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Momentum transport and laminar friction in rough-wall duct flows

Momentum transport and laminar friction in rough-wall duct flows
Momentum transport and laminar friction in rough-wall duct flows
A large number of experiments and numerical simulations have proved that friction factors in laminar channel flows are roughness-dependent provided that the ratios between roughness and channel height (i.e., the relative roughness) exceed some threshold values. However, it is not yet clear what are the causes that lead to this anomalous behaviour. In order to shed light into this issue, this study presents results from two-dimensional Lattice-Boltzmann simulations of laminar flows in channels with rough walls. The Reynolds number, the geometry of the roughness elements and the relative roughness were varied extensively in order to provide a comprehensive set of data. The analysis and interpretation of the data were carried out within the framework of the Spatially Averaged Navier-Stokes equations, which are ideal to investigate momentum transfer mechanisms in flows over rough walls. The results show that for most of the investigated roughness geometries, the pressure gradient driving the flow is balanced by form-drag, viscous drag, and viscous shear stress whereas form-induced stresses remain largely negligible. Furthermore, it was observed that the higher the ratio between the drag acting upon the roughness elements and the total drag, the more friction factors deviate from classical theory. On the basis of these observations, we propose a formula, which predicts the shear stress partitioning and we discuss its relevance within the context of biomedical applications.
channel flow, data analysis, drag, external flows, flow simulation, friction, laminar flow, lattice boltzmann methods, momentum, numerical analysis, pipe flow
1070-6631
1-14
Maggiolo, Dario
3be8c448-9f31-44d9-92d8-d4e8905c974d
Manes, Costantino
7d9d5123-4d1b-4760-beff-d82fe0bd0acf
Marion, Andrea
9c1a820f-e29f-4328-a274-e08da1bd91e9
Maggiolo, Dario
3be8c448-9f31-44d9-92d8-d4e8905c974d
Manes, Costantino
7d9d5123-4d1b-4760-beff-d82fe0bd0acf
Marion, Andrea
9c1a820f-e29f-4328-a274-e08da1bd91e9

Maggiolo, Dario, Manes, Costantino and Marion, Andrea (2013) Momentum transport and laminar friction in rough-wall duct flows. Physics of Fluids, 25 (93603), 1-14. (doi:10.1063/1.4818453).

Record type: Article

Abstract

A large number of experiments and numerical simulations have proved that friction factors in laminar channel flows are roughness-dependent provided that the ratios between roughness and channel height (i.e., the relative roughness) exceed some threshold values. However, it is not yet clear what are the causes that lead to this anomalous behaviour. In order to shed light into this issue, this study presents results from two-dimensional Lattice-Boltzmann simulations of laminar flows in channels with rough walls. The Reynolds number, the geometry of the roughness elements and the relative roughness were varied extensively in order to provide a comprehensive set of data. The analysis and interpretation of the data were carried out within the framework of the Spatially Averaged Navier-Stokes equations, which are ideal to investigate momentum transfer mechanisms in flows over rough walls. The results show that for most of the investigated roughness geometries, the pressure gradient driving the flow is balanced by form-drag, viscous drag, and viscous shear stress whereas form-induced stresses remain largely negligible. Furthermore, it was observed that the higher the ratio between the drag acting upon the roughness elements and the total drag, the more friction factors deviate from classical theory. On the basis of these observations, we propose a formula, which predicts the shear stress partitioning and we discuss its relevance within the context of biomedical applications.

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More information

Published date: 12 September 2013
Keywords: channel flow, data analysis, drag, external flows, flow simulation, friction, laminar flow, lattice boltzmann methods, momentum, numerical analysis, pipe flow
Organisations: Water & Environmental Engineering Group

Identifiers

Local EPrints ID: 357084
URI: http://eprints.soton.ac.uk/id/eprint/357084
ISSN: 1070-6631
PURE UUID: 535eca17-4a86-4987-98f6-0110e0632610

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Date deposited: 04 Oct 2013 12:10
Last modified: 14 Mar 2024 14:55

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Contributors

Author: Dario Maggiolo
Author: Costantino Manes
Author: Andrea Marion

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