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Numerical and Experimental Study on Cavity Flow

空腔流动的数值与实验研究

基本信息

批准号：
04452216
负责人：
KATO Hiroharu
金额：
$ 5.18万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04452216/
关键词：
Cavitation Finite Span Foil Finite Difference Method Viscous Flow Tip Vortex Rotating Blade Bubbly Flow 後退翼実験粘性気泡乱流翼プロペラ

项目摘要

The results of this study can be summarized as follows :1. Computations were made for unsteady viscous cavitating flows around a finite span foil and a rotating blade, using Bubble Two-phase Flow model and a finite difference technique. Since the computations were performed only for low Reynolds numbers, a quantitative agreement with the experimental data was not obtained. However, the computed results expressed the trends of the experiments well, showing the effectiveness of the present flow model for the computation of such flows.2. The tip vortex does not have a simple structure like a Rankine vortex but consists of two cores caused by the boundary layrs on the upper and lower surfaces of the foil, respectively. This is the reason why a tip vortex cavity has a form of a twisting ribbon.3. Increasing cavity size on the foil weakens the tip vortex. But the rotation of tip vortex promotes the separation near the foil tip, resulting in larger cavity near the tip area.4. A cavity lifts up the shear layr, resulting in thicker viscous wake.5. Flow on a rotating blade goes toward the tip because of centrifugal force. As a result, the flow pattern becomes completely different from that on a straight foil.6. It has been shown that a grid generation technique is a key for a high Reynolds number computation in addition to adopting an appropriate turbulence model.7. Accurate experiments were performed using a finite span foil model to measure pressure distribution on the foil and flow field around the foil as well as to observe cavitation. Particularly, the positions and velocity distributions of the tip vortex were measured in detail. These results have been used to clarify the above-mentioned flow structure, together with the detailed analysis of the computed results.

本研究的主要结果如下：1.本文用气泡两相流模型和有限差分法计算了有限翼展翼型和旋转叶片的非定常粘性空化流动。由于计算仅在低雷诺数下进行，因此无法获得与实验数据的定量一致性。然而，计算结果很好地反映了实验的趋势，显示了本流动模型对于计算此类流动的有效性.叶尖涡不像朗肯涡那样具有简单的结构，而是由两个涡核组成，这两个涡核分别由翼型上表面和下表面的边界层引起。这就是叶尖涡腔呈扭曲带状的原因。增加翼型上的空腔尺寸会减弱叶尖涡。但叶尖涡的旋转促进了翼型叶尖附近的分离，导致叶尖附近出现较大的空腔.空腔抬升剪切层，导致粘性尾流变厚.由于离心力的作用，旋转叶片上的气流流向叶尖。结果，流动模式变得完全不同于在直翼上的流动模式。6.研究表明，除了采用合适的湍流模型外，网格生成技术是高雷诺数计算的关键.利用有限翼展翼型模型进行了精确的实验，测量了翼型上的压力分布和翼型周围的流场，并观察了空化现象。详细测量了叶尖涡的位置和速度分布。这些结果已被用来澄清上述流动结构，并详细分析了计算结果。