A STUDY OF THE MECHANISM OF VORTEX BREAKDOWN

涡流击穿机理的研究

• 批准号: 03650153
• 负责人: KIKUCHI Masanori
• 金额: $ 1.34万
• 依托单位: MIYAZAKI,University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1991
• 资助国家: 日本
• 起止时间: 1991 至 1992
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03650153/
• 关键词: vortex breakdown; flow visualization; Laser-Doppler Velocimeter; linear instability theory; acoustic streaming; レーザードップウー流速計; レ-ザ-ドップラ-流速計; vortex breakdown; flow visualization; Laser-Doppler Velocimeter; linear instability theory; acoustic streaming; レーザードップウー流速計; レ-ザ-ドップラ-流速計

The features of the vortex breakdown are that there are three types of breakdown, and it has a stagnation point on the vortex axis and the prominent frequencies of oscillating velocities. We presented an analytical model to explain these all features consistently under the idea that the small velocity disturbances of any wave length lying within a certain region would be amplified and unsteady velocity would produce acoustic streaming. We analyzed the stability and the velocity fields, and compared the calculated streak lines with the observed flow pattern for the three types of vortex breakdown.The three types of vortex breakdown were observed in water flows through a straight pipe by a visualization technique : bubble, spiral and double-helix types. Laser-Doppler velocimeter measurements upstream and in the wakes of breakdown of bubble type are described. Spectra of the fluctuating velocities, as well as timeaveraged swirl and axial velocity profile both inside and outside the recirc … More ulation zone, have been obtained. Spectral analysis of the data indicates that the prominent frequencies of oscillating velocities are constant in the steady recirculation.We made a spinning wave generator(SWG), which is a device to produce, at a specified frequency, a sinusoidal wave disturbance spinning in the circumferential direction, in order to confirm the idea that the azimuthal wave number of the disturbance would determine the type of breakdown. SWG is composed of four pistons, which operate in the cylinders attached to the test pipe wall, and creates four kinds of spinning sinusoidal wave disturbances : four azimuthal wave numbers m = 0, +1, -1, 2. The four kinds of sinusoidal waves with azimuthal wave number were imposed to the swirl flow and the transition process of the breakdown type and location was investigated. It was shown that the m = 0, +1, and 2 sinusoidal wave disturbances produce the bubble, spiral type breakdown, and two-tailed bubble or flattened bubble respectively. Less

涡流分解的特征是分解有三种类型，并且在涡旋轴上有一个停滞点，并且振荡速度的突出频率。我们提出了一个分析模型，以始终如一地解释所有这些特征，即在某个区域内的任何波长的小速度障碍都将被放大，并且不稳定的速度会产生声学流。我们分析了稳定性和速度场，并将计算出的条纹线与观察到的三种涡流分解的观察到的流动模式进行了比较。通过可视化技术，通过直管观察到了三种类型的涡流分解：气泡，螺旋，螺旋和双螺旋。描述了上游和气泡类型崩溃的唤醒中的激光多普勒速度计测量值。波动速度的光谱以及旋转速度和轴向速度曲线的内部和轴向速度的内部和轴向速度均获得了更多的旋转……更多的ulation区域。数据的光谱分析表明，振荡速度的显着频率在稳定的再循环中是恒定的。我们使旋转波生成器（SWG）是一种以指定的频率生产的装置，在特定的频率下，正弦波灾难以圆周的指导旋转，以确认该灾难的Azimuthal波浪数量可以确定破坏类型的Azimuthal波浪数量。 SWG由四个活塞组成，这些活塞在连接到测试管壁上的圆柱体中工作，并创建四种旋转正弦波数M = 0，+1，-1，2。对旋转流量和位置的过渡过程，将四种正弦波和方位型波的正弦波数施加。结果表明，M = 0，+1和2正弦波干扰分别产生气泡，螺旋型崩溃和两尾气泡或扁平的气泡。较少的