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An Empirical Temperature Variance Source Model in Heated Jets
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Author and Affiliation:
Khavaran, Abbas(Science Applications International Corp., Cleveland, OH, United States);
Bridges, James(NASA Glenn Research Center, Cleveland, OH, United States)
Abstract: An acoustic analogy approach is implemented that models the sources of jet noise in heated jets. The equivalent sources of turbulent mixing noise are recognized as the differences between the fluctuating and Favre-averaged Reynolds stresses and enthalpy fluxes. While in a conventional acoustic analogy only Reynolds stress components are scrutinized for their noise generation properties, it is now accepted that a comprehensive source model should include the additional entropy source term. Following Goldstein s generalized acoustic analogy, the set of Euler equations are divided into two sets of equations that govern a non-radiating base flow plus its residual components. When the base flow is considered as a locally parallel mean flow, the residual equations may be rearranged to form an inhomogeneous third-order wave equation. A general solution is written subsequently using a Green s function method while all non-linear terms are treated as the equivalent sources of aerodynamic sound and are modeled accordingly. In a previous study, a specialized Reynolds-averaged Navier-Stokes (RANS) solver was implemented to compute the variance of thermal fluctuations that determine the enthalpy flux source strength. The main objective here is to present an empirical model capable of providing a reasonable estimate of the stagnation temperature variance in a jet. Such a model is parameterized as a function of the mean stagnation temperature gradient in the jet, and is evaluated using commonly available RANS solvers. The ensuing thermal source distribution is compared with measurements as well as computational result from a dedicated RANS solver that employs an enthalpy variance and dissipation rate model. Turbulent mixing noise predictions are presented for a wide range of jet temperature ratios from 1.0 to 3.20.
Publication Date: Oct 01, 2012
Document ID:
20120015916
(Acquired Nov 23, 2012)
Subject Category: ACOUSTICS
Report/Patent Number: NASA/TM-2012-217743, E-18488
Document Type: Technical Report
Contract/Grant/Task Num: G3-BASE-12; WBS 561581.02.08.03.45.02.05
Financial Sponsor: NASA Glenn Research Center; Cleveland, OH, United States
Organization Source: NASA Glenn Research Center; Cleveland, OH, United States
Description: 44p; In English; Original contains color illustrations
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: AERODYNAMIC NOISE; NOISE GENERATORS; JET AIRCRAFT NOISE; NOISE PREDICTION; REYNOLDS AVERAGING; TEMPERATURE RATIO; TURBULENT MIXING; WAVE EQUATIONS; ANALOGIES; PARALLEL FLOW; STAGNATION TEMPERATURE; FLOW EQUATIONS
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