scholarly journals RANS Prediction of Wave-Induced Ship Motions, and Steady Wave Forces and Moments in Regular Waves

2021 ◽  
Vol 9 (12) ◽  
pp. 1459
Author(s):  
Qingze Gao ◽  
Lifei Song ◽  
Jianxi Yao
Keyword(s):  
Wave Amplitude ◽  
Ship Motions ◽  
Wave Forces ◽  
Inertial Effects ◽  
Added Resistance ◽  
Oblique Waves ◽  
Steady Wave ◽  
Head Waves ◽  
Wave Induced ◽  
Hydrodynamic Effects

The wave-induced motions, and steady wave forces and moments for the oil tanker KVLCC2 in regular head and oblique waves are numerically predicted by using the expanded RANS solver based on OpenFOAM. New modules of wave boundary condition are programed into OpenFOAM for this purpose. In the present consideration, the steady wave forces and moments include not only the contribution of hydrodynamic effects but also the contribution of the inertial effects due to wave-induced ship motions. The computed results show that the contribution of the inertial effects due to heave and pitch in head waves is non-negligible when wave-induced motions are of large amplitude, for example, in long waves. The influence of wave amplitude on added resistance in head waves is also analyzed. The dimensionless added resistance becomes smaller with the increasing wave amplitude, indicating that added resistance is not proportional to the square of wave amplitude. However, wave amplitude seems not to affect the heave and pitch RAOs significantly. The steady wave surge force, sway force and yaw moment for the KVLCC2 with zero speed in oblique waves are computed as well. The present RANS results are compared with available experimental data, and very good agreements are found between them.

scholarly journals Prediction of Ship Motions and Added Resistance in Head Waves Base on Linera Strip Theory

2019 ◽  
Vol 8 (2S10) ◽  
pp. 705-709
Keyword(s):  
Ship Design ◽  
Wave Parameter ◽  
Ship Motions ◽  
Wave Forces ◽  
Sea Waves ◽  
Added Resistance ◽  
Ship Routing ◽  
Strip Theory ◽  
Head Waves ◽  
Calculation Results

Prediction of ship motions and added resistance is an importance step in the ship design phases and considerable researches are related to this subject. It plays a unique role in main seakeeping characteristics such as maximum ship speed in sea waves, voluntary and involuntary speed reduction due to wave forces and added resistance as well as ship safety and ship routing, which affect transportation time, fuel consumption and total cost. The effects of environmental condition on calculation results is analyzed by performing some calculation with different wave parameter of JONSWAP spectra. The calculation results for the DTMB vessel are examined by the comparisons with experimental data carried out at Ship Design and Research Centre's towing tank in Poland, and show good agreement, which demonstrates the ability of the present method to assess seakeeping characteristics at the initial ship design phases. The calculation is performed by using the commercial software MAXSURF.

NUMERICAL PREDICTION OF VERTICAL SHIP MOTIONS AND ADDED RESISTANCE

2021 ◽  
Vol 159 (A4) ◽  
Author(s):  
F Cakici ◽  
E Kahramanoglu ◽  
A D Alkan
Keyword(s):  
Deep Water ◽  
High Speed ◽  
Computer Experiments ◽  
Navier Stokes ◽  
Ship Motions ◽  
Added Resistance ◽  
Strip Theory ◽  
Head Waves ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method

Along with the development of computer technology, the capability of Computational Fluid Dynamics (CFD) to conduct ‘virtual computer experiments’ has increased. CFD tools have become the most important tools for researchers to deal with several complex problems. In this study, the viscous approach called URANS (Unsteady Reynolds Averaged Navier-Stokes) which has a fully non-linear base has been used to solve the vertical ship motions and added resistance problems in head waves. In the solution strategy, the FVM (Finite Volume Method) is used that enables numerical discretization. The ship model DTMB 5512 has been chosen for a series of computational studies at Fn=0.41 representing a high speed case. Firstly, by using CFD tools the TF (Transfer Function) graphs for the coupled heave- pitch motions in deep water have been generated and then comparisons have been made with IIHR (Iowa Institute of Hydraulic Research) experimental results and ordinary strip theory outputs. In the latter step, TF graphs of added resistance for deep water have been generated by using CFD and comparisons have been made only with strip theory.

Numerical Prediction of Vertical Ship Motions and Added Resistance

2017 ◽  
Vol 159 (A4) ◽  
Author(s):  
F Cakici ◽  
E Kahramanoglu ◽  
A D Alkan
Keyword(s):  
Deep Water ◽  
High Speed ◽  
Computer Experiments ◽  
Navier Stokes ◽  
Ship Motions ◽  
Added Resistance ◽  
Strip Theory ◽  
Head Waves ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method

Along with the development of computer technology, the capability of Computational Fluid Dynamics (CFD) to conduct ‘virtual computer experiments’ has increased. CFD tools have become the most important tools for researchers to deal with several complex problems. In this study, the viscous approach called URANS (Unsteady Reynolds Averaged Navier-Stokes) which has a fully non-linear base has been used to solve the vertical ship motions and added resistance problems in head waves. In the solution strategy, the FVM (Finite Volume Method) is used that enables numerical discretization. The ship model DTMB 5512 has been chosen for a series of computational studies at Fn=0.41 representing a high speed case. Firstly, by using CFD tools the TF (Transfer Function) graphs for the coupled heave-pitch motions in deep water have been generated and then comparisons have been made with IIHR (Iowa Institute of Hydraulic Research) experimental results and ordinary strip theory outputs. In the latter step, TF graphs of added resistance for deep water have been generated by using CFD and comparisons have been made only with strip theory.

Unsteady Viscous CFD Simulations of KCS Behaviour and Performance in Head Seas

2018 ◽  
Author(s):  
LiXiang Guo ◽  
JiaWei Yu ◽  
JiaJun Chen ◽  
KaiJun Jiang ◽  
DaKui Feng
Keyword(s):  
Degrees Of Freedom ◽  
Transfer Functions ◽  
Resistance Coefficient ◽  
Full Scale ◽  
Body Motion ◽  
Ship Motions ◽  
Added Resistance ◽  
Viscous Effects ◽  
Head Waves ◽  
And Performance

It is critical to be able to estimate a ship’s response to waves, since the added resistance and loss of speed may cause delays or course alterations, with consequent financial repercussions. Traditional methods for the study of ship motions are based on potential flow theory without viscous effects. Results of scaling model are used to predict full-scale of response to waves. Scale effect results in differences between the full-scale prediction and reality. The key objective of this study is to perform a fully nonlinear unsteady RANS simulation to predict the ship motions and added resistance of a full-scale KRISO Container Ship. The analyses are performed at design speeds in head waves, using in house computational fluid dynamics (CFD) to solve RANS equation coupled with two degrees of freedom (2DOF) solid body motion equations including heave and pitch. RANS equations are solved by finite difference method and PISO arithmetic. Computations have used structured grid with overset technology. Simulation results show that the total resistance coefficient in calm water at service speed is predicted by 4 .68% error compared to the related towing tank results. The ship motions demonstrated that the current in house CFD model predicts the heave and pitch transfer functions within a reasonable range of the EFD data, respectively.

scholarly journals WAVE FORCES ON PILES OF VARIABLE DIAMETER

1982 ◽  
Vol 1 (18) ◽  
pp. 108
Author(s):  
Bernard LeMehaute ◽  
James Walker ◽  
John Headland ◽  
John Wang
Keyword(s):  
Wave Field ◽  
Intertidal Zone ◽  
Wave Theory ◽  
Wave Force ◽  
Wave Forces ◽  
Linear Wave ◽  
Inertial Effects ◽  
Linear Wave Theory ◽  
Variable Diameter ◽  
Wave Induced

A method of calculating nonlinear wave induced forces and moments on piles of variable diameter is presented. The method is based on the Morrison equation and the linear wave theory with correction parameters to account for convective inertial effects in the wave field. These corrections are based on the stream function wave theory by Dean (1974). The method permits one to take into account the added wave force due to marine growth in the intertidal zone or due to a protective jacket, and can also be used to calculate forces on braces and an array of piles.

Hydrodynamic Study on Added Resistance Using Unsteady Wave Analysis

2013 ◽  
Vol 57 (04) ◽  
pp. 220-240
Author(s):  
Masashi Kashiwagi
Keyword(s):  
Direct Measurement ◽  
Incident Wave ◽  
Ship Motions ◽  
Analysis Method ◽  
Added Resistance ◽  
Wave Analysis ◽  
Linear Superposition ◽  
The Fourier Transform ◽  
Wave Induced ◽  
Incident Waves

It is known that the added resistance in waves can be computed from ship-generated unsteady waves through the unsteady wave analysis method. To investigate the effects of nonlinear ship-generated unsteady waves and bluntness of the ship geometry on the added resistance, measurements of unsteady waves, wave-induced ship motions, and added resistance were carried out using two different (blunt and slender) modified Wigley models. The ship-generated unsteady waves are also produced by the linear superposition using the waves measured for the diffraction and radiation problems and the complex amplitudes of ship motions measured for the motion-free problem in waves. Then a comparison is made among the values of the added resistance by the direct measurement using a dynamometer and by the wave analysis method using the Fourier transform of measured and superposed waves. It is found that near the peak of the added resistance where ship motions become large, the degree of nonlinearity in the unsteady wave becomes prominent, especially at the forefront part of the wave. Thus, the added resistance evaluated with measured waves at larger amplitudes of incident wave becomes much smaller than the values by the direct measurement and by the wave analysis with superposed waves or measured waves at smaller amplitude of incident wave. Discussion is also made on the characteristics of the added resistance in the range of short incident waves.

scholarly journals CFD Prediction of Ship Seakeeping and Slamming Behaviors of a Trimaran in Oblique Regular Waves

2021 ◽  
Vol 9 (10) ◽  
pp. 1151
Author(s):  
Xiyu Liao ◽  
Zhanyang Chen ◽  
Hongbin Gui ◽  
Mengchao Du
Keyword(s):  
Green Water ◽  
Practical Significance ◽  
Ship Motions ◽  
Oblique Waves ◽  
Motion Responses ◽  
Head Waves ◽  
Grid Technique ◽  
Heading Angle ◽  
Comparative Results ◽  
Cfd Method

The main hull encounters waves at first and causes waves to break, when trimarans are subject to the slamming in head waves. At this moment, emergence phenomena of side hulls will not occur. Thus, the slamming study of trimarans in oblique waves presents further practical significance. In this study, a CFD method is used for trimaran seakeeping and slamming analysis. An overset grid technique is adopted to simulate ship motions in waves. Firstly, to further verify the present method, a series of verification and validation studies is conducted. Then, the motion responses and slamming pressure with different control parameters, such as forward speed and ship heading angle, are calculated and discussed. The comparative results indicate that the seakeeping and slamming behaviors of trimarans differ significantly from those of conventional monohull ships. Finally, severe bow slamming and green water in oblique waves are also observed and investigated, which should be given enough attention during ship design and evaluation.

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