Jet Noise Reduction by Exciting Carefully Selected Natural Instability Waves of the Jet Flow
Abstract
We propose a new way to reduce the noise of high-temperature, high-velocity jets. A major difficulty in jet noise reduction is that the dominant noise sources are located near or slightly downstream of the potential core of the jet. To suppress jet noise, disturbances are, invariably, introduced into a jet flow with the intent that they would interfere positively with the noise generation processes. For practical reason, the injection site of the input disturbances is restricted to the nozzle exit region. Because the jet flow is turbulent, the input disturbances are dissipatedquickly. In most cases, they are unable to reach the main noise source region. Our proposal is to make use of the natural instability waves of the jet flow. Natural jet instabilities actually grow in amplitude as they propagate downstream. Thus, when artificially excited, they should be able toreach the end of the potential core and beyond. The implementation of this noise reduction scheme, however, faces three major challenges. First, a way to select the most promising instability wave modes and frequencies for excitation needs to be developed. Second, how to excite a selected instability wave mode in a jet flow is no simple task. This excitation problem requires a solution. Third, a proof of concept by having an experimental demonstration or a numerical simulation (as a substitute) is essential and necessary. We propose to divide the project into two phases. Phase 1 deals with the first and second challenges. The experimental or numerical demonstration will constitute the principal research work of Phase II. This two phases arrangement has the advantage that it allows a high caliber experimentalist or an expert computational specialist to participate in the last and crucial part of the project. The present proposal is confined to Phase I. It provides overall information and ideas of the project.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2021
- Source ID
- N000142112344
Entities
People
- Christopher Tam
Organizations
- Florida State University
- Office of Naval Research
- United States Navy