scholarly journals Hydrodynamic Characteristics of Different Undulatory Underwater Swimming Positions Based on Multi-Body Motion Numerical Simulation Method

2021 ◽  
Vol 18 (22) ◽  
pp. 12263
Author(s):  
Jin Yang ◽  
Tianzeng Li ◽  
Zhiya Chen ◽  
Chuan Zuo ◽  
Xiaodong Li
Keyword(s):  
Numerical Simulation ◽  
Water Depth ◽  
Water Surface ◽  
Swimming Performance ◽  
Simulation Method ◽  
Lateral Position ◽  
Body Motion ◽  
Hydrodynamic Characteristics ◽  
Joint Center ◽  
Multi Body

The study of hydrodynamic characteristics of swimming is the main way to optimize the swimming movement. The relationship between position, water depth, and swimming performance of undulatory underwater swimming are one of the main concerns of scholars. Therefore, the aim of this study is to analyze the swimming performance of three different undulatory underwater swimming positions under various swimming depths using a numerical simulation method based on multi-body motion. The simulation was conducted using 3D incompressible Navier–Stokes equations using the RNG k-ε turbulence closure equations, and in combination with the VOF method thus that we could include the water surface in our calculations. Different swimming depths based on the distance from the shoulder joint center to the initial water surface were considered. The velocity of the shoulder joint center was captured with a swimming motion monitoring system (KiSwim) and compared with the calculated results. The study found that there was a significant difference in the hydrodynamic characteristics of the three undulatory underwater swimming positions (i.e., the dorsal, lateral, and frontal positions) when swimming near the water surface, and the difference decreased as the swimming depth increased. There was a negative correlation (R(dorsal)= −0.928, R(frontal)= −0.937, R(lateral)= −0.930) between the swimming velocities of the three undulatory underwater swimming positions and the water depth (water depth= 0.2–0.7 m) and that the lateral position had the greatest average velocity. Therefore, it is recommended that swimmers travel at least 0.5 m below the water surface in any undulatory underwater swimming position in order to avoid excessive drag forces. As the swimmer approaches the water surface, the lateral position is worth considering, which has better velocity and hydrodynamic advantage than the other two undulatory underwater swimming positions.

scholarly journals Buried Depth of a Submarine Pipeline Based on Anchor Penetration

2019 ◽  
Vol 7 (8) ◽  
pp. 257
Author(s):  
Xueyuan Zhu ◽  
Qinglong Hao ◽  
Jie Zhang
Keyword(s):  
Numerical Simulation ◽  
Penetration Depth ◽  
Water Depth ◽  
Calculation Method ◽  
Water Surface ◽  
Submarine Pipeline ◽  
Projected Area ◽  
Actual Measurement ◽  
Calculation Results ◽  
The Relationship

Anchor penetration is an important issue involved in the study of submarine pipeline damage accidents. To explore the penetration of a ship’s anchor under certain conditions, this study investigated the motion and force of an anchor and formulated a calculation method for the bottoming speed of an anchor. Meanwhile, the depth of anchor penetration was calculated under different conditions according to bottoming speed through programming. Finally, the reliability of the calculation method for the penetration depth was verified by comparing the actual measurement and the numerical simulation. On the basis of the findings, the calculation results were further analyzed, and conclusions were derived regarding the relationship between anchor mass, the horizontal projected area of the anchor, the anchor height on the water surface, and water depth. The conclusions provide suggestions for the application of anchor penetration in terms of seabed depth with certain reference values.

Research on Collision Mechanism for a Ship Colliding With a Spar Platform

2007 ◽  
Author(s):  
Zhiqiang Hu ◽  
Weicheng Cui ◽  
Longfei Xiao ◽  
Jianmin Yang
Keyword(s):  
Numerical Simulation ◽  
Structural Damage ◽  
Simulation Method ◽  
Hydrodynamic Characteristics ◽  
Spar Platform ◽  
Mooring Lines ◽  
Hull Design ◽  
Truss Spar ◽  
Internal Mechanism ◽  
Double Hull

The collision mechanisms of spar platform haven’t caused so much attention as that of ships in the past, for the short of this kind of collision accidents reported. But this does not mean the impossibility of the collision accident in the future. The research on external mechanism and internal mechanism for a ship colliding with a spar platform is introduced in this paper. A model test is designed to study the external mechanism. The collision scenario is described as a ship colliding with a spar platform moored in 1500 meters water depth. The specifics of the spar’s motions and the tension forces of the mooring lines are gathered, to find the hydrodynamic characteristics in the collision scenario. It is found that the maximal displacements and the maximal pitch angles of the spar platform, and the maximal tension forces of mooring lines are all linearly proportional to the initial velocity of the striking ship basically. Mooring lines play elastic roles in the collision course. The internal mechanism of the ship colliding with the spar platform is achieved by numerical simulation method and the software used is MSC.DYTRAN. A Truss-Spar is taken as the object and a double hull structural design is adopted in the part of hard tank near water surface. The curves of collision characters and the structural damage are obtained. The crashworthiness of the double hull design is verified, through the numerical simulation results.

Three-Dimensional Numerical Simulation of the Flow around Two Side-by-Side Cylinders of Different Diameters

2014 ◽  
Vol 721 ◽  
pp. 199-202
Author(s):  
Zhen Xiao Bi ◽  
Zhi Han Zhu
Keyword(s):  
Numerical Simulation ◽  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Simulation Method ◽  
Scale Model ◽  
Hydrodynamic Characteristics ◽  
Eddy Simulation ◽  
Drag And Lift ◽  
Different Diameters

This paper presents the calculation of hydrodynamic characteristics of two side-by-side cylinders of different diameters in three dimensional incompressible uniform cross flow by using Large-eddy simulation method based on dynamical Smagorinsky-Lilly sub-grid scale model. Solution of the three dimensional N-S equations were obtained by the finite volume method. The numerical simulation focused on investigating the characteristic of the pressure distribution (drag and lift force), vorticity field and turbulence Re=. Results shows that, the asymmetry of the time –averaged velocity distribution in the flow direction behind the two cylinders is very obvious; the frequency of eddy shedding of the small cylinder is about twice of the large one. The turbulence of cylinders is more obvious.

scholarly journals Simulation of vertical tidal turbine based on OpenFOAM and influence of inlet turbulence

2019 ◽  
Vol 272 ◽  
pp. 01017
Author(s):  
Liu Yun-ya ◽  
Yu-chen Yang ◽  
Ya-wen Yang
Keyword(s):  
Numerical Simulation ◽  
Turbulence Model ◽  
Cfd Simulation ◽  
Vertical Axis ◽  
Simulation Method ◽  
Hydrodynamic Characteristics ◽  
Numerical Simulation Method ◽  
Tidal Turbine ◽  
Cfd Method ◽  
Control Equation

This paper first introduces the basic theory of CFD method, including basic control equations, finite volume method, control equation solving algorithm and turbulence model selection. Second, based on OpenFOAM, an open-source fluid mechanics software, a numerical simulation method of vertical axis tidal turbine was proposed by using k-ω SST turbulence model and PIMPLE algorithm. The hydrodynamic characteristics of the vertical axis turbine were studied, and the calculation results were compared with experiments. The higher consistency proves the feasibility of the numerical simulation method proposed in this paper. Finally, the influence of inlet turbulence on numerical simulation was explored, and a set of effective CFD simulation strategies was concluded, which provided a valuable reference for future CFD simulation and research on vertical axis tidal turbines.

scholarly journals Hydrodynamic Model of Diver–DPV Coupled Multi-Body and Its Underwater Cruising Numerical Simulation

2021 ◽  
Vol 9 (2) ◽  
pp. 140
Author(s):  
Hansheng Li ◽  
Fenglei Han ◽  
Haitao Zhu ◽  
Jiawei Zhang ◽  
Weipeng Zhang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Hydrodynamic Model ◽  
High Speed ◽  
Rigid Body Dynamics ◽  
Body Motion ◽  
Final Conclusion ◽  
Unique Problem ◽  
Unmanned Underwater Vehicles ◽  
Friction Resistance ◽  
Multi Body

Diver propulsion vehicles (hereinafter referred to as DPV) are a kind of small vehicle with underwater high-speed used by divers, who are able to grasp or ride on, and operate the volume switch to change the speed. Different from unmanned underwater vehicles (UUVs), the interference caused by diver’s posture changing is a unique problem. In this paper, a Diver–DPV multi-body coupling hydrodynamic model considering rigid body dynamics and fluid disturbance is established by analyzing the existing DPV related equipment. The numerical simulation of multi-body articulated motion is realized by using Star-CCM+ overlapping grid and DFBI 6-DOF body motion method. Five cases of DPVs underwater cruising in a straight-line when restraining diver movement is simulated, and five cases with free diver movement are simulated too. Finally, the influence of the diver’s posture changing on the cruising speed resistance is analyzed, and the motion equation including the disturbance is solved. The final conclusion is that, the disturbance is favorable at high speed, which can reduce the cruising resistance, and unfavorable at low speed, which increases the cruising resistance. The friction resistance Ff always accounts for the main part in all speed cases.

scholarly journals Risk Analysis and Optimization of Water Surface Deviation from Shafts in the Filling–Emptying System of a Mega-Scale Hydro-Floating Ship Lift

Water ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1377
Author(s):  
Jingkai Liu ◽  
Yaan Hu ◽  
Zhonghua Li ◽  
Shu Xue
Keyword(s):  
Numerical Simulation ◽  
Model Theory ◽  
Water Surface ◽  
Cloud Model ◽  
Simulation Method ◽  
Running Safety ◽  
Surface Deviations ◽  
Surface Deviation ◽  
Ship Lift ◽  
Cloud Model Theory

Hydro-floating ship lifts are a milestone in the field of high dam navigation. In order to ensure the running safety of a hydro-floating ship lift, the effective integration of a numerical simulation method and cloud model theory was carried out to deal with the hydrodynamic risks presented by water surface deviations from the shafts in the filling–emptying system such as a lock. In this study, the average values of water surface deviation from the shafts were 0.2, 0.22 and 0.24 m, through numerical simulation on a similar hydro-floating ship lift at the lifting heights of 80, 100 and 120 m, respectively. An increase in the lifting height causes the water surface deviation from the shafts to increase, and the hydrodynamic risk is greatly increased in the equal inertial pipeline filling–emptying system. In addition, the water surface deviations from the shafts of the equal inertial pipeline and longitudinal culvert filling–emptying system like a lock were compared. The longitudinal culvert was better at optimizing running safety in the filling–emptying system and dealing with the uncertainty of water surface deviation from the shafts. The results show that the numerical simulation method and cloud model theory can effectively control the risk of water surface deviation from the shafts and can be used to aid in decision-making for risk prevention in relation to hydro-floating ship lifts.

Three-Dimensional Numerical Simulation of the Hydraulic Characteristics of Spillway in Gushitan Reservoir

2012 ◽  
Vol 256-259 ◽  
pp. 2403-2406
Author(s):  
Shu Guang Jing ◽  
Xue Ping Gao ◽  
Lai Fei Jia ◽  
Li Ping Xu
Keyword(s):  
Numerical Simulation ◽  
Water Surface ◽  
Three Dimensional ◽  
Simulation Method ◽  
Vof Method ◽  
Hydraulic Characteristics ◽  
Bottom Pressure ◽  
Surface Profiles ◽  
Simulation Results ◽  
Good Agreement

Based on standard k-ε turbulence model and the VOF method for tracking free surface, hydraulic characteristics of the spillway in Gushitan Reservoir are simulated with a 3-D numerical model. The discharge capacity, water surface profiles, bottom pressure distribution and flow pattern are studied. Numerical simulation results have been in good agreement with experimental results, showing fine feasibility to study hydraulic characteristics of the spillway with the VOF method. The hydraulic characteristics acquired by the numerical simulation method can be used for spillway design.

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