Fishing boats are usually anchored side by side in the harbor because of the small structural size and poor resistance to wind and waves.A series of physical model experiments are conducted to investigate the motion c...Fishing boats are usually anchored side by side in the harbor because of the small structural size and poor resistance to wind and waves.A series of physical model experiments are conducted to investigate the motion characteristics of multiple fishing boats that are moored together.A decay test in calm water is conducted to study the natural period and damping coefficients.Regular wave experiments are performed to analyze the roll motion response of each boat for four modes(different numbers of boats side-by-side).The results indicate that the“natural period”of each boat for the mode of multi-boats especially three or four boats,is slightly smaller than that of a single boat,whereas the damping coefficient is visibly larger than that of a single boat.The maximum roll angle of each boat does not appear at the same time under a 90°incident wave.Small roll motion energy is generated at low frequencies and high frequencies when multiple boats are moored together.The energy decreases with the increasing wave period.The roll motion responses of each boat in four modes exhibit different trends with the increasing wave frequency.The number of boats and boat position have significant effects on roll motion.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
基金financially supported by Central Public-interest Scientific Institution Basal Research Fund,CAFS(Grant Nos.2023TD88,2024HY-ZC005,and 2024XT0801).
文摘Fishing boats are usually anchored side by side in the harbor because of the small structural size and poor resistance to wind and waves.A series of physical model experiments are conducted to investigate the motion characteristics of multiple fishing boats that are moored together.A decay test in calm water is conducted to study the natural period and damping coefficients.Regular wave experiments are performed to analyze the roll motion response of each boat for four modes(different numbers of boats side-by-side).The results indicate that the“natural period”of each boat for the mode of multi-boats especially three or four boats,is slightly smaller than that of a single boat,whereas the damping coefficient is visibly larger than that of a single boat.The maximum roll angle of each boat does not appear at the same time under a 90°incident wave.Small roll motion energy is generated at low frequencies and high frequencies when multiple boats are moored together.The energy decreases with the increasing wave period.The roll motion responses of each boat in four modes exhibit different trends with the increasing wave frequency.The number of boats and boat position have significant effects on roll motion.
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.
