Riblets Induced Drag Reduction on a Spatially Developing Turbulent Boundary Layer

Bannier, Amaury; Garnier, Éric; Sagaut, Pierre

doi:10.1007/978-3-319-20388-1_19

Cited by 6 publications

(4 citation statements)

References 21 publications

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“…Therefore, these quantities alone cannot meaningfully serve as objectives in the optimisation of active control techniques. The often accepted notion of a decreased with successful control (Jovanovic et al 2005;Bannier et al 2016) is shown to be true only for wall-based control strategies with negligible or no Π c (passive control). This statement, however, follows from a model assuming that control acts at the wall, and results into the well-known upward shift of the logarithmic portion of the mean velocity profile.…”

Section: Discussionmentioning

confidence: 99%

Global energy fluxes in turbulent channels with flow control

et al. 2018

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This paper addresses the integral energy fluxes in natural and controlled turbulent channel flows, where active skin-friction drag reduction techniques allow a more efficient use of the available power. We study whether the increased efficiency shows any general trend in how energy is dissipated by the mean velocity field (mean dissipation) and by the fluctuating velocity field (turbulent dissipation). Direct numerical simulations (DNS) of different control strategies are performed at constant power input (CPI), so that at statistical equilibrium, each flow (either uncontrolled or controlled by different means) has the same power input, hence the same global energy flux and, by definition, the same total energy dissipation rate. The simulations reveal that changes in mean and turbulent energy dissipation rates can be of either sign in a successfully controlled flow. A quantitative description of these changes is made possible by a new decomposition of the total dissipation, stemming from an extended Reynolds decomposition, where the mean velocity is split into a laminar component and a deviation from it. Thanks to the analytical expressions of the laminar quantities, exact relationships are derived that link the achieved flow rate increase and all energy fluxes in the flow system with two wall-normal integrals of the Reynolds shear stress and the Reynolds number. The dependence of the energy fluxes on the Reynolds number is elucidated with a simple model in which the control-dependent changes of the Reynolds shear stress are accounted for via a modification of the mean velocity profile. The physical meaning of the energy fluxes stemming from the new decomposition unveils their inter-relations and connection to flow control, so that a clear target for flow control can be identified.

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Section: Discussionmentioning

confidence: 99%

Global energy fluxes in turbulent channels with flow control

et al. 2018

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“…Furthermore, these grid resolutions were much higher than some previous publications pursuing more re-fined flow structures ), Bannier et al (2016). Evidently, our LES computation was capable of capturing the smallscale dynamics of the turbulent flow in the present near-wall range.…”

Section: Cfd Schemesmentioning

confidence: 91%

Investigation on the Mechanism of Drag Modification over Triangular Riblets

Zhang¹,

Zhang²,

Zhao³

2020

JAFM

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This paper presents experimental and numerical investigations on the modification of local spanwise skinfriction over triangular riblets under the total drag reduction condition. Specifically, the mean and fluctuating vortical flow fields were measured using 2-components X-wires and computed using LES, respectively. Besides, the relationship between local skin-friction along the riblet spanwise and associated vortex evolution was also built using the vortex dynamic method. Based on these results, it was found that, compared with the smooth case, the impaired and enhanced vortex strength, and resultant viscous diffusion/energy dissipation, determined the reduction and augment of the viscous drag force over the local spanwise riblet groove, i.e., decreasing and increasing cases of local drag, respectively. Furthermore, the mean normal diffusion fluxes of normal and spanwise vorticities contributed more to the viscous drag under these two cases. Correspondingly, the relevant flow physics related to these phenomena was discussed in detail.

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“…These characteristics of natural organisms provide inspiration for researchers to explore drag reduction technology, which forms a unique DR discipline: biomimetic DR. Although the basic idea of DR is inspired by biology, combined with a more detailed principle of DR, biomimetic DR can be subdivided into three categories: (1) The superwetting surface drag reduction; , (2) The flexible wall for turbulent drag reduction; and (3) The biomimetic microgroove drag reduction. , Although biomimetic surface engineering has been introduced into the relevant fields of the petroleum industry, such as pipeline inner surface, , anticorrosion , and so on, its combination with the petroleum industry is still in the initial stage, and the case that it can be directly put into the commercial crude oil pipeline has not been reported. At present, researchers are mainly focusing on the mechanism and effect of biomimetic technology on oil flow DR in the laboratory.…”

Section: Drag Reduction With Biomimetic Surfacementioning

confidence: 99%

Drag Reduction Related to Boundary Layer Control in Transportation of Heavy Crude Oil by Pipeline: A Review

Jing,

Guo,

Karimov

et al. 2023

Ind. Eng. Chem. Res.

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With the depletion of conventional light crude oil, heavy crude oil will occupy an increasing share of the energy structure in the 21st century. Heavy crude oil is characterized by an API gravity of 10 to 22.3 or a viscosity of 0.09 to 10 Pa·s. The flow of heavy crude oil in the pipeline is laminar in the higher viscosity range and turbulent in the lower viscosity range, and its flow resistance comes from the viscous force between the oil and the wall or the additional stress of turbulent flow. Hence, pipeline transportation of heavy crude oil is faced with a huge loss of frictional resistance, which means a reduction of the transportation efficiency. To decrease pump power consumption, improving the transportation efficiency of heavy crude oil pipelines is a key factor. In recent years, some biomimetic technologies that reduce the flow resistance of viscous oils have made new progress in improving their fluidity and have not yet been put into use in commercial pipelines. Therefore, it is important and appropriate to discuss the breakthrough achievements and progress made by researchers in the drag reduction (DR) of heavy crude oil and to summarize its advantages, disadvantages, and potential problems. This review discusses boundary layer control methods for heavy crude oil drag reduction. First, conventional DR technologies, such as polymers, surfactants, fiber suspensions, oil–water core annular flow (CAF) and oil–aqueous foam CAF, and potential DR technologies, including oleophobic surfaces, flexible walls, biomimetic microgrooves, and ferrofluid annular DR under magnetic confinement, are presented. Second, the mechanism of DR is investigated and summarized; the highlights and progress of the technology are reviewed, and new ideas to improve the existing DR technology are proposed. Finally, the challenges and prospects of DR are presented.

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Riblets Induced Drag Reduction on a Spatially Developing Turbulent Boundary Layer

Cited by 6 publications

References 21 publications

Global energy fluxes in turbulent channels with flow control

Global energy fluxes in turbulent channels with flow control

Investigation on the Mechanism of Drag Modification over Triangular Riblets

Drag Reduction Related to Boundary Layer Control in Transportation of Heavy Crude Oil by Pipeline: A Review

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