Response of the Mega-Float Equipped With Novel Wave Energy Absorber

2003 ◽  
Author(s):  
Sotaro Masanobu ◽  
Shunji Kato ◽  
Katsuya Maeda ◽  
Yasuhiro Namba
Keyword(s):  
Wave Energy ◽  
Structural Design ◽  
Estimation Method ◽  
The Novel ◽  
Additional Structure ◽  
Energy Absorber ◽  
General Wave ◽  
Wave Drift ◽  
Drift Force ◽  
Hydroelastic Response

The hydroelastic response is significant from the viewpoint of the structural design of a Mega-Float. Equipping a Mega-Float with some additional structures, such as vertical plates, is one of the ways to reduce the hydroelastic response easily. However, in general, wave drift force acting on the Mega-Float may be increased, when the Mega-Float is equipped with the additional structures to reduce the response. In the present study, we developed a novel additional structure that was effective in the reduction of both hydroelastic response and wave drift force. Furthermore, we estimated the response of Mega-Float equipped with the additional structures, and compared the result with the value measured in at-sea experiments. As a result, we confirmed both the effectiveness of the novel additional structure and the validity of the estimation method.

scholarly journals Estimation method of slowly varying wave drift force acting on very large floating structures

2000 ◽  
Vol 2000 (188) ◽  
pp. 287-293
Author(s):  
Yasuhiro Namba ◽  
Shunji Kato ◽  
Hiroshi Sato ◽  
Tomoki Ikoma ◽  
Katsuya Maeda
Keyword(s):  
Estimation Method ◽  
Floating Structures ◽  
Wave Drift ◽  
Drift Force ◽  
Very Large Floating Structures

Hydroelastic Response of a Matlike Floating Circular Plate Advancing in Waves

2007 ◽  
Vol 129 (3) ◽  
pp. 201-210
Author(s):  
Tetsuya Matsui
Keyword(s):  
Circular Plate ◽  
Forward Speed ◽  
Leading Order ◽  
Matching Method ◽  
Field Approach ◽  
Wave Drift ◽  
Drift Force ◽  
Hydroelastic Response ◽  
Plate Geometry ◽  
Scattering And Radiation

The boundary value problem is formulated to predict the hydroelastic response of a matlike floating circular plate advancing slowly in waves. The plate is idealized as an elastic plate with zero draught, and the potential flow theory is employed with low forward-speed assumptions. These assumptions allow the steady disturbance potential due to forward speed to be neglected, simplifying the problem considerably. By applying the eigenfunction-expansion domain-matching method, analytical solutions are derived for the scattering and radiation potentials up to the leading-order terms of the speed-dependent parts. The far-field approach is adopted to obtain the expression for the wave drift force. Numerical results are also presented for the typical plate geometry, which demonstrates the significant effect of the forward speed on the hydroelastic response and wave drift force.

An Experimental Study of Negative Drift Force Acting on a Floating OWC “Backward Bent Duct Buoy”

2008 ◽  
Author(s):  
Yasutaka Imai ◽  
Kazutaka Toyota ◽  
Shuichi Nagata ◽  
Toshiaki Setoguchi ◽  
Junko Oda ◽  
...  
Keyword(s):  
Wave Energy ◽  
Fluid Velocity ◽  
Wave Energy Converter ◽  
Wave Direction ◽  
Regular Waves ◽  
Energy Converter ◽  
Negative Wave ◽  
Wave Drift ◽  
Negative Drift ◽  
Drift Force

The utilization of renewable energy is required immediately since emissions of carbon dioxide are being restricted. To this end, we are investigating the ocean wave energy converter, especially the floating OWC “Backward Bent Duct Buoy” (BBDB). The BBDB, proposed by Masuda in 1986, is a wave energy converter of the ‘moored floating oscillating water column’ type that is composed of an air chamber, an L-shaped bent duct, a buoyancy chamber, and a turbine. The BBDB has certain positive characteristics. Firstly, the primary conversion performance of the BBDB is better than other floating OWCs. Secondly, the length of the BBDB is shorter than other floating OWCs. Thirdly, as the BBDB advances in the incident wave direction with slow speed waves because of the negative wave drift force, the mooring cost can be reduced. In this research, experiments under a various wave periods were carried out to clarify the characteristics and cause of the generation of negative drift force acting on a BBDB in regular waves with a two-dimensional wave tank at Saga University. The length of the BBDB model is 85cm. To measure the wave drift force, the model is moored with horizontal wire-springs. The motions of the BBDB, such as surge, heave, and pitch, are measured by remotely using image processing. The fluid velocity around the BBDB is measured by using particle image velocimetry (PIV). Motion tests of the BBDB without mooring are also carried out to measure the horizontal velocity of the BBDB in waves. From the experimental results, the characteristics and causes of the generation of negative drift force acting on the BBDB in regular waves are discussed.

scholarly journals Cardiorespiratory fitness assessment using risk-stratified exercise testing and dose–response relationships with disease outcomes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tomas I. Gonzales ◽  
Kate Westgate ◽  
Tessa Strain ◽  
Stefanie Hollidge ◽  
Justin Jeon ◽  
...  
Keyword(s):  
Cardiorespiratory Fitness ◽  
Maximal Oxygen Consumption ◽  
Estimation Method ◽  
The Novel ◽  
Exercise Tests ◽  
Metabolic Equivalent ◽  
Fitness Assessment ◽  
Disease Outcomes ◽  
All Cause Mortality ◽  
The Uk

AbstractCardiorespiratory fitness (CRF) is associated with mortality and cardiovascular disease, but assessing CRF in the population is challenging. Here we develop and validate a novel framework to estimate CRF (as maximal oxygen consumption, VO2max) from heart rate response to low-risk personalised exercise tests. We apply the method to examine associations between CRF and health outcomes in the UK Biobank study, one of the world’s largest and most inclusive studies of CRF, showing that risk of all-cause mortality is 8% lower (95%CI 5–11%, 2670 deaths among 79,981 participants) and cardiovascular mortality is 9% lower (95%CI 4–14%, 854 deaths) per 1-metabolic equivalent difference in CRF. Associations obtained with the novel validated CRF estimation method are stronger than those obtained using previous methodology, suggesting previous methods may have underestimated the importance of fitness for human health.

Dynamic Analysis and Configuration Design of a Two-Component Wave-Energy Absorber

2012 ◽  
Author(s):  
Christophe Cochet ◽  
Ronald W. Yeung
Keyword(s):  
Wave Energy ◽  
Degrees Of Freedom ◽  
Outer Cylinder ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Energy Extraction ◽  
Energy Absorber ◽  
Compound Cylinder ◽  
Motion Study ◽  
Heave Motion

The wave-energy absorber being developed at UC Berkeley is modeled as a moored compound cylinder, with an outer cylinder sliding along a tension-tethered inner cylinder. With rigid-body dynamics, it is first shown that the surge and pitch degrees of freedom are decoupled from the heave motion. The heaving motion of the outer cylinder is analyzed and its geometric proportions (radii and drafts ratios) are optimized for wave-energy extraction. Earlier works of Yeung [1] and Chau and Yeung [2,3] are used in the present heave-motion study. The coupled surge-pitch motion can be solved and can provide the contact forces between the cylinders. The concept of capture width is used to characterize the energy extraction: its maximization leads to optimal energy extraction. The methodology presented provides the optimal geometry in terms of non-dimensional proportions of the device. It is found that a smaller radius and deeper draft for the outer cylinder will lead to a larger capture width and larger resulting motion.

Mean Wave Drift Force on a Barge-Type Floating Wind Turbine With Moonpools

2021 ◽  
Author(s):  
Lei Tan ◽  
Tomoki Ikoma ◽  
Yasuhiro Aida ◽  
Koichi Masuda
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Offshore Wind ◽  
Hydrodynamic Performance ◽  
Vertical Axis Wind Turbine ◽  
Rotating Speed ◽  
Wave Drift ◽  
Floating Offshore Wind Turbines ◽  
Drift Force ◽  
Gyroscopic Effects

Abstract The barge-type foundation with moonpool(s) is a promising type of platform for floating offshore wind turbines, since the moonpool(s) could improve the hydrodynamic performance at particular frequencies and reduce the costs of construction. In this paper, the horizontal mean drift force and yaw drift moment of a barge-type platform with four moonpools are numerically and experimentally investigated. Physical model tests are carried out in a wave tank, where a 2MW vertical-axis wind turbine is modelled in the 1:100 scale. By varying the rotating speed of the turbine and the mass of the blades, the gyroscopic effects due to turbine rotations on the mean drift forces are experimentally examined. The wave diffraction and radiation code WAMIT is used to carry out numerical analysis of wave drift force and moment. The experimental results indicate that the influence of the rotations of a vertical-axis wind turbine on the sway drift force is generally not very significant. The predictions by WAMIT are in reasonable agreement with the measured data. Numerical results demonstrate that the horizontal mean drift force and yaw drift moment at certain frequencies could be reduced by moonpool(s).

Numerical analysis of non-aligned inputs M-type micromixers with different shaped obstacles for biomedical applications

2021 ◽  
pp. 095440892110516
Author(s):  
Muhammad Irfan ◽  
Imran Shah ◽  
Usama M Niazi ◽  
Muhsin Ali ◽  
Sadaqat Ali ◽  
...  
Keyword(s):  
Structural Design ◽  
Biomedical Applications ◽  
Structural Changes ◽  
Nanoparticle Synthesis ◽  
Fluid Mixing ◽  
The Novel ◽  
Flow Conditions ◽  
Mixing Index ◽  
Mixing Performance ◽  
Passive Micromixer

Fluid mixing in lab-on-a-chip devices at laminar flow conditions result in a low mixing index. The reason is dominant diffusion over the convection process. The mixing index can be improved by certain changes in the micromixer structural design like introducing obstacles in the path of fluid flow. These obstacles will make dominant the advection process over the diffusion process. The main contribution of this work is based on proposing the novel hybrid type micromixer design for enhancing the mixing quality. Three non-aligned M-type and non-aligned M-type with obstacles passive type micromixers are analyzed by COMSOL5.5. These designs are hybrid types because different structural changes are combined in a single design for mixing improvement. First of all the straight non-aligned inlets, M-type passive micromixer (SMTM) is analyzed. It is observed that mixing performance is improved because of M-shaped mixing units and non-aligned inlets. This improvement is deemed to be not enough so different shaped obstacles are introduced in the micromixer design. These designs based on obstacles are named horizontal rectangular M-type micromixer, square M-type micromixer, and vertical rectangular M-type micromixer. The mixing index for SMTM, square M-type micromixer, horizontal rectangular M-type micromixer, and vertical rectangular M-type micromixer at Reynolds number Re = 60 is respectively given by 71.1%, 83.21%, 84.45%, and 89.99%. The mixing index of vertical rectangular M-type micromixer was 59.34% − 87.65% for Re = 0.5–100. Vertical rectangular M-type micromixer is concluded with the better-mixing capability design among the proposed ones. Based on these simulation results, the vertical rectangular M-type micromixer design can be utilized for mixing purposes in biomedical applications like nanoparticle synthesis and biomedical sample preparation for drug delivery.

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