Log in

Relevant bibliographies by topics / Flow over rough surfaces / Journal articles

To see the other types of publications on this topic, follow the link: Flow over rough surfaces.

Journal articles on the topic 'Flow over rough surfaces'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 journal articles for your research on the topic 'Flow over rough surfaces.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Balachandar, R., K. Hagel, and D. Blakely. "Velocity distribution in decelerating flow over rough surfaces." Canadian Journal of Civil Engineering 29, no. 2 (April 1, 2002): 211–21. http://dx.doi.org/10.1139/l01-089.

Full text

Abstract:

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's shape parameter were examined. Three different methods for determining the friction velocity were investigated for use in sloping channels. The inner region of the boundary layer was found not to be influenced by the channel slope. The log-law slope and intercept were found to be the same as that noted for canonical boundary layers. The skin friction coefficient for the sloping smooth surface tests was found to be slightly higher than that noticed for flow over a horizontal surface. As indicated by the wake parameter, the free surface, the channel slope, and the roughness of the channel affected the outer region of the boundary layer.Key words: decelerating flow, open channel, log-law, friction velocity, power law.

APA, Harvard, Vancouver, ISO, and other styles

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 (September 15, 1996): 20745–58. http://dx.doi.org/10.1029/96jc01824.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

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

Full text

APA, Harvard, Vancouver, ISO, and other styles

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 (June 2021): 593–601. http://dx.doi.org/10.1007/s42241-021-0039-3.

Full text

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 surface. This boundary condition represents the tensorial generalization of the classical Navier slip condition. We derive this condition, in the limit of small microscopic Reynolds numbers, using a multi-scale technique that yields a closed system of equations, the solution of which allows the slip tensor to be univocally calculated, once the roughness geometry is specified. We validate this generalized slip condition by considering the flow about a rough sphere, the surface of which is covered with a hexagonal lattice of cylindrical protrusions. Comparisons with direct numerical simulations performed in both laminar and turbulent regimes allow us to assess the validity and limitations of this condition and of the mathematical model underlying the determination of the slip tensor ${\mathcal{L}}$.

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 fluids and which depends on the dynamic interaction between the film and the fluid. Limiting cases are identified in which the film dynamics can be decoupled from the outer flow.

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 the graphite sample being positively skewed (peak-dominated) and the grit-blasted surface being negatively skewed (valley-dominated). For both cases, numerical simulations were conducted at seven different Reynolds numbers, ranging from $Re_{\unicode[STIX]{x1D70F}}=90$ to $Re_{\unicode[STIX]{x1D70F}}=720$. The positively skewed surface gives rise to higher friction factors than the negatively skewed surface in all cases. For the highest Reynolds numbers, the flow has values of the roughness function $\unicode[STIX]{x0394}U^{+}$ well in excess of $7$ for both surfaces and the bulk flow profile has attained a constant shape across the full height of the channel except for the immediate vicinity of the roughness, which would indicate fully rough flow. However, the mean flow profile within and directly above the rough surface still shows considerable Reynolds-number dependence and the ratio of form to viscous drag continues to increase, which indicates that at least for some types of rough surfaces the flow retains aspects of the transitionally rough regime to values of $\unicode[STIX]{x0394}U^{+}$ or $k^{+}$ well in excess of the values conventionally assumed for the transitionally to fully rough threshold. This is also reflected in the changes that the near-wall flow undergoes as the Reynolds number increases: the viscous sublayer, within which the surface roughness is initially buried, breaks down and regions of reverse flow intensify. At the highest Reynolds numbers, a layer of near-wall flow is observed to follow the contours of the local surface. The distribution of thickness of this ‘blanketing’ layer has a mixed scaling, showing that viscous effects are still significant in the near-wall flow.

APA, Harvard, Vancouver, ISO, and other styles

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 (March 1, 1985): 55–60. http://dx.doi.org/10.1115/1.3242440.

Full text

Abstract:

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 all axial positions and all values of P/K and K/D.

APA, Harvard, Vancouver, ISO, and other styles

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 (June 1, 1995): 234–41. http://dx.doi.org/10.1115/1.2817135.

Full text

Abstract:

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 model is applied to water flow over a fixed sand dune for which extensive experimental data are available. The solutions are found to be in agreement with data, including the flow in the separation eddy and its recovery after reattachment. The results suggest that this modeling approach may be extended to other types of surface roughness, and to more complex flows.

APA, Harvard, Vancouver, ISO, and other styles

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 (April 1, 2002): 256–66. http://dx.doi.org/10.1139/l01-093.

Full text

Abstract:

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 the flume at three different Froude numbers (Fr ~ 0.3, 0.8, 1.0). The lowest Froude number was selected to obtain data in the range of most other open channel testing programs and to represent a low subcritical Froude number. For each surface, the Reynolds number based on the boundary layer momentum thickness was varied from about 600 to 3000. In view of the recent questions concerning the applicability of the log-law and the debate regarding log-law versus power law, the turbulent inner region of the boundary layer is inspected. The fit of one type of power law for shallow flows over a smooth surface is considered. The appropriateness of extending this law to flows over rough surfaces is also examined. Alternate methods for determining the friction velocity of flows over smooth and rough surfaces are considered and compared with standard methods currently in use.Key words: power law, open channel flow, velocity profile, surface roughness.

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 Chung et al. (J. Fluid Mech., vol. 773, 2015, pp. 418–431) to accurately determine the Hama roughness function, $\unicode[STIX]{x0394}U^{+}$. Good agreement of the second-order statistics in the near-wall roughness-affected region between minimal- and full-span rough-wall channels is observed. In the sparse regime of roughness ($\unicode[STIX]{x1D6EC}\lesssim 0.15$) the roughness function increases with increasing solidity, while in the dense regime the roughness function decreases with increasing solidity. It was found that the dense regime begins when $\unicode[STIX]{x1D6EC}\gtrsim 0.15{-}0.18$, in agreement with the literature. A model is proposed for the limit of $\unicode[STIX]{x1D6EC}\rightarrow \infty$, which is a smooth wall located at the crest of the roughness elements. This model assists with interpreting the asymptotic behaviour of the roughness, and the rough-wall data presented in this paper show that the near-wall flow is tending towards this modelled limit. The peak streamwise turbulence intensity, which is associated with the turbulent near-wall cycle, is seen to move further away from the wall with increasing solidity. In the sparse regime, increasing $\unicode[STIX]{x1D6EC}$ reduces the streamwise turbulent energy associated with the near-wall cycle, while increasing $\unicode[STIX]{x1D6EC}$ in the dense regime increases turbulent energy. An analysis of the difference of the integrated mean momentum balance between smooth- and rough-wall flows reveals that the roughness function decreases in the dense regime due to a reduction in the Reynolds shear stress. This is predominantly due to the near-wall cycle being pushed away from the roughness elements, which leads to a reduction in turbulent energy in the region previously occupied by these events.

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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- and rough-wall data exhibit, over an inertial sublayer, regions of logarithmic dependence in the mean velocity and streamwise velocity variance. These logarithmic slopes are apparently the same between smooth and rough walls, indicating similar dynamics are present in this region. The streamwise mean velocity defect and skewness profiles each show convincing collapse in the outer region of the flow, suggesting that Townsend’s (The Structure of Turbulent Shear Flow, vol. 1, 1956, Cambridge University Press.) wall-similarity hypothesis is a good approximation for these statistics even at these finite friction Reynolds numbers. Outer-layer collapse is also observed in the rough-wall streamwise velocity variance, but only for flows with ${\it\delta}_{99}^{+}\gtrsim 14\,000$. At Reynolds numbers lower than this, profile invariance is only apparent when the flow is fully rough. In transitionally rough flows at low ${\it\delta}_{99}^{+}$, the outer region of the inner-normalised streamwise velocity variance indicates a dependence on $k_{s}^{+}$ for the present rough surface.

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

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

Full text

APA, Harvard, Vancouver, ISO, and other styles

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 (May 1, 1989): 568–72. http://dx.doi.org/10.1115/1.3250716.

Full text

APA, Harvard, Vancouver, ISO, and other styles

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 (February 1, 2005): 318–30. http://dx.doi.org/10.1115/1.2218572.

Full text

Abstract:

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 distributed spalls with realistic surface roughness. The results indicate that bypass transition occurred very early in the flow over the model and that the boundary layer remained unstable (transitional) throughout the entire length of the test plate. Results from the rough patch study indicate the boundary layer thickness and momentum thickness Reynolds numbers increased over the rough patch and the shape factor increased over the rough patch but then decreased downstream of the patch. It was also found that flow downstream of the patch experienced a gradual retransition to laminar-like behavior but in less time and distance than in the smooth plate case. Additionally, the rough patch caused a significant increase in streamwise turbulence intensity and normal turbulence intensity over the rough patch and downstream of the patch. In addition, the skin friction coefficient over the rough patch increased by nearly 2.5 times the smooth plate value. Finally, the rough patch caused the Reynolds shear stresses to increase in the region close the plate surface.

APA, Harvard, Vancouver, ISO, and other styles

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 (September 1, 1993): 383–88. http://dx.doi.org/10.1115/1.2910150.

Full text

Abstract:

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 rough surface. It is shown that fully rough mean velocity profiles collapse together when scaled as a function of momentum thickness, as was reported previously. However, this similarity cannot be used to distinguish roughness flow regimes, since a similar degree of collapse is observed in the transitionally rough data. Observation of the new data shows that scaling on the momentum thickness alone is not sufficient to produce similar velocity profiles for flows over surfaces of different roughness character. The skin friction coefficient data versus the ratio of the momentum thickness to roughness height collapse within the data uncertainty, irrespective of roughness flow regime, with the data for each rough surface collapsing to a different curve. Calculations made using the previously published discrete element prediction method are compared with data from the rough surfaces with well-defined roughness elements, and it is shown that the calculations are in good agreement with the data.

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 provide supporting evidence for the existence of this secondary flow.

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 momentum and scalar fluxes, especially below the top of the roughness elements. In general, turbulence is found to transport momentum more efficiently than scalars, while the reverse applies to the dispersive contributions. The effects of varying surface geometries, measured by the frontal density, are pronounced on turbulent fluxes and even more so on dispersive fluxes. Increasing frontal density induces a general transition in the flow from a wall bounded type to a mixing layer type. This transition results in an increase in the efficiency of turbulent momentum transport, but the reverse occurs for scalars due to reduced contributions from large-scale motions in the roughness sublayer. This study highlights the need for distinct parameterizations of the turbulent and dispersive fluxes, as well as the importance of considering the contrasts between momentum and scalar transport for flows over very rough surfaces.

APA, Harvard, Vancouver, ISO, and other styles

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 (April 1, 2004): 259–67. http://dx.doi.org/10.1115/1.1740779.

Full text

Abstract:

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 different from surfaces with sparse, ordered, and deterministic roughness elements. Modifications made to the discrete element roughness method to extend the validation to real gas turbine surface roughness are detailed. Two rough surfaces found on high-hour gas turbine blades were characterized using a Taylor-Hobson Form Talysurf Series 2 profilometer. Two rough surfaces and two elliptical-analog surfaces were generated for wind tunnel testing using a three-dimensional printer. The printed surfaces were scaled to maintain similar boundary layer thickness to roughness height ratio in the wind tunnel as found in gas turbine operation. The results of the wind tunnel skin friction and Stanton number measurements and the discrete element method predictions for each of the four surfaces are presented and discussed. The discrete element predictions made considering the gas turbine roughness modifications are within 7% of the experimentally measured skin friction coefficients and are within 16% of the experimentally measured Stanton numbers.

APA, Harvard, Vancouver, ISO, and other styles

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 (January 5, 2021): 439–71. http://dx.doi.org/10.1146/annurev-fluid-062520-115127.

Full text

Abstract:

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 topography and drag behavior, focusing on canonical and fully turbulent incompressible flow over rigid roughness. These advances are beginning to spill over into multiphysical areas of roughness, such as heat transfer, and promise broad increases in predictive reliability.

APA, Harvard, Vancouver, ISO, and other styles

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 (November 20, 2019): 331–54. http://dx.doi.org/10.1007/s10494-019-00074-4.

Full text

Abstract:

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 induce an over 200% increase in the roughness function ΔU+, compared to their streamwise anisotropic (SAR > 1) equivalent. Furthermore, we find that the relationship between the roughness function ΔU+ and the SAR parameter approximately follows an exponentially decaying function. The statistical response of the near-wall flow is studied using a “double-averaging” methodology in order to distinguish form-induced “dispersive” stresses from their turbulent counterparts. Outer-layer similarity is recovered for the mean velocity defect profile as well as the Reynolds stresses. The dispersive stresses all attain their maxima within the roughness canopy. Only the streamwise dispersive stress reaches levels that are comparable to the equivalent Reynolds stress, with surfaces of high SAR attaining the highest levels of streamwise dispersive stress. The Reynolds stress anisotropy also shows distinct differences between cases with strong streamwise anisotropy that stay close to an axisymmetric, rod-like state for all wall-normal locations, compared to cases with spanwise anisotropy where an axisymmetric, disk-like state of the Reynolds stress anisotropy tensor is observed around the roughness mean plane. Overall, the results from this study underline that the drag penalty incurred by a rough surface is strongly influenced by the surface topography and highlight its impact upon the mean momentum deficit in the outer flow as well as the Reynolds and dispersive stresses within the roughness layer.

APA, Harvard, Vancouver, ISO, and other styles

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 (April 1996): 215–23. http://dx.doi.org/10.1016/0304-3894(95)00073-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 / Di, of 1.5, 1.75 and 2.0 with diffuser width ratio, b / Di, of 0.055. The rotating stall pattern with one stall cell was dominant over the pattern with two cells which appeared at flow rates lower than the critical. In addition, the instability in the diffuser was delayed to a lower flow coefficient when rough surfaces were attached to one or both walls of the diffuser with the lowest values achieved by attaching the rough surface to the shroud wall. Results show that the roughness has no significant effect on stall cell frequencies.

APA, Harvard, Vancouver, ISO, and other styles

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 (January 2000): 251–62. http://dx.doi.org/10.1016/s0017-9310(99)00128-3.

Full text

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

APA, Harvard, Vancouver, ISO, and other styles

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 (January 2021): 100229. http://dx.doi.org/10.1016/j.taml.2021.100229.

Full text

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 fluctuations are modelled using a local equilibrium wall model (log-law or Monin–Obukhov similarity), but the required hydrodynamic roughness length must be specified. It is expressed as the product of the subgrid-scale root-mean-square of the height distribution and an unknown dimensionless quantity, α, the roughness parameter. Instead of specifying this parameter in an ad hoc empirical fashion, a dynamic methodology is proposed based on test-filtering the surface forces and requiring that the total drag force be independent of filter scale or resolution. This dynamic surface roughness (DSR) model is inspired by the Germano identity traditionally used to determine model parameters for closing subgrid-scale stresses in the bulk of a turbulent flow. A series of LES of fully developed flow over rough surfaces are performed, with surfaces built using random-phase Fourier modes with prescribed power-law spectra. Results show that the DSR model yields well-defined, rapidly converging, values of α. Effects of spatial resolution and spectral slopes are investigated. The accuracy of the DSR model is tested by showing that predicted mean velocity profiles are approximately independent of resolution for the dynamically computed values of α, whereas resolution-dependent results are obtained when using other, incorrect, α values. Also, strong dependence of α on βs is found, where α ranges from α ~ 0.1 for βs = −1.2 to α ~ 10−5 for βs = −3.

APA, Harvard, Vancouver, ISO, and other styles

30

Ghanem, Roger, and Bernard Hayek. "Probabilistic Modeling of Flow Over Rough Terrain." Journal of Fluids Engineering 124, no. 1 (November 12, 2001): 42–50. http://dx.doi.org/10.1115/1.1445138.

Full text

Abstract:

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 respect to the basis formed by the Polynomial Chaos random variables. A system of linear algebraic deterministic equations are derived for estimating these coordinates.

APA, Harvard, Vancouver, ISO, and other styles

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 (April 28, 2005): 1146–53. http://dx.doi.org/10.1115/1.2073288.

Full text

Abstract:

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 correlation that relates the skin friction, Cf, to the ratio of the displacement and boundary layer thicknesses, δ*∕δ, which is valid for both smooth and rough wall flows. The results indicate that the ratio Cf1∕2∕(δ*∕δ) is approximately constant, irrespective of the Reynolds number and surface condition.

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 profile over the grit surface exhibits self-similarity (in the form of a logarithmic law) within the limited range of 0.04≤y/h≤0.06, but the profile over the mesh surface does not, even though the mean velocity deficit and higher moments (up to the fourth order) all exhibit outer scaling over both surfaces. The distinction between self-similarity and outer similarity is clarified and the importance of the former is explained. The wake strength is shown to increase slightly over the grit surface but decrease over the mesh surface. The latter result is contrary to recent measurements in rough-wall boundary layers. Single- and two-point velocity correlations reveal the presence of large-scale streamwise structures with circulation in the plane orthogonal to the mean velocity. Spanwise correlation length scales are significantly larger than corresponding ones for both internal and external smooth-wall flows.

APA, Harvard, Vancouver, ISO, and other styles

33

Zhang, Hanzhong, Mohammad Faghri, and Frank M. White. "A New Low-Reynolds-Number k-ε Model for Turbulent Flow Over Smooth and Rough Surfaces." Journal of Fluids Engineering 118, no. 2 (June 1, 1996): 255–59. http://dx.doi.org/10.1115/1.2817371.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

34

Koh, Yang-Moon. "Turbulent Flow Near a Rough Wall." Journal of Fluids Engineering 114, no. 4 (December 1, 1992): 537–42. http://dx.doi.org/10.1115/1.2910065.

Full text

Abstract:

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 factors and skin friction coefficients. These equations are consistent with existing experimental observations and embrace well-known equations (e.g., Prandtl’s friction law for smooth pipes and Colebrook’s formula etc.) as special cases.

APA, Harvard, Vancouver, ISO, and other styles

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 (September 1, 1998): 434–44. http://dx.doi.org/10.1115/1.2820682.

Full text

Abstract:

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 at Princeton University are analyzed along with those of previous experiments on the boundary layer on an axisymmetric body to identify features of near-wall flow at high Reynolds numbers that are useful in modeling. The study is complemented by a review of some computations in simple and complex flows to reveal the strengths and weaknesses of turbulence models used in modern CFD methods. Similarly, principal results of classical experiments on the effects of sand-grain roughness are reviewed, along with various models proposed to account for these effects in numerical solutions. Models that claim to resolve the near-wall flow are applied to the flow in rough-wall pipes and channels to illustrate their power and limitations. The need for further laboratory and numerical experiments is clarified as a result of this study.

APA, Harvard, Vancouver, ISO, and other styles

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 (June 1, 1985): 251–57. http://dx.doi.org/10.1115/1.3242469.

Full text

Abstract:

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 data from well-accepted experiments. Predictions using the model are compared with additional data for fully-developed and boundary layer flows. The predictions are shown to compare equally well with both transitionally rough and fully rough turbulent flows without modification of the roughness model.

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 of parameter combinations and several shape functions by direct numerical simulations. It is possible to cover the full spectrum of rough flows ranging from hydraulically smooth through transitionally rough to fully rough cases. By using different parameter combinations and shape functions, it is possible to match the effects of different types of rough surfaces. Mean flow and standard turbulence statistics have been used to compare the results to recent experimental and numerical studies and a good qualitative agreement has been found. Outer scaling is preserved for the streamwise velocity for both the mean profile as well as its mean square fluctuations in all but extremely rough cases. The structure of the turbulent flow shows a trend towards more isotropic turbulent states within the roughness layer. In extremely rough cases, spanwise structures emerge near the wall and the turbulent state resembles a mixing layer. A direct comparison with the study of Ashrafian, Andersson & Manhart (Intl J. Heat Fluid Flow, vol. 25, 2004, pp. 373–383) shows a good quantitative agreement of the mean flow and Reynolds stresses everywhere except in the immediate vicinity of the rough wall. The proposed roughness force term may be of benefit as a wall model for direct and large-eddy numerical simulations in cases where the exact details of the flow over a rough wall can be neglected.

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 understand its effect on slip and drag reduction ($DR$). For the laminar Couette flow case, the presence of the surface roughness is felt up to $40\,\%$ of the channel height in the wall-normal direction. Nonlinear dependence of $DR$ on $h$ is observed with three distinct regions. A nonlinear curve fit is obtained for gas fraction $\unicode[STIX]{x1D719}_{g}$ as a function of $h$, where $\unicode[STIX]{x1D719}_{g}$ determines the amount of slip area exposed to the flow. A power law fit is obtained from the data for the effective slip length as a function of $\unicode[STIX]{x1D719}_{g}$ and is compared to those derived for structured geometry. For the turbulent channel flow, statistics of the flow field are compared to that of a smooth wall to understand the effects of roughness and $h$. Four cases are simulated ranging from fully wetted to fully covered and two intermediate regions in between. Scaling laws for slip length, slip velocity, roughness function and $DR$ are obtained for different penetration depths and are compared to past work for structured geometry. $DR$ is shown to depend on a competing effect between slip velocity and turbulent losses due to the Reynolds shear stress contribution. Presence of trapped air in the cavities significantly alters near-wall flow physics where we examine near-wall structures and propose a physical mechanism for their behaviour. The fully wetted roughness increases the peak value of turbulent intensities, whereas the presence of the interface suppresses them. The pressure fluctuations have competing contributions between turbulent pressure fluctuations and stagnation due to asperities, the near-wall structure is altered and breaks down with increasing slip. Overall, there exists a competing effect between the interface and the asperities, the interface suppresses turbulence whereas the asperities enhance them. The present work demonstrates DNS over a realistic multiphase SHS for the first time, to the best of our knowledge.

APA, Harvard, Vancouver, ISO, and other styles

39

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 (September 20, 2006): 369–83. http://dx.doi.org/10.1098/rspa.2006.1768.

Full text

Abstract:

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 lesser giving rise to wake flow. On the other hand, in the composite inner layer close to the bed, the viscous shear stress exists together with the turbulent stress. Thus, for the outer layer, a logarithmic law having modified coefficients from the traditional logarithmic law is obtained for the streamwise velocity, whereas for the inner layer, a fifth-degree polynomial including effective height of protrusions holds. The exact velocity expressions for inner and outer layer, which contain principal terms in addition to infinitesimally small terms, are in agreement with the experimental data obtained from laboratory measurements through an acoustic Doppler velocimeter. The experiments were run on two conditions of no seepage and a low upward seepage. Expressions for the Reynolds stress are also derived and computed for validation by the experimental data.

APA, Harvard, Vancouver, ISO, and other styles

40

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

Full text

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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. It is shown that appropriately re-written versions of the former can be used to collapse all the data, irrespective of the nature of the roughness, unless the surface is very rough, meaning that the typical roughness element height exceeds some 50% of the boundary-layer momentum thickness, corresponding to about $h/\delta\,{\widetilde{>}}\,0.2$.

APA, Harvard, Vancouver, ISO, and other styles

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.

Full text

Abstract:

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 at least 13% in the fully rough regime. The mean velocity profiles support Townsend's similarity hypothesis for flow over rough surfaces.

APA, Harvard, Vancouver, ISO, and other styles

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 (August 29, 2006): 325–32. http://dx.doi.org/10.1115/1.2427087.

Full text

Abstract:

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, topology, periodicity, and the gap between cylinders on the hydrodynamics of flow, especially drag and lift forces, is studied. It was noted that even very little surface roughness, with amplitude on the order of a few nanometers, can influence the drag forces. Both roughness texture and the number of roughening elements affects the drag and lift coefficients. The gap between the cylinders showed to be an effective parameter, especially on the lift force for flow over the nanoscale cylinders.

APA, Harvard, Vancouver, ISO, and other styles

44

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

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

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 (March 2010): 1796. http://dx.doi.org/10.1121/1.3384028.

Full text

APA, Harvard, Vancouver, ISO, and other styles

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 (August 1991): 2053–62. http://dx.doi.org/10.1016/0017-9310(91)90216-2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

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 (December 1, 1988): 380–84. http://dx.doi.org/10.1115/1.3243567.

Full text

Abstract:

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 the previously published discrete element prediction approach of Taylor, Coleman, and Hodge. The agreement between the data and the predictions is excellent.

APA, Harvard, Vancouver, ISO, and other styles

48

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.

Full text

Abstract:

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 for the two-dimensional case are obtained. It is shown that in certain cases a traction force develops on the surface at an angle with the direction of the flow.

APA, Harvard, Vancouver, ISO, and other styles

49

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 (May 2008): 3128. http://dx.doi.org/10.1121/1.2933068.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

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 (June 2004): 417–40. http://dx.doi.org/10.1023/b:boun.0000016599.75196.17.

Full text

APA, Harvard, Vancouver, ISO, and other styles

We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!