Research On Optimization of Two-Dimensional Supersonic Jet Noise Reduction.

1995 Fiscal Year Final Research Report Summary

• Project/Area Number: 05555259
• Research Category: Grant-in-Aid for Developmental Scientific Research (B)
• Allocation Type: Single-year Grants
• Research Field: Aerospace engineering
• Research Institution: The University of Tokyo
• Principal Investigator: KAJI Shojiro School of Engineering, The University of Tokyo, Professor., 大学院工学系研究科, 教授 (80013704)
• Co-Investigator(Kenkyū-buntansha): KOBAYASHI Hiroshi Thermofluid Dynamics Division, National Aerospace Laboratory, Branch Chief, 熱流体力学部, 室長
• Project Period (FY): 1993 – 1995
• Keywords: supersonic jet noise / jet screech / porous plug nozzle / mixer nozzle / ejector nozzle

Research Abstract

For the purpose of reducing supersonic jet noise, application of porous plug nozzle as well as ejector nozzle was investigated. In the case where an airfoil shaped porous plug was inserted into two dimensional rectangular nozzle, its effect on screech and shock associate noise was studied. When the porous plug was placed a little far downstream from the jet nozzle, sound of the edge-tone type mechanism appeared. When the leading edge of the porous plug approached the jet nozzle exit, edge tone disappeared but screech appeared. Further, when the leading edge of the porous plug was inserted into the jet nozzle, screech also vanished. Such tendency was considered to be ascribable to the highly turbulent flow around the porous plug though holes which was observed by flow visualization.
The method to reduce noise by rapidly reducing the velocity of high speed jet by use of mixer-ejector nozzle was studied. Measurement of fluctuating pressures on ejector wall showed that in the upstream part of the mixer-ejector nozzle the lower frequency component was dominant while the higher frequency component became dominant in the downstream part, and further, the level of both components increased as we went downstream.
The flow field showing the mixing process in the mixer-ejector nozzle was simulated by the computational fluid dynamics. It was revealed that in the mixing process of core and secondary flows, the supersonic core flow repeats compression and expansion several times, then the rolling up of a large scale streamwise vortex starts which is strengthened as the flow proceeds downstream.