Characterization and noise-control of application-oriented jet flowfields
Abstract
Acoustic radiation from high-power aircraft engines expose military personnel to around 150dBof sound, resulting in adverse health impacts. Noise control of such turbulent jets remains a challenging goal, despite an extensive body of literature on axisymmteric jets and its sound sources. An outstanding issue is a lack of understanding of the exact manner in which energy in turbulenceis channeled into the acoustic response of the jet. The scenario is further complicated in the case of certain jets that are particularly relevant to naval applications, due to the additional challenges imposed by three specific factors: (a) non-axisymmetric geometry, (b) heated plume, and (c) imperfectly-expanded operating conditions. The proposed effort aims to address this issue by adopting a novel approach to quantify the acoustic component in the above application-oriented jets, and further identify source mechanisms that energize this component, resulting in sound radiation. The resulting insights will inform suitable control strategies that either modify topology of the turbulent flow (order-one), or take advantage of small-perturbation-sensitivity in these jets (order-epsilon), to mitigate noise. The study is enabled through high-fidelity simulations of applicationoriented jets, that are anchored in reliable experimental databases. An analytic technique, which we denote fluid-thermodynamic (FT) analyses, is utilized to deconstruct the simulated turbulent jet flowfields into its fundamental components - hydrodynamic, acoustic and entropic. Along with an energy analysis that govern their inter-component energy transfer, this provides a holistic framework that identifies hydrodynamic sources in the turbulent flow and the resulting acoustic response.The entropic component facilitates a direct quantification of thermal dynamics in the heated jets, particularly its role in modifying source terms for the acoustic component. Specifically, we simulate and perform FT analyses on three configurations: circular, rectangular and diamond-shapednozzles, that operate under imperfectly expanded conditions. This will provide a comprehensive characterization of key variations induced in the acoustic component, and source mechanisms that induce maximum acoustic gain, in application-oriented jet flows, as compared to well-studiedcanonical free-shear layers. Further, the acoustic component will be utilized to generate efficient reduced-order representation of these complex nozzle flows, resulting in computationally efficient farfield modeling and prediction capabilities. Based on the fundamental insights obtained into mechanisms that energize the acoustic component, we will evaluate order-one and order-epsiloncontrol inputs, to identify those with the potential to most effectively mitigate noise radiation.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2021
- Source ID
- N000142112318
Entities
People
- S. Unnikrishnan
Organizations
- Florida State University
- Office of Naval Research
- United States Navy