The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Zhipeng Zang - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic responses and efficiency analyses of a heaving-buoy Wave energy converter with PTO damping in regular and irregular Waves
Renewable Energy, 2018Co-Authors: Zhipeng Zang, Qinghe ZhangAbstract:Abstract Experimental investigation on the power performance of a heaving-buoy Wave energy converter (WEC) with power take-off (PTO) damping was conducted under regular and irregular Waves. The effects of the main influential parameters, including the Incident Wave Height, Wave frequency and PTO damping, on the maximum heave displacement, phase difference between the buoy velocity and Wave elevation, and capture width ratio were quantitatively studied. For regular Waves, with decreasing Incident Wave Height or increasing PTO damping, the nonlinearity between the heave motion and surrounding Wave elevation became pronounced and three modes of the buoy, i.e., linear motion, non-linear motion and non-motion, can be found. Based on analyses of the capture width ratio in both regular and irregular Waves, the present WEC can obtain an optimal power efficiency at frequency ratio of ω / ω n ≈ 0.8 and PTO damping ratio of ζ p ≈ 0.5. It has been examined that H 1/10 can generally provide better approximation of the Incident Wave energy than H 1/3 and H AVG for irregular Waves based on the linear Wave theory. The statistical power performance of the WEC in irregular Waves generally has the same trend as that in regular Waves. The capture width ratio in irregular Waves is found to be (approximately 5–40%) higher than that in regular Waves for the same Wave parameters, though the absolute Incident and absorbed Wave power in irregular Waves are only half of those in regular Waves. Finally, the flow structures around the heaving buoy are analyzed. The formation of vortices around the bottom corner provides flow interpretation on the viscous loss of Wave energy for a heaving-buoy WEC with a flat bottom.
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Flow mechanism of impulsive Wave forces and improvement on hydrodynamic performance of a comb-type breakwater
Coastal Engineering, 2018Co-Authors: Zhipeng Zang, Zhuo Fang, Ningchuan ZhangAbstract:Abstract The interactions between Waves and a comb-type breakwater (CTB) are numerically simulated in a 3D numerical Wave flume, which is based on an internal Wave generation method. The comb-type breakwater (CTB) is a new type of gravity breakwater and evolved from the conventional caisson breakwater, with part of the rectangular caisson being replaced by a thin side plate. Thus, a chamber is formed by the side plate and the bottom of superstructure between two adjacent rectangular caissons. It is found that impulsive Wave pressure on the CTB is mainly induced by the chamber, which can be simplified into a vertical wall with a horizontal cantilever slab in the 2D cross-section. The synchronous analyses on Wave profiles, velocity vectors, vorticity contours and Wave pressure distributions are conducted to reveal the flow mechanism of the impulsive Wave force. In the previous studies, the impulsive Wave pressure on a vertical wall with a horizontal cantilever slab was merely observed under breaking or broken Wave conditions. However, in the present results, the impulsive Wave pressure was also observed on such structure under non-breaking Waves. The impulsive Wave force occurs when the Incident Wave Height is comparable to the clearance between the still water level and the bottom of the super structure for non-breaking Waves. Then, a non-dimensional governing parameter, which included the effects of the water depth, the bottom of the superstructure and the Incident Wave Height, was proposed to quantify the critical conditions for impulsive Wave force. Finally, a concept designs of openings on the bottom of the superstructure is proposed to reduce the impulsive Wave force. The results show that even a 20% opening on the bottom of superstructure can reduce the maxima of impulsive Wave pressure by up to 40%.
David W. Watt - One of the best experts on this subject based on the ideXlab platform.
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Surface Waves impinging on a vertical wall
Physics of Fluids, 1998Co-Authors: John Mchugh, David W. WattAbstract:Flow visualization experiments have been performed which consider a solitary Wave impinging on a vertical wall. Several stages of motion appear as the Incident Wave Height is increased in subsequent runs. Small amplitude Incident Waves reflect off the vertical wall without a significant change in shape. Higher Wave amplitudes form a liquid sheet at impact, which ascends the vertical wall and has a ridge of fluid at the leading edge. Small Waves form behind the ridge, and the ridge may form droplets. Large Incident Wave amplitudes form spilling breaking Waves, which result in much more complicated motion in the ascending sheet, including the formation of spray.
Qinghe Zhang - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic responses and efficiency analyses of a heaving-buoy Wave energy converter with PTO damping in regular and irregular Waves
Renewable Energy, 2018Co-Authors: Zhipeng Zang, Qinghe ZhangAbstract:Abstract Experimental investigation on the power performance of a heaving-buoy Wave energy converter (WEC) with power take-off (PTO) damping was conducted under regular and irregular Waves. The effects of the main influential parameters, including the Incident Wave Height, Wave frequency and PTO damping, on the maximum heave displacement, phase difference between the buoy velocity and Wave elevation, and capture width ratio were quantitatively studied. For regular Waves, with decreasing Incident Wave Height or increasing PTO damping, the nonlinearity between the heave motion and surrounding Wave elevation became pronounced and three modes of the buoy, i.e., linear motion, non-linear motion and non-motion, can be found. Based on analyses of the capture width ratio in both regular and irregular Waves, the present WEC can obtain an optimal power efficiency at frequency ratio of ω / ω n ≈ 0.8 and PTO damping ratio of ζ p ≈ 0.5. It has been examined that H 1/10 can generally provide better approximation of the Incident Wave energy than H 1/3 and H AVG for irregular Waves based on the linear Wave theory. The statistical power performance of the WEC in irregular Waves generally has the same trend as that in regular Waves. The capture width ratio in irregular Waves is found to be (approximately 5–40%) higher than that in regular Waves for the same Wave parameters, though the absolute Incident and absorbed Wave power in irregular Waves are only half of those in regular Waves. Finally, the flow structures around the heaving buoy are analyzed. The formation of vortices around the bottom corner provides flow interpretation on the viscous loss of Wave energy for a heaving-buoy WEC with a flat bottom.
John Mchugh - One of the best experts on this subject based on the ideXlab platform.
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Surface Waves impinging on a vertical wall
Physics of Fluids, 1998Co-Authors: John Mchugh, David W. WattAbstract:Flow visualization experiments have been performed which consider a solitary Wave impinging on a vertical wall. Several stages of motion appear as the Incident Wave Height is increased in subsequent runs. Small amplitude Incident Waves reflect off the vertical wall without a significant change in shape. Higher Wave amplitudes form a liquid sheet at impact, which ascends the vertical wall and has a ridge of fluid at the leading edge. Small Waves form behind the ridge, and the ridge may form droplets. Large Incident Wave amplitudes form spilling breaking Waves, which result in much more complicated motion in the ascending sheet, including the formation of spray.
Marlin J Atkinson - One of the best experts on this subject based on the ideXlab platform.
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Wave driven circulation of a coastal reef lagoon system
Journal of Physical Oceanography, 2009Co-Authors: Ryan J Lowe, James L Falter, Stephen G Monismith, Marlin J AtkinsonAbstract:Abstract The response of the circulation of a coral reef system in Kaneohe Bay, Hawaii, to Incident Wave forcing was investigated using field data collected during a 10-month experiment. Results from the study revealed that Wave forcing was the dominant mechanism driving the circulation over much of Kaneohe Bay. As predicted theoretically, Wave setup generated near the reef crest resulting from Wave breaking established a pressure gradient that drove flow over the reef and out of the two reef channels. Maximum reef setup was found to be roughly proportional to the offshore Wave energy flux above a threshold root-mean-square Wave Height of 0.7 m (at which Height setup was negligible). On the reef flat, the Wave-driven currents increased approximately linearly with Incident Wave Height; however, the magnitude of these currents was relatively weak (typically <20 cm s−1) because of (i) the mild fore-reef slope of Kaneohe Bay that reduced setup resulting from a combination of frictional Wave damping and its re...
