CFD SIMULATION OF MOTION RESPONSES OF A TRIMARAN IN REGULAR HEAD WAVES

2021 ◽  
Vol 162 (A1) ◽  
Author(s):  
L Nowruzi ◽  
H Enshaei ◽  
J Lavroff ◽  
S S Kianejad ◽  
M R Davis
Keyword(s):  
High Speed ◽  
Cfd Simulation ◽  
Turbulence Models ◽  
Breaking Waves ◽  
Resonance Phenomenon ◽  
Time Step ◽  
Rans Equations ◽  
Strip Theory ◽  
Head Waves ◽  
Regular Head Waves

CFD has proved to be an effective method in solving unsteady Reynolds–Averaged Navier-Stokes (RANS) equations for analysing ships in free surface viscous flow. The research reported in this paper is intended to develop a better understanding of the parameters influencing high-speed trimaran motions responses. Variations of gridding system and time step have been investigated and reliability analysis was performed in solving the RANS equations. Different turbulence models were investigated, and the SST Menter K Omega turbulence model proved a more accurate model than Realizable K-epsilon model. In order to validate the CFD method, the results of the motions response of a high- speed trimaran are compared against a set of experimental and numerical results from a 1.6 m trimaran model tested in various head seas conditions. The results suggest that CFD offers a reliable method for predicting pitch and heave motions of trimarans in regular head waves when compared to traditional low speed strip theory methods. Unlike strip theory, the effect of breaking waves, hull shape above waterline and green seas are considered in CFD application. A wave resonance phenomenon was observed and wave deformation as a result of wave-current-wind interaction in CFD was identified as the main source of discrepancy. The results from this work form the basis for future analysis of trimaran motions in oblique seas for developing a better understanding of the parameters influencing the seakeeping response, as well as passenger comfort.

CFD Simulation of Motion Response of a Trimaran in Regular Head Waves

2020 ◽  
Vol 162 (A1) ◽  
Author(s):  
L Nowruzi ◽  
H Enshaei ◽  
J Lavroff ◽  
S S Kianejad ◽  
M R Davis
Keyword(s):  
High Speed ◽  
Cfd Simulation ◽  
Turbulence Models ◽  
Breaking Waves ◽  
Resonance Phenomenon ◽  
Time Step ◽  
Rans Equations ◽  
Strip Theory ◽  
Head Waves ◽  
Regular Head Waves

CFD has proved to be an effective method in solving unsteady Reynolds–Averaged Navier-Stokes (RANS) equations for analysing ships in free surface viscous flow. The research reported in this paper is intended to develop a better understanding of the parameters influencing high-speed trimaran motions responses. Variations of gridding system and time step have been investigated and reliability analysis was performed in solving the RANS equations. Different turbulence models were investigated, and the SST Menter K Omega turbulence model proved a more accurate model than Realizable K-epsilon model. In order to validate the CFD method, the results of the motions response of a highspeed trimaran are compared against a set of experimental and numerical results from a 1.6 m trimaran model tested in various head seas conditions. The results suggest that CFD offers a reliable method for predicting pitch and heave motions of trimarans in regular head waves when compared to traditional low speed strip theory methods. Unlike strip theory, the effect of breaking waves, hull shape above waterline and green seas are considered in CFD application. A wave resonance phenomenon was observed and wave deformation as a result of wave-current-wind interaction in CFD was identified as the main source of discrepancy. The results from this work form the basis for future analysis of trimaran motions in oblique seas for developing a better understanding of the parameters influencing the seakeeping response, as well as passenger comfort.

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.

scholarly journals High-fidelity CFD simulation of wave run-up for single/multiple surface-piercing cylinders in regular head waves

2016 ◽  
Vol 59 ◽  
pp. 687-708 ◽  
Author(s):  
Sung-Hwan Yoon ◽  
Dong-Hwan Kim ◽  
Hamid Sadat-Hosseini ◽  
Jianming Yang ◽  
Frederick Stern
Keyword(s):  
Cfd Simulation ◽  
High Fidelity ◽  
Head Waves ◽  
Run Up ◽  
Regular Head Waves

Operation of T-Foils and Stern Tabs to Improve Passenger Comfort on High-Speed Ferries

2021 ◽  
pp. 1-20
Author(s):  
Michael R. Davis
Keyword(s):  
Time Domain ◽  
High Speed ◽  
Transfer Functions ◽  
Passenger Comfort ◽  
Strip Theory ◽  
Head Waves ◽  
Similar Range ◽  
Vertical Accelerations ◽  
The Time Domain ◽  
Passenger Discomfort

High-speed ferries of around 100 m length cruising at around 40 knots can cause significant passenger discomfort in head waves. This is due to the frequencies of encountering waves, of maximum hull response to encountered waves and of maximum passenger discomfort all falling within a similar range. In this paper, the benefit obtained by fitting active T-foils and stern tabs to control heave and pitch in head waves is considered. Ship motion responses are computed by numerical integration in the time domain including unsteady control actions using a time domain, high-speed strip theory. This obviates the need to identify transfer functions, the computed time responses including nonlinear hull immersion terms. The largest passenger vertical accelerations occur at forward locations and are best controlled by a forward located T-foil acting in combination with active stern tabs. Various feedback control algorithms have been considered and it is found that pitch damping control gives the greatest improvement in passenger comfort at forward positions. Operation in adaptive and nonlinear modes so that the control deflections are maximized under all conditions give the greatest benefit and can reduce passenger motion sickness incidence (MSI) by up to 25% in a 3-m head sea on the basis of International Organization for Standardization (ISO) recommendations for calculation of MSI for a 90-minute seaway passage.

Analysis and Prediction of Slamming-Induced Loads of a High-Speed Monohull in Regular Waves

2008 ◽  
Vol 52 (01) ◽  
pp. 71-86
Author(s):  
Daniele Dessi ◽  
Riccardo Mariani
Keyword(s):  
High Speed ◽  
Body Motion ◽  
Elastic Response ◽  
Shipbuilding Industry ◽  
Head Waves ◽  
Impulsive Loads ◽  
Slamming Load ◽  
Important Trend ◽  
The Impact ◽  
Regular Head Waves

In recent years, an important trend in the shipbuilding industry has been the increase in the length and speed of high-speed crafts, thus demanding lighter structures. High-speed vehicles with their increased flexibility are more likely to be excited by impulsive loads, such as slamming, which has been extensively studied and discussed by the scientific community. Nevertheless, ship design still demands plain and reliable procedures (numerical and/or experimental) to evaluate the time-dependent global loads in structural dynamics. In this paper, the aim is to explore the possibility of combining the conservation of fluid momentum with the two-dimensional numerical estimation of the effective wetted length in order to improve the prediction of the impact loads without losing the simplicity and efficiency of analytical methods. In order to evaluate the prediction capability of the proposed formulation, the numerical computation of the slamming force is based on processing the model test data relative to the incoming waves and rigid-body motion, and the attained results are compared with the hydrodynamic force experimentally identified. The presented analysis is applied to the slamming tests in regular head waves of a segmented model, supported by an elastically scaled beam, of a fast ferry. By using the slamming load obtained with the theoretical model, the elastic response in terms of bending moments is computed and compared with that provided by direct measurement with strain gauges. Finally, the uncertainty analysis relative to both numerical and experimental results is performed.

Numerical Simulation for Predicting Ship Resistance and Vertical Motions in Regular Head Waves

2019 ◽  
Author(s):  
Adham S. Bekhit ◽  
Adrian Lungu
Keyword(s):  
Experimental Data ◽  
Stokes Equations ◽  
Numerical Results ◽  
Computational Grids ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Head Waves ◽  
Volume Method ◽  
Regular Head Waves

Abstract The present study is concerned with predicting the resistance and vertical motions of the surface combatant DTMB5512 ship model in regular head waves. A series of numerical simulations are performed for various wave lengths, heights and different ship speeds. Computations are performed by making use of the ISIS-CFD solver of the commercial software Fine™/Marine provided by NUMECA, where the discretization in space is based on finite volume method using unstructured grid. The unsteady Reynolds-Averaged Navier-Stokes equations are numerically solved while the turbulence is modeled by making use of the k-ω SST model. The free-surface is captured through an air-water interface based on the Volume of Fluid (VOF) method. Computed results are validated through direct comparisons with the experimental data provided by IIHR test cases. For the sake of numerical results verification, a grid convergence study is performed on four computational grids and a time step convergence test is also included. Validation of the numerical results shows a reasonable agreement with the experimental data.

CFD Simulation of Flexible Ship in Regular Head Waves

2013 ◽  
Author(s):  
Changhong Hu ◽  
Kangping Liao ◽  
Wenyang Duan
Keyword(s):  
Cfd Simulation ◽  
Free Surface Flows ◽  
Immersed Boundary ◽  
Regular Waves ◽  
One Dimensional ◽  
Hull Girder ◽  
Head Waves ◽  
Dimensional Finite Element ◽  
Nonlinear Free Surface ◽  
Regular Head Waves

The ship springing is continuous vibration of the hull girder due to encountered wave excitation, which is considered as a typical fluid-structure interaction (FSI) problem. In this study, a CFD approach is proposed for modeling ship springing induced by large amplitude regular waves. In the CFD model, nonlinear free surface flows are solved by a finite difference method based on CIP (Constraint Interpolation Profile) method. Flexible structure is calculated using one dimensional finite element method by idealizing the ship structure as a beam. A volume weighted method, which is based on IB (Immersed Boundary) method, is applied to couple the FDM and the FEM. The proposed numerical model is validated against an experiment on a flexible barge in regular waves. Discussions are made on the numerical results.

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