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.

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.

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.

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.

Isolation Performance of Intelligent Seismic Isolation System Using Air Bearing

2009 ◽  
Author(s):  
Satoshi Fujita ◽  
Keisuke Minagawa ◽  
Mitsuru Miyazaki ◽  
Go Tanaka ◽  
Toshio Omi ◽  
...  
Keyword(s):  
Seismic Isolation ◽  
Seismic Waves ◽  
Three Dimensional ◽  
Vertical Motion ◽  
Air Bearings ◽  
Natural Period ◽  
Isolation System ◽  
Vertical Excitation ◽  
Long Period ◽  
Isolation Performance

This paper describes three-dimensional isolation performance of seismic isolation system using air bearings. Long period seismic waves having predominant period of from a few seconds to a few ten seconds have recently been observed in various earthquakes. Also resonances of high-rise buildings and sloshing of petroleum tanks in consequence of long period seismic waves have been reported. Therefore the isolation systems having very long natural period or no natural period are required. In a previous paper [1], we proposed an isolation system having no natural period by using air bearings. Additionally we have already reported an introduction of the system, and have investigated horizontal motion during earthquake in the previous paper. It was confirmed by horizontal vibration experiment and simulation in the previous paper that the proposed system had good performance of isolation. However vertical motion should be investigated, because vertical motion varies horizontal frictional force. Therefore this paper describes investigation regarding vertical motion of the proposed system by experiment. At first, a vertical excitation test of the system is carried out so as to investigate vertical dynamic property. Then a three-dimensional vibration test using seismic waves is carried out so as to investigate performance of isolation against three-dimensional seismic waves.

scholarly journals Theoretical analysis and experimental research on multi-layer elastic damping track structure

2021 ◽  
Vol 13 (2) ◽  
pp. 168781402199497
Author(s):  
Guanghui Xu ◽  
Shengkai Su ◽  
Anbin Wang ◽  
Ruolin Hu
Keyword(s):  
Finite Element ◽  
Analytical Solution ◽  
Finite Element Simulation ◽  
Reaction Force ◽  
Vibration Reduction ◽  
Vertical Direction ◽  
Propagation Path ◽  
Track Structure ◽  
Test Results ◽  
Element Simulation

The increase of axle load and train speed would cause intense wheelrail interactions, and lead to potential vibration related problems in train operation. For the low-frequency vibration reduction of a track system, a multi-layer track structure was proposed and analyzed theoretically and experimentally. Firstly, the analytical solution was derived theoretically, and followed by a parametric analysis to verify the vibration reduction performance. Then, a finite element simulation is carried out to highlight the influence of the tuned slab damper. Finally, the vibration and noise tests are performed to verify the results of the analytical solution and finite element simulation. As the finite element simulation indicates, after installation of the tuned slab damper, the peak reaction force of the foundation can be reduced by 60%, and the peak value of the vertical vibration acceleration would decrease by 50%. The vibration test results show that the insertion losses for the total vibration levels are 13.3 dB in the vertical direction and 21.7 dB in the transverse direction. The noise test results show that the data of each measurement point is smoother and smaller, and the noise in the generating position and propagation path can be reduced by 1.9 dB–5.5 dB.

Debonding Behaviors of CFRP Strengthened RC Beams with Weak Interfaces

2013 ◽  
Vol 351-352 ◽  
pp. 587-591
Author(s):  
Sen Li ◽  
Xiao Gang Wang ◽  
Xin Gang Zhou
Keyword(s):  
Tensile Strain ◽  
Structural Integrity ◽  
Structural Performance ◽  
Rc Beams ◽  
Test Results ◽  
Weak Interface ◽  
Premature Rupture ◽  
Loading Process ◽  
Interface Effects

Debonding behaviors of CFRP strengthened RC beams were experimentally investigated under the influence of weak interfaces, which are induced either by defective bonding of replaced cover or expansive cracks. Shown by test results, weak interfaces impaired considerably the structural integrity of strengthening systems during loading, and easily led to CFRP debonding failure. U-strips worked effectively in preventing the integral debonding and guarantee the structural performance of flexural sheets. However, local cover delamination in the loading process and premature rupture of flexural CFRP could still take place due to the weak interface effects. Therefore, allowable tensile strain of flexural CFRP should be reduced, and more strict confinement and anchorage measures should be taken in this case.

scholarly journals Estimation of Outdoor PM2.5 Infiltration into Multifamily Homes Depending on Building Characteristics Using Regression Models

2021 ◽  
Vol 13 (10) ◽  
pp. 5708
Author(s):  
Bo-Ram Park ◽  
Ye-Seul Eom ◽  
Dong-Hee Choi ◽  
Dong-Hwa Kang
Keyword(s):  
Regression Analysis ◽  
Correlation Analysis ◽  
Field Test ◽  
Outer Surface ◽  
Regression Models ◽  
Field Tests ◽  
Test Results ◽  
Correlation And Regression Analysis ◽  
Building Characteristics ◽  
Pm2.5 Concentration

The purpose of this study was to evaluate outdoor PM2.5 infiltration into multifamily homes according to the building characteristics using regression models. Field test results from 23 multifamily homes were analyzed to investigate the infiltration factor and building characteristics including floor area, volume, outer surface area, building age, and airtightness. Correlation and regression analysis were then conducted to identify the building factor that is most strongly associated with the infiltration of outdoor PM2.5. The field tests revealed that the average PM2.5 infiltration factor was 0.71 (±0.19). The correlation analysis of the building characteristics and PM2.5 infiltration factor revealed that building airtightness metrics (ACH50, ELA/FA, and NL) had a statistically significant (p < 0.05) positive correlation (r = 0.70, 0.69, and 0.68, respectively) with the infiltration factor. Following the correlation analysis, a regression model for predicting PM2.5 infiltration based on the ACH50 airtightness index was proposed. The study confirmed that the outdoor-origin PM2.5 concentration in highly leaky units could be up to 1.59 times higher than that in airtight units.

Field Tests of Guide Vanes and Runner Blades of a Large Bulb Turbine for Output Deficiency Diagnosis

2012 ◽  
Vol 212-213 ◽  
pp. 1057-1061 ◽  
Author(s):  
Zhong Liu ◽  
Zhu Qing Huang ◽  
Shu Yun Zou ◽  
Hong De Rao
Keyword(s):  
Field Tests ◽  
Economic Loss ◽  
Hydropower Plant ◽  
Test Results ◽  
Guide Vanes ◽  
Factors Affecting ◽  
Runner Blade ◽  
Main Factors ◽  
Theoretical Analyses ◽  
Bulb Turbine

The 3# bulb turbine in Hongjiang Hydropower Plant has faced the problem of output deficiency since its commission in Sept. 2003, which caused a large economic loss. Following simple theoretical analyses on the main factors affecting the turbine’s output and efficiency, the field test schemes were determined to measure the shapes and intervals of guide vanes and runner blades of the 3#, 5# and 6# turbines. The test results discover that the average blade intervals of the 3# turbine are generally less than those of the 5# one. Suggestions on runner blade installation adjustment and combined curve modification are given.

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.

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