scholarly journals Ship-to-Ship Interaction during Overtaking Operation in Shallow Water

2015 ◽  
Vol 59 (03) ◽  
pp. 172-187
Author(s):  
Zhi-Ming Yuan ◽  
Paula Kellet ◽  
Atilla Incecik ◽  
Osman Turan ◽  
Evangelos Boulougouris
Keyword(s):  
Shallow Water ◽  
Hydrodynamic Interaction ◽  
Contributory Factor ◽  
Test Results ◽  
Loss Of Life ◽  
Narrow Channels ◽  
Rankine Source ◽  
Wave Patterns ◽  
Computational Fluid Dynamics Cfd ◽  
Numerical Program

Hydrodynamic interaction continues to be a major contributory factor in marine casualties and hazardous incidents, in particular, in the case of overtaking operations. The situation becomes even worse when the overtaking operation occurs in shallow and narrow channels, where the interaction can cause the vessels to collide and, in one case has caused the capsizal of the smaller vessel with loss of life. The aim of this article is to propose a methodology, as well as to discuss the development of a numerical program, to predict the ship-to-ship interaction during overtaking operations in shallow water. Since the vessels involved in this study have different forward speeds, an uncoupled method will be used to solve the boundary value problem. The in-house multibody hydrodynamic interaction program MHydro, which is based on the 3D Rankine source method, is used and extended here to investigate the interactive forces and wave patterns between two ships during an overtaking operation. The calculations given in this article are compared with model test results as well as published computational fluid dynamics (CFD) calculations. Very satisfactory agreement has been obtained, which indicates that the proposed methodology and developed program are successfully validated to predict the hydrodynamic interaction between two ships advancing in confined waters. The discussions also highlight the speed effects.

scholarly journals A Fast Algorithm for the Prediction of Ship-Bank Interaction in Shallow Water

2020 ◽  
Vol 8 (11) ◽  
pp. 927
Author(s):  
Jin Huang ◽  
Chen Xu ◽  
Ping Xin ◽  
Xueqian Zhou ◽  
Serge Sutulo ◽  
...  
Keyword(s):  
Shallow Water ◽  
Hydrodynamic Interaction ◽  
Surface Boundary ◽  
Complex Flow ◽  
Ship Maneuvering ◽  
Interaction Forces ◽  
Rankine Source ◽  
Bank Effect ◽  
Sinkage And Trim ◽  
Navigation Safety

The hydrodynamic interaction induced by the complex flow around a ship maneuvering in restricted waters has a significant influence on navigation safety. In particular, when a ship moves in the vicinity of a bank, the hydrodynamic interaction forces caused by the bank effect can significantly affect the ship’s maneuverability. An efficient algorithm integrated in onboard systems or simulators for capturing the bank effect with fair accuracy would benefit navigation safety. In this study, an algorithm based on the potential-flow theory is presented for efficient calculation of ship-bank hydrodynamic interaction forces. Under the low Froude number assumption, the free surface boundary condition is approximated using the double-body model. A layer of sources is dynamically distributed on part of the seabed and bank in the vicinity of the ship to model the boundary conditions. The sinkage and trim are iteratively solved via hydrostatic balance, and the importance of including sinkage and trim is investigated. To validate the numerical method, a series of simulations with various configurations are carried out, and the results are compared with experiment and numerical results obtained with RANSE-based and Rankine source methods. The comparison and analysis show the accuracy of the method proposed in this paper satisfactory except for extreme shallow water cases.

Hydrodynamic Interaction Between Two Ships Arranged Side by Side in Shallow Water

2014 ◽  
Author(s):  
Zhiming Yuan ◽  
Atilla Incecik ◽  
Shi He
Keyword(s):  
Shallow Water ◽  
Hydrodynamic Interaction ◽  
Wave Pattern ◽  
Present Calculation ◽  
Water Effect ◽  
Green Function Method ◽  
Rankine Source ◽  
The Mean ◽  
Shallow Water Effect ◽  
Good Agreement

The hydrodynamic interaction between two ships with side-by-side arrangement is analyzed by using 3-D Rankine source panel code. The source points are distributed over the mean wetted body surface as well as on the free surface. The shallow water effect has been taken into consideration. Moreover, the influence of the distance between the vessels is also investigated. To verify the present code, two Wigley III hulls are simulated both in beam sea and head sea conditions. The wave pattern and the motion RAOs of 6-DOF are calculated by present code and compared with WADAM program which is based on Green function method. From the comparisons, good agreement is found between present calculation and Wadam results. It is found that the hydrodynamic interactions are generally important especially in beam sea case. The resonant frequency is greatly influenced by the distance between the vessels.

Optimum Distance Between Two Advancing Ships Arranged Side by Side

2015 ◽  
Author(s):  
Zhi-Ming Yuan ◽  
Atilla Incecik ◽  
Sandy Day
Keyword(s):  
Hydrodynamic Interaction ◽  
Optimization Method ◽  
Hydrodynamic Interactions ◽  
Far Field ◽  
Theoretical Assumption ◽  
Rankine Source ◽  
Wave Patterns ◽  
Exciting Forces ◽  
Wave Exciting Forces ◽  
Field Wave

The hydrodynamic interaction between two advancing ships is very important. Because of the hydrodynamic interactions, even relatively small waves can induce large motions of the smaller ship due to the proximity of the larger ship. The aim of this paper is to develop a method to optimize the spacing between two advancing ships, in order to minimize the hydrodynamic interactions. The optimization method is based on the far-field wave patterns produced by a translating and oscillating source point. For values of the parameter τ > 0.25 (τ = ωeu/g) there is a fan-shaped quiescent region in front of the vessel. As τ increases, the range of the fan-shaped quiescent region will be expanded. It can be supposed that if the two ships are located in each other’s fan-shaped quiescent region, the hydrodynamic interactions can be minimized. This assumption was validated through the numerical simulation, which was based on a 3-D Rankine source panel method. We calculated and compared the wave exciting forces and wave patterns of two Wigley hulls advancing in waves side by side. The numerical results were consistent with our theoretical assumption.

An anti-crystallization design of selective catalytic reduction nozzle holder

2021 ◽  
pp. 095440702097084
Author(s):  
Dewen Liu ◽  
Kai Lu ◽  
Shusen Liu ◽  
Yan Wu ◽  
Shuzhan Bai
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Injection System ◽  
Test Results ◽  
Verification Methods ◽  
Crystallization Risk ◽  
Protective Cover ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Good Agreement

From the aspect of reducing the risk of crystallization on nozzle surface, a new design of nozzle protective cover was to solve the problem in selective catalytic reduction (SCR) urea injection system. The simulation calculation and experimental verification methods were used to compare different schemes. The results show that reducing the height of nozzle holder can reduce the vortex currents near nozzle surface and effectively reduce the risk of crystallization on the nozzle surface. It is proposed to install a protective cover in the nozzle holder under the scheme of reducing the height of nozzle holder, which can further eliminate the vortex. Simulation and test results demonstrate good agreement under the rated running condition. The scheme of adding a protective cover in the nozzle holder shows the least crystallization risk by computational fluid dynamics (CFD) method. The crystallization cycle test shows that, after the height of nozzle holder is reduced, the risk of crystallization on the nozzle surface is reduced correspondingly. The addition of a protective cover in the nozzle holder solves the problem of crystallization on the nozzle surface, which provides a new method for anti-crystallization design.

A Simple Approach to the Study of Wave Patterns

2014 ◽  
Vol 156 (A3) ◽  
Keyword(s):  
Numerical Methods ◽  
Shallow Water ◽  
Froude Number ◽  
Critical Speed ◽  
Graphical Method ◽  
Three Dimensional ◽  
Simple Approach ◽  
Critical Depth ◽  
Simple Manner ◽  
Wave Patterns

The paper revisits some pioneering work of Sir Thomas Havelock on wave patterns with particular attention focused on his graphical method of analysis. Motivated by a desire to explore this method further using numerical methods, it is extended in a simple manner to give three-dimensional illustrations of the wave patterns of a point disturbance in deep and shallow water. All results are confined to the sub- and trans-critical regimes with some obtained very close to the critical Depth Froude Number. Some conclusions are drawn on the wave types produced when operating close to the critical speed and their decay with distance off.

The Mechanism and Solution of Harmonic Gear Whine Noise in Automotive Transmission Systems

2007 ◽  
Author(s):  
Jaegon Yoo ◽  
Koo-Tae Kang ◽  
Jin-Wook Huh ◽  
Chimahn Choi
Keyword(s):  
Surface Structure ◽  
Design Parameters ◽  
Test Results ◽  
Gear Noise ◽  
Transfer Path ◽  
Gear Design ◽  
Automotive Transmission ◽  
Wave Patterns ◽  
Tooth Modification ◽  
Harmonic Noise

Since gear noise in automotive is one of the most unpleasant noises for passengers, various solutions, such as gear design optimization, tooth modification and transfer path reformations in the vehicle have been developed. But, these attempts are mainly focused on the fundamental mesh excitation of the gear set without any consideration of their harmonic noise (1st, 2nd or higher). Harmonic gear whine noise is easily audible in the vehicle because of their high frequency characteristics in spite of low sound pressure level. This annoying pure-tone noise is usually issued in the transmission system composed of the gears produced by grinding process. This paper will present the main sources of this harmonic gear whine noise with the test results of gears with identical design parameters but having different surface structure (roughness parameters, wave patterns). Additionally, manufacturing guidelines of gear surface structure will be proposed at the end of this paper.

scholarly journals Numerical Study on Wave-Ice Interaction in the Marginal Ice Zone

2020 ◽  
Vol 9 (1) ◽  
pp. 4
Author(s):  
Tiecheng Wu ◽  
Wanzhen Luo ◽  
Dapeng Jiang ◽  
Rui Deng ◽  
Shuo Huang
Keyword(s):  
Sea Ice ◽  
Numerical Study ◽  
Test Results ◽  
Towing Tank ◽  
Marginal Ice Zone ◽  
Computational Fluid Dynamics Cfd ◽  
Numerical Research ◽  
Ice Floes ◽  
Cfd Method ◽  
Six Degree Of Freedom

The effect of waves on ice sheet is critical in the marginal ice zone (MIZ). Waves break large sea ice into small pieces and cause them to collide with each other. Simultaneously, the interaction between sea ice and waves attenuates these waves. In this study, a numerical research is conducted based on a computational fluid dynamics (CFD) method to investigate the response of single ice floe to wave action. The obtained results demonstrate that the sea ice has a violent six degree of freedom (6DoF) motion in waves. Ice floes with different sizes, thicknesses, and shapes exhibit different 6DoF motions under the action of waves. The heave and surge response amplitude operator (RAO) of the sea ice are related to wavelength. Furthermore, the overwash phenomenon can be observed in the simulation. The obtained results are compared with the model test in the towing tank based on artificial ice, and they agree well with test results.

An Analytical and Experimental Assessment of a Diffuser Flow Phenomenon as a Precursor to Stall

2012 ◽  
Author(s):  
James M. Sorokes ◽  
Jorge E. Pacheco ◽  
Clementine Vezier ◽  
Syed Fakhri
Keyword(s):  
Rotating Stall ◽  
Flow Coefficient ◽  
Centrifugal Impeller ◽  
Test Results ◽  
Vaneless Diffuser ◽  
Diffuser Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Analyses ◽  
Validation Testing ◽  
Lower Flow Rate

The paper describes an experimental and analytical study on the vaneless diffuser downstream of a high flow coefficient, high inlet relative Mach number centrifugal impeller. The diffuser flowfield exhibited a unique behavior in which the low momentum zone typically found along the shroud side of a centrifugal compressor diffuser suddenly shifted to the hub side of the diffuser just prior to the onset of diffuser rotating stall. The phenomenon was observed in the computational fluid dynamics (CFD) analyses conducted as well as in the experimental data obtained during stage validation testing. A review of the analytical and test results suggested that the phenomenon was at least partially attributable to the level of diffusion in the vaneless diffuser. Modifications made to reduce the diffusion rate were shown by CFD analysis to move the onset of the unusual shift of low momentum flow to a much lower flow rate. The modifications also increased the efficiency of the overall stage by 1.2%.

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