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Journal articles on the topic 'Flow over rough surfaces'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Balachandar, R., K. Hagel, and D. Blakely. "Velocity distribution in decelerating flow over rough surfaces." Canadian Journal of Civil Engineering 29, no. 2 (2002): 211–21. http://dx.doi.org/10.1139/l01-089.

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An experimental program was undertaken to study turbulent boundary layers formed in decelerating open channel flows. The flows over a smooth surface and three rough surfaces were examined. Tests were conducted at a subcritical Froude number (~0.2) and varying depth Reynolds numbers (64 000 < Red < 88 000). The corresponding momentum thickness Reynolds numbers were small (1000 < Reθ < 2100). The velocity measurements were undertaken using a one-component laser-Doppler anemometer. Variables such as the shear velocity, the longitudinal mean velocity, Coles' wake parameter, and Clauser

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2

Giménez-Curto, Luis A., and Miguel A. Corniero Lera. "Oscillating turbulent flow over very rough surfaces." Journal of Geophysical Research: Oceans 101, no. C9 (1996): 20745–58. http://dx.doi.org/10.1029/96jc01824.

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3

Myers, T. G. "Modeling laminar sheet flow over rough surfaces." Water Resources Research 38, no. 11 (2002): 12–1. http://dx.doi.org/10.1029/2000wr000154.

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4

Han, Yu, Shi-yu Wang, Jian Chen, Shuqing Yang, Liu-chao Qiu, and Nadeesha Dharmasiri. "Resistance of the flow over rough surfaces." Journal of Hydrodynamics 33, no. 3 (2021): 593–601. http://dx.doi.org/10.1007/s42241-021-0039-3.

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5

Zampogna, Giuseppe A., Jacques Magnaudet, and Alessandro Bottaro. "Generalized slip condition over rough surfaces." Journal of Fluid Mechanics 858 (November 6, 2018): 407–36. http://dx.doi.org/10.1017/jfm.2018.780.

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A macroscopic boundary condition to be used when a fluid flows over a rough surface is derived. It provides the slip velocity $\boldsymbol{u}_{S}$ on an equivalent (smooth) surface in the form $\boldsymbol{u}_{S}=\unicode[STIX]{x1D716}{\mathcal{L}}\boldsymbol{ : }{\mathcal{E}}$, where the dimensionless parameter $\unicode[STIX]{x1D716}$ is a measure of the roughness amplitude, ${\mathcal{E}}$ denotes the strain-rate tensor associated with the outer flow in the vicinity of the surface and ${\mathcal{L}}$ is a third-order slip tensor arising from the microscopic geometry characterizing the rough

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6

Miksis, Michael J., and Stephen H. Davis. "Slip over rough and coated surfaces." Journal of Fluid Mechanics 273 (August 25, 1994): 125–39. http://dx.doi.org/10.1017/s0022112094001874.

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We study the effect of surface roughness and coatings on fluid flow over a solid surface. In the limit of small-amplitude roughness and thin lubricating films we are able to derive asymptotically an effective slip boundary condition to replace the no-slip condition over the surface. When the film is absent, the result is a Navier slip condition in which the slip coefficient equals the average amplitude of the roughness. When a layer of a second fluid covers the surface and acts as a lubricating film, the slip coefficient contains a term which is proportional to the viscosity ratio of the two f

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7

Busse, A., M. Thakkar, and N. D. Sandham. "Reynolds-number dependence of the near-wall flow over irregular rough surfaces." Journal of Fluid Mechanics 810 (November 24, 2016): 196–224. http://dx.doi.org/10.1017/jfm.2016.680.

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The Reynolds-number dependence of turbulent channel flow over two irregular rough surfaces, based on scans of a graphite and a grit-blasted surface, is studied by direct numerical simulation. The aim is to characterise the changes in the flow in the immediate vicinity of and within the rough surfaces, an area of the flow where it is difficult to obtain experimental measurements. The average roughness heights and spatial correlation of the roughness features of the two surfaces are similar, but the two surfaces have a significant difference in the skewness of their height distributions, with th

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8

Nourmohammadi, Khosrow, P. K. Hopke, and J. J. Stukel. "Turbulent Air Flow Over Rough Surfaces: II. Turbulent Flow Parameters." Journal of Fluids Engineering 107, no. 1 (1985): 55–60. http://dx.doi.org/10.1115/1.3242440.

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The objective of the present study was to examine experimentally the turbulent flow structure in a repeated rib geometry rough wall surface as a function of the ratio of the roughness height to the pipe diameter (K/D), the ratio of the spacing between the elements to the roughness height (P/K), the axial position within a rib cycle, and the Reynolds number. For small P/K values, the turbulent intensities and Reynolds shear stress variations were similar to those found for smooth wall pipe flow. Unique relationships for the u′ and v′ were found that were valid in the outer layer of the flow for

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9

Patel, V. C., and J. Y. Yoon. "Application of Turbulence Models to Separated Flow Over Rough Surfaces." Journal of Fluids Engineering 117, no. 2 (1995): 234–41. http://dx.doi.org/10.1115/1.2817135.

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Principal results of classical experiments on the effects of sandgrain roughness are briefly reviewed, along with various models that have been proposed to account for these effects in numerical solutions of the fluid-flow equations. Two models that resolve the near-wall flow are applied to the flow in a two-dimensional, rough-wall channel. Comparisons with analytical results embodied in the well-known Moody diagram show that the k–ω model of Wilcox performs remarkably well over a wide range of roughness values, while a modified two-layer k–ε based model requires further refinement. The k–ω mo

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10

Balachandar, R., D. Blakely, and J. Bugg. "Friction velocity and power law velocity profile in smooth and rough shallow open channel flows." Canadian Journal of Civil Engineering 29, no. 2 (2002): 256–66. http://dx.doi.org/10.1139/l01-093.

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This paper examines the mean velocity profiles in shallow, turbulent open channel flows. Velocity measurements were carried out in flows over smooth and rough beds using a laser-Doppler anemometer. One set of profiles, composed of 29 velocity distributions, was obtained in flows over a polished smooth aluminum plate. Three sets of profiles were obtained in flows over rough surfaces. The rough surfaces were formed by two sizes of sand grains and a wire mesh. The flow conditions over the rough surface are in the transitional roughness state. The measurements were obtained along the centerline of

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11

MacDonald, M., L. Chan, D. Chung, N. Hutchins, and A. Ooi. "Turbulent flow over transitionally rough surfaces with varying roughness densities." Journal of Fluid Mechanics 804 (September 8, 2016): 130–61. http://dx.doi.org/10.1017/jfm.2016.459.

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We investigate rough-wall turbulent flows through direct numerical simulations of flow over three-dimensional transitionally rough sinusoidal surfaces. The roughness Reynolds number is fixed at $k^{+}=10$, where $k$ is the sinusoidal semi-amplitude, and the sinusoidal wavelength is varied, resulting in the roughness solidity $\unicode[STIX]{x1D6EC}$ (frontal area divided by plan area) ranging from 0.05 to 0.54. The high cost of resolving both the flow around the dense roughness elements and the bulk flow is circumvented by the use of the minimal-span channel technique, recently demonstrated by

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12

Squire, D. T., C. Morrill-Winter, N. Hutchins, M. P. Schultz, J. C. Klewicki, and I. Marusic. "Comparison of turbulent boundary layers over smooth and rough surfaces up to high Reynolds numbers." Journal of Fluid Mechanics 795 (April 14, 2016): 210–40. http://dx.doi.org/10.1017/jfm.2016.196.

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Turbulent boundary layer measurements above a smooth wall and sandpaper roughness are presented across a wide range of friction Reynolds numbers, ${\it\delta}_{99}^{+}$, and equivalent sand grain roughness Reynolds numbers, $k_{s}^{+}$ (smooth wall: $2020\leqslant {\it\delta}_{99}^{+}\leqslant 21\,430$, rough wall: $2890\leqslant {\it\delta}_{99}^{+}\leqslant 29\,900$; $22\leqslant k_{s}^{+}\leqslant 155$; and $28\leqslant {\it\delta}_{99}^{+}/k_{s}^{+}\leqslant 199$). For the rough-wall measurements, the mean wall shear stress is determined using a floating element drag balance. All smooth- a

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13

K. Mitani, Noriko, Hans-Georg Matuttis, and Toshihiko Kadono. "Density and size segregation in chute flow over rough surfaces." Journal of the Geological Society of Japan 117, no. 3 (2011): 116–21. http://dx.doi.org/10.5575/geosoc.117.116.

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14

Yuan, J., and U. Piomelli. "Numerical simulations of sink-flow boundary layers over rough surfaces." Physics of Fluids 26, no. 1 (2014): 015113. http://dx.doi.org/10.1063/1.4862672.

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15

Taylor, R. P., H. W. Coleman, and B. K. Hodge. "Prediction of Heat Transfer in Turbulent Flow Over Rough Surfaces." Journal of Heat Transfer 111, no. 2 (1989): 568–72. http://dx.doi.org/10.1115/1.3250716.

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16

McIlroy, Hugh M., and Ralph S. Budwig. "The Boundary Layer Over Turbine Blade Models With Realistic Rough Surfaces." Journal of Turbomachinery 129, no. 2 (2005): 318–30. http://dx.doi.org/10.1115/1.2218572.

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Results are presented of extensive boundary layer measurements taken over a flat, smooth plate model of the front one-third of a turbine blade and over the model with an embedded strip of realistic rough surface. The turbine blade model also included elevated freestream turbulence and an accelerating freestream in order to simulate conditions on the suction side of a high-pressure turbine blade. The realistic rough surface was developed by scaling actual turbine blade surface data provided by U.S. Air Force Research Laboratory. The rough patch can be considered to be an idealized area of distr

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17

Hosni, M. H., H. W. Coleman, and R. P. Taylor. "Measurement and Calculation of Fluid Dynamic Characteristics of Rough-Wall Turbulent Boundary-Layer Flows." Journal of Fluids Engineering 115, no. 3 (1993): 383–88. http://dx.doi.org/10.1115/1.2910150.

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Experimental measurements of profiles of mean velocity and distributions of boundary-layer thickness and skin friction coefficient from aerodynamically smooth, transitionally rough, and fully rough turbulent boundary-layer flows are presented for four surfaces—three rough and one smooth. The rough surfaces are composed of 1.27 mm diameter hemispheres spaced in staggered arrays 2, 4, and 10 base diameters apart, respectively, on otherwise smooth walls. The current incompressible turbulent boundary-layer rough-wall air flow data are compared with previously published results on another, similar

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18

Gong, W., Peter A. Taylor, and Andreas Dörnbrack. "Turbulent boundary-layer flow over fixed aerodynamically rough two-dimensional sinusoidal waves." Journal of Fluid Mechanics 312 (April 10, 1996): 1–37. http://dx.doi.org/10.1017/s0022112096001905.

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Results from a wind tunnel study of aerodynamically rough turbulent boundary-layer flow over a sinusoidal surface are presented. The waves had a maximum slope (ak) of 0.5 and two surface roughnesses were used. For the relatively rough surface the flow separated in the wave troughs while for the relatively smooth surface it generally remained attached. Over the relatively smooth-surfaced waves an organized secondary flow developed, consisting of vortex pairs of a scale comparable to the boundary-layer depth and aligned with the mean flow. Large-eddy simulation studies model the flows well and p

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19

Li, Qi, and Elie Bou-Zeid. "Contrasts between momentum and scalar transport over very rough surfaces." Journal of Fluid Mechanics 880 (October 7, 2019): 32–58. http://dx.doi.org/10.1017/jfm.2019.687.

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Large-eddy simulations are conducted to contrast momentum and passive scalar transport over large, three-dimensional roughness elements in a turbulent channel flow. Special attention is given to the dispersive fluxes, which are shown to be a significant fraction of the total flux within the roughness sublayer. Based on pointwise quadrant analysis, the turbulent components of the transport of momentum and scalars are found to be similar in general, albeit with increasing dissimilarity for roughnesses with low frontal blockage. However, strong dissimilarity is noted between the dispersive moment

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20

McClain, Stephen T., B. Keith Hodge, and Jeffrey P. Bons. "Predicting Skin Friction and Heat Transfer for Turbulent Flow Over Real Gas Turbine Surface Roughness Using the Discrete Element Method." Journal of Turbomachinery 126, no. 2 (2004): 259–67. http://dx.doi.org/10.1115/1.1740779.

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The discrete element method considers the total aerodynamic drag on a rough surface to be the sum of shear drag on the flat part of the surface and the form drag on the individual roughness elements. The total heat transfer from a rough surface is the sum of convection through the fluid on the flat part of the surface and the convection from each of the roughness elements. The discrete element method has been widely used and validated for predicting heat transfer and skin friction for rough surfaces composed of sparse, ordered, and deterministic elements. Real gas turbine surface roughness is

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21

Chung, Daniel, Nicholas Hutchins, Michael P. Schultz, and Karen A. Flack. "Predicting the Drag of Rough Surfaces." Annual Review of Fluid Mechanics 53, no. 1 (2021): 439–71. http://dx.doi.org/10.1146/annurev-fluid-062520-115127.

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Reliable full-scale prediction of drag due to rough wall-bounded turbulent fluid flow remains a challenge. Currently, the uncertainty is at least 10%, with consequences, for example, on energy and transport applications exceeding billions of dollars per year. The crux of the difficulty is the large number of relevant roughness topographies and the high cost of testing each topography, but computational and experimental advances in the last decade or so have been lowering these barriers. In light of these advances, here we review the underpinnings and limits of relationships between roughness t

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22

Busse, Angela, and Thomas O. Jelly. "Influence of Surface Anisotropy on Turbulent Flow Over Irregular Roughness." Flow, Turbulence and Combustion 104, no. 2-3 (2019): 331–54. http://dx.doi.org/10.1007/s10494-019-00074-4.

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AbstractThe influence of surface anisotropy upon the near-wall region of a rough-wall turbulent channel flow is investigated using direct numerical simulation (DNS). A set of nine irregular rough surfaces with fixed mean peak-to-valley height, near-Gaussian height distributions and specified streamwise and spanwise correlation lengths were synthesised using a surface generation algorithm. By defining the surface anisotropy ratio (SAR) as the ratio of the streamwise and spanwise correlation lengths of the surface, we demonstrate that surfaces with a strong spanwise anisotropy (SAR < 1) can i

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23

Peters, Wayne D., Steven R. Cogswell, and James E. S. Venart. "Dense gas simulation flows over rough surfaces." Journal of Hazardous Materials 46, no. 2-3 (1996): 215–23. http://dx.doi.org/10.1016/0304-3894(95)00073-9.

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24

Ahmed, Saad. "Control of Unstable Flow Using Rough Surfaces." Applied Mechanics and Materials 431 (October 2013): 155–60. http://dx.doi.org/10.4028/www.scientific.net/amm.431.155.

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The function of centrifugal blowers/compressors is limited at low-mass flow rates by fluid flow instabilities leading to rotating stall. These instabilities limit the flow range in which they can operate. An experimental investigation was conducted to investigate a model of radial vaneless diffuser at stall as well as stall-free operating conditions. The speed of the blower was kept constant at 2000 RPM, while the mass flow rate was reduced gradually to investigate the steady and unsteady flow characteristics of the diffuser. These measurements were reported for diffuser diameter ratios, Do /

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25

Turner, A. B., S. E. Hubbe-Walker, and F. J. Bayley. "Fluid flow and heat transfer over straight and curved rough surfaces." International Journal of Heat and Mass Transfer 43, no. 2 (2000): 251–62. http://dx.doi.org/10.1016/s0017-9310(99)00128-3.

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26

Khaled, CHAIB, NEHARI Driss, and SAD CHEMLOUL Nouredine. "CFD Simulation of Turbulent Flow and Heat Transfer Over Rough Surfaces." Energy Procedia 74 (August 2015): 909–18. http://dx.doi.org/10.1016/j.egypro.2015.07.826.

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27

Zhang, Wen, Minping Wan, Zhenhua Xia, Jianchun Wang, Xiyun Lu, and Shiyi Chen. "Constrained large-eddy simulation of turbulent flow over inhomogeneous rough surfaces." Theoretical and Applied Mechanics Letters 11, no. 1 (2021): 100229. http://dx.doi.org/10.1016/j.taml.2021.100229.

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28

Kadivar, Mohammadreza, David Tormey, and Gerard McGranaghan. "A review on turbulent flow over rough surfaces: Fundamentals and theories." International Journal of Thermofluids 10 (May 2021): 100077. http://dx.doi.org/10.1016/j.ijft.2021.100077.

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29

ANDERSON, W., and C. MENEVEAU. "Dynamic roughness model for large-eddy simulation of turbulent flow over multiscale, fractal-like rough surfaces." Journal of Fluid Mechanics 679 (May 3, 2011): 288–314. http://dx.doi.org/10.1017/jfm.2011.137.

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Many flows especially in geophysics involve turbulent boundary layers forming over rough surfaces with multiscale height distribution. Such surfaces pose special challenges for large-eddy simulation (LES) when the filter scale is such that only part of the roughness elements of the surface can be resolved. Here we consider LES of flows over rough surfaces with power-law height spectra Eh(k) ~ kβs (−3 ≤ βs < −1), as often encountered in natural terrains. The surface is decomposed into resolved and subgrid-scale height contributions. The effects of the unresolved small-scale height fluctuatio

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30

Ghanem, Roger, and Bernard Hayek. "Probabilistic Modeling of Flow Over Rough Terrain." Journal of Fluids Engineering 124, no. 1 (2001): 42–50. http://dx.doi.org/10.1115/1.1445138.

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This paper presents a method for the propagation of uncertainty, modeled in a probabilistic framework, through a model-based simulation of rainflow on a rough terrain. The adopted model involves a system of conservation equations with associated nonlinear state equations. The topography, surface runoff coefficient, and precipitation data are all modeled as spatially varying random processes. The Karhunen-Loeve expansion is used to represent these processes in terms of a denumerable set of random variables. The predicted state variables in the model are identified with their coordinates with re

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31

Bergstrom, D. J., O. G. Akinlade, and M. F. Tachie. "Skin Friction Correlation for Smooth and Rough Wall Turbulent Boundary Layers." Journal of Fluids Engineering 127, no. 6 (2005): 1146–53. http://dx.doi.org/10.1115/1.2073288.

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In this paper, we propose a novel skin friction correlation for a zero pressure gradient turbulent boundary layer over surfaces with different roughness characteristics. The experimental data sets were obtained on a hydraulically smooth and ten different rough surfaces created from sand paper, perforated sheet, and woven wire mesh. The physical size and geometry of the roughness elements and freestream velocity were chosen to encompass both transitionally rough and fully rough flow regimes. The flow Reynolds number based on momentum thickness ranged from 3730 to 13,550. We propose a correlatio

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32

BIRCH, DAVID M., and JONATHAN F. MORRISON. "Similarity of the streamwise velocity component in very-rough-wall channel flow." Journal of Fluid Mechanics 668 (December 3, 2010): 174–201. http://dx.doi.org/10.1017/s0022112010004647.

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The streamwise velocity component is studied in fully developed turbulent channel flow for two very rough surfaces and a smooth surface at comparable Reynolds numbers. One rough surface comprises sparse and isotropic grit with a highly non-Gaussian distribution. The other is a uniform mesh consisting of twisted rectangular elements which form a diamond pattern. The mean roughness heights (±) the standard deviation) are, respectively, about 76(±42) and 145(±150) wall units. The flow is shown to be two-dimensional and fully developed up to the fourth-order moment of velocity. The mean velocity p

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33

Zhang, Hanzhong, Mohammad Faghri та Frank M. White. "A New Low-Reynolds-Number k-ε Model for Turbulent Flow Over Smooth and Rough Surfaces". Journal of Fluids Engineering 118, № 2 (1996): 255–59. http://dx.doi.org/10.1115/1.2817371.

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A new low-Reynolds-number k-ε model is proposed to simulate turbulent flow over smooth and rough surfaces by including the equivalent sand-grain roughness height into the model functions. The simulation of various flow experiments shows that the model can predict the log-law velocity profile and other properties such as friction factors, turbulent kinetic energy and dissipation rate for both smooth and rough surfaces.

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34

Koh, Yang-Moon. "Turbulent Flow Near a Rough Wall." Journal of Fluids Engineering 114, no. 4 (1992): 537–42. http://dx.doi.org/10.1115/1.2910065.

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By introducing the equivalent roughness which is defined as the distance from the wall to where the velocity gets a certain value (u/uτ ≈ 8.5) and which can be represented by a simple function of the roughness, a simple formula to represent the mean-velocity distribution across the inner layer of a turbulent boundary layer is suggested. The suggested equation is general enough to be applicable to turbulent boundary layers over surfaces of any roughnesses covering from very smooth to completely rough surfaces. The suggested velocity profile is then used to get expressions for pipe-friction fact

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35

Patel, V. C. "Perspective: Flow at High Reynolds Number and Over Rough Surfaces—Achilles Heel of CFD." Journal of Fluids Engineering 120, no. 3 (1998): 434–44. http://dx.doi.org/10.1115/1.2820682.

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The law of the wall and related correlations underpin much of current computational fluid dynamics (CFD) software, either directly through use of so-called wall functions or indirectly in near-wall turbulence models. The correlations for near-wall flow become crucial in solution of two problems of great practical importance, namely, in prediction of flow at high Reynolds numbers and in modeling the effects of surface roughness. Although the two problems may appear vastly different from a physical point of view, they share common numerical features. Some results from the ’superpipe’ experiment

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36

Taylor, R. P., H. W. Coleman, and B. K. Hodge. "Prediction of Turbulent Rough-Wall Skin Friction Using a Discrete Element Approach." Journal of Fluids Engineering 107, no. 2 (1985): 251–57. http://dx.doi.org/10.1115/1.3242469.

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A discrete element model for turbulent flow over rough surfaces has been derived from basic principles. This formulation includes surface roughness form drag and blockage effects as a constituent part of the partial differential equations and does not rely on a single-length-scale concept such as equivalent sandgrain roughness. The roughness model includes the necessary empirical information on the interaction between three-dimensional roughness elements and the flow in a general way which does not require experimental data on each specific surface. This empirical input was determined using da

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37

Busse, A., and N. D. Sandham. "Parametric forcing approach to rough-wall turbulent channel flow." Journal of Fluid Mechanics 712 (September 27, 2012): 169–202. http://dx.doi.org/10.1017/jfm.2012.408.

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AbstractThe effects of rough surfaces on turbulent channel flow are modelled by an extra force term in the Navier–Stokes equations. This force term contains two parameters, related to the density and the height of the roughness elements, and a shape function, which regulates the influence of the force term with respect to the distance from the channel wall. This permits a more flexible specification of a rough surface than a single parameter such as the equivalent sand grain roughness. The effects of the roughness force term on turbulent channel flow have been investigated for a large number o

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38

Alamé, Karim, and Krishnan Mahesh. "Wall-bounded flow over a realistically rough superhydrophobic surface." Journal of Fluid Mechanics 873 (June 28, 2019): 977–1019. http://dx.doi.org/10.1017/jfm.2019.419.

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Direct numerical simulation (DNS) is performed for two wall-bounded flow configurations: laminar Couette flow at $Re=740$ and turbulent channel flow at $Re_{\unicode[STIX]{x1D70F}}=180$, where $\unicode[STIX]{x1D70F}$ is the shear stress at the wall. The top wall is smooth and the bottom wall is a realistically rough superhydrophobic surface (SHS), generated from a three-dimensional surface profile measurement. The air–water interface, which is assumed to be flat, is simulated using the volume-of-fluid (VOF) approach. The two flow cases are studied with varying interface heights $h$ to underst

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Bose, Sujit K., and Subhasish Dey. "Theory of free surface flow over rough seeping beds." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 463, no. 2078 (2006): 369–83. http://dx.doi.org/10.1098/rspa.2006.1768.

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A new theory is developed for the steady free surface flow over a horizontal rough bed with uniform upward seepage normal to the bed. The theory is based on the Reynolds averaged Navier–Stokes (RANS) equations applied to the flow domain that is divided into a fully turbulent outer layer and an inner layer (viscous sublayer plus buffer layer), which is a transition zone from viscous to turbulent regime. In the outer layer, the Reynolds stress far exceeds viscous shear stress, varying gradually with vertical distance. Near the free surface, the velocity gradient in vertical direction becomes les

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40

Alferov, O. A., and A. G. Petrov. "Two-layer turbulent flow over a rough rotating surface." Fluid Dynamics 30, no. 4 (1995): 537–43. http://dx.doi.org/10.1007/bf02030328.

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41

CASTRO, IAN P. "Rough-wall boundary layers: mean flow universality." Journal of Fluid Mechanics 585 (August 7, 2007): 469–85. http://dx.doi.org/10.1017/s0022112007006921.

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Mean flow profiles, skin friction, and integral parameters for boundary layers developing naturally over a wide variety of fully aerodynamically rough surfaces are presented and discussed. The momentum thickness Reynolds number Reθ extends to values in excess of 47000 and, unlike previous work, a very wide range of the ratio of roughness element height to boundary-layer depth is covered (0.03 < h/δ > 0.5). Comparisons are made with some classical formulations based on the assumption of a universal two-parameter form for the mean velocity profile, and also with other recent measurements.

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42

LANGELANDSVIK, L. I., G. J. KUNKEL, and A. J. SMITS. "Flow in a commercial steel pipe." Journal of Fluid Mechanics 595 (January 8, 2008): 323–39. http://dx.doi.org/10.1017/s0022112007009305.

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Mean flow measurements are obtained in a commercial steel pipe with krms/D = 1/26 000, where krms is the roughness height and D the pipe diameter, covering the smooth, transitionally rough, and fully rough regimes. The results indicate a transition from smooth to rough flow that is much more abrupt than the Colebrook transitional roughness function suggests. The equivalent sandgrain roughness was found to be 1.6 times the r.m.s. roughness height, in sharp contrast to the value of 3.0 to 5.0 that is commonly used. The difference amounts to a reduction in pressure drop for a given flow rate of a

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43

Ziarani, A. S., and A. A. Mohamad. "Nanoscale Fluid Flow Over Two Side-by-Side Cylinders With Atomically Rough Surface." Journal of Fluids Engineering 129, no. 3 (2006): 325–32. http://dx.doi.org/10.1115/1.2427087.

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A molecular dynamics simulation of flow over two side-by-side cylinders with atomically rough surfaces is presented. The model is two-dimensional with 3×105 liquid argon atoms. The surface roughness is constructed by external protrusion of atoms on the surface of the cylinders with specified amplitude and width. Two cylinders, with diameters of d=79.44 (molecular units), are placed at a distance of D in a vertical line. The solids atoms are allowed to vibrate around their equilibrium coordinates to mimic the real solid structure. The influence of various parameters, such as roughness amplitude

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Patil, Sunil, and Danesh Tafti. "Two-Layer Wall Model for Large-Eddy Simulations of Flow over Rough Surfaces." AIAA Journal 50, no. 2 (2012): 454–60. http://dx.doi.org/10.2514/1.j051228.

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Glegg, Stewart, and William Devenport. "The noise from flow over rough surfaces with small and large roughness elements." Journal of the Acoustical Society of America 127, no. 3 (2010): 1796. http://dx.doi.org/10.1121/1.3384028.

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46

Han, Lit S. "A mixing length model for turbulent boundary layers over rough surfaces." International Journal of Heat and Mass Transfer 34, no. 8 (1991): 2053–62. http://dx.doi.org/10.1016/0017-9310(91)90216-2.

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Taylor, R. P., W. F. Scaggs, and H. W. Coleman. "Measurement and Prediction of the Effects of Nonuniform Surface Roughness on Turbulent Flow Friction Coefficients." Journal of Fluids Engineering 110, no. 4 (1988): 380–84. http://dx.doi.org/10.1115/1.3243567.

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The status of prediction methods for friction coefficients in turbulent flows over nonuniform or random rough surfaces is reviewed. Experimental data for friction factors in fully developed pipe flows with Reynolds numbers between 10,000 and 600,000 are presented for two nonuniform rough surfaces. One surface was roughened with a mixture of cones and hemispheres which had the same height and base diameter and were arranged in a uniform array. The other surface was roughened with a mixture of two sizes of cones and two sizes of hemispheres. These data are compared with predictions made using th

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Sarkar, Kausik, and Andrea Prosperetti. "Effective boundary conditions for Stokes flow over a rough surface." Journal of Fluid Mechanics 316 (June 10, 1996): 223–40. http://dx.doi.org/10.1017/s0022112096000511.

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Ensemble averaging combined with multiple scattering ideas is applied to the Stokes flow over a stochastic rough surface. The surface roughness is modelled by compact protrusions on an underlying smooth surface. It is established that the effect of the roughness on the flow far from the boundary may be represented by replacing the no-slip condition on the exact boundary by a partial slip condition on the smooth surface. An approximate analysis is presented for a sparse distribution of arbitrarily shaped protrusions and explicit numerical results are given for hemispheres. Analogous conclusions

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Goody, Michael, Jason Anderson, Devin Stewart, and William Blake. "Experimental investigation of sound from flow over a rough surface." Journal of the Acoustical Society of America 123, no. 5 (2008): 3128. http://dx.doi.org/10.1121/1.2933068.

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Xie, Zhengtong, Peter R. Voke, Paul Hayden, and Alan G. Robins. "Large-Eddy Simulation of Turbulent Flow Over a Rough Surface." Boundary-Layer Meteorology 111, no. 3 (2004): 417–40. http://dx.doi.org/10.1023/b:boun.0000016599.75196.17.

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