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首页> 外文期刊>Journal of Fluids and Structures >Apparent and effective drag for circular cylinders oscillating transverse to a free stream
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Apparent and effective drag for circular cylinders oscillating transverse to a free stream

机译：横向于自由流摆动的圆柱体的视在有效阻力

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摘要

This communication brings forward the concept of an effective drag for circular cylinders undergoing controlled or self-excited oscillation transverse to a free stream. A relationship between the effective drag and the apparent drag customarily measured by force transducers, is derived on the basis of the average rate of energy dissipation in the fluid. The effective drag is employed to gain insight into the fluid dynamics of vortex-induced vibrations using available data from the published literature. It is shown that the effective drag varies almost continuously as a function of the true reduced velocity except for a sudden decrease near conditions of maximum amplitude. The variation displays similarities but also important differences among independent experiments, which highlight the importance of various influencing parameters whose effect on the free response is currently not well understood. Some evidence is found that self-excited oscillations occur at points in the frequency-amplitude space where the effective drag is comparatively low avoiding the region where energy transfer from the fluid to the structure is most efficient. A total energy balance is employed to reveal the effect of mechanical damping on the free response which indicates that the amplitude scales with the inverse of the square root of damping in conformity with experimental data. The dimensionless damping parameters proposed by Vandiver are examined in light of the present analysis, and alternative empirical formulas are suggested for organizing the free vibration response.
机译：这种交流提出了一种有效的阻力概念，用于横向于自由流经受受控或自激振荡的圆柱体。基于流体中能量的平均耗散率，得出有效阻力和通常由力传感器测量的视在阻力之间的关系。使用有效阻力，利用已发表文献中的可用数据来深入了解涡激振动的流体动力学。结果表明，除了在最大振幅条件下突然减小外，有效阻力几乎是作为真实减小速度的函数连续变化的。该变化显示出相似性，但在独立实验之间也显示出重要差异，这凸显了各种影响参数的重要性，这些参数对自由反应的影响目前尚不清楚。发现一些证据表明，自激振荡发生在频率幅度空间中的有效阻力相对较低的点，从而避免了从流体到结构的能量转移最有效的区域。采用总能量平衡来揭示机械阻尼对自由响应的影响，这表明振幅与阻尼平方根的倒数成比例，与实验数据一致。根据目前的分析研究了Vandiver提出的无量纲阻尼参数，并提出了替代的经验公式来组织自由振动响应。

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