水流作用下悬跨管道振动的实验研究

为了比较得到水下管道安全悬跨长度的判别条件并验证其合理性。使用弹性力一重力相似理论设计模型实验，管道两端均采用固定约束，管道与水流之间的角度分别为90°、75°、60°、45°和30°，悬跨管长分别为1．00m、0．81m、0．73rn、0．70rn。通过实验比较fn≥10fs、fn≥（0．7）-1．fs、fn=5fs（fn为悬跨管道固有频率；六为水流激振频率）3种条件对悬跨管道振动的判别情况。研究表明，根据fn=5fs，即约化速度K=1的条件，计算得到的临界长度较安全、合理，并由fn=5f条件给出了不同管径、壁厚和流速条件下管道临界长度的规律图，研究结果可为水下悬跨管道的安全评价提供借鉴。（图3，表2，参13）

Experimental study on vibration of free spanning pipeline caused by water flow

In order to identify and justify the conditions for discriminating safe spanning length of an underwater pipeline, a model experiment is designed according to the elastic force-gravity similarity theory. The pipeline is fixed at both ends, having an angle with water flow of 90°, 75°, 60°, 45° and 30° respectively and freely spanning for 1.00 m, 0.81 m, 0.73 m and 0.70 m respectively. During the experiment, the free spanning pipeline is discriminated for vibration under 3 conditions, i.e., f. 〉 10 fs, fn 〉 （0.7）-] fs and fn = 5 fs （f, is the natural frequency of free spanning pipeline, f, is the vibration frequency of water flow）. The results show a safe and reasonable critical length atfn = 5 fs （i.e., the reduced velocity Vr = 1）. The critical lengths are plotted under the condition of fn = 5 fs, depending on diameter, wall thickness and flow rate. This study can provide references for safety assessment of free spanning pipeline underwater. （3 Figures, 2 Tables, 13 References）