Extracting Energy From the Hydrodynamic Instability of a Yawing Flat Plate

2012 ◽  
Author(s):  
Antonio Carlos Fernandes ◽  
Mohammadmehdi Armandei
Keyword(s):  
Flat Plate ◽  
Natural Frequency ◽  
Hydrodynamic Instability ◽  
Concurrent Schedule ◽  
Water Current ◽  
Maximum Efficiency ◽  
Energy Extraction ◽  
Torsion Spring ◽  
Extraction Behavior ◽  
Mass Moment

The extraction of energy from currents is still an issue. Both design point and off-design behavior should be addressed conveniently. In the present study, a new concept based on the flow-induced instability of an elastic structure is introduced by which the energy can be extracted from the water current. The energy extractor device is named “Fernandes-Armandei”, which consists of a simple flat plate attached to a torsion spring and located vertically in the water current. The flat plate has only 1 DOF that is yawing about its axis, which is in its mid chord length. A concurrent-schedule research (Armandei and Fernandes, 2012) demonstrates that one such motion becomes dynamically unstable, as the velocity exceeds a special threshold. The motivation of doing this research was the robustness of the oscillations created due to the flow-induced instability. Two different cases (a) and (b) are studied, case (a) with larger natural frequency and case (b) with larger mass moment and added moment of inertia. A damper is also applied in the device as a transmission system which converts oscillation to rotation. The rotary motion is utilized to lift a weight up to a prescribed height, to assess the energy extraction behavior of each case. The results show that case (b) can lift heavier weights than case (a). However, the maximum efficiency of case (a) (9.18%) is about three times more than the maximum efficiency of case (b) (3.26%).

van der Pol-Duffing Modeling for Torsional Galloping

2014 ◽  
Author(s):  
Antonio Carlos Fernandes ◽  
Mohammadmehdi Armandei
Keyword(s):  
Stability Analysis ◽  
Flat Plate ◽  
Phenomenological Model ◽  
Current Speed ◽  
Water Current ◽  
Van Der Pol ◽  
Angular Oscillation ◽  
Torsion Spring ◽  
Aforementioned Study ◽  
Torsional Galloping

This study is a continuation of the study presented in OMAE 2012 entitled: “Stability Analysis of a Yawing Flat Plate into the Water Current”[1]. The structure in the aforementioned study consists of a rectangular flat plate with an elastic axis in its mid-chord length. The elasticity is provided by torsion spring. The flat plate has only one degree of freedom which is angular oscillation about its axis. It is observed that as the current speed exceeds a critical velocity, the flat plate becomes unstable. The instability leads to torsional galloping occurrence, as a result of which the flat plate begins to oscillate angularly about the elastic axis. Through the present study, a phenomenological model is developed based on van der Pol-Duffing equation, in order to explain the instability leading to the torsional galloping.

Stability Analysis of a Yawing Flat Plate Into the Water Current

2012 ◽  
Author(s):  
Mohammadmehdi Armandei ◽  
Antonio Carlos Fernandes
Keyword(s):  
Stability Analysis ◽  
Flat Plate ◽  
Least Square Method ◽  
Least Square ◽  
Water Current ◽  
Torsion Spring ◽  
Flutter Derivative ◽  
Liapunov Stable ◽  
The Stability ◽  
Derivatives Of

The present study deals with the stability analysis of an oscillating flat plate into the water current. The flat plate, which is attached to a torsion spring and located vertically in the water current, has only 1 DOF that is yawing motion. The experiments have shown that as the current velocity exceeds a special threshold, the flat plate becomes unstable and begins to oscillate. This oscillation can be utilized to extract energy. A free vibration experimental technique is used in this study. The experimental results are analyzed using the flutter derivative theory, in which the flutter derivatives of the motion are extracted using GLS (General Least-Square) method. The results confirm that the flat plate becomes dynamically unstable. Also, there is a Liapunov stable fixed point on the origin at the phase portrait of the yawing motion.

scholarly journals ENERGY EXTRACTION FROM GRAVITATIONAL COLLAPSE TO STATIC BLACK HOLES

2003 ◽  
Vol 12 (01) ◽  
pp. 121-127 ◽  
Author(s):  
REMO RUFFINI ◽  
LUCA VITAGLIANO
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Extraction Process ◽  
Maximum Efficiency ◽  
Energy Extraction ◽  
Mass Energy ◽  
Classical Level ◽  
Static Black Hole ◽  
Exact Analytic Expression ◽  
Analytic Expression

The mass-energy formula of black holes implies that up to 50% of the energy can be extracted from a static black hole. Such a result is reexamined using the recently established analytic formulas for the collapse of a shell and the expression for the irreducible mass of a static black hole. It is shown that the efficiency of energy extraction process during the formation of the black hole is linked in an essential way to the gravitational binding energy, the formation of the horizon and the reduction of the kinetic energy of implosion. Here a maximum efficiency of 50% in the extraction of the mass energy is shown to be generally attainable in the collapse of a spherically symmetric shell: surprisingly this result holds as well in the two limiting cases of the Schwarzschild and extreme Reissner–Nordström space–times. Moreover, the analytic expression recently found for the implosion of a spherical shell to an already formed black hole leads to a new exact analytic expression for the energy extraction which results in an efficiency strictly less than 100% for any physical implementable process. There appears to be no incompatibility between General Relativity and Thermodynamics at this classical level.

Augmented Diffuser for Horizontal Axis Marine Current Turbine

2016 ◽  
Vol 7 (1) ◽  
pp. 235 ◽  
Author(s):  
Aly Hassan Elbatran ◽  
Omar Yaakob ◽  
Yasser Ahmed ◽  
Firdaus Abdallah
Keyword(s):  
Tidal Current ◽  
Renewable Energy Sources ◽  
Research Work ◽  
Horizontal Axis ◽  
Offshore Wind ◽  
Water Current ◽  
Maximum Efficiency ◽  
Marine Current Turbine ◽  
Marine Current ◽  
Current Turbine

<span>The potential of renewable energy sources is enormous as they can make a major contribution to the future of energy needs. The ocean has a great potential to become a practical and predictable energy source compared to other energy resources such as solar, wind, and nuclear. It offers different sources of energy which can be utilized namely wave, tidal, offshore wind, thermal, and tidal current. Among these sources, marine tidal current has major advantages such as higher power availability and predictability. The main objective of this research work is to design and develop a horizontal axis marine current turbine (HAMCT) that suitable for operating within Malaysian ocean, which has low speed current (0.5 – 1 m/s average). A prototype of augmented diffuser 4-bladed HAMCT applying NACA 0014 was proposed in the current study. The turbine model has 0.666 m diameter, and it was designed to produce as much as power from flowing water current. Model was constructed and tested at Marine Technology Center (MTC) in three conditions, namely, free tow testing, ducted tow testing, and ducted diffuser tow testing in order to predict the power and efficiency of the turbine system. The results showed that the application of duct was significant to concentrate the flow and diffuser arrangement was effective when it was placed behind of the rotor in this condition of low water current speed. The maximum efficiency Cp obtained in the current system was 0.58.</span>

scholarly journals Effect of wall inclination on the dynamic behaviour of an oscillating water column system

2020 ◽  
Vol 307 ◽  
pp. 01021
Author(s):  
Abdelhamid El Barakaz ◽  
Abdellatif El Marjani ◽  
Hamid Mounir
Keyword(s):  
Water Column ◽  
Natural Frequency ◽  
Wave Energy ◽  
Maximum Efficiency ◽  
Oscillating Water Column ◽  
Wave Energy Converters ◽  
Column System ◽  
Resonance Domain ◽  
Pneumatic Chamber ◽  
Chamber Model

The Oscillating Water Column device (OWC) is one of the most used Wave Energy Converters (WECs) for wave energy harvesting. It consists essentially of two parts: the pneumatic chamber made of concrete and the bidirectional turbine linked to a generator group for energy production. In this study we are interested in the water motion oscillation inside the chamber resulting from the water level perturbation. This process is characterized by its own natural frequency and global damping. The vertical OWC chamber model is limited by the number of parameters defining the natural frequency and the global damping. The objective of this paper is to improve the performances obtained for the vertical OWC by considering an OWC with inclined sidewalls. For maximum efficiency, the device must operate in the resonance domain where the damping is low and the frequency of incoming waves matches with the natural frequency of the OWC. This will theoretically amplify the pneumatic energy to be converted to a mechanical one in the turbine.

Generating Power From Ocean Waves Using a Float With Excessive Buoyancy: Theory and Dynamic Model Results

2003 ◽  
Author(s):  
T. MacCready ◽  
T. Zambrano ◽  
B. D. Hibbs
Keyword(s):  
Numerical Model ◽  
Natural Frequency ◽  
Power Output ◽  
Ocean Surface ◽  
Ocean Waves ◽  
The Body ◽  
Energy Extraction ◽  
Ocean Energy ◽  
Wave Conditions ◽  
Rich Data

We are exploring a new approach to ocean energy extraction through a device that we refer to as the NAF (an acronym for Non-Archimedean Float). The NAF is a fully submerged body with excess buoyancy; i.e., the mass of the body is far less than the mass of the water it displaces. When such a float is tethered beneath the ocean surface the buoyancy yields a large force vector in the direction perpendicular to the isobaric surfaces that parallel the water/air interface. The constant shifting of the wave troughs provides the opportunity for energy extraction using turbines affixed to the float. We are exploring the NAF concept because its simplicity results in many inherent benefits. The device has few moving parts, gathers energy from waves coming in any direction, and exists as a non-obtrusive, completely submerged installation. A numerical model of the NAF has been created to determine the dynamic behavior and power output for various configurations and under various wave conditions. The numerical model is set up to calculate the various forces experienced by the NAF float, and from these it calculates the velocity and position of the float through time series steps. The model effectively demonstrates which variables are important and how power output relates to NAF dimensions. One early finding from the model result relates to tuning the natural frequency of the NAF to match the natural frequency of the waves. The NAF moves like an inverted pendulum, and its natural frequency is primarily dependent on the length of the pendulum. Regardless of the actual float buoyancy, the 6 to 12 second periods that typify average wave conditions dictate that the NAF tether should be between 30-m and 60-m long. Also, a scale version of this novel energy device consisting of a float tethered beneath the ocean surface was deployed off the coast of southern California. The deployment yielded rich data sequences that are sufficient for comparison with a dynamic numerical model.

Experimental Investigation of Flow Induced Rotation of Hinged Plates With Shapes to Avoid Fluttering

2011 ◽  
Author(s):  
Antonio Carlos Fernandes ◽  
Sina Mirzaei Sefat ◽  
Fabio Moreira Coelho ◽  
Amanda Silva Albuquerque
Keyword(s):  
Experimental Investigation ◽  
Flat Plate ◽  
Flow Velocity ◽  
Natural Frequency ◽  
Dimensional Analysis ◽  
Vertical Axis ◽  
Incoming Flow ◽  
Stabilizing Effect ◽  
Plate Width ◽  
Angle Of Rotation

This paper addresses the flow induced rotation phenomena of plates hinged to allow flow induced rotating about their vertical axis. Different transversal shape configurations are studied. The aim of this study is to simplify the fluttering problem that may occur with falling objects in water during installation of offshore devices. The investigation intent is to propose an optimized configuration for stabilizing the fluttering motion of pendulous installation method of manifolds. The experiments and dimensional analysis confirmed that natural frequency is linearly proportional to the incoming flow velocity and inversely proportional to the flat plate width, and also the equivalent harmonic angle of rotation for small oscillation angles is approximately constant in different velocities. Experiments show that the bluffer plates (plate with two stabilizers and plate with stabilizers and nose), by increasing of period of rotation and also decreasing of equivalent harmonic angle of rotation have stabilizing effect in the fluttering motion of falling objects.

scholarly journals Development of Low-Cost Solar Water Heater Using Recycled Solid Waste for Domestic Hot Water Supply

2018 ◽  
Vol 150 ◽  
pp. 04010
Author(s):  
Abdul Talib Din ◽  
Khairul Azri Azlan
Keyword(s):  
Flat Plate ◽  
Solid Waste ◽  
Solar Collector ◽  
Low Cost ◽  
Maximum Efficiency ◽  
Solar Water Heater ◽  
Water Heater ◽  
Solar Water ◽  
Heat Absorber ◽  
Heat Collector

This research is focused on the development of a low-cost solar water heater (SWH) system by utilizing solid waste material as part of system elements. Available technologies of the solar water heater systems, heat collectors and its components were reviewed and the best system combinations for low cost design were chosen. The passive-thermosiphon system have been chosen due to its simplicity and independency on external power as well as conventional pump. For the heat collector, flat plate type was identified as the most suitable collector for low cost design and suits with Malaysia climate. Detail study on the flat plate collector components found that the heat absorber is the main component that can significantly reduce the solar collector price if it is replaced with recycled solid waste material. Review on common solid wastes concluded that crushed glass is a non-metal material that has potential to either enhance or become the main heat absorber in solar collector. A collector prototype were then designed and fabricated based on crashed glass heat collector media. Thermal performance test were conducted for three configurations where configuration A (black painted aluminum absorber) used as benchmark, configuration B (crushed glass added partially) that use glass for improvement, and lastly configuration C (black colored crushed glass) that use colored glass as main absorber. Result for configuration B have shown a negative effect where the maximum collector efficiency is 26.8% lower than configuration A. Nevertheless, configuration C which use black crushed glass as main heat absorber shown a comparable maximum efficiency which is at 82.5% of the maximum efficiency for configuration A and furthermore have shown quite impressive increment of efficiency at the end of the experiment. Hence, black colored crushed glass is said to have quite a good potential as the heat absorber material and therefore turn out to be a new contender to other non-metal heat absorber such as plastic and rubber.

Passive Energy Extraction Through Oscillation of a Yawing Flat Plate Operating in a Uniform Current

2011 ◽  
Author(s):  
Antonio Carlos Fernandes ◽  
Mohammadmehdi Armandei
Keyword(s):  
Flat Plate ◽  
Leading Edge ◽  
Experimental Tests ◽  
Energy Extraction ◽  
Unique Combination ◽  
Transversal Section ◽  
Waves And Currents ◽  
Axis Position ◽  
Uniform Current ◽  
Spring Coefficient

The work studies the behavior of a plate positioned vertically to incoming current allowed only to yaw. The intention is to use this or similar device to extract energy from the current. Soon, it became clear that positioning a forward disturbance in front of the flat plate creates a wake that improves dramatically the energy extraction. This disturbance was made by a pile with a semi circle transversal section (D-section pile). Several tests have been run, all with the same dimensions of the flat plate and the D-section pile, but each with a unique combination of the incoming velocity (U), the yawing axis position (a/c), the external spring coefficient (k), the distance between the D-section pile and the leading edge of the flat plate (d). The experimental tests are done in LOC (Laborato´rio de Ondas e Correntes — Waves and Currents Laboratory) in COPPE/Federal University of Rio de Janeiro. The results demonstrate that one such system, if controlled appropriately, has the ability to extract energy efficiently.

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