국내 최대 기계 및 로봇 연구정보

기술보고서

기술보고서 게시판 내용
타이틀	An Empirical Temperature Variance Source Model in Heated Jets
저자	Khavaran, Abbas;; Bridges, James
Keyword	AERODYNAMIC NOISE;; ANALOGIES;; FLOW EQUATIONS;; JET AIRCRAFT NOISE;; NOISE GENERATORS;; NOISE PREDICTION;; PARALLEL FLOW;; REYNOLDS AVERAGING;; STAGNATION TEMPERATURE;; TEMPERATURE RATIO;; TURBULENT MIXING;; WAVE EQUATIONS
URL	http://hdl.handle.net/2060/20120015916
보고서번호	NASA/TM-2012-217743
발행년도	2012
출처	NTRS (NASA Technical Report Server)
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.