Field and Laboratory Measurement of ATV Vertical Motion Characteristics

1989 ◽  
Author(s):  
George F. Sushinsky
Keyword(s):  
Vertical Motion ◽  
Laboratory Measurement ◽  
Motion Characteristics

Motion Characteristics of Composite-Type Sea Cage under Pure Wave

2012 ◽  
Vol 490-495 ◽  
pp. 3405-3409
Author(s):  
Chun Liu Li ◽  
Yun Peng Zhao
Keyword(s):  
Experimental Data ◽  
Wave Height ◽  
Vertical Motion ◽  
Data Acquisition System ◽  
Horizontal Motion ◽  
Wave Condition ◽  
Composite Type ◽  
Motion Range ◽  
Motion Characteristics ◽  
Sea Cage

To study motion range changes with wave condition and motion relationship between cages, physical model experiments were carried out. The authors designed 2 models of composite-type sea cages. Experimental data obtained by the CCD data acquisition system. The experiment results showed that 1.in the same period, horizontal motion range,vertical motion range and inclination changes of float collar increase with wave height; 2.In the same wave height, horizontal motion range of the float collar increases with period; 3.The laws between vertical motion and period are not obvious 4.The laws between inclination changes and period are not obvious 5.Motion range of the first cage along the direction of waves is less than other cages.

Turbulence Measurements from Compliant Moorings. Part I: Motion Characterization

2017 ◽  
Vol 34 (6) ◽  
pp. 1235-1247 ◽  
Author(s):  
Samuel Harding ◽  
Levi Kilcher ◽  
Jim Thomson
Keyword(s):  
Vertical Direction ◽  
Vertical Motion ◽  
Inertial Subrange ◽  
Motion Sensors ◽  
Similar Frequency ◽  
Dynamic Motion ◽  
Flow Speeds ◽  
Motion Characterization ◽  
Motion Characteristics ◽  
Vessel Motion

AbstractHigh-fidelity measurements of turbulence in the ocean have long been challenging to collect, in particular in the middle of the water column. In response, a measurement technique has been developed to deploy an acoustic Doppler velocimeter (ADV) to midwater locations on a compliant mooring. A variety of instrumentation platforms have been deployed as part of this work with a range of dynamic motion characteristics. The platforms discussed herein include the streamlined StableMoor buoy (SMB), the Tidal Turbulence Mooring (TTM) system based on a conventional 0.9-m spherical buoy, and a 100-lb sounding weight suspended from the stern of a research vessel. The ADV head motion is computed from inertial motion sensors integrated into an ADV, and the spectra of these signals are investigated to quantify the motion of each platform. The SMB with a single ADV head mounted on the nose provided the most stable platform for the measurement of tidal turbulence in the inertial subrange for flow speeds exceeding 1.0 m s−1. The modification of the SMB with a transverse wing configuration for multiple ADVs showed a similar frequency response to the nose configuration in the horizontal plane but with large contamination in the vertical direction as a result of platform roll. While the ADV motion on the TTM was significant in the horizontal directions, the vertical motion of this configuration was the most stable of all configurations tested. The sounding weight measurements showed the greatest motion at the ADV head but are likely to be influenced by both prop-wash and vessel motion.

scholarly journals Heave and Pitch Motion Performances of a Ship Towing System Incorporated with Symmetrical Bridle Towline Model

2019 ◽  
Vol 2 (1) ◽  
pp. 28-33
Author(s):  
Ahmad Fitriadhy ◽  
Nur Adlina Aldin ◽  
Nurul Aqilah Mansor ◽  
Nur Aqilah Hanis Zalizan
Keyword(s):  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Vertical Motion ◽  
Subsequent Increase ◽  
Pitch Motion ◽  
Insignificant Effect ◽  
Motion Characteristics ◽  
Heave Motion ◽  
Real Challenge ◽  
Naval Architect

An investigation on vertical motion characteristics of a ship towing system incorporated with symmetrical bridle towline configuration set a real challenge for the naval architect engineer. This paper presents a Computational Fluid Dynamic (CFD) approach to analyse heave and pitch motion performances in waves. Several towing parameters such as various towline length and towing’s velocity have been taken into account. Here, 1B (barge) is employed in the simulation; and designated as a towed ship. The results revealed that the subsequent increase of the towline lengths has been basically proportional with the increase of her heave motion; while inversely decrease in pitch motions. In addition, the effect of the extending towline length  = 1.0 to 3.0 resulted in insignificant effect to the towline tension. However, the increase of the towing’s velocity from 0.509 m/s to 0.728 m/s has led to significantly increase her heave motion and the towline tension by 40.46% and 24%, respectively; meanwhile, the pitch motion barge has sufficiently decreased by 35.94%. This simulation has been beneficial for the towing operator to ensure a higher level of the safety navigation of ship towing system.

A State of Art FPSO With Dry Tree System

2009 ◽  
Author(s):  
Chunqun Ji
Keyword(s):  
Environmental Conditions ◽  
Vertical Direction ◽  
Vertical Motion ◽  
Wide Range ◽  
Floating System ◽  
Motion Characteristics ◽  
Heave Motion ◽  
State Of Art

This paper provides a state of art dry tree floating system by using a moored column-buoy connected to a ship shaped vessel. The Buoy Moored Floating Production Storage and Offloading system (BMFPSO) uses a column-buoy instead of the turret in a conventional FPSO design. Similar to the turret, the column-buoy allows the vessel to weather vane about the column-buoy. In addition, the vessel can move in vertical direction relative to the column-buoy. Thus vertical motion of the column-buoy is de-coupled from the FPSO hull motion. The buoy will have relatively small heave motion allowing the use of proven top tensioned riser technology. The motion characteristics of the system make it operable in a wide range of environmental conditions.

Numerical Analysis of Pontoon Effect on Flow-Induced Forces of the Deep Draft Semisubmersible in a Cross-Flow

2015 ◽  
Author(s):  
Mingyue Liu ◽  
Longfei Xiao ◽  
Haining Lyu ◽  
Longbin Tao
Keyword(s):  
Cross Flow ◽  
Vertical Motion ◽  
Cfd Simulations ◽  
Strong Current ◽  
Exciting Forces ◽  
Wave Exciting Forces ◽  
Computational Fluid Dynamics Cfd ◽  
Heading Angle ◽  
Motion Characteristics ◽  
Cfd Analyses

Deep draft semisubmersible (DDS) concepts have been developed recently in order to improve the vertical motion characteristics of the platform, due to the smaller wave exciting forces on the pontoons than a conventional semisubmersible. However, the DDS may experience critical vortex-induced motions (VIM) stemming from the fluctuating forces in a strong current environment. Aiming to investigate the excitation loads and the mechanism of VIM, Computational Fluid Dynamics (CFD) analyses are performed to study the flow around the DDS in a cross-flow. Special attentions are paid to the effect of the pontoon and the heading angle. Good agreement between CFD simulations and model test results for the current loads of a DDS is observed. Detailed computational results including hydrodynamic loads and flow patterns are presented.

Study of Landing and Lift-Off Operation for Wind Turbine Components on a Ship Deck

2012 ◽  
Author(s):  
Mateusz Graczyk ◽  
Peter Christian Sandvik
Keyword(s):  
Wind Turbines ◽  
Vertical Motion ◽  
Offshore Wind ◽  
Factors Affecting ◽  
Offshore Wind Turbines ◽  
Maintenance Work ◽  
Lift Off ◽  
Motion Characteristics ◽  
Light Components ◽  
Lifting System

Access to offshore wind turbines is much more challenging and costly than for the land-based turbines. One of the factors affecting choice of the vessel to perform the maintenance work is its performance in waves. Performance of two different ships that may be used for exchange of light components for offshore wind turbines is analyzed. Vertical motion characteristics (displacement and velocity) and forces/accelerations acting on such components and lifting system during lift-off and disposal operation are investigated. Based on the analysis performed for a monohull and a catamaran, limiting sea-states are calculated and weather windows allowing for performing exchange operations are identified.

The Heave Response of a Central Spar Fish Cage

2002 ◽  
Author(s):  
David W. Fredriksson ◽  
M. Robinson Swift ◽  
James D. Irish ◽  
Barbaros Celikkol
Keyword(s):  
Structural Integrity ◽  
Damping Ratio ◽  
Vertical Direction ◽  
Field Tests ◽  
Vertical Motion ◽  
Nonlinear Damping ◽  
Test Results ◽  
Natural Period ◽  
Reynolds Number Effects ◽  
Motion Characteristics

As the aquaculture industry considers moving into the open ocean, understanding the dynamic response of fish containment structures becomes critical. Identification of possible resonant conditions and motion characteristics is necessary for system structural integrity and maximizing fish survivability. In this study, heave (vertical motion) free release tests of a central spar fish cage were conducted using a combination of physical and finite element models and field observations. These tests were performed to investigate the added mass, damping ratio and natural period of the system in the vertical direction. The test results were analyzed considering both linear and nonlinear damping. The comparison of these tests show that (1) the damped natural period of this fish cage is longer than 20 seconds, (2) the numerical model underestimates the damping and the cage oscillates longer and at a higher frequency than observed with the field tests and (3) the physical model is nearly critically damped near equilibrium due to Reynolds number effects at the model scale.

scholarly journals CFD ANALYSIS ON VERTICAL MOTION OF A FULL-SCALE FLOATING JETTY

2020 ◽  
Vol 15 (6) ◽  
pp. 100-110
Author(s):  
AHMAD FITRIADHY ◽  
◽  
AMIRA ADAM
Keyword(s):  
Cfd Simulation ◽  
Vertical Motion ◽  
Cfd Analysis ◽  
Subsequent Increase ◽  
Pitch Motion ◽  
Motion Responses ◽  
Harsh Environmental Condition ◽  
Computational Fluid Dynamics Cfd ◽  
Response Amplitude Operators ◽  
Motion Characteristics

A floating jetty often experiences several vertical motions i.e., heave and pitch motion responses due to harsh environmental condition. This inherently makes discomfort to everyone during berthing on a floating; and even it potentially leads to loss of life due to falling down into the sea. A preliminary analysis using Computational Fluid Dynamics (CFD) simulation is necessary to be conducted to ensure user’s safety. The CFD analysis focused on the interaction between wave motions and the floating jetty and its effects on the vertical motions. The vertical motions of floating jetty were quantified by the Response Amplitude Operators (RAO). Several effects due to variation of wavelength (λ/L) have been studied. The CFD results revealed that the lower wavelength (λ/L<2.25) resulted in the increase of the heave and pitch motion amplitudes proportionally. However, the subsequent increase of wavelength (2.25>λ/L) has given results to less heave and pitch motion amplitudes. In general, it is shown that the vertical motion characteristics of the floating jetty predominantly depend on wave properties.

The Heave Response of a Central Spar Fish Cage

2003 ◽  
Vol 125 (4) ◽  
pp. 242-248 ◽  
Author(s):  
David W. Fredriksson ◽  
James D. Irish ◽  
M. Robinson Swift ◽  
Barbaros Celikkol
Keyword(s):  
Structural Integrity ◽  
Vertical Direction ◽  
Field Tests ◽  
Vertical Motion ◽  
Nonlinear Damping ◽  
Test Results ◽  
Natural Period ◽  
Aquaculture Industry ◽  
Reynolds Number Effects ◽  
Motion Characteristics

As the aquaculture industry considers moving into the open ocean, understanding the dynamic response of fish containment structures becomes critical. Identification of possible resonant conditions and motion characteristics is necessary for system structural integrity and maximizing fish survivability. In this study, heave (vertical motion) free release tests of a central spar fish cage were conducted using a combination of physical and finite-element (FE) models and field observations. These tests were performed to investigate the added mass, damping and natural period characteristics of the system in the vertical direction. The test results were analyzed considering both linear and nonlinear damping. The comparison of these tests show that: the damped natural period of this fish cage is longer than 20 seconds; the numerical model underestimates the damping and the cage oscillates longer and at a higher frequency than observed with the field tests; and the physical model is nearly critically damped near equilibrium due to Reynolds number effects at the model scale.

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