Hydrodynamic Characteristics of ROVs During Deployment Through Wave-Affected Zones

2015 ◽  
Author(s):  
Musa B. Bashir ◽  
Mahesh Menon ◽  
Simon D. Benson ◽  
Rob Eastwood ◽  
Alan J. Murphy ◽  
...  
Keyword(s):  
Potential Theory ◽  
Scale Model ◽  
Hydrodynamic Characteristics ◽  
Splash Zone ◽  
Load Prediction ◽  
Hydrodynamic Analysis ◽  
Motion Response ◽  
Recovery System ◽  
Maximum Range ◽  
Wave Induced

The prediction of wave-induced loads on Remotely Operated Vehicles (ROVs) during deployment through the splash zone is an important requirement to the design of a launch and recovery system. This paper presents the results of numerical and experimental hydrodynamic analysis of the motion response and wave-induced loads on a subsea trencher ROV during its deployment through the splash zone. The main focus of the study is to determine the maximum wave-induced loads and also to establish the maximum range of sea conditions in which the ROV can be operated safely. The numerical measurement of the hydrodynamic responses is completed using a 3D potential theory–based solver. The results obtained are compared with the predicted experimental responses measured using a 1/12 scale model of the ROV in a wave tank. A further comparison of the numerical responses with a box-shaped model of approximately similar overall dimensions to the ROV is performed in order to establish the validity of using a simplified shape to represent the actual ROV in various modelling scenarios. The result of this comparison shows that using a box-shaped model grossly over-predicts the responses and can lead to overly conservative load prediction.

Effects of Cnoidal Wave-Induced Seepage on Vertical Breakwater Resting on Permeable Elastic Seabed

2014 ◽  
Vol 716-717 ◽  
pp. 284-288
Author(s):  
Jian Kang Yang ◽  
Hua Huang ◽  
Lin Guo ◽  
Jing Rong Lin ◽  
Qing Yong Zhu ◽  
...  
Keyword(s):  
Shallow Water ◽  
Wave Theory ◽  
Cnoidal Wave ◽  
Load Prediction ◽  
Wave Load ◽  
Seepage Pressure ◽  
Theoretical Investigations ◽  
Nonlinearity Effect ◽  
Wave Nonlinearity ◽  
Wave Induced

Theoretical investigations on cnoidal waves interacting with breakwater resting on permeable elastic seabed are presented in this paper. Based on the shallow water reflected wave theory and Biot consolidation theory on wave-induced seepage pressure, the analytical solutions to first order cnoidal wave reflection and wave-induced seepage pressure are obtained by the eigenfunction expansion approach. Numerical results are presented to show the effects of depth of water, breakwater geometry on cnoidal wave-induced seepage uplift force and overturning moment. Compared with Airy wave theory, in certain shallow water conditions, the shallow water wave theory can more effectively illustrate wave nonlinearity effect in wave load prediction.

Multi Vessel Interaction in Shallow Water

2009 ◽  
Author(s):  
Hans Fabricius Hansen ◽  
Stefan Carstensen ◽  
Erik Damgaard Christensen ◽  
Jens Kirkegaard
Keyword(s):  
Shallow Water ◽  
Wave Model ◽  
Irregular Waves ◽  
Numerical Code ◽  
Scale Model ◽  
Hydrodynamic Characteristics ◽  
Mooring Line ◽  
Industry Standard ◽  
Physical Scale ◽  
The Time Domain

A numerical package for simulating vessel motions in the time domain, WAMSIM, is extended to handle multiple moving bodies interconnected through a nonlinear mooring system. WAMSIM relies on the industry standard program WAMIT to calculate the hydrodynamic characteristics and interaction of multiple bodies in the frequency domain. The numerical code is used to simulate the motions and mooring line and fender forces of two LNG tankers moored side-by-side in shallow water. One of the gas tankers is moored to the sea floor through a turret with chain catenaries. Realistic short-crested irregular waves obtained from a Boussinesq wave model are used to force the model. Motion spectra of the simulated motions are compared to measured motions from physical scale model tests. The model shows good agreement with measured motions and mooring line forces.

Hydrodynamic Analysis of Submarine of the Wave Glider

2013 ◽  
Vol 834-836 ◽  
pp. 1505-1511 ◽  
Author(s):  
Li Juan Jia ◽  
Xuan Ming Zhang ◽  
Zhan Feng Qi ◽  
Yu Feng Qin ◽  
Xiu Jun Sun
Keyword(s):  
Wave Motion ◽  
Inflection Point ◽  
Design Parameters ◽  
Hydrodynamic Characteristics ◽  
Hydrodynamic Analysis ◽  
Critical Design ◽  
Ocean Wave Energy ◽  
Lift Curve ◽  
Wave Glider

Wave glider harvests the abundant ocean wave energy for long term ocean cruising due to its particular two-part architecture. Its submerged part named glider converts vertical fluctuation of waves to horizontally forward propulsion. Because of the uncertainty of the ocean condition and irregularity of its wave motion, the design parameters of the submerged glider vary in a confined range in the state of art design models. In order to indicate the hydrodynamic characteristics and summarize the dynamic law of the submerged glider with different design parameters, this paper concentrates on three critical design details: profile of the wings, interval space of the arrayed multiple flapping wings and maximum rotating angle of wings, and performs the corresponding CFD analysis. Finally, we conclude that the lift curve of NACA0006 and plate profile is almost the same with small waves at sea, but NACA0006 profile can generate much larger forward lift than the plate profile with seawater velocity up to 0.5m/s; Decreasing space of intermittent causes more obvious decrement of forward lift while space of intermittent overpasses the inflection point at 20cm; With the decrement of the maximum rotating angle, the forward lift occurs to take a sharp decline if the angle strides the inflection point.

Physical Model Testing of the TetraSpar Demo Floating Wind Turbine Prototype

2019 ◽  
Author(s):  
Michael Borg ◽  
Anthony Viselli ◽  
Christopher K. Allen ◽  
Matthew Fowler ◽  
Christoffer Sigshøj ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Numerical Models ◽  
Model Testing ◽  
Offshore Wind ◽  
Scale Model ◽  
Test Facility ◽  
Hydrodynamic Characteristics ◽  
Ocean Engineering ◽  
Floating Wind Turbine ◽  
Floating Offshore Wind Turbines

Abstract As part of the process of deploying new floating offshore wind turbines, scale model testing is carried out to de-risk and verify the design of novel foundation concepts. This paper describes the testing of a 1:43 Froude-scaled model of the TetraSpar Demo floating wind turbine prototype that shall be installed at the Metcentre test facility, Norway. The TetraSpar floating foundation concept consists of a floater tetrahedral structure comprising of braces connected together through pinned connections, and a triangular keel structure suspended below the floater by six suspension lines. A description of the experimental setup and program at the Alfond W2 Ocean Engineering Lab at University of Maine is given. The objective of the test campaign was to validate the initial design, and contribute to the development of the final demonstrator design and numerical models. The nonlinear hydrodynamic characteristics of the design are illustrated experimentally and the keel suspension system is shown to satisfy design criteria.

CFD Analysis on Similarity Criteria of Hydrodynamic Characteristics for Gravity-Installed Anchors

2019 ◽  
Author(s):  
Jiancai Gao ◽  
Haixiao Liu
Keyword(s):  
Model Testing ◽  
Model Tests ◽  
Similarity Criteria ◽  
Scale Model ◽  
Hydrodynamic Characteristics ◽  
Cfd Analysis ◽  
Cfd Simulations ◽  
Tests Of Gravity ◽  
Free Falling ◽  
Reduced Scale

Abstract For reduced-scale model tests of gravity-installed anchors (GIAs), it is of great significance to extrapolate the testing results to prototype. This highlights the necessity of investigation of similarity criteria. The present work aims to find the similarity criteria of three prioritized hydrodynamic characteristics including VT, HP, and Cd for GIAs during installation in water through CFD simulations. In the present study, free falling processes of different reduced-scale T98 anchor models and prototype anchor is simulated, from which VT, HP, and Cd are extracted and analyzed to get the fitting curves for these three characteristics over reduced-scale λ. Based on these curves, hydrodynamic characteristics for prototype and other reduced-scale model can be extrapolated from model testing results. And, the researching procedure in this paper sets an example and reference to study about similarity criteria for other hydrodynamic characteristics.

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 Experimental Investigation of Wave-Induced Ship Hydroelastic Vibrations by Large-Scale Model Measurement in Coastal Waves

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Jialong Jiao ◽  
Huilong Ren ◽  
Shuzheng Sun ◽  
Christiaan Adika Adenya
Keyword(s):  
Large Scale ◽  
Testing Procedure ◽  
Scale Model ◽  
Sea Waves ◽  
Load Pressure ◽  
Large Scale Model ◽  
Wide Range ◽  
Hydroelastic Vibrations ◽  
Wave Induced ◽  
Model Measurement

Ship hydroelastic vibration is an issue involving mutual interactions among inertial, hydrodynamic, and elastic forces. The conventional laboratory tests for wave-induced hydroelastic vibrations of ships are performed in tank conditions. An alternative approach to the conventional laboratory basin measurement, proposed in this paper, is to perform tests by large-scale model measurement in real sea waves. In order to perform this kind of novel experimental measurement, a large-scale free running model and the experiment scheme are proposed and introduced. The proposed testing methodology is quite general and applicable to a wide range of ship hydrodynamic experimental research. The testing procedure is presented by illustrating a 5-hour voyage trial of the large-scale model carried out at Huludao harbor of China in August 2015. Hammer tests were performed to identify the natural frequencies of the ship model at the beginning of the tests. Then a series of tests under different sailing conditions were carried out to investigate the vibrational characteristics of the model. As a postvoyage analysis, load, pressure, acceleration, and motion responses of the model are studied with respect to different time durations based on the measured data.

scholarly journals Motion Prediction of Catamaran with a Semisubmersible Bow in Wave

2016 ◽  
Vol 23 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Hanbing Sun ◽  
Fengmei Jing ◽  
Yi Jiang ◽  
Jin Zou ◽  
Jiayuan Zhuang ◽  
...  
Keyword(s):  
Grid Method ◽  
Scale Model ◽  
Small Scale ◽  
Motion Prediction ◽  
Vertical Acceleration ◽  
Overset Grid ◽  
Motion Response ◽  
Movement Data ◽  
Seakeeping Performance ◽  
Head Waves

Abstract Compared with standard vessels, a slender catamaran with a semi-submerged bow (SSB) demonstrates superior seakeeping performance. To predict the motion of an SSB catamaran, computational fluid dynamics methods are adopted in this study and results are validated through small-scale model tests. The pitch, heave, and vertical acceleration are calculated at various wavelengths and speeds. Based on the overset grid and motion region methods, this study obtains the motion responses of an SSB catamaran in regular head waves. The results of the numerical studies are validated with the experimental data and show that the overset grid method is more accurate in predicting the motion of an SSB catamaran; the errors can be controlled within 20%. The movement data in regular waves shows that at a constant speed, the motion response initially increases and then decreases with increasing wavelength. This motion response peak is due to the encountering frequency being close to the natural frequency. Under identical sea conditions, the motion response increases with the increasing Froude number. The motion prediction results, that derive from a short-term irregular sea state, show that there is an optimal speed range that can effectively reduce the amplitude of motion.

scholarly journals Hydrodynamic Performance of a Hybrid System Combining a Fixed Breakwater and a Wave Energy Converter: An Experimental Study

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5740
Author(s):  
Wei Peng ◽  
Yingnan Zhang ◽  
Xueer Yang ◽  
Jisheng Zhang ◽  
Rui He ◽  
...  
Keyword(s):  
Experimental Study ◽  
Hybrid System ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Hydrodynamic Performance ◽  
Scale Model ◽  
Wave Power ◽  
Energy Converter ◽  
Power Extraction ◽  
Wave Induced

In this paper, a hybrid system integrating a fixed breakwater and an oscillating buoy type wave energy converter (WEC) is introduced. The energy converter is designed to extract the wave power by making use of the wave-induced heave motions of the three floating pontoons in front of the fixed breakwater. A preliminary experimental study is carried out to discuss the hydrodynamic performance of the hybrid system under the action of regular waves. A scale model was built in the laboratory at Hohai University, and the dissipative force from racks and gearboxes and the Ampere force from dynamos were employed as the power take-off (PTO) damping source. During the experiments, variations in numbers of key parameters, including the wave elevation, free response or damped motion of the floating pontoons, and the voltage output of the dynamos were simultaneously measured. Results indicate that the wave overtopping and breaking occurring on the upper surfaces of floating pontoons have a significant influence on the hydrodynamic performance of the system. For moderate and longer waves, the developed system proves to be effective in attenuating the incident energy, with less than 30% of the energy reflected back to the paddle. More importantly, the hydrodynamic efficiency of energy conversion for the present device can achieve approximately 19.6% at the lowest wave steepness in the model tests, implying that although the WEC model harnesses more energy in more energetic seas, the device may be more efficient for wave power extraction in a less energetic sea-state.

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