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.

Rigid Body dynamics and decoupled control architecture for two strongly interacting manipulators

Robotica ◽  
1991 ◽  
Vol 9 (4) ◽  
pp. 421-430 ◽  
Author(s):  
M.A. Unseren
Keyword(s):  
Rigid Body ◽  
Degrees Of Freedom ◽  
Position Control ◽  
Equations Of Motion ◽  
Joint Space ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Control Architecture ◽  
Reduced Order ◽  
Closed Chain

SUMMARYA rigid body dynamical model and control architecture are developed for the closed chain motion of two structurally dissimilar manipulators holding a rigid object in a three-dimensional workspace. The model is first developed in the joint space and then transformed to obtain reduced order equations of motion and a separate set of equations describing the behavior of the generalized contact forces. The problem of solving the joint space and reduced order models for the unknown variables is discussed. A new control architecture consisting of the sum of the outputs of a primary and secondary controller is suggested which, according to the model, decouples the force and position-controlled degrees of freedom during motion of the system. The proposed composite controller enables the designer to develop independent, non-interacting control laws for the force and position control of the complex closed chain system.

Heave Motion Performance of Multiple Wave Energy Converters Arrayed in a Water Channel Resonator

2020 ◽  
Author(s):  
Jeongrok Kim ◽  
Il-Hyoung Cho
Keyword(s):  
Wave Energy ◽  
Water Channel ◽  
Standing Waves ◽  
Low Density ◽  
Energy Extraction ◽  
Multiple Wave ◽  
Wave Energy Converters ◽  
Internal Fluid ◽  
Heave Motion ◽  
Energy Converters

Abstract The performance of multiple wave energy converters (WECs) arranged in a Y-shaped water channel resonator (WCR) for amplifying the wave energy with low density was investigated. The WCR consists of a long channel and waveguide installed at the entrance. If the period of the incident wave coincides with the natural period of the fluid in the WCR, then resonance occurs, and the internal fluid is greatly amplified in the form of standing waves. The WECs were positioned at the anti-nodes of standing waves formed in the WCR to maximize energy extraction. We dealt with the heave motion, time-averaged power, and capture width ratio (CWR) of WECs, which are composed of a heaving cylinder and a linear generator. For this purpose, we used the boundary element method and WAMIT commercial code. In parallel, systematic model tests were conducted at the 2D wave tank in Jeju National University to validate the numerical solution. Both results were in good agreement. WECs with a short draft are efficient in energy extraction compared with WECs with a long draft. Numerical and experimental results reveal that the WECs arranged in a WCR have higher efficiency over a wide band of periods than a single WEC without a WCR. Therefore, the wave energy with low density can be amplified by the resonance of the internal fluid in the WCR.

Point Absorber Design for a Combined Wind and Wave Energy Converter on a Tension-Leg Support Structure

2013 ◽  
Author(s):  
Erin E. Bachynski ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Wave Energy ◽  
Environmental Conditions ◽  
Energy Extraction ◽  
Energy Converter ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Single Column ◽  
Extraction Device ◽  
Heave Motion

A combined wind and wave energy extraction device is studied, consisting of a single column tension leg platform (TLP) which supports a 5MW wind turbine (WT) and 3 point absorber wave energy converters (WECs). Two variations of the WECs are considered: one that is constrained to purely heave motion relative to the TLP hull, and a hinged device which moves in coupled surge and pitch as well as heave. The effects of both types of WECs on the WT power takeoff; on structural loads in the turbine tower and blades, WEC supporting structure, and tendons; and on the platform motions are examined for operational and 50-year extreme environmental conditions.

On the Performance of a Dual-Cylinder Wave-Energy Converter: Single Versus Two Degrees of Freedom

2016 ◽  
Author(s):  
Lu Wang ◽  
Daewoong Son ◽  
Ronald W. Yeung
Keyword(s):  
Wave Energy ◽  
Degrees Of Freedom ◽  
Early Stage ◽  
Outer Cylinder ◽  
Electrical Energy ◽  
Coaxial Cylinder ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Energy Converter ◽  
Two Degrees Of Freedom

A recently developed dual (coaxial-)cylinder wave-energy converter (WEC) consists of inner and outer-cylinders, with the outer one sliding over the inner one. An effective design was to tension-tether the inner cylinder (Son and Yeung, OMAE2014-#24582) while the outer cylinder acts as a floater heaving in response to incident waves. Even though the idea was a success, there was significant scientific curiosity in our early stage of the design in the following context: if both cylinders were allowed to heave simultaneously and independently, what would be the implications on the energy-extraction performance and power-take-off constraints? In this paper, we report the detailed analysis conducted at the time of the design. To begin with, the hydrodynamic coefficients, namely, the added mass, radiation-damping, and wave-exciting force for the individually moving cylinders were solved using the method of matched eigenfunction expansions (Chau and Yeung, OMAE2012-#83987). We expanded that capability to allow coupling or interference hydro-dynamic coefficients to be computed in the current work. This coupling is shown to lead to two degrees of freedom of motion, one for each cylinder, with excitation forces on each based on reciprocity (Haskind’s) relations. The resulting relative heave motion between the cylinders is used to drive the permanent magnet linear generator (PMLG) to capture electrical energy. The performance of the WEC, in terms of capture width, is calculated for both regular-wave and irregular-wave conditions and is compared with that for the one degree-of-freedom system, fixed inner cylinder and heaving outer cylinder. The change in WEC performance in response to changing generator damping was found to be very different for the two cases. This behavior leads to very different optimal generator damping values in regular and irregular waves. The advantages and shortcomings of the two systems are compared and explained.

scholarly journals Slipping–rolling transitions of a body with two contact points

2021 ◽  
Author(s):  
Mate Antali ◽  
Gabor Stepan
Keyword(s):  
Rigid Body ◽  
Contact Point ◽  
Static Friction ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Friction Forces ◽  
Contact Points ◽  
Body Dynamics ◽  
Coulomb Model ◽  
Rigid Surfaces

AbstractIn this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling or slipping state at each contact point, four kinematic scenarios occur. In the two-point rolling case, the contact forces are undetermined; consequently, the condition of the static friction forces cannot be checked from the Coulomb model to decide whether two-point rolling is possible. However, this issue can be resolved within the scope of rigid body dynamics by analysing the nonsmooth vector field of the system at the possible transitions between slipping and rolling. Based on the concept of limit directions of codimension-2 discontinuities, a method is presented to determine the conditions when the two-point rolling is realizable without slipping.

The Principle of an Integrated Generation Unit for Offshore Wind Power and Ocean Wave Energy

2017 ◽  
Author(s):  
Weixing Chen ◽  
Feng Gao
Keyword(s):  
Wind Power ◽  
Wave Energy ◽  
Degrees Of Freedom ◽  
Mechanical Energy ◽  
Ocean Wave ◽  
Offshore Wind ◽  
Offshore Wind Power ◽  
Ocean Wave Energy ◽  
Energy Conversion Devices ◽  
Generation Unit

Energy resources of offshore wind and ocean wave are clean, renewable and abundant. Various technologies have been developed to utilize the two kinds of energy separately. This paper presents the principle of an integrated generation unit for offshore wind power and ocean wave energy. The principle of the unit includes that: The wind rotor with retractable blades and the 3-DOF (degrees of freedom) mechanism with the hemispherical oscillating body are used to collect the irregular wind and wave power, respectively; The energy conversion devices (ECDs) are utilized to convert mechanical energy from both the wind rotor and the 3-DOF mechanism into hydraulic energy; The hydraulic energy is used to drive the hydraulic motors and electrical generators to produce electricity. Some analyses and experiments of the unit is conducted.

Evaluation of 3-D Computational Model of Oscillating Water Column Converter with Constructal Design with Three Degrees of Freedom and Limited Chimney Height

2021 ◽  
Vol 407 ◽  
pp. 128-137
Author(s):  
Vinícius Bloss ◽  
Camila Fernandes Cardozo ◽  
Flávia Schwarz Franceschini Zinani ◽  
Luiz Alberto Oliveira Rocha
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Mechanical Energy ◽  
Ocean Waves ◽  
Response Surfaces ◽  
Oscillating Water Column ◽  
Promising Source ◽  
Three Degrees Of Freedom

Theoretically, ocean waves contain enough mechanical energy to supply the entire world’s demand and, as of late, are seen as a promising source of renewable energy. To this end, several different technologies of Wave Energy Converters (WEC) have been developed such as Oscillating Water Column (OWC) devices. OWCs are characterized by a chamber in which water oscillates inside and out in a movement similar to that of a piston. This movement directs air to a chimney where a turbine is attached to convert mechanical energy. The analysis conducted was based on the Constructive Design Method, in which a numerical study was carried out to obtain the geometric configuration that maximized the conversion of wave energy into mechanical energy. Three degrees of freedom were used: the ratio of height to length of the hydropneumatic chamber (H1/L), the ratio of the height of the chimney to its diameter (H2/d) and the ratio of the width of the hydropneumatic chamber to the width of the wave tank (W/Z). A Design of Experiments (DoE) technique coupled with Central Composite Design (CCD) allowed the simulation of different combinations of degrees of freedom. This allowed the construction of Response Surfaces and correlations for the efficiency of the system depending on the degrees of freedom (width and height of the chamber), as well as the optimization of the system based on the Response Surfaces.

scholarly journals Wave power extraction from a bottom-mounted oscillating water column converter with a V-shaped channel

2014 ◽  
Vol 470 (2167) ◽  
pp. 20140074 ◽  
Author(s):  
Zhengzhi Deng ◽  
Zhenhua Huang ◽  
Adrian W. K. Law
Keyword(s):  
Water Column ◽  
Water Depth ◽  
Wave Energy ◽  
High Efficiency ◽  
Expansion Method ◽  
Opening Angle ◽  
Energy Extraction ◽  
Oscillating Water Column ◽  
Wave Direction ◽  
Power Extraction

An analytical theory is developed for an oscillating water column (OWC) with a V-shaped channel to improve the pneumatic efficiency of wave energy extraction. An eigenfunction expansion method is used in a cylindrical coordinate system to investigate wave interaction with the OWC converter system. Auxiliary functions are introduced to capture the singular behaviours in the velocity field near the salient corners and cusped edges. Effects of the OWC dimensions, the opening angle and length of the V-shaped channel, as well as the incident wave direction, on the pneumatic efficiency of wave energy extraction are examined. Compared with a system without the V-shaped channel, our results show that the V-shaped channel can significantly increase the conversion efficiency and widen the range of wave frequency over which the OWC system can operate at a high efficiency. For typical coastal water depths, the OWC converter system can perform efficiently when the diameter of the OWC chamber is in the range of 1 5 – 1 2 times the water depth, the opening angle of the V-shaped channel is in the range of [ π /2, 3 π /4] and the length of the V-shaped channel is in the range of 1–1.5 times the water depth.

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