Experimental investigation of flow past a confined bluff body: Effects of body shape, blockage ratio and Reynolds number

Wang, Xikun; Chen, Jiaqi; Zhou, Bo; Li, Yajie; Xiang, Qingjiang

doi:10.1016/j.oceaneng.2020.108412

Cited by 22 publications

(6 citation statements)

References 49 publications

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“…Figure 8 depicts several researchers' variations in the St with the Ar and Br. The St falls significantly as the Ar increases, but just somewhat as the Re increases, which is similar to the findings of Igarashi [23] and Wang [20]. As indicated in the graph, when the Br grew from 0.067 to 0.25, the St increased by almost 25%.…”

Section: Space-time Correlation Analysissupporting

confidence: 86%

“…Furthermore, at this time, the frequency of vortex shedding increases as the Re increases, which is why the VIVACE device requires a specific flow velocity to function. Moreover, the frequency of vortex shedding decreases as the Ar increases, and the blockage effect can increase the frequency of vortex shedding [20,21]. The average drag coefficient and the Strouhal number (St = f × D/U 0 ) will also increase as the Br increases.…”

Section: Introductionmentioning

confidence: 99%

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Flow around a Rectangular Cylinder Placed in a Channel with a High Blockage Ratio under a Subcritical Reynolds Number

Shi

Dong

Yan

et al. 2021

Water

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With the depletion of fossil energy sources, clean energy has become a growing concern for scholars. Vortex-Induced Vibration Aquatic Clean Energy (VIVACE), a device that uses water flow energy to generate electricity, has attracted much attention for its broad applicability and other advantages. Particle Image Velocimetry (PIV) experiments were conducted to improve the efficiency of the VIVACE device in low-velocity areas. The present study investigated the effects of the Blockage ratio (Br), Reynolds number (Re = ρU0D/μ), and Aspect ratio (Ar = B/D, width-to-height) of rectangular cylinders on flow characteristics. The influence of the Ar, Br, and Re on the flow field structure was systematically analyzed in terms of the time-averaged flow field, Reynolds shear stress, space–time correlation, vorticity field, and water pressure characteristics. The vorticity field was deconstructed by Proper Orthogonal Decomposition (POD). The results show that the first two orders of POD modal energy accounted for 75% of the total energy, indicating that the first two modes can be used to identify the large-scale vortex structure. The main water pressure frequency and vortex shedding frequency (f) had a high degree of consistency. Thus, vortex shedding was the main cause of wall water pressure fluctuations. Given the blockage effect, the shear layer’s development spanwise was restricted. Moreover, the blockage effect increased the local flow velocity and accelerated the vortex shedding. The dimensionless time-averaged flow velocity U/U0 increased to 1.5, and the frequency of vortex shedding increased by approximately 25% when the Br increased from 0.067 to 0.25. The frequency increased by 25% when the Ar decreased from 0.5 to 0.2. The experimental results also provide a new idea for optimizing the VIVACE device.

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Section: Space-time Correlation Analysissupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Flow around a Rectangular Cylinder Placed in a Channel with a High Blockage Ratio under a Subcritical Reynolds Number

Shi

Dong

Yan

et al. 2021

Water

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“…Numerical studies at low Reynolds numbers showed that the wall increases the drag coefficient [55,56]. Experimentation at high Reynolds numbers (above 3000) on a cylinder, flat plates, and a square bar indicates the effects of walls on the pattern of the vortex-shedding [57]. The presence of the flow meter upstream of the sample, as mentioned previously, should have affected the force reading.…”

Section: 𝐹mentioning

confidence: 80%

Open Water Flume for Fluid Mechanics Lab

Wulandana

2021

Fluids

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Open water flume tanks with closed-loop circulation driven by centrifugal pumps are essential for hydro experimentation in academic settings as well as research centers. The device is also attractive due to its versatility and easy-to-maintain characteristics. Nevertheless, commercial open flume systems can be expensive and become less prioritized in engineering schools. This paper describes the design and fabrication of an affordable, medium-size water flume tank, suitable for education purposes. The central piece of the system is a transparent observation chamber where fluid experiments are typically conducted and observed. The expected maximum average water speed in the observation chamber of about 60 cm per second was achieved by the inclusion of a 3 hp centrifugal pump. The size and capacity of the current design were constrained by space limitation and available funds. The educational facility was assigned as a two-semester multi-disciplinary capstone senior design project incorporating students and faculty of mechanical, electrical, and computer engineering programs in our campus. The design process provides a training platform for skills in the area of Computer Aided Designs (CAD), Finite Element Analysis (FEA), Computational Fluid Dynamics (CFD), manufacturing, and experimentation. The multi-disciplinary project has contributed to the improvement of soft skills, such as time management, team working, and professional presentation, of the team members. The total material cost of the facility was less than USD 6000, which includes the pump and its variable frequency driver. The project was made possible due to the generous sponsor of the Vibration Institute.

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“…The effects of confinement on the transition to three-dimensionality behind a square cylinder was also studied by Madhavan et al 227 for Re ≤ 250 and a blockage ratio of 0.25. Mean flow patterns, dynamic vortex shedding and pairing, critical blockage ratio and Reynolds shear stress of three bluff bodies, namely circular cylinder, square cylinder and flat plate, were analysed and compared by Wang et al 228 for blockage ratios from 0.25 to 0.5 at Reynolds numbers of 3200, 4600 and 5400. They showed that vortex shedding pattern is a strong function of blockage ratio rather than Reynolds number particularly for the flat plate.…”

Section: Confinement or Blockagementioning

confidence: 99%

A review of experiments on stationary bluff body wakes

Feshalami

Scarano

et al. 2022

Physics of Fluids

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Experimental studies dealing with the wake of isolated stationary bluff-bodies are reviewed. After briefly recalling the pioneering works in this domain, the paper focuses on recent research conducted with the latest experimental methods and techniques. The review encompasses a range of topics, including, the effects of bluff-body geometry (non-circular cross sections and nonuniformity in spanwise direction), steady and unsteady (periodic and non-periodic) inflow conditions; surface proximity (rigid wall, confinement and water free surface) and non-Newtonian fluids. Focus is brought to the flow physics of the wakes, including especially the complex threedimensional and oscillatory behaviours induced by the periodic vortex shedding phenomenon. The paper aims to offer a critical and systematic review of new knowledge and findings on the subject area, as well as emerging? and the most frequently adopted experimental techniques. The review also helps identifying knowledge gaps in the literature that need to be addressed in future investigations.

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Experimental investigation of flow past a confined bluff body: Effects of body shape, blockage ratio and Reynolds number

Cited by 22 publications

References 49 publications

Flow around a Rectangular Cylinder Placed in a Channel with a High Blockage Ratio under a Subcritical Reynolds Number

Flow around a Rectangular Cylinder Placed in a Channel with a High Blockage Ratio under a Subcritical Reynolds Number

Open Water Flume for Fluid Mechanics Lab

A review of experiments on stationary bluff body wakes

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