Investigation of the Vibration Behavior of Fluidelastic Instability in Closely Packed Square Tube Arrays

Flow-induced vibrations in heat exchanger tubes have led to numerous accidents and economic losses in the past. Fluidelastic instability is the most critical flow-induced vibration mechanism in heat exchangers. Both experimental and computational studies conducted to determine fluidelastic instability were presented in this paper. In the experiment, a water channel was built, and a closely packed normal square tube array with a pitch-to-diameter ratio of 1.28 was tested, and significant fluidelastic instability was observed. A numerical model adopting large-eddy simulation and moving mesh was established using ANSYS CFX, and results showed good agreement with the experimental findings. The vibration behaviors of fluidelastic instability were discussed, and results showed that the dominant vibration direction of the tubes changed from streamwise to transverse beyond a critical velocity. A 180° phase lag between adjacent tubes was observed in both the experiment and simulations. Normal and rotated square array cases with pitch-to-diameter ratios of 1.28 and 1.5 were also simulated. The results of this study provide better insights into the vibration characteristics of a square tube array and will help improve the fundamental research and safety design of heat exchangers.

换热器管束中的流体弹性不稳定性

文中重点讨论了管壳式换热器管束中的流体弹性不稳定性．从工程实用的观点出发，应用了Ｌｅｖｅｒ与Ｗｅａｖｅｒ的“流管”模型，在建立管子振动的基本方程时则认为管子作周期性的衰减（或发散）运动，以复数解法进行求解．根据所获得的对比流速与质量阻尼参数之间的关系画出的稳定区图，可用来确定管子的流体弹性不稳定性或该时的临界流速．实验数据表明，理论计算结果是令人满意的．

管束的流体弹性不稳定性的研究

基于Lever与Weaver的“流管”模型,本文对换热器管束的流体弹性不稳定性进行了较深入的研究。认为管子作周期性的衰减(或发散)运动。基本方程以复数形式表示,并用复数解法来求解。证明了作用在管上的流体力与管子运动时的位移、速度、加速度密切相关。作出的稳定区图可用来判断管子是否发生流体弹性不稳定现象。将节径比为1.25,1.32与1.41的正方形排列的管束,依次放入风洞中进行试验,取得了令人满意的结果。

换热器管束的流体弹性不稳定性

基于Lever与Weavar的“流管”模型,对换热器管束的流体弹性不稳定进行了研究。基本方程利用复数解法进行求解。证明了作用在管上的流体力与管子运动时的位移、速度、加速度密切相关,得出的稳定区图可用来判断管子是否发生流体弹性不稳定现象。模型管束为正方形排列,节径比为1.25、1.32与1.41。试验在风洞中进行。计算结果与实验数据相符。

影响管阵流体弹性不稳定性因素的研究

研究了管阵中管数,纵向流的作用以及U形管等对管阵流体弹性不稳定性的影响。介绍了用求解模态展开后的振动方程计算管阵的临界流速的方法。给出了简化处理耦合问题的单一振型法和频率截断法。并推导出考虑非均勻流、纵向流存在和U形管的基本方程。