Showing papers on "Wave power published in 1992"

Modelling of a plasma column sustained by a travelling circularly polarized electromagnetic wave ( m = 1 mode) in the presence of a constant axial magnetic field

Abstract: We present a set of equations modelling a low-pressure plasma column sustained by a travelling electromagnetic wave in the dipolar mode in the presence of a constant external magnetic field. It is shown that, from a practical point of view, only the m = 1 mode (the right-hand-polarized wave) can sustain plasma columns in a wide region of gas-discharge conditions: plasma radius R, wave frequency ωo, magnetic field Bo and low pressures, irrespective of the nature of the gas. We have examined two gas-discharge regimes: freefall/diffusion and recombination respectively. For a given gas-discharge regime the axial column structure and wave-field characteristics are specified by two numerical parameters: σ = ωR/c and ω = ωc/ω, where c is the speed of light and ωc the electron-cyclotron frequency. The main result of our study is that the magnetic field-makes it possible to sustain a plasma column for values of σ smaller than σcr = 0.3726, below which, in the absence of a magnetic field, the dipolar wave cannot produce a plasma. Moreover, at a fixed wave power, the magnetic field – in contrast with the case of plasma columns sustained by azimuthally symmetric waves – increases the plasma density and its axial gradient. The limit of an infinite external magnetic field (Ω → ∞) is also considered. A three-dimensional wave structure is obtained, and it indicates that the wave can be a generalized surface mode, a pure surface or a pseudosurface one.

At-sea Experiment of a Floating Offshore Structure

Abstract: This paper is concerned with simulations and statistical prediction of total second order responses, including slow drift motions caused by waves and wind, of a full scale offshore structure “POSEIDON”. The at-sea experiment was carried out from June, 1986 till July, 1990 at the Japan Sea. In order to simulate the total second order motion, hydrodynamic and restoring characteristics were examined using data from full scale free oscillation tests. Second order force characteristics have been investigated through comparison between experimental results from cross bispectral analysis of slow drift motion and waves and numerical ones from potential theory. And from multi input analysis of motion, waves, instantaneous wave power and wind fluctuations the contribution rate of wind fluctuation to slow drift motion has also been studied.Comparisons between measured time series of slow drift motion and simulations on the basis of above investigations have been carried out.Both a Monte-Carlo simulation model and nonlinear statistical etimate method are newly devloped. The former is based on the assumption that the second order force process can be approximated by diffrence of two gamma processes. The latter is a statistical estimates method taking into account not only second order wave forces but also wind fluctuations and it is an extended method of nonlinear statistical theory suggested previously by authors.Both measured sample data and statistical values estimated by two new methods are compared.Main results are as follows : 1) In order to simulate total second order motions, in-line and transverse wind fluctuations should be taken into account even though mean wind direction is head. As a wind spectrum representing wind fluctuations, a spectrum form with significant low frequency power compared with Davenport and Hino spectra, e. g. spectrum forms suggested by Ochi-Shin and one of authors, should be used.2) It is confirmed that the linear prediction method based on Longuet-Higgins' significantly underestimates the measured results while the present method estimates them very well.3) Extreme statistics by Monte-Carlo simulation model significantly scatter. Especially, estimates from a simulation data with the number of peaks of about 300, i.e. a five hour simulation, scatter from 2.5 to 5.0 as a value of extreme value/standard deviation. Attention is needed.

Method for measuring fundamental wave power and higher harmonic power of strain wave power supply

Abstract: PURPOSE:To measure fundamental wave power and higher harmonic power by measuring the effective values of voltage and a current by an effective value indication type meter and storing the waveforms of both of them in a waveform memory apparatus and measuring average power by a voltmeter. CONSTITUTION:The effective values of voltage and a current are measured and the waveforms of both are simultaneously stored and average power is measured by a voltmeter. Next, the stored waveforms are subjected to FFT analysis to respectively determine the ratios of respective higher harmonics to a fundamental wave. By taking the sum of the values obtained by squaring the respective ratios from the order corresponding to the fundamental wave to the order of higher harmonics to be considered, the ratio of the effective value of a strain wave to the effective value of the fundamental wave is calculated and the fundamental wave effective values of line voltage and a phase current are determined. From the stored waveforms, the phase difference of the voltage and current of the fundamental wave is calculated. The phase difference of the fundamental waves of phase voltage and line voltage is 30 (150) deg. because both of a power supply and load are in an equilibrium state. By correcting this phase difference, fundamental wave power is calculated. Next, higher harmonic power is calculated by subtracting the calculated fundamental wave power from the average power of a wattmeter.

Characteristics of Pneumatic Wave Power Conversion System with Water Valve Rectifier

Abstract: Energy conversion characteristics of a new wave power conversion device are discussed. In this system, water valves, not mechanically operated, are combined with air chambers. The advantage of this...

Damping and scattering of electromagnetic waves by small ferrite spheres suspended in an insulator

Abstract: The intentional degradation of electromagnetic waves by their penetration into a media comprised of somewhat sparsely distributed energy absorbing ferrite spheres suspended in an electrical insulator is investigated. Results are presented in terms of generalized parameters involving wave length and sphere size, sphere resistivity, permeability, and spacing; their influence on dissipation of wave power by eddy currents, magnetic hysteresis, and scattering is shown.

Arrangement for generating energy

Abstract: Arrangement for generating energy and oxygenating water in seas and lakes by using wave power. The arrangement consists of a vertical pipe 21 which is located on the bottom of the sea or lake and in which there is a turbine 22 which is connected to a generator 23 located at the upper end of the pipe 21. A number of collecting lines 20 extend radially from the lower part of the pipe 21. Connected to each of these collecting lines 20 is a number of pumps 2. These pumps 2 each consist of pipes 8, 9 running one in another with non-return valves 6, 7. The upper pipe 8 is connected via a wire 4 to a float 3 which is moved vertically by the wave movements and in this connection brings about a one-way pumping of water from higher water layers through the turbine 22, which drives the generator 23, onward through the collecting lines 20 and through the pumps 2 out into water layers at the bottom. Said water circulation brings about both energy generation and environmentally valuable oxygenation of the bottom water of seas and lakes.

Coastal air wash system

Abstract: A system for washing the air in a coastal environment in which a volume of air moves from a land mass to a water mass. The system includes a plurality of fountains 12 mounted offshore which spray a volume of water into the path of the air flow. Water is stored under pressure and selectively released to form the spray. In specific embodiments, wave motion is used to provide the power to pressurize the stored water. Wave power is extracted by dual reciprocating pumps 50 and 51 connected to a float 40. Wave power is amplified by lenses 20 which focus the waves onto the floats 40. A control system 100 senses pollution and controls the generation of the spray. In addition, wave motion is sensed and used to control the position of the lens 20 for optimum performance and minimum wear.

Wind power/wave power/tidal power generator

Abstract: PURPOSE:To high efficiently utilize natural energy by constituting a generator of a plurality of Darrieus type propellers collected in one line. CONSTITUTION:A plurality of Darrieus type propellers are arranged in a line so as to prevent kinetic energy in a vertical direction relating to a surface from so escaping. The individual Darrieus type propeller is lengthened to decrease a radius of the bottom surface. The Darrieus type propellers, arranged in one line, are horizontally set up in a suitable position of a strong frame (1) and partitions (2) to constitute a wave power generator. A wind power generation (3) of similar constitution is concurrently provided in an upper part of a floating structure.