Low-dimensional dynamical characteristics of shock-wave turbulent boundary layer interaction in overexpanded conical nozzles
The proposed research aims to characterize the transient interaction between a shock wave and a turbulent boundary layer in a conical flow at various nozzle pressure ratios. In conical flows, the transient motion of the shock wave causes an asymmetric separation of the boundary layer resulting in unpredictable lateral forces and excessive thermal loads on the structure. Significant discrepancies between the dominant frequencies of the shock motion and the characteristic frequencies of the incoming turbulent boundary layer have been observed, suggesting that this interaction is non-linear. Higher-order stochastic models are thus necessary in order to fully characterize the mechanisms responsible for provoking an interaction between the shock wave and the turbulent boundary layer. The study will employ an experimental investigation of both the velocity field and the fluctuating wall pressure signatures in the vicinity of the shock wave and at various nozzle pressure ratios in a thrust optimized, parabolic contoured axisymmetric nozzle. Funding for this study is graciously provided by the Air-Force Office of Scientific Research under grant number: FA9550-11-1-0203, Dr. John Schmisseur, program manager.
Acoustic characterization of rocket engine ignition in an acoustically treated testing facility
During launch, space vehicles are subject to violent vibro-acoustic loads caused by the intense sound pressure levels and transient side-loads produced during rocket engine ignition. These loads are known to cause electronic and mechanical component failures, to increase the likelihood of fatigue failure on lightweight exterior structures such as aerodynamic fins and thermal protection systems, as well as produce adverse environmental conditions for vehicle occupants and payload. It is understood that performance increases of next generation sea-level rocket nozzles are strongly dependent on a reduction of these vibro-acoustic loads. The proposed research focuses on performing a series of high fidelity measurements on two pairs of nozzle test articles (TIC and TOP) provided by NASA Marshall Space Flight Facility (NASA-MSFC). The measurements comprise detailed surveys of the static and dynamic wall pressure along the interior surface of all four nozzles as well as the near far-field acoustics sampled along an array of microphones positioned within 20 nozzle exit diameters. The study is being conducted at The University of Texas at Austin’s (UT-Austin) new fully anechoic chamber and high-speed flow testing laboratory. Acoustic surveys are being performed in order to gather early information about the vibro-acoustical loads produced during Main Engine Ignition, (MEI). An accurate assessment of these signatures is important to developing reliable estimates of the side loads acting on the rocket nozzle during launch. Funding for this study is graciously provided by the Space Shuttle Main Engine Project, NASA Engineering and Safety Center, the Space Shuttle Loads Panel with Mr. Edward Burns as Technical Monitor. Research is being coordinated by Mr. Joseph Ruf in collaboration with members of the Nozzle Test Facility team at NASA Marshall Space Flight Center and NASA Johnson Space Center.
Toward Active Control of Noise from Hot Supersonic Jets
Noise generated by low bypass turbine engines is one of the most acute noise sources for the Department of Navy and contributes to noise-induced hearing loss for Navy personnel, structural degradation of airframes, and restrictions to maintenance, testing, and training schedules due to noise pollution of communities surrounding Naval installations. The proposed research aims to alleviate this technical deficiency through high fidelity characterization of heated, over-expanded supersonic jets. The research is being conducted in collaboration with Dr. Nathan Murray of the Jamie Whitten National Center for Physical Acoustics (NCPA) at the University of Mississippi, Dr. Brian Thurow of the Dept. of Aerospace Engineering at Auburn University and Mr. Neeraj Sinha of Combustion Research and Flow Technology, Inc. (CRAFT Tech). Funding for this project is graciously provided by the Office of Naval Research, ONR award number N00014-11-1-0752 with Dr. Joseph Doychak as technical monitor.
Acoustic and wake studies of scaled rotorcraft in forward and descent flight
The objectives of the proposed research are to quantify the relevant scaling parameters that will allow the acoustic and rotor wake characteristics of a full-scale main rotor to be accurately predicted from smaller (~%10), laboratory scaled systems. This will be addressed by establishing a comprehensive series of both near and far-field acoustics and PIV measurements of a 10% scaled main rotor during hover, forward flight and descent maneuvers. The scaled rotor will replicate key characteristics of a BO-105 main rotor, (rotating frequencies, solidity, blade loadings), so that the proposed test matrix can complement several existing databases such as the HART-II program (40% scaled BO-105 main rotor) and previous full-scale studies. While full-scale tests are still very much needed in order to alleviate uncertainties associated with Reynolds number and aeroelasticity effects, the successful execution of the proposed research will allow new and emerging technologies to be problem solved in advance of large scale tests in order to make better use of the larger research centers currently being operated in the United States and abroad. The project is being developed in collaboration with Prof. Jayant Sirohi of the ASE/EM department at The University of Texas at Austin. The long term goal of this program is to develop effective control strategies for reducing the acoustic and unsteady blade loads that occur during helicopter flight. A complete characterization of the physical system must be performed first before any such effective strategies for control can be developed. Performance increases and the reliability of next generation rotor craft and tilt rotor craft vehicles are strongly dependent on a reduction of these load.
Active control of turbulent boundary layers over acoustic receiver arrays
The emphasis of the proposed research is two fold. The first is to develop a comprehensive understanding of an underwater acoustic receiver array's sensitivity to flow induced noise based on coupled measurements of the fluctuating wall pressure and velocity field in a fully turbulent two-dimensional boundary layer at various flow speeds. The scalability of the measurements for different Reynolds number will be an important part of this study and will set the stage for developing a tool capable of predicting full scale conditions. The second objective of the research will be to study the feasibility of using active control to relaminarize the boundary layer without introducing new contaminating sources of noise. A trade study will quantify the power consumed by the control device in order to determine the feasibility of this technology for use on Unmanned Underwater Vehicles. It is asserted that an inspection of the fundamental behaviors responsible for causing detrimental flow noise will lead to a more comprehensive understanding of the base noise levels and spectra as a function of flow speed. If successful, the knowledge gained from this study will provide invaluable information for improving existing threat detection technology currently in use on full-scale naval vessels. This project is being developed in collaboration with Steve Morrissette and Dr. Michael Haberman at the United States Navy Applied Research Laboratory located at the J.J. Pickle Research Center in Austin Texas.
Longhorn Rocket Association
The LRA is a student-run amateur rocketry group at the University of Texas at Austin. Their mission is to enhance undergraduate education by applying classroom knowledge to design, build, and launch our own rockets. Currently the LRA has three main projects: (1) a second transonic rocket, (2) a second "1 lb - 1 mile" rocket, and (3) a rocket designed to reach 100,000 ft. More information about these and past projects can be found at the LRA homepage. The LRA also builds small model rockets, sometimes from kits and sometimes from scratch, and hold local launches (usually one per semester) at the J. J. Pickle Research Campus in north Austin. Additionally, the LRA is involved in many outreach events geared toward getting young kids interested in the field of aerospace engineering. These include UT's "Introduce a Girl to Engineering Day", Explore UT, and several other events throughout the year.
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