Ultrasonically Absorptive Coatings for Hypersonic; Final rept

摘要

Laminar flow control (LFC) technologies reduce heat-transfer rates as well as the weight and complexity of thermal protection system (TPS). The laminar run can be substantially increased using an ultrasonically absorptive coating (UAC). The project is focused on maturing of the UAC-LFC methodology. Key components of the effort include wind-tunnel experiments, theoretical analysis, direct numerical simulation, fabrication and testing of ceramic materials that integrate UAC and TPS functions. To aid in the design of UAC with regular microstructure to be tested the CUBRC LENS I tunnel, parametric studies of the UAC-LFC performance have been conducted. The UAC parameters providing significant (more than twice) increase of the laminar run were predicted. Our theoretical model dealing with UAC of random microstructure has been refined. Direct numerical simulation of UAC roughness and pore-end effects has been started. A method of ceramic UAC fabrication was formulated and first ceramic UAC samples were made. An apparatus for benchmark measurements of UAC ultrasonic absorption was assembled and its robustness was demonstrated at low ambient pressures relevant to high-altitude flight conditions. The cone model with the felt-metal coating has been prepared for transition experiments in the ITAM AT-303 tunnel at Mach=8. The UAC-LFC technology is now approaching the large-scale demonstration stage in the CUBRC LENS tunnel as well as fabrication of ceramic UAC samples integrated into TPS.