Active Control of Flow and Acoustics in Military-Style Supersonic Rectangular Twin Jets
Abstract
Jet noise has been an environmental concern since the advent of jet aircraft. Jet noise from high performance military aircraft, especially during takeoff from and landing on aircraft carriers, has also received growing attention in recent years, as it has contributed to hearing impairment of deck crews. The continuous drive to higher specific thrust and agility results in increasing jet noise levels. Integration of propulsion and aerodynamics in next generation tactical aircraft, especially for naval applications, will require non-axisymmetric (e.g. rectangular) nozzle geometries. Closely-spaced twin jet engines are commonly used in military aircraft. The near-field pressure and acoustic fields of closely-spaced jets interact and the strength and nature of the interaction strongly depends upon the distance between the two jets and the jets operating regime, which is dictated by the flight regime and mission profile. In some tactical aircraft, the jets are separated about one jet diameter causing strong jet-to-jet flow and acoustic field interactions. In such cases, coupling of the flow and acoustic fields has resulted in aircraft structural damage, as well as significant near-field and far-field pressure and noise amplification. Under our current ONR grant, we have designed a new twin rectangular supersonic jet facility with military-style converging-diverging nozzles. The nozzle aspect ratio is 2, the design Mach number is 1.5, and the distance between the nozzles is one De (area-based nozzle equivalent diameter). We are using plasma actuators, distributed around the nozzle exit, to actively control the development of large-scale structures in the shear layers of the jets. It has been known for over 50 years that these structures are responsible for the peak far-field noise, screech and broadband shock associated noise, and the coupling between the two jets. In our current research, we have shown tremendous control authority in completely decoupling the two jets, eliminating screech, and completely altering the nature of the jet flow and acoustic fields. We have also been collaborating with an ONR funded group (Colonius, Schmidt, and Bres) to advance the large eddy simulation technologies as well as to advance active noise mitigation technology. We have also begun discussions with three newly funded (by ONR) theoretical and computational groups (Tam, Mankbadi, and Unnikrishnan) to collaborate on active noise reduction technology. A three-year experimental research project is proposed to extend our current active jet noise control research (in twin supersonic rectangular jets with low-aspect ratio, military-style converging-diverging nozzles) from unheated to heated jets and from active control of jet coupling, screech, and shock associated noise reduction to simultaneously decoupling the two jets and reducing screech, broadband shock associated noise, and far-field radiated noise. Therefore, the primary objectives of the proposed research are threefold: (1) to extend the focus of the current research from unheated to heated jets; (2) to further advance the control technology from the current jet-column mode frequency range (Strouhal number of 0.2 to 0.6) to jet shear layer mode frequency range (Strouhal number larger than 2.0) to simultaneously control the jets’ coupling, screech, broadband shock associated noise, and the far-field radiated noise; and (3) to work in advancing the active jet noise control technology in close consultation with ONR and NAVAIR and in close collaboration with our theoretical and computational partners. The focus of the proposed research is on advancing active jet noise mitigation technology in rectangular military-style supersonic twin jets.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 01, 2022
- Source ID
- N000142212227
Entities
People
- Mohammad Samimy
Organizations
- Office of Naval Research
- Ohio State University
- United States Navy