Control of laminar flow separation over a backward-facing rounded ramp with C-D riblets – The effects of riblet height, spacing and yaw angle

Guo, Tongbiao; Zhong, Shan; Craft, Tim

doi:10.1016/j.ijheatfluidflow.2020.108629

Cited by 20 publications

(13 citation statements)

References 35 publications

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“…Illustrations of: (a) applied coating, 29 (b) bio-inspired riblets, 34 and (c) regularly-shaped riblets. 39 …”

Section: Classification and Description Of Flow Control Methodsmentioning

confidence: 99%

“…Raayai-Ardakani and McKinley 38 numerically investigated how geometrical parameters of denticles as well as Re affect drag reduction. Guo et al 39,40 describe systematic computations undertaken to examine the effects of riblet geometry (height, wavelength, and yaw angle illustrated in Figure 1(c)) on the strength of the generated secondary flow as well as the extent of the flow separation zone. The authors report the suppression of the LSB, but not the net reduction in the total pressure losses, although they point out that further research is possible.…”

Section: Classification and Description Of Flow Control Methodsmentioning

confidence: 99%

“…The dimples on golf balls are a well-known and wellproven mechanism to accelerate transition to 34 and (c) regularly-shaped riblets. 39 turbulence. An experimental study described by Choi et al 44 provides a good clarification of this flow phenomenon.…”

Section: Passive Flow Controlmentioning

confidence: 99%

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Current state and future trends in boundary layer control on lifting surfaces

Svorcan

Wang

Griffin

2022

Advances in Mechanical Engineering

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Successful flow control may bring numerous benefits, such as flow stabilization, flow reattachment, separation delay, drag reduction, lift increase, aerodynamic performance improvement, energy efficiency increase, shock delay or weakening, noise reduction, etc. For these purposes, many different flow control devices, which can be classified as passive, semi-active and active, have been designed and tested. This review paper aims to highlight the most promising and commonly employed boundary layer control methods as well as outline their potential in specific applications in aerospace and energy engineering. Referenced studies, performed on various geometries (flat plates, channels, airfoils, wings, blades, cylinders), are primarily numerical or experimental. Although enhanced aerodynamic performance is achieved in many cases, further research is required to draw general conclusions. This paper aims to demonstrate that, in the future, we may expect further developments of flow control actuators, as well as their increased application.

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“…Illustrations of: (a) applied coating, 29 (b) bio-inspired riblets, 34 and (c) regularly-shaped riblets. 39 …”

Section: Classification and Description Of Flow Control Methodsmentioning

confidence: 99%

Section: Classification and Description Of Flow Control Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Current state and future trends in boundary layer control on lifting surfaces

Svorcan

Wang

Griffin

2022

Advances in Mechanical Engineering

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“…They reported that using C-D riblets led to an increase of drag and attributed this to the enhanced momentum exchange caused by the large scale secondary flow motions. Guo et al 12 undertook detailed numerical simulations of a fully developed lami-nar channel flow, in which a section of C-D riblets was applied upstream of a backward-facing rounded ramp at a Reynolds number of Re b = 400 based on the inlet channel height and the bulk velocity. They found that a stronger roll mode not only led to a greater control effect but also was accompanied by a greater pressure loss or drag.…”

Section: Introductionmentioning

confidence: 99%

Energy-based drag decomposition analyses for a turbulent channel flow developing over convergent–divergent riblets

et al. 2022

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Direct numerical simulations of a turbulent channel flow developing over convergent–divergent (C–D) riblets are performed at a Reynolds number of Reb = 2800, based on the half channel height δ and the bulk velocity. To gain an in-depth understanding of the origin of the drag generated by C–D riblets, a drag decomposition method is derived from kinetic energy principle for a turbulent channel flow with wall roughness. C–D riblets with a wavelength, Λ, ranging from 0.25δ to 1.5δ, are examined to understand the influence of secondary flow motions on the drag. It is found that as Λ increases, the intensity of the secondary flow motion increases first and then decreases, peaking at Λ/δ=1. At Λ/δ≥1, some heterogeneity appears in the spanwise direction for the turbulent kinetic energy (TKE) and vortical structures, with the strongest enhancement occurring around regions of upwelling. All the riblet cases examined here exhibit an increased drag compared to the smooth wall case. From the energy dissipation/production point of view, such a drag increase is dominated by the TKE production and the viscous dissipation wake component. While the drag contribution from the TKE production shear component decreases as Λ increases, the drag contribution from the wake component of both the TKE production and viscous dissipation follows the same trend as the intensity of the secondary flow motion. From the work point of view, the drag increase in the riblet case at Λ/δ=0.25 comes mainly from the work of the Reynolds shear stresses, whereas at Λ/δ≥1, the drag augmentation is dominated by the work of the dispersive stresses. At Λ/δ=0.5, both components play an important role in the increase in the drag, which also exhibits a peak.

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“…In contrast, the drag with regard to spanwise heterogeneous roughness pattern (e.g. C-D riblets) is much less studied, which has a potential in separation control [9,8,19], heat transfer enhancement and mixing [20], owing to the induced large-scale secondary flow. As a result, they can be used in microelectro-mechanical systems [21], cooling systems [22] and biomedical problems [20].…”

Section: Introductionmentioning

confidence: 99%