Flow over a forward-facing step with a flexible membrane at its leading edge

Liu, Zhiwei; Wang, Hanfeng; Zhao, Chongyu

doi:10.1016/j.expthermflusci.2023.110922

Cited by 4 publications

(8 citation statements)

References 45 publications

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“…The 2000 PIV snapshots are randomly distributed among the 20 phase bins, with approximately 100 snapshots in each bin. The phase-averaged procedure for pressure signal is similar to that of the flow field, and specific details can be found in Liu et al (2023). The phase-averaged results have been verified that the number of samples and the sampling time are large enough to satisfy the requirements of convergence.…”

Section: Phase Averaged Methodsmentioning

confidence: 81%

“…Therefore, it is not possible to obtain phase variations of the velocity field from PIV images. Given the strong correlation between the unsteady pressure fluctuation and the flapping motion of the FM (Wang et al, 2022;Liu et al, 2023;Zhao et al, 2023), the pressure signal can be used as a reference to identify the phase of the flapping motion as shown in Fig. 4.…”

Section: Phase Averaged Methodsmentioning

confidence: 99%

“…Generally, the structural responses are significantly modulated by periodic vortex shedding, which is manifested by the strong coupling between the structural frequency and the wake frequency (Sarpkaya, 2004). For the FM with a low c, recent experiments by Liu et al (2023) showed that the periodic flapping frequency of the FM is highly consistent with the dominant wake frequency. They also revealed that a pair of counter-rotating flapping-induced vortices (FIVs) are generated in each flapping cycle of the FM.…”

Section: Introductionmentioning

confidence: 99%

“…The authors attributed the reduction in aerodynamic forces to the FIVs, which induce high-speed fluid from the flow over the cylinder free end downwards into the near wake. More recently, Liu et al (2023) found a periodically flapping FM at the leading edge of the forward-facing step (FFS) significantly enhances the momentum transport over the step. Vortices generated from the trailing and two side edges of the flapping FM construct a n-shape coherent vortical structure downstream.…”

Section: Introductionmentioning

confidence: 99%

“…Although Liu et al (2023) revealed the n-shape FIVs downstream of the flapping FM, the effects of incoming flow velocity on the flapping mode of the FM and the associated FIVs have not been systematically elucidated yet. The purpose of this paper is to enhance our understanding of the flapping behaviors and corresponding near wake characteristics of a wall-clamped FM at the leading edge of a FFS at various oncoming velocities, corresponding to different Reynolds numbers (Re) and c. The pressure fluctuation on the FFS was also measured simultaneously.…”

Section: Introductionmentioning

confidence: 99%

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Flapping dynamics of a flexible membrane attached to the leading edge of a forward-facing step

Liu,

Wang,

et al. 2024

Physics of Fluids

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The flapping dynamics of a flexible membrane (FM) and its effect on the flow fields over and pressure fluctuations on a forward-facing step (FFS) have been investigated experimentally. The two-dimensional FM with 40 mm in length and 0.15 mm in thickness was vertically attached to the leading edge of a FFS with 40 mm in height. The deformation of the flapping FM was recorded by a high-speed camera. Velocity data in the vertical central plane and the pressure fluctuations on the step surface were measured by planar particle image velocimetry and pressure sensors, respectively. The results demonstrate that as the dimensionless bending rigidity (γ) of the FM decreases, the FM displayed two distinct modes, i.e., the bending mode and the flapping mode. In the bending mode, the bent FM is similar to a curved barrier, which elevates the shear layer and delays the reattachment of separation flow. In the flapping mode, the amplitude of the FM increases with the decrease in γ, which in turn effects the scale of flapping-induced vortices (FIVs). In proper orthogonal decomposition analysis, the results reveal a transition in the dominant flow structure from large-scale separation to FIVs with reducing γ. The FIVs significantly affect the pressure distribution on the step surface of the FFS, and the range where the coherent contribution dominates expands with the decreasing γ.

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Section: Phase Averaged Methodsmentioning

confidence: 81%

Section: Phase Averaged Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Flapping dynamics of a flexible membrane attached to the leading edge of a forward-facing step

Liu,

Wang,

et al. 2024

Physics of Fluids

Self Cite

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Control of the nonlinear flutter of a rectangular cylinder using auxiliary flexible films

Zhang,

Yin,

Wang

2024

Nonlinear Dyn

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Effects of a detached splitter on the vortex-induced vibration of a 5:1 rectangular cylinder

Liu,

Li,

Wang

et al. 2024

Physics of Fluids

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The present paper examines the vortex-induced vibration (VIV) of a 5:1 rectangular cylinder with a detached splitter in its near wake. The tested gap ratio between the cylinder and the splitter (g/D, where g is the gap between the cylinder rear and the splitter and D is the depth of the rectangular cylinder) ranges from 0.5 to 2.0, with an increment of 0.5. To serve as a reference case, the rectangular cylinder without the splitter is also tested under the same conditions. The test Reynolds number ranges from 32 320 to 56 507. This study delves into the vibration response, pressure distributions, and power spectral densities (PSD) of the cylinder under varying gap ratios. Based on qualitative and quantitative analyses between the cylinder and the splitter using phase average techniques, smoke-wire visualization, and numerical simulation, the different vortex shedding modes according to different gap ratios were identified. Experimental and numerical results show that the detached splitter and its gap ratio play important roles in determining the cylinder VIV properties. For g/D = 0.5, the detached splitter has a sensible mitigation on the cylinder VIV. However, as the gap ratio increases, the VIV response initially recovers to the reference case at g/D = 1.0 and subsequently enlarges at g/D = 1.5 and 2.0. The pressure distribution results showed that the detached splitter demonstrates its effects primarily through fluctuations in the pressure field rather than the mean field. In addition, at g/D = 0.5, a sensibly decayed PSD is observed, while at g/D = 1.0–2.0, an intensified PSD is detected. The underlying mechanism of the detached splitter on the VIV of the 5:1 rectangular cylinder should be attributed to the von Kármán vortex street compared to the reference case.

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Flow over a forward-facing step with a flexible membrane at its leading edge

Cited by 4 publications

References 45 publications

Flapping dynamics of a flexible membrane attached to the leading edge of a forward-facing step

Flapping dynamics of a flexible membrane attached to the leading edge of a forward-facing step

Control of the nonlinear flutter of a rectangular cylinder using auxiliary flexible films

Effects of a detached splitter on the vortex-induced vibration of a 5:1 rectangular cylinder

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