vehicle, it is becoming more necessary for experimental data to aid in our understanding of the flow phenomena surrounding re-entry vehicles. The educational research interest area discussed will be a direct study of these phenomena and can be used to aid in the development and design of new heat shields as well as provide excellent research experience to the student. The research will experimentally investigate the flow phenomena associated with a Thermal Protection System (or TPS). This research will have several objectives, namely, to increase the fundamental understanding of ablative TPS by replicating the combined effects on the near-wall turbulence of the roughness of the ablative surface and the emission or blowing of fluid from a surface. In addition, the student will gain useful insight into the design principles behind TPS. The information gained from this study can then be used to improve modeling of the TPS flow physics. This project intends to use lab facilities available at the University of Kentucky to expand upon ongoing research into the flow physics involved with TPS. These specialized lab facilities will be adapted to provide more detailed data on the near-wall flow physics than is currently available. Furthermore, an in-depth analysis of the data will be completed in order to provide relevancy to our understanding of both turbulent flow structures and its applicability to TPS design. The first component of this research will involve expanding on research currently being undertaken in the University of Kentucky Turbulent Channel Flow Facility (TCFF). This facility has been specifically designed to produce 2-D, plane, turbulent flow and is ideal for the study of turbulent boundary layers. The TCFF has been outfitted with a flow injection device over its test section which will inject air into the TCFF test section through a wavy surface. Using hot-wire anemometers (HWA), which are capable of measuring the streamwise velocity component, and Particle Image Velocimetry (PIV), which can capture the velocity field of an entire area, data will be gathered on the flow field. It is also desired to replicate the actual surface roughness of a physical TPS by altering the surface roughness in the TCFF test section with a scaled TPS surface. This will allow further investigation of the turbulent flow structure near the wall, and provide data which will be useful for producing more accurate numerical simulations of heat shields. It is further suggested that this research be continued in a compressible flow facility, which will further aid in advancing the state of the art. The proposed research area accomplishes two objectives: to provide new and relevant data to NASA designers and researchers and to provide invaluable research experience to the student in an area of interest to the student. The nature of the research is such that preceding work in the specific area of interest is relatively small. Thus, possibilities of continuing studies (beyond the scope of this application) are numerous and very applicable to future research and design projects involving turbulent flow structures and TPS development. More »