Showing papers on "Wave power published in 1998"

The dependence of high‐latitude PcS wave power on solar wind velocity and on the phase of high‐speed solar wind streams

Abstract: We have calculated the integrated ULF wave power in the Pc5 band at two stations, Kevo (part of the International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer array in Scandinavia, at auroral zone latitudes), and Cape Dorset (part of the Magnetometer Array for Cusp and Cleft Studies (MACCS) in Arctic Canada, at cusp latitudes), and compared this power against the solar wind velocity for the last six months of 1993, a period characterized by two persistent high-speed solar wind streams. We find for both local noon at Cape Dorset, and for local morning at Kevo, the Pc5 band power (0.002 – 0.010 Hz) integrated over a six-hour period exhibits a clear power-law dependence on the solar wind velocity. At Cape Dorset we found power α Vsw4, with a correlation coefficient r = 0.73, and at Kevo we found power α Vsw6.5, with r = 0.74. Much of the remaining variation in Pc5 power is due to temporal patterns evident at both stations in response to recurrent high speed streams. Power was strongest at the leading edge of each high speed stream and subsequently decreased more quickly than Vsw. Our observations suggest that it is insufficient to make estimates of Pc5-range ULF wave power on the basis of Vsw alone: one must consider other physical factors, either intrinsic to the solar wind or related to its interaction with Earth's magnetosphere. The Kelvin-Helmholtz instability is often considered to play a dominant role in this interaction, and the level of instability depends on both velocity and density. By means of a simple simulation using typical density and velocity values during the passage of a high speed stream, we were able to obtain good agreement with the temporal variations we observed. Finally, this study indicates that ground-based pulsation observations can provide reliable proxies of the initial passage of high speed solar wind streams past Earth.

Water desalination system

Abstract: A system and method for producing potable water from a brine source uses an Archimedean screw to elevate water to an elevated point The water is then filtered to desalinate the water through a series of filters arranged in a vertical shaft using gravity to move the water through the filters The vertical nature of the screw and shaft reduce land requirements and costs A power source turns the screw and relies on renewable energy sources, such as solar, wind, and tidal/wave power A turbine is used to recapture any energy in the descending water The screw, renewable energy power source, and turbine reduce the energy requirements and costs A brine recycling system recovers the removed brine and various elements and minerals are separated

Mechanism for formation of lutoclines by waves

Abstract: The mechanism by which a suspended fine-sediment-induced pycnocline, or lutocline, is generated under wave action is examined. The steady-state form of the turbulent kinetic energy balance is used along with commonly invoked phenomenological arguments to obtain a formula for the height of the lutocline as a function of wave and suspended sediment properties. This formula is then used in conjunction with data on equilibrium heights of lutoclines of a suspended clay mixture in a wave flume to show that the formula holds promise as a first-order predictor of lutocline height. This height is also shown to correlate empirically with wave energy.

Performance Prediction of Contrarotating Wells Turbines for Wave Energy Converter Design

Abstract: Wave energy can be captured and converted to a vertical pistonlike oscillatory motion by semiinsertion of a chamber with a submerged opening into the ocean. The roof of the chamber will open onto a ducted Wells air turbine, which will be driven by the oscillatory airflow developed by the forcing action of the surface of the Oscillating Water Column (OWC) inside the chamber. The design of such an OWC conversion plant is considered with particular reference to the air turbine stage and its synthesis into the system. Consequently, a semiempirical method for predicting the performance of the contrarotating Wells turbine configuration is presented, notably, detailing aerofoil performance into the stall region. The predicted turbine performance is subsequently utilized to facilitate the design of a 310 kW plant, including efficient accommodation of the pneumatic power levels for maximal aerodynamic conversion.

Solar wind control of ultralow‐frequency wave activity at L = 3

Abstract: This study explores the statistical relationships between 2 years of solar wind data recorded by the IMP 8 spacecraft and data from the Mount Clemens magnetometer station (L = 3) to improve our understanding of possible energy sources of ULF wave activity. Within the four frequency bands, f = 4–8 mHz, 8–16 mHz, 16–32 mHz, and 32–64 mHz, that are studied, two distinct types of waves are found. One is at high frequencies corresponding to Pc3 pulsations, and the other is at low frequencies corresponding to Pc5 and low-frequency Pc4 pulsations. The high-frequency part clearly has an energy source in the upstream foreshock. However, our analysis shows that the magnetospheric cusps do not appear to be the conduit of energy for the wave activity in this low-latitude region. The low-frequency activity occurs most frequently and has greater wave power when the interplanetary magnetic field is southward. This correlation suggests that the major energy source of these low-frequency waves is substorm-related or is related to the reconnection on the dayside magnetopause.

Study On a Wells Turbine For Wave Power Conversion: Improvement of Performance By the Use of Porous Fences

Abstract: In order to improve the performance of a Wells turbine, porous fences have been installed on the hub wall upstream and downstream of the rotor. The effects of the gap between the porous fence and rotor, porosity and height of the porous fence have been investigated by model testing. The results have been compared with those of the case without porous fences. It is found that the starting characteristics are improved by the porous fences. Furthermore most of the configurations tested have shown improvements in the operation range primarily by postponement of stall. A suitable choice of design parameters for the turbine is suggested. *ISOPE Member. Received March 7, 1998: revised manuscript received by the editors July 8, 1998. The original version (prior to the final revised manuscript) was presented at the Eighth International Offshore and Polar Engineering Conference (ISOPE-98), Montréal, Canada, May 24-29, 1998.