Particle image velocimetry measurements of the separated flow behind a rearward facing step

Grant, Ian; Owens, Edward H.; Yan, Y.-Y.; Xiong, Shuidong

doi:10.1007/bf00187301

Cited by 15 publications

(6 citation statements)

References 16 publications

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“…(5) shows a promising similarity profile corresponding to the shear layer structure between the sliding jet and the recirculation zone for different Y c / H ratios and different crosssections from the vertical drop. Figure 9 presents the comparison of similarity profiles for the mean streamwise velocity U s obtained in the present study [16]) and cavity shear flow (Kuo and Jeng, [19]) are also included in Fig. 9., showing the overall trend of data points measured in different separated shear layers is in good agreement with these three similarity curves.…”

Section: Mean Velocity Profiles In Shear Layer Between Sliding Jet Anmentioning

confidence: 95%

“…A bunch of papers can be found in the literature, e.g., Etheridge and Kemp [13], Armaly et al [14], Troutt et al [15], Grant et al [16], Pereira and Sousa [17], Kuo et al [18] and Kuo and Jeng [19]. All of these works mainly focused on the velocity distributions or the coherent-structure dynamics in the separated shear flow, the mixing behavior in the recirculation bubble, the variation of reattachment length, the redeveloping turbulent boundary layer beyond separationreattachment point, and so on.…”

Section: Introductionmentioning

confidence: 98%

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Flow Field in a Skimming Flow Over a Vertical Drop Without End-Sill

Lin

Hsieh

Lin³

et al. 2012

J. mech.

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The flow structure in the shear layer and in the recirculation zone of a skimming flow downstream of a vertical drop without end-sill measured using high speed particle image velocimetry (HSPIV) and flow visualization method is presented. The interface between the sliding jet and the recirculation zone (zone below sliding jet) was enhanced through non-ventilation condition between the drop structure and the jet. The flow field measured through HSPIV was used to represent the characteristics of mean streamwise velocity in the shear layer and mean horizontal velocity in the recirculation zone. With the growth of shear layer as the jet slides down over the recirculation zone, the momentum exchange from the sliding jet into the recirculation zone via the shear layer increases along with energy loss. Hence, it was observed that the amount of energy dissipated in the skimming flow at the drop structure without ventilation is greater than that with ventilation by an average value of 50% for Y c / H ≥ 0.2 (where Y c = critical depth and H = drop height). However, the flow structure in the recirculation zone is found to be analogous to that of turbulent plane wall jet. The nonlinear regression analysis is used to fit the regressed velocity profiles to the measured HSPIV mean velocity distributions. Further, the appropriate characteristic velocity and length scales are selected to attain the unique similarity profiles both in the shear layer and in the recirculation zone of the skimming flow. The selection of the characteristic scales is also discussed. The similarity profiles are well comparable with those of napped flow without end-sill and with ventilation as well as of skimming flow with end-sill and without ventilation. It is interesting to observe that, the proposed similarity profiles for the shear layer also map the data of backward-facing step flow and cavity shear flow. In addition, the turbulence characteristics in the shear layer, including turbulence intensities, turbulent kinetic energy, viscous and Reynolds shear stresses, and turbulence energy-budget balance, are illustrated in detail. From the variation of turbulence production it is observed that near the drop structure the energy exchange is from the chaotic recirculation zone to the sliding-jet flow, while in the later part it is reversed. Furthermore, the analysis of turbulence energy-budget balance indicates very significant role of turbulence production, pressure diffusion and turbulence diffusion as compared with turbulence advection that has very minor role in turbulence energy-budget balance for the central part of the shear layer.

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Section: Mean Velocity Profiles In Shear Layer Between Sliding Jet Anmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 98%

Flow Field in a Skimming Flow Over a Vertical Drop Without End-Sill

Lin

Hsieh

Lin³

et al. 2012

J. mech.

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“…[2,5,6,9,10,11,12,13,14,15]). Armaly et al [2] performed Laser-Doppler measurements of velocity distribution and reattachment length downstream of a BFS mounted in a 18:1 aspect ratio (step span/step height) channel for a wide range of Reynolds number, 70 < Re < 8000.…”

Section: Introductionmentioning

confidence: 99%

Particle image velocimetry investigation of steady flow over a backwardfacing step

Dol

2016

EPJ Web of Conferences

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Abstract. The backward-facing step (BFS) is a heuristic example, allowing for complex phenomena to arise in a simple geometry. Particle Image Velocimetry (PIV) investigations of mean-velocity distributions of backward-facing step flow with steady inlet condition were carried out and good agreement was obtained between current and previously published results for 50 Re 400. This confirms that the current experimental capabilities can provide detailed and accurate velocity information. The flow behaviour downstream the step depends on the strength of separated shear layer, which the circulation depends on the bulk flow, recirculation zone length and vortex formation time. Since the vortex formation process is governed by the circulation flux convected along the wall layer from the step, for Re 400, all of the circulation contained in the shear layer is drawn into the recirculation region. Thus, in a case where the shear layer characteristics are modified (e.g. in higher Reynolds number and unsteady flows), the balance of circulation is modified that would result in shedding.

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“…However, in order to obtain a better understanding of the complex reattachment process, the separated #ow behind a 2-D backward-facing step has frequently been chosen as an environment for validating new experimental measuring techniques [e.g. Goldstein et al (1970), Eaton et al (1979), Armaly et al (1983), Driver et al (1987), Grant et al (1992)] and/or numerical #uid dynamics simulation codes [e.g., Gartling (1990), Mateescu et al (1994)]. Recently, the locations of the reattachment and laminar separation points induced by a 2-D step under steady #ow conditions were measured nonintrusively by Lee & Mateescu (1998) using multiple hot-"lm sensor arrays, and compared to their numerical predictions for Re ( "u H/ , where u is the inlet average velocity based on inlet volumetric #ow rate and the cross-sectional area, H is the step height, and is the #uid kinematic viscosity) (1300 and an expansion ratio ER ("H B /H S , where H S and H B are the channel heights upstream and downstream of the step, respectively) of 2.…”

Section: Introductionmentioning

confidence: 99%