In this paper,the hydrodynamically generated noise by the flow over an open cavity is studied.First,aeroacoustic theories and computational aeroacoustic(CAA) methodologies are reviewed in light of hydrodynamic acousti...In this paper,the hydrodynamically generated noise by the flow over an open cavity is studied.First,aeroacoustic theories and computational aeroacoustic(CAA) methodologies are reviewed in light of hydrodynamic acoustics,based on which,a hybrid method is presented.In the coupling procedure,the unsteady cavity flow field is computed using large-eddy simulation(LES) ,while the radiated sound is calculated by the Ffowcs Williams-Hawkings(FW-H) acoustic analogy with acoustic source terms extracted from the time-dependent solutions of the unsteady flow.The hybrid LES-FW-H acoustic analogy method is tested with an open cavity flow at Mach number of 0.006 and Reynolds number of 105 .Following the reflection theorem of Powell,the contributions from different source terms are quantified,and the terms involving wall-pressure fluctuations are found to account for most of the radiated intensity.The radiation field is investigated in the frequency domain.For the longitudinal direction,the sound propagates with a dominant radiation downstream the cavity in the near-field and a flatter directivity in the far-field,while for the spanwise direction,the acoustic waves have a similar propagation along+z and-z directions,with no visible directivity.展开更多
Measurements were carried out in a shallow open cavity with particle image velocimetry technique.The cavity has a lengthto-depth ratio of 4:1,and the upstream inflow conditions include laminar,transient,and turbulent ...Measurements were carried out in a shallow open cavity with particle image velocimetry technique.The cavity has a lengthto-depth ratio of 4:1,and the upstream inflow conditions include laminar,transient,and turbulent regimes at seven different Reynolds numbers.The measured instantaneous velocities were analyzed through ensemble average,vortex extraction,and proper orthogonal decomposition(POD)to investigate overall flow circulations,Reynolds stress distribution,spanwise vortex population,and the characteristics of the POD modes.The results reveal distinctive Reynolds number dependence of the cavity flow,e.g.an increase in Reynolds number results in constant migration of the overall circulation,enhancement of Reynolds stress,reduction of correlation between vortex and Reynolds stress,and decrease of fractional energy of the characteristic POD modes.Finally,a phenomenological model was proposed to describe various features of cavity flow.展开更多
基金Supported by National High Technology Research and Development Program of China("863"Program,No.2006AA09A312)National NaturalScience Foundation of China(No.50705063)
文摘In this paper,the hydrodynamically generated noise by the flow over an open cavity is studied.First,aeroacoustic theories and computational aeroacoustic(CAA) methodologies are reviewed in light of hydrodynamic acoustics,based on which,a hybrid method is presented.In the coupling procedure,the unsteady cavity flow field is computed using large-eddy simulation(LES) ,while the radiated sound is calculated by the Ffowcs Williams-Hawkings(FW-H) acoustic analogy with acoustic source terms extracted from the time-dependent solutions of the unsteady flow.The hybrid LES-FW-H acoustic analogy method is tested with an open cavity flow at Mach number of 0.006 and Reynolds number of 105 .Following the reflection theorem of Powell,the contributions from different source terms are quantified,and the terms involving wall-pressure fluctuations are found to account for most of the radiated intensity.The radiation field is investigated in the frequency domain.For the longitudinal direction,the sound propagates with a dominant radiation downstream the cavity in the near-field and a flatter directivity in the far-field,while for the spanwise direction,the acoustic waves have a similar propagation along+z and-z directions,with no visible directivity.
基金supported by the National Natural Science Foundation of China(Grant No.51127006)
文摘Measurements were carried out in a shallow open cavity with particle image velocimetry technique.The cavity has a lengthto-depth ratio of 4:1,and the upstream inflow conditions include laminar,transient,and turbulent regimes at seven different Reynolds numbers.The measured instantaneous velocities were analyzed through ensemble average,vortex extraction,and proper orthogonal decomposition(POD)to investigate overall flow circulations,Reynolds stress distribution,spanwise vortex population,and the characteristics of the POD modes.The results reveal distinctive Reynolds number dependence of the cavity flow,e.g.an increase in Reynolds number results in constant migration of the overall circulation,enhancement of Reynolds stress,reduction of correlation between vortex and Reynolds stress,and decrease of fractional energy of the characteristic POD modes.Finally,a phenomenological model was proposed to describe various features of cavity flow.
