Sound Generation by Interactions among Vortex, Heat and Shock Wave

通过计算和实验研究了涡旋、热和激波相互作用下声音的产生机理和性质。Inoue开发了一种高精度、可压缩的Navier-Stokes代码（空间上为6阶，时间上为4阶），并将其应用于激波-涡旋互拍卖问题。结果表明：(1)单个涡旋与平面激波相互作用可连续产生三种声音；(2)每种声音具有四极性；(3)声音的强度既取决于激波的强度，也取决于涡旋的强度。Inoue还将代码应用于一对涡旋和激波之间的相互作用，并澄清了由相互作用产生的声音的数量和声音的特征性质取决于这对涡旋是与激波方向相同还是相反。Inoue还研究了直升机周围的可压缩流场，并首次阐明了旋涡环状态和自旋状态下的f…More低场特性。结果表明，直升机旋翼流场的声场产生与旋翼包叶与尖涡的相互作用密切相关。Fukunishi在紊流边界层上施加声波，并研究了边界层内的涡旋运动。Fukunishi发现湍流边界层可以被声波有效地激发。Sasoh对高速列车（新干线）在隧道出口产生的声音噪声进行了实验研究，发现新干线产生的冲击波衰减是减少声音噪声的必然选择。Sasoh建议在隧道中使用伪穿孔墙。Ju利用二维Navier-Stokes码对H2和空气的预混气体与激波相互作用产生的流场进行了数值研究，发现所谓的richmyer - meshkov不稳定性在涡旋的产生从而声音的产生中起着重要作用。Hattori数值模拟了两个涡旋环正面碰撞产生的声压场，发现了以下重要结果。(1)当两个涡旋环的强度相等时，产生两种声音，每种声音都具有四极性质。(2)当两个涡旋环的强度不相等时，会产生四种声音，声音的传播方向受到两个涡旋环强度差的影响。Hattori和loue还研究了两个涡旋环斜碰撞产生的声音的特征性质，并用数值方法捕获了八极声音的产生。少

Generation mechanism and natures of sound through vortex, heat and shock wave interactions are studied both computationally and experimentally. Inoue developped a highly-accurate, compressible Navier-Stokes code (6th-order in space and 4th-order in time) and applied it to shock-vortex interauction problems. The results show that, (1) three sounds are generated successively by the interaction between a single vortex and a plane shock wave, (2) each sound has a quadrupolar nature, and (3) the strengths of the sounds depend both on the strengths of a shock wave and a vortex. Inoue also applied the code to the interaction between a pair of vortices and a shock wave, and clarified that the number of sound generated by the interaction and the characteristic naturcs of the sounds depend on whether the pair of vortices moves in the same direction as the shock wave or opposite to it. Inoue also studied compressible flowfields around a helicopter and clarified the characteristic natures of the f … More lowfields in a vortex ring state and in an autorotation state for the first time. The results suggest strongly that the sound generation in the helicopter rotor flowfield is closely related to the interaction between the tip-vortices and the rotor baleds. Fukunishi imposed a sound wave on a turbulent boundary layr, and examined the vortical motion in the boundary layr. Fukunishi found that the turbulent boundary layr can be effectively excited by the sound wave. Sasoh studied experimentally the sound noise at the exit of a tunnel produced by a highspeed bullet train (Shinkansen), and found that attenuation of a shock wave produced by a Shinkansen is inevitable to reduce the sound noise. Sasoh proposes the use of pseudo-perforated walls in a tunnel. By using a two-dimensional Navier-Stokes code, Ju studied numerically flowfields produced by the interaction of premixed gases of H2 and air with a shock wave, and found that the so-called Richtmyer-Meshkov instability plays an important role in the generation of vortices and thus the generation of sound. Hattori simulated numerically sound pressure fields generated by the head-on collision of two vortex rings, and found the following important results. (1) When the strengths of the two vortex rings are equal, two sounds are generated and each sound has quadrupolar nature. (2) When the strengths of the two vortex rings are not equal, four sounds are generated and the direction of the sound propagation is affected by the difference of the strengths of the two vortex rings. Hattori and lnoue also studied the characteristic natures of sound generated by oblique collisions of two vortex rings, and captured numerically the generation of octupolar sounds. Less