Innovative Methods for Parametric Bleed Pattern Variation in Wind Tunnel Models

ABSTRACT: A research effort to investigate innovative approaches to rapid and simple variation of bleed patterns in high-speed inlet wind tunnel models is proposed. Variation of inlet bleed patterns in high-speed wind tunnel models are typically implemented by selectively filling or opening holes in plates that incorporate large arrays of bleed holes. Holes are filled with plaster or other substances, which can be labor-intensive and require significant facility down-time to accomplish. The proposed effort will identify new approaches to vary inlet bleed pattern. Innovative hole-filling materials will be investigated, with the goal of ease of application and short cure times. The use of additive-manufacturing techniques to fabricate easily-installed bleed surfaces is also proposed. Finally, mechanically-actuated parametric bleed variation concepts will be developed. The objective will be to identify a system that will allow remotely-variable actuation of the bleed pattern, while introducing minimal additional complexity to the test hardware. Following a review with AFRL, one or more approaches will be selected for further development in a Phase II effort, and conceptual design approaches to implementing the chosen concepts in a selected research model and wind tunnel test facility will be developed. BENEFIT: Because development of an effective bleed system is critical to the design of a viable high-speed inlet system, the ability to test multiple bleed patterns and configurations in an experimental research program is essential. As the cost of wind tunnel testing continues to rise, the potential benefits of reducing test facility occupancy time are becoming increasingly significant. In the past, varying inlet model bleed patterns has been time-consuming, since the state-of-the-art has been selective filling and/or opening of individual holes to change the bleed pattern. This approach typically requires facility down-time to make the change, and to allow for the filler material to cure. The development of rapid, simple approaches to bleed pattern alterations, while allowing variation and measurement of the amount of flow removed, will enhance the inlet technologists ability to develop an effective bleed system while reducing the time and cost of experimental research and development. The proposed technology will be useful to government agencies performing aerodynamic research on supersonic and hypersonic airbreathing propulsion systems (such as the Air Force, Navy, and NASA), as well as to U.S. aerospace companies developing high-speed aircraft for military and commercial use.