Research on the Analysis of Vortex structure around a Oscillating Bluff Body in a Uniform Flow and a Development of the Tree-Dimensional Vortex Method

本文从数值和实验两方面研究了受迫同轴振动圆柱体周围的涡系结构，作为流致振动问题的基础研究内容，发展了一种无网格拉格朗日直接模拟方法--三维涡旋法，并应用于球体绕流的数值模拟。主要研究结果如下：(1)在无因次频率STb=0.0-0.48范围内，研究了雷诺数为1000，柱体振动幅值比a/D=0.14的受迫振动圆柱体的绕流问题。模拟结果表明，除STb[相似或相等]0.46外，当STb=0.0-0.25时，除STb[相似或相等]0.46外，三维涡结构均消失；当STb[相似或相等]为0.46时，涡脱落由不对称涡脱落变为对称涡脱落，非对称涡脱落和对称涡脱落交替出现。研究发现，随着柱面频率的增加，三维旋涡结构逐渐减少，但在向锁定现象的过渡区域，旋涡结构逐渐增加，并且从不对称的旋涡脱落变为对称的旋涡脱落。(2)发展了三维旋涡方法，并应用于雷诺数Re分别为100和1000的球体绕流的数值模拟。阻力系数、典型流型等计算结果与实验结果吻合较好。结果表明，三维旋涡方法是模拟三维流场的有效工具之一。

In this research, the vortex structure around a forced in-line oscillating circular cylinder was studied numerically and experimentally as a fundamental research of flow induced vibration problems and the three-dimensional vortex method, which is a grid free Lagrangian direct simulation method, was developed and applied to the simulation of flow around a sphere. The following results were obtained.(1) Flow around an in-line forced oscillating circular cylinder was investigated at the Reynolds number = 1000, at the amplitude ratio of cylinder oscillation a/D = 0.14, in the range of the non-dimensional frequency Stb = 0.0 - 0.48. It was simulated that three dimensional vortex structure appeared for Stb = 0.0 - 0.25 and disappeared for Stb = 0.3 - 0.48, except for Stb 【similar or equal】 0.46, and that the vortex shedding changed from asymmetrical vortex shedding to symmetrical one at Stb = 0.48 and the vortex shedding wa observed asymmetrical vortex shedding and symmetrical one alternatively at Stb 【similar or equal】 0.46. It was found out that the three-dimensional vortex structure is decreased with increasing the frequency of cylinder but increasing at the transition regime to the lock-in phenomenon and to the changing of vortex shedding from asymmetrical vortex shedding to symmetrical one, which were also observed in the experiment.(2) Thee-dimensional vortex method were developed and applied to the simulation of flow around a sphere at the Reynolds number Re = 100 and 1000. The calculation results, such as drag coefficient and typical flow patterns were in good agreement with those of experiment. It is confirmed that the three dimensional vortex method is one of the efficient tool for the simulation of three dimensional flow fields.