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Effect of Mass Ratio on Hydrodynamic Response of a Flexible Cylinder

Journal of Marine Science and Application 2016年第1期15卷 50-62页

作者： haoyang cen.rupp carriveau David S-K Ting Turbulence and Energy Laboratory Centre for Engineering Innovation University of Windsor Ontario N9B 3P4 Canada

The effect of the mass ratio on the flow-induced vibration （FIV） of a flexible circular cylinder is experimentally investigated in a towing tank. A Tygon tube with outer and inner diameters of 7.9 mm and 4.8 mm, respectively, was employed for the study. The tube was connected to a carriage and towed from rest to a steady speed up to 1.6 m/s before slowing down to rest again over a distance of 1.6 m in still water. Reynolds number based on the cylinder＇s outer diameter was 800-13,000, and the reduced velocity （velocity normalized by the cylinder＇s natural frequency and outer diameter） spanned from 2 to 25. When connected, the cylinder was elongated from 420 mm to 460 mm under an axial pre-tension of 11 N. Based on the cylinder＇s elongated length, the aspect ratio （ratio of the cylinder＇s length to outer diameter） was calculated as 58. Three mass ratios （ratio of the cylinder＇s structural mass to displaced fluid mass, m＊） of 0.7, 1.0, and 3.4 were determined by filling the cylinder＇s interior with air, water, and alloy powder （nickel-chromium-boron matrix alloy）, respectively. An optical method was adopted for response measurements. Multi-frequency vibrations were observed in both in-line （IL） and cross-flow （CF） responses; at high Reynolds number, vibration modes up to the 3rd one were identified in the CF response. The mode transition was found to occur at a lower reduced velocity for the highest tested mass ratio. The vibration amplitude and frequency were quantified and expressed with respect to the reduced velocity. A significant reduced vibration amplitude was found in the IL response with increasing mass ratios, and only initial and upper branches existed in the IL and CF response amplitudes. The normalized response frequencies were revealed to linearly increase with respect to the reduced velocity, and slopes for linear relations were found to be identical for the three cases tested.

关键词： flow-induced vibration low mass ratio flexible cylinder multi-frequency response hydrodynamic response

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Flow Past an Accumulator Unit of an Underwater Energy Storage System： Three Touching Balloons in a Floral Configuration

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Journal of Marine Science and Application 2014年第4期13卷 467-476页

作者： Ahmadreza Vasel-Be-Hagh rupp carriveau David S-K Ting Turbulence and Energy Laboratory Centre for Engineering Innovation University of Windsor Ontario N9B 3P4 Canada

An LES simulation of flow over an accumulator unit of an underwater compressed air energy storage facility was conducted. The accumulator unit consists of three touching underwater balloons arranged in a floral configuration. The structure of the flow was examined via three dimensional iso surfaces of the Q criterion. Vortical cores were observed on the leeward surface of the balloons. The swirling tube flows generated by these vortical cores were depicted through three dimensional path lines. The flow dynamics were visualized via time series snapshots of two dimensional vorticity contours perpendicular to the flow direction; revealing the turbulent swinging motions of the aforementioned shedding-swirling tube flows. The time history of the hydrodynamic loading was presented in terms of lift and drag coefficients. Drag coefficient of each individual balloon in the floral configuration was smaller than that of a single balloon. It was found that the total drag coefficient of the floral unit of three touching balloons, i.e. summation of the drag coefficients of the balloons, is not too much larger than that of a single balloon whereas it provides three times the storage capacity. In addition to its practical significance in designing appropriate foundation and supports, the instantaneous hydrodynamic loading was used to determine the frequency of the turbulent swirling-swinging motions of the shedding vortex tubes; the Strouhal number was found to be larger than that of a single sphere at the same Reynolds number.

关键词： droplet-shaped bluff body LES swirling flow swinging flow shedding vortex tubes underwater balloons

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Response Characteristics of Flexible Risers in Offshore Compressed Air Energy Storage Systems

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Journal of Marine Science and Application 2019年第3期18卷 353-365页

作者： Bo Hu Zhiwen Wang Hongwang Du Wei Xiong Zuwen Wang Institute of Ship Electromechanical Equipment Dalian Maritime UniversityDalian 116026China Turbulence and Energy Laboratory Ed Lumley Centre for Engineering InnovationUniversity of WindsorWindsorOntario N9B 3P4Canada

With the rapid development of marine renewable energy technologies, the demand to mitigate the fluctuation of variable generators with energy storage technologies continues to increase. Offshore compressed air energy storage (OCAES) is a novel flexible-scale energy storage technology that is suitable for marine renewable energy storage in coastal cities, islands, offshore platforms, and offshore renewable energy farms. For deep-water applications, a marine riser is necessary for connecting floating platforms and subsea systems. Thus, the response characteristics of marine risers are of great importance for the stability and safety of the entire OCAES system. In this study, numerical models of two kinds of flexible risers, namely, catenary riser and lazy wave riser, are established in OrcaFlex software. The static and dynamic characteristics of the catenary and the lazy wave risers are analyzed under different environment conditions and internal pressure levels. A sensitivity analysis of the main parameters affecting the lazy wave riser is also conducted. Results show that the structure of the lazy wave riser is more complex than the catenary riser;nevertheless, the former presents better response performance.

关键词： Offshore compressed air energy storage Flexible riser Marine energy Catenary Lazy wave Sensitivity analysis

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