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
说质能关系E=mc^(2)是爱因斯坦的成就是对爱因斯坦的羞辱。——作者(接51卷第6期)17黑体辐射与相对论黑体辐射的学问从一开始就是相对论统计,因为它的对象是光。实际上,1905年狭义相对论甫一问世,普朗克即将之用于在相对论热力学方向上...说质能关系E=mc^(2)是爱因斯坦的成就是对爱因斯坦的羞辱。——作者(接51卷第6期)17黑体辐射与相对论黑体辐射的学问从一开始就是相对论统计,因为它的对象是光。实际上,1905年狭义相对论甫一问世,普朗克即将之用于在相对论热力学方向上培养博士,且学生于1906年即毕业了[Kurd von Mosengeil,Theorie der stationären Strahlung in einem gleichförmig bewegten Hohlraum(匀速运动空腔内静态辐射的理论),Annalen der Physik 22,867-904(1907)]。热的传导方式之一是热辐射,黑体辐射也叫热辐射,因此用相对论的眼光看热力学是自然的。没有relativistic thermodynamics一章的热力学教程是不完备的。粗略算来,相对论热力学应该至少包括如下三方面的内容:(1)黑体辐射公式的推导;(2)运动空腔辐射体的运动学问题,这指向质能关系;(3)温度T的洛伦兹变换。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.
文摘说质能关系E=mc^(2)是爱因斯坦的成就是对爱因斯坦的羞辱。——作者(接51卷第6期)17黑体辐射与相对论黑体辐射的学问从一开始就是相对论统计,因为它的对象是光。实际上,1905年狭义相对论甫一问世,普朗克即将之用于在相对论热力学方向上培养博士,且学生于1906年即毕业了[Kurd von Mosengeil,Theorie der stationären Strahlung in einem gleichförmig bewegten Hohlraum(匀速运动空腔内静态辐射的理论),Annalen der Physik 22,867-904(1907)]。热的传导方式之一是热辐射,黑体辐射也叫热辐射,因此用相对论的眼光看热力学是自然的。没有relativistic thermodynamics一章的热力学教程是不完备的。粗略算来,相对论热力学应该至少包括如下三方面的内容:(1)黑体辐射公式的推导;(2)运动空腔辐射体的运动学问题,这指向质能关系;(3)温度T的洛伦兹变换。
