This study presents an innovative theoretical approach to predicting the scour depth around a foundation in large-scale model tests based on small-scale model tests under combined waves and currents.In the present app...This study presents an innovative theoretical approach to predicting the scour depth around a foundation in large-scale model tests based on small-scale model tests under combined waves and currents.In the present approach,the hydrodynamic parameters were designed based on the Froude similitude criteria.To avoid the cohesive behavior,we scaled the sediment size based on the settling velocity similarity,i.e.,the suspended load similarity.Then,a series of different scale model tests was conducted to obtain the scour depth around the pile in combined waves and currents.The fitting formula of scour depth from the small-scale model tests was used to predict the results of large-scale tests.The accuracy of the present approach was validated by comparing the prediction values with experimental data of large-scale tests.Moreover,the correctness and accuracy of the present approach for foundations with complex shapes,e.g.,the tripod foundation,was further checked.The results indicated that the fitting line from small-scale model tests slightly overestimated the experimental data of large-scale model tests,and the errors can be accepted.In general,the present approach was applied to predict the maximum or equilibrium scour depth of the large-scale model tests around single piles and tripods.展开更多
A numerical model was used to analyze the motion response and mooring tension of a submerged fish reef system. The system included a net attached to a rigid structure suspended up from the bottom with a single, high t...A numerical model was used to analyze the motion response and mooring tension of a submerged fish reef system. The system included a net attached to a rigid structure suspended up from the bottom with a single, high tension mooring by fixed flotation. The analysis was performed by using a Morison equation type finite element model configured with truss elements. Input forcing parameters into the model consisted of both regular and irregular waves, with and without a steady current. Heave, surge and pitch dynamic calculations of the reef structure were made. Tension response results of the attached mooring line were also computed. Results were analyzed in both the time and frequency domain in which appropriate, linear transfer functions were calculated. The influence of the current was more evident in the tension and heave motion response data. This is most likely the result of the large buoyancy characteristics of the reef structure and the length of the mooting cable. Maximum mooting component tension was found to be 13.9 kN and occurred when the reef was subjected to irregular waves with a co-linear current of 1.0 m/s velocity. The results also showed that the system had little damping （in heave） with damped natural periods of 2.8 s. This combination of system characteristics promotes a possible resonating situation in typical open sea conditions with similar wave periods.展开更多
Based on the linear wave theory, the lift force on the cylinder under the action of both regular waves and currents related to inline force and the resultant force has been investigated. The relationship between the h...Based on the linear wave theory, the lift force on the cylinder under the action of both regular waves and currents related to inline force and the resultant force has been investigated. The relationship between the hydrodynamic coefficients of resultant force Cf, of drag force Cd, of inertia force Cm and of lift force CL and the redefined KC number is reported. It is indicated that in a certain region of KC number, the influence of lift force on the resultant force can not be ignored.展开更多
Erosion,scour and sedimentation are the most common phenomena which should be considered in the design of marine structures.Seas and oceans are dynamic environments,hence studying them in more details,gathering more i...Erosion,scour and sedimentation are the most common phenomena which should be considered in the design of marine structures.Seas and oceans are dynamic environments,hence studying them in more details,gathering more information about their bathymetric changes and pursuing their historical evolution could be beneficial in the efficient design of marine structures such as:jetties,groins and breakwaters.To achieve this goal one desperately needs to know about currents and waves and the effects of their interactions as well as the rate of sedimentation(Net Gain),and erosion(Net Loss)in the field.On the other hand,to obtain a sufficient depth to facilitate marine traffics in the harbors the rate of sediment deposition must be calculated,offering effective annual dredging programs.In this research the pool of Nowshahr port and some parts to the east and west were modeled.Sediment transport direction was compatible with the counter-clock-wise circulation of the Sothern part of Caspian Sea.Wind data,water surface elevation,and hydrographic points from the bathymetric surveys applied in the hydrodynamic module of Mike 21 and the output of the hydrodynamic module(HD)were used as inputs for sediment transport module(ST).The result of the ST module shows that the main direction considering dominant waves is from northwest of the Caspian Sea to the southeast.Also,net rate of sediment transfer is from west to east.By approaching to the main breakwater arms from the west side sediment transport rate decreases which means deposition occurs behind the western arm.展开更多
基金financially supported by the Fundamental Research Funds for the Central Universities(No.202061027)the National Natural Science Foundation of China(No.41572247)。
文摘This study presents an innovative theoretical approach to predicting the scour depth around a foundation in large-scale model tests based on small-scale model tests under combined waves and currents.In the present approach,the hydrodynamic parameters were designed based on the Froude similitude criteria.To avoid the cohesive behavior,we scaled the sediment size based on the settling velocity similarity,i.e.,the suspended load similarity.Then,a series of different scale model tests was conducted to obtain the scour depth around the pile in combined waves and currents.The fitting formula of scour depth from the small-scale model tests was used to predict the results of large-scale tests.The accuracy of the present approach was validated by comparing the prediction values with experimental data of large-scale tests.Moreover,the correctness and accuracy of the present approach for foundations with complex shapes,e.g.,the tripod foundation,was further checked.The results indicated that the fitting line from small-scale model tests slightly overestimated the experimental data of large-scale model tests,and the errors can be accepted.In general,the present approach was applied to predict the maximum or equilibrium scour depth of the large-scale model tests around single piles and tripods.
基金supported by the Korea Research Foundation Grant funded by the Korean Government(MOEHRD)(KRF-2007-313-F00073)Technology Development Program for Food,Agriculture,Forestry and Fisheries,Republic of Korea
文摘A numerical model was used to analyze the motion response and mooring tension of a submerged fish reef system. The system included a net attached to a rigid structure suspended up from the bottom with a single, high tension mooring by fixed flotation. The analysis was performed by using a Morison equation type finite element model configured with truss elements. Input forcing parameters into the model consisted of both regular and irregular waves, with and without a steady current. Heave, surge and pitch dynamic calculations of the reef structure were made. Tension response results of the attached mooring line were also computed. Results were analyzed in both the time and frequency domain in which appropriate, linear transfer functions were calculated. The influence of the current was more evident in the tension and heave motion response data. This is most likely the result of the large buoyancy characteristics of the reef structure and the length of the mooting cable. Maximum mooting component tension was found to be 13.9 kN and occurred when the reef was subjected to irregular waves with a co-linear current of 1.0 m/s velocity. The results also showed that the system had little damping （in heave） with damped natural periods of 2.8 s. This combination of system characteristics promotes a possible resonating situation in typical open sea conditions with similar wave periods.
文摘Based on the linear wave theory, the lift force on the cylinder under the action of both regular waves and currents related to inline force and the resultant force has been investigated. The relationship between the hydrodynamic coefficients of resultant force Cf, of drag force Cd, of inertia force Cm and of lift force CL and the redefined KC number is reported. It is indicated that in a certain region of KC number, the influence of lift force on the resultant force can not be ignored.
文摘Erosion,scour and sedimentation are the most common phenomena which should be considered in the design of marine structures.Seas and oceans are dynamic environments,hence studying them in more details,gathering more information about their bathymetric changes and pursuing their historical evolution could be beneficial in the efficient design of marine structures such as:jetties,groins and breakwaters.To achieve this goal one desperately needs to know about currents and waves and the effects of their interactions as well as the rate of sedimentation(Net Gain),and erosion(Net Loss)in the field.On the other hand,to obtain a sufficient depth to facilitate marine traffics in the harbors the rate of sediment deposition must be calculated,offering effective annual dredging programs.In this research the pool of Nowshahr port and some parts to the east and west were modeled.Sediment transport direction was compatible with the counter-clock-wise circulation of the Sothern part of Caspian Sea.Wind data,water surface elevation,and hydrographic points from the bathymetric surveys applied in the hydrodynamic module of Mike 21 and the output of the hydrodynamic module(HD)were used as inputs for sediment transport module(ST).The result of the ST module shows that the main direction considering dominant waves is from northwest of the Caspian Sea to the southeast.Also,net rate of sediment transfer is from west to east.By approaching to the main breakwater arms from the west side sediment transport rate decreases which means deposition occurs behind the western arm.
