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Nonreflecting boundary conditions based on nonlinear multidimensional characteristics
, 2007
"... Nonlinear characteristic boundary conditions based on multidimensional wave modeling are proposed for two and threedimensional full compressible NavierStokes equations with/without scalar transport equations. This model is consistent with the physics of flows and transport properties. Based on th ..."
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Cited by 4 (1 self)
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Nonlinear characteristic boundary conditions based on multidimensional wave modeling are proposed for two and threedimensional full compressible NavierStokes equations with/without scalar transport equations. This model is consistent with the physics of flows and transport properties. Based on the theory of characteristics, the multidimensional flows can be decomposed into acoustic, entropy, and vorticity waves. In order to obtain appropriate nonreflecting boundary conditions, the corresponding characteristic variables of incoming waves are set to zeros, and the source terms of the incoming acoustic wave are partially damped. The plane waves are analyzed to obtain the optimal damping coefficient. This new approach substantially minimizes the spurious wave reflections of pressure, density, temperature, and velocity as well as vorticity from the artificial boundaries, where strong multidimensional flow effects exist. The proposed method has advantages of simplicity, robustness, and numerical accuracy, due to the fact that it conforms to the flow physics. The multidimensional characteristicsbased nonreflecting boundary conditions are tested on two benchmark problems: cylindrical acoustic waves propagation and the wake flow after cylinder with periodic strong vortex convected out of the computational domain. These numerical simulations yield accurate results and verify that the method substantially improve the onedimensional characteristicsbased nonreflecting boundary conditions for the complex multidimensional flows. Key words: nonreflecting boundary conditions; nonlinear multidimensional characteristics; complex multidimensional flows; compressible NavierStokes equations; LODI; spurious wave reflection. ∗ Corresponding author.
Response of MultiPanel Assembly to Noise From A Jet
 In Forward Motion,&quot; AIAA Paper
, 1995
"... A model of the interaction of the noise from a spreading subsonic jet with a 4 panel assembly is studied numerically in two dimensions. The e ect of forward motion of the jet is accounted for by considering a uniform ow eld superimposed on a mean jet exit pro le. The jet is initially excited by a pu ..."
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Cited by 3 (2 self)
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A model of the interaction of the noise from a spreading subsonic jet with a 4 panel assembly is studied numerically in two dimensions. The e ect of forward motion of the jet is accounted for by considering a uniform ow eld superimposed on a mean jet exit pro le. The jet is initially excited by a pulselike source inserted into the ow eld. The pulse triggers instabilities associated with the inviscid instability of the jet shear layer. These instabilities generate sound which in turn serves to excite the panels. We compare the sound from the jet, the responses of the panels and the resulting acoustic radiation for the static jet and the jet in forward motion. The far eld acoustic radiation, the panel response and sound radiated from the panels are all computed and compared to computations of a static jet. The results demonstrate that for a jet in forward motion there is a reduction in sound in downstream directions and an increase in sound in upstream directions in agreement with experiments. Furthermore, the panel response and radiation for a jet in forward motion exhibits a downstream attenuation as compared with the static case.
Response of a panel structure forced by the noise from a nearly sonic jet
, 1996
"... A model of a high subsonic jet with a nearby array of exible, aircrafttype panels is studied numerically in two dimensions. The jet is excited by a limited duration, spatially localized starter pulse in the potential core. The long time evolution of unsteady disturbances in the jet, the responses o ..."
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Cited by 1 (0 self)
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A model of a high subsonic jet with a nearby array of exible, aircrafttype panels is studied numerically in two dimensions. The jet is excited by a limited duration, spatially localized starter pulse in the potential core. The long time evolution of unsteady disturbances in the jet, the responses of the panels and the ensuing radiation are computed. The results show that the spectral response of both the jet and the panels is concentrated in a relatively narrow frequency band centered at a Strouhal number (based on jet exit velocity) of approximately 0.25 and associated harmonics. The loading on the panels generally increases with downstream distance. Panel radiation is weakest in upstream directions. Interior zones of silence, due to destructive interference of radiation from the panels, are observed. The rst author was supported by NASA Langley Research Center while in residence under a National
unknown title
, 1983
"... Gridsize reduction in flow calculations on infinite domains by higherorder farfield asymptotics in numerical boundary conditions * ..."
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Gridsize reduction in flow calculations on infinite domains by higherorder farfield asymptotics in numerical boundary conditions *
INFORMATION TO USERS
, 1993
"... A solution adaptive structuredunstructured grid procedure for unsteady flows ..."
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A solution adaptive structuredunstructured grid procedure for unsteady flows
An Integrated Modeling and Simulation Approach for FlowGenerated Sound Prediction
, 2007
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ON THE INTERACTION OF JET NOISE WITH A NEARBY FLEXIBLE STRUCTURE
, 1997
"... The model of the interaction of the noise from a spreading subsonic jet with a panelstringer assembly is studied numerically in two dimensions. The radiation resulting from this �ow�acoustic�structure coupling is computed and analyzed in both the time and frequency domains. The jet is initially exci ..."
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The model of the interaction of the noise from a spreading subsonic jet with a panelstringer assembly is studied numerically in two dimensions. The radiation resulting from this �ow�acoustic�structure coupling is computed and analyzed in both the time and frequency domains. The jet is initially excited by a pulselike source inserted into the �ow �eld. The pulse triggers instabilities associated with the inviscid instability of the jet mean �ow shear layer. These instabilities in turn generate sound which provides the primary loading for the panels. The resulting structural vibration and radiation depends strongly on their placement relative to the jet�nozzle con�guration. Results are obtained for the panel responses as well as the transmitted and incident pressure. The e�ect of the panels is to act as a narrow �lter, converting the relatively broad band forcing, heavily in�uenced by jet instabilities, into radiation concentrated in narrow spectral bands.
Numerical Wave Propagation And SteadyState Solutions
, 1992
"... CONTENTS ACKNOWLEDGEMENTS : : : : : : : : : : : : : : : : : : : : : : : : : : ii LIST OF FIGURES : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : vi LIST OF APPENDICES : : : : : : : : : : : : : : : : : : : : : : : : : : : : xiii CHAPTER I. INTRODUCTION : : : : : : : : : : : : : : : : : ..."
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CONTENTS ACKNOWLEDGEMENTS : : : : : : : : : : : : : : : : : : : : : : : : : : ii LIST OF FIGURES : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : vi LIST OF APPENDICES : : : : : : : : : : : : : : : : : : : : : : : : : : : : xiii CHAPTER I. INTRODUCTION : : : : : : : : : : : : : : : : : : : : : : : : : : : 1 1.1 Wavelike Solutions to PDE's : : : : : : : : : : : : : : : : : : 1 1.1.1 Nondispersive Scalar Equations : : : : : : : : : : : 2 1.1.2 Dispersive Scalar Equations : : : : : : : : : : : : : 3 1.1.3 Systems of Equations : : : : : : : : : : : : : : : : : 5 1.2 Behavior of the Euler Equations : : : : : : : : : : : : : : : : 8 1.2.1 Euler Equations : : : : : : : : : : : : : : : : : : : : 8 1.3 Error Waves or Residual Waves : : : : : : : : : : : : : : : : : 14 1.3.1 Experimental study of Residual Waves<
Response Of MultiPanel Assembly To Noise
 In Forward Motion,&quot; AIAA Paper
, 1995
"... A model of the interaction of the noise from a spreading subsonic jet with a 4 panel assembly is studied numerically in two dimensions. The effect of forward motion of the jet is accounted for by considering a uniform flow field superimposed on a mean jet exit profile. The jet is initially excite ..."
Abstract
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A model of the interaction of the noise from a spreading subsonic jet with a 4 panel assembly is studied numerically in two dimensions. The effect of forward motion of the jet is accounted for by considering a uniform flow field superimposed on a mean jet exit profile. The jet is initially excited by a pulselike source inserted into the flow field. The pulse triggers instabilities associated with the inviscid instability of the jet shear layer. These instabilities generate sound which in turn serves to excite the panels. We compare the sound from the jet, the responses of the panels and the resulting acoustic radiation for the static jet and the jet in forward motion. The far field acoustic radiation, the panel response and sound radiated from the panels are all computed and compared to computations of a static jet. The results demonstrate that for a jet in forward motion there is a reduction in sound in downstream directions and an increase in sound in upstream directions in agreement with experiments. Furthermore, the panel response and radiation for a jet in forward motion exhibits a downstream attenuation as compared with the static case.
Response Of A Panel Structure Forced By The Noise From A Nearly Sonic Jet
, 1996
"... A model of a high subsonic jet with a nearby array of flexible, aircrafttype panels is studied numerically in two dimensions. The jet is excited by a limited duration, spatially localized starter pulse in the potential core. The long time evolution of unsteady disturbances in the jet, the responses ..."
Abstract
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A model of a high subsonic jet with a nearby array of flexible, aircrafttype panels is studied numerically in two dimensions. The jet is excited by a limited duration, spatially localized starter pulse in the potential core. The long time evolution of unsteady disturbances in the jet, the responses of the panels and the ensuing radiation are computed. The results show that the spectral response of both the jet and the panels is concentrated in a relatively narrow frequency band centered at a Strouhal number (based on jet exit velocity) of approximately 0.25 and associated harmonics. The loading on the panels generally increases with downstream distance. Panel radiation is weakest in upstream directions. Interior zones of silence, due to destructive interference of radiation from the panels, are observed. 1 Introduction This paper describes the results of a numerical simulation of jet noise in the presence of four flexible aircrafttype panels in a panelstringer assembly. The simula...