Turbulent Coanda wall jets are present in a multitude of natural and man-made applications. Their... more Turbulent Coanda wall jets are present in a multitude of natural and man-made applications. Their obvious advantages in terms of flow deflection are often outweighed by disadvantages related to the increased noise levels associated with these jets. Primary high-frequency noise sources are turbulent mixing noise (TMN) and shock-associated noise (SAN). Clearly, accurate modeling of these noise sources will facilitate better predictions of the behavior of such jet noise with physical characteristics. This paper, which focuses on SAN, shows how the Method of Characteristics can be applied to a steady two-dimensional axisymmetric supersonic flow to rewrite the three governing partial differential equations in terms of two ordinary differential equations; the characteristic equation and the compatibility equation. The Euler predictor-corrector numerical integration algorithm is then used to rewrite these equations as finite difference equations and solve them at points in the flare jet fl...
The Journal of the Acoustical Society of America, 2011
Curved three-dimensional turbulent Coanda wall jets are present in a multitude of natural and eng... more Curved three-dimensional turbulent Coanda wall jets are present in a multitude of natural and engineering applications. The mechanism by which they form a shock-cell structure is poorly understood, as is the accompanying shock-associated noise (SAN) generation. This paper discusses these phenomena from both a modeling and experimental perspective. The Method of Characteristics is used to rewrite the governing hyperbolic partial differential equations as ordinary differential equations, which are then solved numerically using the Euler predictor-corrector method. The effects of complicating factors -- such as radial expansion and streamline curvature -- on the prediction of shock-cell location are then discussed. This paper next compares the theoretical calculations of the shock-wave structure with associated schlieren flow visualization results. Related acoustical measurements are also addressed. In this way, critical flow characteristics for shock-cell formation are identified, and their influence on SAN...
The Journal of the Acoustical Society of America, 2011
Although Coanda surfaces are extremely useful for applications in industrial exhaust, the generat... more Although Coanda surfaces are extremely useful for applications in industrial exhaust, the generation of noise in supersonic flows around such surfaces is not well understood. In order to effectively engineer a solution to this noise problem, the noise generation must be able to be accurately modeled. The two dominating generators of sound are turbulent mixing noise and shock associated noise (SAN). The first step necessary to model SAN is a precise predictor of the shock structure within the jet. A MATLAB algorithm is developed to translate Schlieren photos of the flow into qualitative shock location data. This data will be used in conjunction with the method of characteristics to create a model which predicts shock location around a Coanda surface for several slot widths and exit pressures.
Turbulent Coanda wall jets are present in a multitude of natural and man-made applications. Their... more Turbulent Coanda wall jets are present in a multitude of natural and man-made applications. Their obvious advantages in terms of flow deflection are often outweighed by disadvantages related to the increased noise levels associated with these jets. Primary high-frequency noise sources are turbulent mixing noise (TMN) and shock-associated noise (SAN). Clearly, accurate modeling of these noise sources will facilitate better predictions of the behavior of such jet noise with physical characteristics. This paper, which focuses on SAN, shows how the Method of Characteristics can be applied to a steady two-dimensional axisymmetric supersonic flow to rewrite the three governing partial differential equations in terms of two ordinary differential equations; the characteristic equation and the compatibility equation. The Euler predictor-corrector numerical integration algorithm is then used to rewrite these equations as finite difference equations and solve them at points in the flare jet fl...
The Journal of the Acoustical Society of America, 2011
Curved three-dimensional turbulent Coanda wall jets are present in a multitude of natural and eng... more Curved three-dimensional turbulent Coanda wall jets are present in a multitude of natural and engineering applications. The mechanism by which they form a shock-cell structure is poorly understood, as is the accompanying shock-associated noise (SAN) generation. This paper discusses these phenomena from both a modeling and experimental perspective. The Method of Characteristics is used to rewrite the governing hyperbolic partial differential equations as ordinary differential equations, which are then solved numerically using the Euler predictor-corrector method. The effects of complicating factors -- such as radial expansion and streamline curvature -- on the prediction of shock-cell location are then discussed. This paper next compares the theoretical calculations of the shock-wave structure with associated schlieren flow visualization results. Related acoustical measurements are also addressed. In this way, critical flow characteristics for shock-cell formation are identified, and their influence on SAN...
The Journal of the Acoustical Society of America, 2011
Although Coanda surfaces are extremely useful for applications in industrial exhaust, the generat... more Although Coanda surfaces are extremely useful for applications in industrial exhaust, the generation of noise in supersonic flows around such surfaces is not well understood. In order to effectively engineer a solution to this noise problem, the noise generation must be able to be accurately modeled. The two dominating generators of sound are turbulent mixing noise and shock associated noise (SAN). The first step necessary to model SAN is a precise predictor of the shock structure within the jet. A MATLAB algorithm is developed to translate Schlieren photos of the flow into qualitative shock location data. This data will be used in conjunction with the method of characteristics to create a model which predicts shock location around a Coanda surface for several slot widths and exit pressures.
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