scholarly journals Theory of the synchronous motion of an array of floating flap gates oscillating wave surge converter

2016 ◽  
Vol 472 (2192) ◽  
pp. 20160174 ◽  
Author(s):  
Simone Michele ◽  
Paolo Sammarco ◽  
Michele d’Errico
Keyword(s):  
Maximum Efficiency ◽  
Width Ratio ◽  
Angle Of Incidence ◽  
Axially Symmetric ◽  
Mathieu Functions ◽  
Synchronous Motion ◽  
Natural Modes ◽  
Capture Width Ratio ◽  
Random Seas ◽  
Design Estimate

We consider a finite array of floating flap gates oscillating wave surge converter (OWSC) in water of constant depth. The diffraction and radiation potentials are solved in terms of elliptical coordinates and Mathieu functions. Generated power and capture width ratio of a single gate excited by incoming waves are given in terms of the radiated wave amplitude in the far field. Similar to the case of axially symmetric absorbers, the maximum power extracted is shown to be directly proportional to the incident wave characteristics: energy flux, angle of incidence and wavelength. Accordingly, the capture width ratio is directly proportional to the wavelength, thus giving a design estimate of the maximum efficiency of the system. We then compare the array and the single gate in terms of energy production. For regular waves, we show that excitation of the out-of-phase natural modes of the array increases the power output, while in the case of random seas we show that the array and the single gate achieve the same efficiency.

Experiments on the flow past an inclined disk

1967 ◽  
Vol 29 (4) ◽  
pp. 691-703 ◽  
Author(s):  
J. R. Calvert
Keyword(s):  
Vortex Shedding ◽  
Free Stream ◽  
Stream Velocity ◽  
Length Scale ◽  
Angle Of Incidence ◽  
Axially Symmetric ◽  
Periodic Motions ◽  
Reference Velocity ◽  
Shedding Frequency ◽  
A Chain

The wake of a disk at an angle to a stream contains marked periodic motions which arise from the regular shedding of vortices from the trailing edge. The vortices are in the form of a chain of irregular rings, each one linked to the succeeding one, and they move downstream at about 0·6 of free-stream velocity. The prominence of the vortex shedding increases as the angle of incidence (measured from the normal) increases up to at least 50°. The shedding frequency increases with the angle of incidence, but by a suitable choice of reference velocity and length scale, may be described by a wake Strouhal number which has the constant value 0·21 for all angles of incidence above zero, up to at least 40°.Axially-symmetric bodies at zero incidence shed vortices in a similar manner, except that the orientation of the plane of vortex shedding is not fixed and varies from time to time.

A new method of solving Oseen’s equations and its application to the flow past an inclined elliptic cylinder

1954 ◽  
Vol 224 (1157) ◽  
pp. 141-160 ◽  
Keyword(s):  
Reynolds Number ◽  
Elliptic Cylinder ◽  
Cylindrical Body ◽  
Thickness Ratio ◽  
Successive Approximations ◽  
Angle Of Incidence ◽  
Mathieu Functions ◽  
Flow Past ◽  
Transcendental Functions ◽  
Lift And Drag

In this paper is developed a general method of solving Oseen’s linearized equations for a two-dimensional steady flow of a viscous fluid past an arbitrary cylindrical body. The method is based on the fact that the velocity in the neighbourhood of the cylinder can be generally expressed in terms of a pair of analytic functions, the determination of which from the appropriate boundary condition can be effected by successive approximations in powers of the Reynolds number, R . The method enables one to obtain the velocity distribution near the cylinder and the lift and drag acting on it in the form of power series in R , without recourse to manipulation of higher transcendental functions such as Bessel and Mathieu functions for circular and elliptic cylinders, respectively. As an example of the application of the method, the uniform flow past an elliptic cylinder at an arbitrary angle of incidence is considered. Analytical expressions for the lift and drag coefficients are obtained, which are correct to the order of R , the lowest order terms being O ( R -1 ) and numerical calculations are carried out for the thickness ratio t = 0, 0.1, 0.5, 1 and the Reynolds number R = 0.1, 1. It is found that drag increases slightly with increase of either thickness ratio or angle of incidence, and that lift decreases with increase of thickness ratio while, as a function of the angle of incidence, it has a maximum at about 45°.

scholarly journals Experimental Study on Operation Performance of Two-Body Wave Energy Generator

2021 ◽  
Author(s):  
S Wu ◽  
Y J Liu
Keyword(s):  
Energy Conversion ◽  
Wave Energy ◽  
External Load ◽  
Wave Frequency ◽  
Width Ratio ◽  
Operation Performance ◽  
Motion Response ◽  
Piston Cylinder ◽  
Capture Width Ratio ◽  
Physical Experiments

The two-body oscillating type wave energy converter (WEC) is a hot research topic at present. A two-body device with damping disc was taken as the test model in this paper. The two bodies were connected by a hydraulic piston cylinder to realize the relative motion energy conversion. Physical experiments were carried out in a wave-making flume to study the operation performance. The effects of wave elements and load on the hydrodynamic characteristics and capture width ratio (CWR) of the model were analysed respectively. The results showed that wave frequency and external load were the main factors affecting the motion response and energy conversion of the device. With the increase of wave frequency and external load, the response amplitude operator (RAO) and the capture width ratio both increase first and then decrease. Wave height has little effect on system characteristics. There exists a best-matching wave period condition, and the optimal motion response and energy conversion are obtained.

scholarly journals Analytical Study on an Oscillating Buoy Wave Energy Converter Integrated into a Fixed Box-Type Breakwater

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Xuanlie Zhao ◽  
Dezhi Ning ◽  
Chongwei Zhang ◽  
Yingyi Liu ◽  
Haigui Kang
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Hydrodynamic Performance ◽  
Maximum Efficiency ◽  
Width Ratio ◽  
Geometrical Parameters ◽  
Linear Potential ◽  
Energy Converter ◽  
Transmission Coefficients ◽  
Incident Waves

An oscillating buoy wave energy converter (WEC) integrated to an existing box-type breakwater is introduced in this study. The buoy is installed on the existing breakwater and designed to be much smaller than the breakwater in scale, aiming to reduce the construction cost of the WEC. The oscillating buoy works as a heave-type WEC in front of the breakwater towards the incident waves. A power take-off (PTO) system is installed on the topside of the breakwater to harvest the kinetic energy (in heave mode) of the floating buoy. The hydrodynamic performance of this system is studied analytically based on linear potential-flow theory. Effects of the geometrical parameters on the reflection and transmission coefficients and the capture width ratio (CWR) of the system are investigated. Results show that the maximum efficiency of the energy extraction can reach 80% or even higher. Compared with the isolated box-type breakwater, the reflection coefficient can be effectively decreased by using this oscillating buoy WEC, with unchanged transmission coefficient. Thus, the possibility of capturing the wave energy with the oscillating buoy WEC integrated into breakwaters is shown.

FEM Analysis of Active Reduction of Torsional Vibrations of Clamped-Free Beam by Piezoelectric Elements for Separated Modes

2015 ◽  
Vol 39 (4) ◽  
pp. 639-644 ◽  
Author(s):  
Elżbieta Augustyn ◽  
Marek S. Kozień ◽  
Michał Pracik
Keyword(s):  
Cross Section ◽  
Rectangular Cross Section ◽  
Fem Analysis ◽  
Width Ratio ◽  
Torsional Vibrations ◽  
Fem Simulations ◽  
Natural Modes ◽  
Piezoelectric Elements ◽  
Large Length ◽  
Free Beam

Abstract Beams with rectangular cross-section, with large length-to-width ratio, can be excited to torsional vibrations. If the piezoelectric elements are mounted to the beam in pairs at the same cross-section with two separated elements positioned on the same side of the beam, and the voltages applied to them are in the opposite phase, they produce twisting moments which can be applied to reduce the torsional vibrations. Results of FEM simulations are presented and analysed in the paper. All analyses are performed for a steel free-clamped beam. The piezoelectric elements made of PZT material are mounted in pairs on one side of the beam. The analyses are done for separated natural modes.

scholarly journals Reduction of local scouring at round-nosed rectangular piers using a downstream bed sill

2021 ◽  
Vol 63 (3) ◽  
pp. 1-9
Author(s):  
E Sanadgol ◽  
M Heidarpour ◽  
R Mohammadpour
Keyword(s):  
Laboratory Experiments ◽  
Local Scour ◽  
Maximum Efficiency ◽  
Width Ratio ◽  
Scour Depth

This study investigated the effectiveness of bed sills in reducing the scour depth with time at rectangular piers in a laboratory. Experiments were conducted just below the threshold of sediment motion (U/Uc = 0.95) for round-nosed piers with the length-to-width ratios of L/b = 1, 2, 3 and 4. Accordingly, a 1 cm thick PVC section as wide as the channel was used as the bed sill, which was flush with the bed and located at various distances, D, in the downstream of the piers, i.e. D/b = 0, 1, 2 and 3. It was found that the efficiency of the bed sill for a rectangular pier was significantly less than that for the circular one; there was a decrease in efficiency and scour depth with an increase of the pier length. The maximum efficiency obtained for the round-nosed piers with L/b = 1, 2, 3 and 4 was 32.5%, 21.3%, 14.4% and 5.7%, respectively. The application of a bed sill to reduce the local scour in round-nosed rectangular piers, when the length-to-width ratio exceeds 2, is therefore not recommended. Furthermore, the efficiency of the bed sill is the best when it is attached to the downstream end of the pier; its efficiency is decreased when increasing its distance from the pier.

scholarly journals Wave Energy Harnessing in Shallow Water through Oscillating Bodies

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2730 ◽  
Author(s):  
Marco Negri ◽  
Stefano Malavasi
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Wave Energy ◽  
Multibody System ◽  
Physical Models ◽  
Width Ratio ◽  
Wave Flume ◽  
Capture Width Ratio ◽  
Single Body ◽  
Two Systems

This paper deals with wave energy conversion in shallow water, analyzing the performance of two different oscillating-body systems. The first one is a heaving float, which is a system known in the literature. The second one is obtained by coupling the heaving float with a surging paddle. In order to check the different behaviors of the multibody system and the single-body heaving float, physical models of the two systems have been tested in a wave flume, by placing them at various water depths along a sloping bottom. The systems have been tested with monochromatic waves. For each water depth, several tests have been performed varying the geometrical and mechanical parameters of the two systems, in order to find their best configurations. It has been found that the multibody system is more energetic when the float and the paddle are close to each other. Capture width ratio has been found to significantly vary with water depth for both systems: in particular, capture width ratio of the heaving float (also within the multibody system) increases as water depth increases, while capture width ratio of the paddle (within the multibody system) increases as water depth decreases. At the end, the capture width ratio of the multibody system is almost always higher than that of the heaving float, and it increases as water depth increases on average; however, the multibody advantage over single body is significant for water depth less than the characteristic dimension of the system, and decreases as water depth increases.

Experimental investigation on hydrodynamic performance of a dual pontoon–power take-off type wave energy converter integrated with floating breakwaters

2018 ◽  
Vol 233 (4) ◽  
pp. 991-999 ◽  
Author(s):  
Dezhi Ning ◽  
Xuanlie Zhao ◽  
Ming Zhao ◽  
Haigui Kang
Keyword(s):  
Transmission Coefficient ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Hydrodynamic Performance ◽  
Width Ratio ◽  
Frequency Range ◽  
Effective Frequency ◽  
Energy Converter ◽  
Damping Force ◽  
Capture Width Ratio

As an extension of the single pontoon wave energy converter–type breakwater, a wave energy converter–type breakwater equipped with dual pontoon–power take-off system is proposed to broaden the effective frequency range (for transmission coefficient KT < 0.5 and capture width ratio η > 20%). The wave energy converter–type breakwater with dual pontoon–power take-off system consists of a pair of heave-type pontoons and power take-off systems for which the power take-off system is installed to harvest the kinetic energy of heave motion of the pontoon. In this paper, we experimentally confirm the advantage of the wave energy converter–type breakwater with dual pontoon–power take-off system over the one with a single pontoon–power take-off system. Both wave energy converter–type breakwater with dual pontoon–power take-off system and that with single pontoon–power take-off system are tested in regular waves. A (electronic) current controller–magnetic powder brake system is used to simulate the power take-off system. The characteristics of power take-off system are investigated and results showed that the power take-off system can simulate the (approximate) Coulomb damping force well. Experimental results reveal that the wave energy converter–type breakwater with dual pontoon–power take-off system broadens the effective frequency range compared with the single pontoon–power take-off system with the same pontoon volume (i.e. the displacement of the pontoon). Specifically, the transmission coefficient of the system is smaller while the system in relative longer waves. Furthermore, the capture width ratio of system can be improved.

scholarly journals Energy Efficiency Analysis of Multi-Type Floating Bodies for a Novel Heaving Point Absorber with Application to Low-Power Unmanned Ocean Device

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3282 ◽  
Author(s):  
Dongsheng Cong ◽  
Jianzhong Shang ◽  
Zirong Luo ◽  
Chongfei Sun ◽  
Wei Wu
Keyword(s):  
Energy Efficiency ◽  
Low Power ◽  
Wave Energy ◽  
Wave Force ◽  
Geometric Parameters ◽  
Floating Body ◽  
Width Ratio ◽  
Floating Bodies ◽  
Point Absorber ◽  
Capture Width Ratio

Long-term energy supplies hinder the application of the low-power unmanned ocean devices to the deep sea. Ocean wave energy is a renewable resource with amount stores of enormous and high density. The wave energy converter (WEC) could be miniaturized so that it can be integrated into the devices to make up the power module. In this paper, a small novel heaving point absorber of energy supply for low-power unmanned ocean devices is developed based on the counter-rotating self-adaptive mechanism. The floating body as an important part of the heaving point absorber, the geometric parameters is optimized to increase the efficiency of power production. Through constructing the constitutive relation between the geometric parameters, the wave force, the motion displacement, the motion velocity, and the capture width ratio of the floating body, the energy efficiency characteristics of the multi-type floating bodies are calculated, and the optimal shape is selected. On the other hand, in the calculation process of the wave force, the Froude-Krylov method is an effective method to accurately calculate the wave excitation force. Meanwhile, nonlinear static and dynamic Froude-Krylov force effectively overcomes the inaccuracy of the linear models and reduces the time consumed to simulate. Finally, the wave force, heaving velocity, heaving displacement, and capture width ratio of the three floating bodies are compared and analyzed, and the results show that the cylindrical floater that is vertically placed on the wave surface is more suitable for the novel heaving wave energy point absorber.

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