本文研究用有限元法计算桥梁涡激振动的时程响应。应用条带假设和半经验半解析的Scanlan第二涡激作用力模型实现涡激作用力在时间和空间上的离散化;针对Scanlan模型中Van der Pol性质的时间频率混合项,引入时频混合格式的AFT方法来计算...本文研究用有限元法计算桥梁涡激振动的时程响应。应用条带假设和半经验半解析的Scanlan第二涡激作用力模型实现涡激作用力在时间和空间上的离散化;针对Scanlan模型中Van der Pol性质的时间频率混合项,引入时频混合格式的AFT方法来计算涡振时程响应,并通过算例验证了该方法的可行性。与传统的连续模型和随机振动理论计算桥梁涡激响应方法相比,时程计算可以考虑多振型的组合作用,结构非线性等多种影响,具有更大的灵活性。展开更多
One of the challenges in predicting the dynamic response of deepwater risers under vortex-induced vibration （VIV） is that it runs short of believable fluid loading model. Moreover, the hydrodynamic loading is also d...One of the challenges in predicting the dynamic response of deepwater risers under vortex-induced vibration （VIV） is that it runs short of believable fluid loading model. Moreover, the hydrodynamic loading is also difficult to be measured directly in the VIV experiments without disturbing the fluid field. In the present work, by means of a finite element analysis method based on the experimental data of the response displacements, the total instantaneous distributions of hydrodynamic forces together with the hydrodynamic coefficients on the riser model with large aspect ratio （length/ddiameter） of 1750 are achieved. The steady current speeds considered in the experiments of this work are ranging from 0.15 rn/s to 0.60 m/s, giving the Reynolds Number between 2400 and 9600. The hydrodynamic coefficients are evaluated at the fundamental frequency and in the higher order frequency components for both in-line and cross-flow directions. It is found that the Root-Mean Squared hydrodynamic forces of the higher order response frequency are larger than those of the fundamental response frequency. Negative lift or drag coefficients are found in the numerical results which is equivalent to the effect of fluid damping.展开更多
文摘本文研究用有限元法计算桥梁涡激振动的时程响应。应用条带假设和半经验半解析的Scanlan第二涡激作用力模型实现涡激作用力在时间和空间上的离散化;针对Scanlan模型中Van der Pol性质的时间频率混合项,引入时频混合格式的AFT方法来计算涡振时程响应,并通过算例验证了该方法的可行性。与传统的连续模型和随机振动理论计算桥梁涡激响应方法相比,时程计算可以考虑多振型的组合作用,结构非线性等多种影响,具有更大的灵活性。
基金supported by the 863 Program of China (Grant No. 2006AA09A103)partially supported by the National Natural Science Foundation of China (Grant No. 50921001)the open fund from the State Key Laboratory of Coastal and Offshore Engineering (Grant No. LP0904)
文摘One of the challenges in predicting the dynamic response of deepwater risers under vortex-induced vibration （VIV） is that it runs short of believable fluid loading model. Moreover, the hydrodynamic loading is also difficult to be measured directly in the VIV experiments without disturbing the fluid field. In the present work, by means of a finite element analysis method based on the experimental data of the response displacements, the total instantaneous distributions of hydrodynamic forces together with the hydrodynamic coefficients on the riser model with large aspect ratio （length/ddiameter） of 1750 are achieved. The steady current speeds considered in the experiments of this work are ranging from 0.15 rn/s to 0.60 m/s, giving the Reynolds Number between 2400 and 9600. The hydrodynamic coefficients are evaluated at the fundamental frequency and in the higher order frequency components for both in-line and cross-flow directions. It is found that the Root-Mean Squared hydrodynamic forces of the higher order response frequency are larger than those of the fundamental response frequency. Negative lift or drag coefficients are found in the numerical results which is equivalent to the effect of fluid damping.
