长江航道规划设计研究院

Channel is the navigable area for ships in rivers and canals. The analyses of flow details and experiences of engineers are extensively used for the design of channel nowadays, without thorough consideration of the fluid-structure interaction between flow and ships. In this paper, an inland channel design method based on ship hydrodynamic response is proposed. First of all, the secondary development is undertaken based on Fluent for the problem of ship-flow interaction, in which flow domain is simulated by using the finite volume method, and governing equations of ship are embedded through user defined function (UDF) and solved by using the fourth-order Runge-Kutta method. The dynamic mesh technique is adopted to update the changing computation domains. The hydrodynamic motion response of freely drifting ships in inland waterway is simulated, as well as trajectory. Then, the weighted least square method is used for curve fitting from the drifting trajectories of different ships, by which the channel boundaries are designed. The weight coefficients are obtained through the statistic of sailing frequencies of different ships. Dongliu route with typical navigation obstructions of curve and branch is chosen for the verification of the channel design method. It is found that the channel designed by the method with consideration of ship-flow interaction is consistent with the existing one. Besides, the analyses of flow details and ship responses indicate that ships sailing in this channel can avoid the influences of oblique flow and make use of the energy of flow, which maintains the sailing safety and economy.

The construction of large reservoirs causes water level adjustment downstream of dams, which exerts a significant impact on river regimes, navigation, flood control and ecology. To explore the characteristics of water level variations and their causes in the Hankou—Jiujiang reach of the Middle Yangtze River following the operation of the Three Gorges Dam (TGD), the trend in water level change from 1988 to 2022 was analyzed by the Mann-Kendall analysis method. With the use of the analysis method for the water level amplitude based on the abnormal residual and a one-dimensional hydrodynamic model, in this paper, the contributions of river erosion and silting, downstream control water level and resistance variation to water level change under different discharge levels were estimated. The results showed the following : ① Before the operation of the TGD, the water level at all discharge levels showed nonsignificant changes except for a significant decrease in the low water level (at low discharge levels) at the Jiujiang station. ② After the operation of the TGD, the variation trend in the water level at the Jiujiang station was the same as that before TGD operation. However, the water levels at the Hankou and Huangshigang stations showed significant decreases with decreasing amplitudes of 0.072 and 0.045 m/a and 0.048 and 0.027 m/a, respectively, under discharge levels of 12 000 and 20 000 m3/s, respectively. The critical conversion discharge of water level change was approximately 30 000 m3/s, and there was no obvious water level change near this discharge value. When the discharge was higher than 30 000 m3/s, the water level showed a nonsignificant upward trend, and the increase amplitudes at 45 000 m3/s were 0.037 and 0.049 m/a, respectively. ③ The main reason for the observed water level decrease is river erosion when the discharge is lower than the critical conversion discharge. The main reason why there is no obvious water level change near the critical conversion discharge is that the effect of an increased resistance nearly offsets the influence of river erosion. The main reason for the water level increase is the higher resistance when the discharge exceeds the critical conversion discharge. The obvious increase in the flood water level in individual years is due to the effect of downstream water level jacking.

ObjectiveIn order to improve the safety of ship navigation, this study focuses on virtually aided ship navigation strategies.MethodsTwo different inland river routes are chosen for the simulation of virtually aided ship navigation models based on the fluid-structure interaction mechanism, while taking the navigation rules and flow details of the rivers into consideration. The simulation of the ship sailing process on a typical inland river route under specific current conditions provides the corresponding virtually aided navigation plan in which the ship's velocity, location and course are obtained in a timely manner. ResultsIt is found that the simulation method established on the basis of Fluent can be used to solve the problems of multi-degree-of-freedom motion and fluid-structure interaction. When sailing through bends or branches, steering with a small rudder angle over long distances ensures safe navigation and prevents speed reduction and significant lateral displacement.ConclusionThe proposed method can be effectively combined with the flow field information of digital channels to simulate the ship sailing process, thereby providing data support for the decision-making of intelligent navigation on inland river routes.

A systematic analysis on the effects of the changed interactive relationships between rivers and lakes on fairway depth can help to support the sustainable development of the "Gold waterway" of the Yangtze River.In this study,we investigate the variation characteristics of water and sediment,and the relationships between the evolution of shoals and channels and the fairway depth,in the Lake Dongting-Jingjiang Reach confluence of the Yangtze River.The results indicate that since the operation of the Three Gorges Project,the split ratio of watersplit and the sediment distribution of the three outlets of Lake Dongting continued to decrease.Along with the decreasing flow of Lake Dongting,the relative increase in the runoff of the Jingjiang Reach increases the riverbed erosion scouring intensity,which keep the split ratio of water split and the sediment distribution of the three outlets at a lower value.The riverbed erosion scouring of the Jingjiang Reach has created a promising foundation for an increase in the waterway dimensions.However,the length of the reach fail to meet the requirement of 4.5 m× 200 m（water depth × width） is 12.6 km in the river-lake confluence,accounting for 68.35% of the total length of obstructed navigation.The mechanisms of the obstructed navigation are as follow:at the reach affected by the first outlet（Songzikou）,a 4.5 m flume has been formed,but its width is less than 200 m.The instability of water split and the shrinkage of bottomland restrict the stability of channel conditions.Moreover,the reductions of low-flow water level and the phenomenon of "steep slope and rapid current" affect the ships’ safety.At the reach（Taipingkou） affected by the second outlet,the shrinkage of the bottomland,and the intersecting braided river channels make the low-flow routes unstable,the water depth being less than 4.5 m.At the reach（Ouchikou） affected by the third outlet,the shoreline of the reach has collapsed and retreated significantly.Additionally,point bar beach erosion scouring has led to the downstream movement of sediment,which have caused the downstream waterway width at the reach to be reduced to less than 200 m or formed shoals with a water depth of less than 4.5 m.Owing to the characteristics of scouring and deposition in the bends reaches and the jacking effect of the lake’s outflow backwater,the water depth of some shoals are less than 4.5 m in the navigation waterway.However,the jacking effect of the lake’s outflow backwater is weakening,which benefits the improvement of channel conditions.