1,720,962 research outputs found
Predictions of the hydrodynamic performance of the wave rotor wave energy device
No full textThis paper provides a linear solution for the Wave Rotor, a wave energy device that comprises two parallel counter rotating cylinders in orbital motion. Theoretical results are obtained for the radiated waves generated by the device, and for its efficiency. Comparisons with earlier measurements of radiated waves show very promising agreement.<br/
Hydrodynamic damping of the vertical motion of a horizontal cylinder beneath waves at large scale
No full textLarge-scale laboratory measurements are presented of the hydrodynamic damping of the vertical oscillations of a circular cylinder beneath waves, where the wave crests are parallel to the cylinder axis. In two series of tests, the Stokes parameter ? was 647 000 and 997 000, and the Keulegan Carpenter number of the cylinder motion was in the range 0·01–0·1. Observations of the decaying motion of the cylinder, and of steady-state oscillations generated by continuous force excitation, were in reasonable agreement with the vector form of the relative velocity Morison equation with constant coefficients. In some conditions, the motion of the cylinder became phase locked to the wave-induced flow, at an integer frequency ratio
Transient motion of a vertical cylinder: Measurements and computations of the free surface
No full textIn recent years there have been concerns in the offshore oil industry over the violent motions of the water surfaceproduced around a vertical cylinder by relatively large steep waves (say height/diameter = 1, height/length =0.1)
A parametric model for ocean wave period from Ku band altimeter data
No full textUsing a large collocated data set of altimeter and buoy measurements, we examine the relationship between the altimeter Ku-band measurements of significant wave height, H s , backscatter coefficient, ? 0, and the buoy wave period. This is used to derive an empirical altimeter wave period model for TOPEX, Poseidon, Jason-1, ERS-2, Envisat, and GEOSAT follow-on. We show that there is a step change in the response of ? 0 at around 13 dB and above this value ? 0 is not related to wave period. The results are compared to algorithms proposed by two previous authors (Gommenginger et al., 2003; Quilfen et al., 2004) and examined in terms of absolute accuracy (RMS error), ability to replicate the joint distribution of wave height and period, and residual trends with various parameters. The new algorithm is shown to perform better than the previous algorithms in all metrics considered. Finally, we demonstrate that there is a limiting accuracy achievable for a function of the form f(H s , ? 0) and that our model comes close to this
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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