Relevant bibliographies by topics / Flow over rough surfaces

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
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Academic literature on the topic 'Flow over rough surfaces'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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Journal articles on the topic "Flow over rough surfaces"

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.

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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'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.
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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.

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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.

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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.

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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 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 ${\mathcal{L}}$.
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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 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.
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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 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.
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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.

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

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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 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.
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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.

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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 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.
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Dissertations / Theses on the topic "Flow over rough surfaces"

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Andersson, Robin. "Flow Over Large-Scale Naturally Rough Surfaces." Licentiate thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-136.

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The fluid mechanical field of rough surface flows has been developed ever since the first experiments by Haagen (1854) and Darcy (1857). Although old, the area still holds merit and a surprising amount of information have to this day yet to be fully understood, which surely is a proof of its complexity. Many equations and CFD tools still rely on old, albeit reliable, concepts for simplifying the flow to be able to handle the effects of surface roughness. This notion is, however, likely to change within a not so unforeseeable future. The advancement of computer power has opened the door for more advanced CFD tools such as Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES). It can be argued that once a given flow situation has been fully accessible by numerical simulations, it is likely to be fully understood within a few years 1 . However, DNS is still limited to small scales of roughness and relatively low Reynolds number which is in contrast with given hydropower conditions today. The hydropower industry annually supplies Sweden with about 45% of its electricity production, and tunnels of various types are regularly used for conveying water to or from turbines within hydropower stations. The tunnels are a vital part of the system and their survival is of the essence. Depending on the manner of excavation, the walls of the tunnels regularly exhibit a roughness, this roughness may range from a few mm to m, which is true especially if the tunnel have been subjected to damage. For natural roughness e.g. hydropower tunnels, there is no clear way to distinguish between rough surface flows and flow past obstacles. Yet, to be able to distinguish between the two cases has proven to be important. This work is aimed to increase the understanding of how the wall roughness affects the flow, and how to treat it numerically. Paper A employs the use of pressure sensors to evaluate local deviations in pressure as well as head loss due to the surface roughness. Paper B is aimed at using PIV to evaluate the flow using averaging techniques and characteristic length scales. Paper C Further investigates the data from the PIV and pressure measurements and Evaluates the possibility to use basic but versatile turbulence models to evaluate the flow in such tunnels.
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Watt, Robert McFarlane. "Effects of surface roughness on the boundary-layer characteristics of turbine aerofoils." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330065.

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McClain, Stephen Taylor. "A discrete-element model for turbulent flow over randomly-rough surfaces." Diss., Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-04032002-140007.

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Thakkar, Manan. "Investigation of turbulent flow over irregular rough surfaces using direct numerical simulations." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/415836/.

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Incompressible turbulent flow in irregular rough channels is investigated using a finite-difference direct numerical simulation code which includes an iterative embedded boundary treatment to resolve the roughness. Seventeen industrially relevant rough surfaces with a wide variation in surface topography are considered. Various studies are conducted to understand the flow physics and the relationship between key flow parameters and surface topography. Studies at low values of friction Reynolds number, Reτ, for a single surface, show that the flow is laminar up to Reτ = 89 and begins to develop quasi-periodic fluctuations at Reτ = 89.5. Fluctuations in the three velocity components continue to grow until Reτ = 91, and the flow is turbulent for Reτ ≥ 92. Transition depends on the surface topography as some roughness peaks trigger fluctuations before others. For all the surfaces, mean and turbulent flow statistics are computed at Reτ = 180, for which the flow is fully turbulent but transitionally rough. All surfaces are scaled to the same physical roughness height. Nevertheless, a wide range of roughness function, ∆U+, values is obtained, indicating that it depends not only on the roughness height but also on the detailed roughness topography. Other mean and turbulence flow statistics also vary considerably depending on the surface topography. Next, based on the simulation results database at Reτ = 180, a newly formulated method, that determines which surface topographical properties are important and how new properties can be added to an empirical model, is tested. Optimised models with several roughness parameters are systematically developed for ∆U+ and profile peak turbulent kinetic energy. In determining ∆U+, besides the known parameters of solidity and skewness, it is shown that the streamwise correlation length and rms roughness height are also significant. The peak turbulent kinetic energy is determined by the skewness and rms roughness height, along with the mean forward-facing surface angle and spanwise effective slope. A Reynolds number dependence study is conducted for a single surface, wherein the roughness height in viscous units, k+, is varied from the transitionally rough to the fully-rough regime in the range 3.75 ≤ k+ ≤ 120. Excellent agreement with the experimental data of Nikuradse (Laws of flow in rough pipes, NACA Technical Memorandum 1292, 1933) is observed. The value of equivalent sand-grain roughness height, k+s,eq, thus obtained is close to the mean peak-to-valley height.
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LIU, WEN. "TRANSPORT PHENOMENA ASSOCIATED WITH LIQUID METAL FLOW OVER TOPOGRAPHICALLY MODIFIED SURFACES." UKnowledge, 2012. http://uknowledge.uky.edu/me_etds/16.

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Brazing and soldering, as advanced manufacturing processes, are of significant importance to industrial applications. It is widely accepted that joining by brazing or soldering is possible if a liquid metal wets the solids to be joined. Wetting, hence spreading and capillary action of liquid metal (often called filler) is of significant importance. Good wetting is required to distribute liquid metal over/between the substrate materials for a successful bonding. Topographically altered surfaces have been used to exploit novel wetting phenomena and associated capillary actions, such as imbibitions (a penetration of a liquid front over/through a rough, patterned surface). Modification of surface roughness may be considered as a venue to tune and control the spreading behavior of the liquids. Modeling of spreading of liquids on rough surface, in particular liquid metals is to a large extent unexplored and constitutes a cutting edge research topic. In this dissertation the imbibitions of liquid metal has been considered as pertained to the metal bonding processes involving brazing and soldering fillers. First, a detailed review of fundamentals and the recent progress in studies of non-reactive and reactive wetting/capillary phenomena has been provided. An imbibition phenomenon has been experimentally achieved for organic liquids and molten metals during spreading over topographically modified intermetallic surfaces. It is demonstrated that the kinetics of such an imbibition over rough surfaces follows the Washburn-type law during the main spreading stage. The Washburn-type theoretical modeling framework has been established for both isotropic and anisotropic non-reactive imbibition of liquid systems over rough surfaces. The rough surface domain is considered as a porous-like medium and the associated surface topographical features have been characterized either theoretically or experimentally through corresponding permeability, porosity and tortuosity. Phenomenological records and empirical data have been utilized to verify the constructed model. The agreement between predictions and empirical evidence appears to be good. Moreover, a reactive wetting in a high temperature brazing process has been studied for both polished and rough surfaces. A linear relation between the propagating triple line and the time has been established, with spreading dominated by a strong chemical reaction.
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Grissom, Dustin Leonard. "A Study of Sound Generated by a Turbulent Wall Jet Flow Over Rough Surfaces." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28336.

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The far field acoustics generated by turbulent flow over rough surfaces has been experimentally investigated in an acoustically treated wall jet facility. The facility allows direct measurement of the far field sound from small patches of surface roughness, without contamination from edge or other aerodynamic noise sources. The facility is capable of generating turbulent boundary layer flows with momentum thickness Reynolds numbers between 450 and 1160. The variation of surface conditions tested cover the range from hydrodynamically smooth surfaces through most of the transitional range, with h+ variations from 3 to 85. Single microphone narrow band acoustic spectra, measured in the far field, show sound levels as much as 15 dB above the background from 0.186 m2 roughness patches. The measurements revealed the spectral shape and level variations with flow velocity, boundary layer thickness, and roughness size; providing the first data set large enough to assess the affects of many aerodynamic properties on the acoustic spectra. Increases in the size of grit type roughness produced significant increases in acoustic levels. Patches of hydrodynamically smooth roughness generated measurable acoustic levels, confirming that acoustic scattering is at least one of the physical mechanisms responsible for roughness noise. The shapes of the measured spectra show a strong dependence on the form of the surface roughness. The acoustic spectra generated by periodic two-dimensional surfaces have a much narrower louder peak than that generated by three-dimensional grit type roughness. Measurements also show the orientation of the two-dimensional surface significantly affects the acoustic levels and directivity. The variation of sound levels with flow velocity and roughness size suggests the acoustic field is significantly affected by changes in the near wall flow due to the presence of the roughness. Current models of noise generated by rough surfaces predict the general trends seen in measurements for flows over grit and two-dimensional roughness in the range of 20Ph. D.
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Letherman, Sophie Bella. "Turbulence modelling of oscillatory flows over smooth and rough surfaces." Thesis, University of Manchester, 2000. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488128.

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This study investigates turbulence models for application to boundary layer flows. Firstly, steady channel flow and transient pipe flows are considered. Calculations of a low-Reynolds-number k-epsilon model, a k-epsilon-S model (a strain parameter model which has not been applied to unsteady flows previously) and a Reynolds Stress Transport model are compared with experimental and DNS data. The eddy viscosity turbulence models (k-epsilon, k-epsilon-S) satisfactorily predict the mean flow parameters of steady channel flow. However the k-epsilon-S model proves superior in comparison with turbulence quantities. Near to the pipe wall, the k-epsilon-S model best captures the details of periodic pipe flow detail, whereas in the outer flow region the RSTM gives closest agreement with the experimental data. The high-Reynolds-number k-epsilon and k-l eddy viscosity turbulence models are examined in a separate study of oscillatory flows over smooth and rough beds. The computations are considered over a wider range of experimental parameters than previously investigated. The turbulence models are assessed by comparison with field measurements and laboratory data sets including a new set of experimental measurements. Both models predict the bed shear stress and velocity adequately, but the k-epsilon model emerges as the superior scheme when considering turbulence quantities. An attempt is made to quantify the uncertainty in the Reynolds shear stress and eddy viscosity experimental data. The k-epsilon model calculations more frequently lie within the experimental uncertainty bands. However this uncertainty range is wide; any improvement would require a corresponding improvement in the experimental resolution of rough bed flows.
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Smith, Benjamin Scott. "Wall Jet Boundary Layer Flows Over Smooth and Rough Surfaces." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/27597.

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The aerodynamic flow and fluctuating surface pressure of a plane, turbulent, two-dimensional wall jet flow into still air over smooth and rough surfaces has been investigated in a recently constructed wall jet wind tunnel testing facility. The facility has been shown to produce a wall jet flow with Reynolds numbers based on the momentum thickness, Re&delta = &deltaUm/&nu, of between 395 and 1100 and nozzle exit Reynolds numbers, Rej = Umb/&nu, of between 16000 and 45000. The wall jet flow properties (&delta, &delta*, &theta, y1/2, Um, u*, etc.) were measured and characterized over a wide range of initial flow conditions and measurement locations relative to the wall jet source. These flow properties were measured for flow over a smooth flow surface and for flow over roughness patches of finite extent. The patches used in the current study varied in length from 305 mm to 914 mm (between 24 and 72 times the nozzle height, b) and were placed so that the leading edge of the patch was fixed at 1257 mm (x/b = 99) downstream of the wall jet source. These roughness patches were of a random sand grain roughness type and the roughness grain size was varied throughout this experiment. The tests covered roughness Reynolds numbers (k+) ranging from less than 2 to over 158 (covering the entire range of rough wall flow regimes from hydrodynamically smooth to fully rough). For the wall jet flows over 305 mm long patches of roughness, the displacement and momentum thicknesses were found to vary noticeably with the roughness grain size, but the maximum velocity, mixing layer length scale, y1/2, and the boundary layer thickness were not seen to vary in a consistent, determinable way. Velocity spectra taken at a range of initial flow conditions and at several distinct heights above the flow surface showed a limited scaling dependency on the skin friction velocity near the flow surface. The spectral density of the surface pressure of the wall jet flow, which is not believed to have been previously investigated for smooth or rough surfaces, showed distinct differences with that seen in a conventional boundary layer flow, especially at low frequencies. This difference is believed to be due to the presence of a mixing layer in the wall jet flow. Both the spectral shape and level were heavily affected by the variation in roughness grain size. This effect was most notable in overlap region of the spectrum. Attempts to scale the wall jet surface pressure spectra using outer and inner variables were successful for the smooth wall flows. The scaling of the rough wall jet flow surface pressure proved to be much more difficult, and conventional scaling techniques used for ordinary turbulent boundary layer surface pressure spectra were not able to account for the changes in roughness present during the current study. An empirical scaling scheme was proposed, but was only marginally effective at scaling the rough wall surface pressure.
Ph. D.
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Alhinai, Almajd. "An investigation of classifying the flow over rough surfaces into k- and d- type in turbulent channel flow." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/11255/.

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This thesis is concerned with the classification of roughness into k- and d- type in turbulent channel flow. Despite the practical importance of this type of flow, the literature review suggest that advancements in the field have been slow due to the difficulty of making accurate measurements close to the wall when using experimental methods. In recent years, numerical modelling has provided a good alternative to studying this type of flow. In this work, an Implicit Large Eddy Simulation (ILES) approach was developed to carry out numerical simulations for turbulent channel flow over rough surfaces. The application was developed based on the Finite Element Method and implemented using the Multi-Physics platform COMSOL. Verification and validation of the numerical model was carried out to asses the predictive capabilities of the model, including sensitivity analysis to quantify the uncertainty and comparison with results from literature to validate the model. In our analysis, we considered rough surfaces with square and triangular roughness elements with a constant roughness height and varying distributions of the roughness elements. The results demonstrated that the model is capable of resolving the coherent large eddy structures associated with the k- and d- type behaviours. The classification reported here is based on the coherent structures associated with the k- and d- type behaviours. Furthermore, we investigated the effects of roughness geometry on the k- and d- type behaviours. To this end, flow visualizations were used to study the interaction between the inner and outer layer of the flow. The results demonstrated that the geometry of the roughness elements has little effect on the coherent structures associated with the k- and d-type behaviours, these effects of the roughness geometry are confined to the inner region. However, the results show that the roughness geometry has a strong influence on the interaction between the inner and outer flow regions.
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Seddighi-Moormani, Mehdi. "Study of turbulence and wall shear stress in unsteady flow over smooth and rough wall surfaces." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=166096.

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Flows over hydraulically smooth walls are predominant in turbulence studies whereas real surfaces in engineering applications are often rough. This is important because turbulent flows close to the two types of surface can exhibit large differences. Unfortunately, neither experimental studies nor theoretical studies based on conventional computational fluid dynamics (CFD) can give sufficiently accurate, detailed information about unsteady turbulent flow behaviour close to solid surfaces, even for smooth wall cases. In this thesis, therefore, use is made of a state of the art computational method “Direct Numerical Simulation (DNS)” to investigate the unsteady flows. An “in-house” DNS computer code is developed for the study reported in this thesis. Spatial discretization in the code is achieved using a second order, finite difference method. The semi-implicit (Runge-Kutta & Crank-Nicholson) time advancement is incorporated into the fractional-step method. A Fast Fourier Transform solver is used for solving the Poisson equation. An efficient immersed Boundary Method (IBM) is used for treating the roughness. The code is parallelized using a Message Passing Interface (MPI) and it is adopted for use on a distributed-memory computer cluster at University of Aberdeen as well as for use at the UK’s national high-performance computing service, HECToR. As one of the first DNS of accelerating/decelerating flows over smooth and rough walls, the study has produced detailed new information on turbulence behaviours which can be used for turbulence model development and validations. The detailed data have enabled better understanding of the flow physics to be developed. The results revealed strong non-equilibrium and anisotropic behaviours of turbulence dynamics in such flows. The preliminary results on the rough wall flow show the response of turbulence in the core and wall regions, and the relationship between the axial and the other components are significantly different from those in smooth wall flows.
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Books on the topic "Flow over rough surfaces"

1

Conrad, Jeffrey G. Propagation of vertically polarized waves over rough ocean surfaces. Monterey, Calif: Naval Postgraduate School, 1997.

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Merrill, Craig F. Spray generation for liquid wall jets over smooth and rough surfaces. Monterey, Calif: Naval Postgraduate School, 1998.

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Craig, Ken. Computational study of the aerodynamics and control by blowing of asymmetric vortical flows over Delta wings. Stanford, Calif: Stanford University, Dept. of Aeronautics and Astronautics, 1991.

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Craig, Ken. Computational study of the aerodynamics and control by blowing of asymmetric vortical flows over Delta wings. Stanford, Calif: Stanford University, Dept. of Aeronautics and Astronautics, 1991.

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Tantirige, Sunil Chithranjan *. A flow visualization investigation of the turbulent boundary layer over regularly rough surfaces. 1989.

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Boundary Layer Flow over Elastic Surfaces. Elsevier, 2012. http://dx.doi.org/10.1016/c2011-0-06221-x.

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Zhao, Wancheng. High schmidt number mass transfer at rough surfaces in pipe flow. 1995.

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Spray Generation from Liquid Wall Jets Over Smooth and Rough Surfaces. Storming Media, 1998.

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Boundary Layer Flow Over Elastic Surfaces And Combined Method Of Drag Reduction. Butterworth-Heinemann, 2012.

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Escudier, Marcel. Oblique shockwaves and expansion fans. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198719878.003.0012.

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External supersonic gas flow in which changes in the fluid and flow properties are brought about by direction change is analysed in this chapter. In addition, it is shown that flow over a corner between two flat surfaces resulted in an oblique shockwave if the angle between the two surfaces is less than 180° (a concave corner). The analysis of flow through an oblique shockwave is based upon the superposition of the flowfield for a normal shock onto a uniform flow parallel to the shock. It is also shown that both weak and strong oblique shocks can occur. For an angle in excess of 180° (a convex corner), the flow is turned through an isentropic Prandtl-Meyer expansion fan. Analysis of a Prandtl-Meyer expansion fan starts from consideration of an infinitesimal flow deflection through a Mach wave.
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Book chapters on the topic "Flow over rough surfaces"

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Amir, M., and I. P. Castro. "Mean Flow and Turbulence over Rough Surfaces." In Springer Proceedings in Physics, 669–72. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03085-7_161.

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Blake, William K., and Jason M. Anderson. "The Acoustics of Flow over Rough Elastic Surfaces." In Flinovia - Flow Induced Noise and Vibration Issues and Aspects, 1–23. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-09713-8_1.

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Aupoix, B. "Modelling of Boundary Layer Flows Over Rough Surfaces." In Fluid Mechanics and Its Applications, 16–20. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0457-9_4.

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Thakkar, M., A. Busse, and N. D. Sandham. "Turbulent Fluid Flow over Aerodynamically Rough Surfaces Using Direct Numerical Simulations." In Direct and Large-Eddy Simulation X, 281–87. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-63212-4_35.

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McLelland, Stuart J. "Coherent Secondary Flows Over a Water-Worked Rough Bed in a Straight Channel." In Coherent Flow Structures at Earth's Surface, 275–88. Chichester, UK: John Wiley & Sons, Ltd, 2013. http://dx.doi.org/10.1002/9781118527221.ch18.

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Rodrigues, Abel, Raul Albuquerque Sardinha, and Gabriel Pita. "Flow Over Modified Surfaces." In Fundamental Principles of Environmental Physics, 133–57. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-69025-0_5.

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Ginevsky, A. S., and A. I. Zhelannikov. "Wind Flow Over Rough Terrain." In Foundations of Engineering Mechanics, 99–104. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-01760-5_6.

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Castro, Ian P. "Turbulent flow over rough walls." In Springer Proceedings in Physics, 381–88. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03085-7_92.

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Erickson, David. "Electroosmotic Flow over Heterogeneous Surfaces." In Encyclopedia of Microfluidics and Nanofluidics, 899–908. New York, NY: Springer New York, 2015. http://dx.doi.org/10.1007/978-1-4614-5491-5_448.

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Erickson, David. "Electroosmotic Flow over Heterogeneous Surfaces." In Encyclopedia of Microfluidics and Nanofluidics, 1–11. Boston, MA: Springer US, 2014. http://dx.doi.org/10.1007/978-3-642-27758-0_448-2.

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Conference papers on the topic "Flow over rough surfaces"

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Anderson, Jason M., Devin O. Stewart, and William K. Blake. "Experimental Investigations of Sound From Flow Over Rough Surfaces." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-11445.

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Turbulent boundary layer flows over rough surfaces are known to produce elevated far-field acoustic sound levels. The nature by which surface irregularities alter the near-field surface pressures and subsequently affect the sound generation to the scattering of high wavenumber convective pressures to low wavenumber acoustic pressures, which is typically interpreted as a dipole-like source. The focus of the current investigation is the experimental interrogation of both near- and far-field pressures due to the flow over roughened surfaces in order to identify the source mechanisms and to validate physical models of roughness sound. For rough surfaces composed of large geometrical elements (defined by large Reynolds numbers based on roughness height and friction velocity), such as hemispheres and cubes, the measured near-field surfaces pressures indicate that the local interstitial flows become important in determining the sound radiation characteristics. In order to describe the aeroacoustic source region, scaling laws are developed for surface pressures at locations around the roughness elements for various roughness configurations and flow speeds. Relationships between surface pressures amongst the rough surface elements and far-field pressures measured at several directional aspects were examined to identify roughness sound source mechanisms. Measurements of a dipole directivity pattern and dipole efficiency factors obtained when normalizing radiated sound by surface pressures offer support to the scattering theories for roughness sound. Using existing pressure scattering models as a basis, an empirical model for roughness sound is generated.
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Fan, H., and R. Bowersox. "Numerical analysis of high-speed flow over rough surfaces." In 35th Joint Propulsion Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1999. http://dx.doi.org/10.2514/6.1999-2381.

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Peters, Wayne D., James E. S. Venart, and Charles R. Dutcher. "GRAVITY CURRENT FLOWS OVER ROUGH SURFACES." In International Heat Transfer Conference 10. Connecticut: Begellhouse, 1994. http://dx.doi.org/10.1615/ihtc10.3130.

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Chochua, Gocha, and Wei Shyy. "Computational Modeling of Turbulent Flows Over Rough Surfaces." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41063.

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Turbulent flows over rough surfaces are often encountered in nature and engineering practices and are often difficult to analyze. In this study, combined modeling and computational techniques is involved to investigate such flows over a surface covered with a large-scale roughness pattern. A simplified empirical engineering model is validated by taking area average of the flow field data over the surface. The approach can interpret fluid physics based on the empirical correlation. The area-averaged mean momentum transport resulting from the wall-normal time-averaged velocity component is found to be a significant contributing term into the near-boundary shear stress balance. This makes its behavior different from the flow over a smooth surface. Comparing alternative approaches for estimating the roughness coefficients, it is found that the mass-flow-rate-deficit approach produces superior results. Flow in a channel with one wall covered with an array of cylindrical cavities and the other smooth is used as an example. The extended wall functions, based on the k-ε closure and the simplified engineering model, can be applied for a large-scale roughness pattern. The approach can significantly reduce required computational cost. On the other hand, the small domain periodic computations are needed to produce roughness lengths for a particular surface geometry. This model can develop a general correlation relating the roughness lengths to a surface geometry to aid engineering design.
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Adane, Kofi, Mark Tachie, Martin Agelinchaab, and Mohammad Shah. "Low Reynolds Number Turbulent Flow Over Smooth and Transitionally Rough Surfaces." In 39th AIAA Fluid Dynamics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2009. http://dx.doi.org/10.2514/6.2009-3565.

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Wray, Timothy, and Ramesh K. Agarwal. "Extension of Wray-Agarwal Turbulence Model for Flow Over Rough Surfaces." In 45th AIAA Fluid Dynamics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2015. http://dx.doi.org/10.2514/6.2015-2785.

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Anderson, Jason, Devin Stewart, Michael Goody, and Paul Zoccola. "Sound From Flow Over a Rough Surface." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41847.

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The mechanism for sound production from flow over a rough surface is not well understood. Measurements of radiated noise and low-wavenumber unsteady surface pressures were carried out in order to better understand the sound production mechanism. The initial results of an ongoing experimental investigation of the sound produced by flow over a rough surface are presented. In order to investigate scaling relationships, the flow speed, roughness height, and roughness element distribution were varied. Previous investigations have reported roughness noise levels that scale on flow velocity, roughness height, and fetch area and have indicated that the sound production may be dipole or quadrupole in nature. Prevailing analytical models assume that both types of sources are present. The scaling of roughness noise for large roughness height (k+ = uτk/ν of order 1000) has not been investigated previously and is part of the current study. The scaling behavior of low-wavenumber surface pressures is discussed, in addition to the comparison of radiated noise spectra obtained by phased microphone array measurements.
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Cherubini, S., M. D. de Tullio, P. De Palma, and G. Pascazio. "Optimal Perturbations in Boundary Layer Flows Over Rough Surfaces." In ASME 2012 Fluids Engineering Division Summer Meeting collocated with the ASME 2012 Heat Transfer Summer Conference and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/fedsm2012-72219.

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This work provides a three-dimensional energy optimization analysis, looking for perturbations inducing the largest energy growth at a finite time in a boundary-layer flow in the presence of roughness elements. Amplification mechanisms are described which by-pass the asymptotical growth of Tollmien–Schlichting waves. The immersed boundary technique has been coupled with a Lagrangian optimization in a three-dimensional framework. Two types of roughness elements have been studied, characterized by a different height. The results show that even very small roughness elements, inducing only a weak deformation of the base flow, can strongly localize the optimal disturbance. Moreover, the highest value of the energy gain is obtained for a varicose perturbation, pointing out the importance of varicose instabilities for such a flow and a different behavior with respect to the secondary instability theory of boundary layer streaks.
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FLEMING, KENTON, and ROBERT TAYLOR. "Incompressible Navier-Stokes algorithm for flow and heat transfer over rough surfaces." In 27th Thermophysics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1992. http://dx.doi.org/10.2514/6.1992-2925.

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Mikulich, V., and C. Brücker. "Flow and motion behavior of particle suspensions in shear flow over a rough surface." In MULTIPHASE FLOW 2013. Southampton, UK: WIT Press, 2013. http://dx.doi.org/10.2495/mpf130221.

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Reports on the topic "Flow over rough surfaces"

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Gregg, Michael C., and Parker MacCready. Stratified Flow over Rough, Sloping Topography. Fort Belvoir, VA: Defense Technical Information Center, September 1999. http://dx.doi.org/10.21236/ada629721.

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MacCready, Parker. Drag Mechanisms in Flow Over Rough Topography. Fort Belvoir, VA: Defense Technical Information Center, September 2001. http://dx.doi.org/10.21236/ada624680.

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Janaswamy, Ramakrishna. Development of Analytical Techniques for Wave Propagation Over Large Rough Surfaces. Fort Belvoir, VA: Defense Technical Information Center, September 2006. http://dx.doi.org/10.21236/ada612184.

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Rydalch, Andrew J. Turbulent Boundary Layer Flow over Superhydrophobic Surfaces. Fort Belvoir, VA: Defense Technical Information Center, May 2013. http://dx.doi.org/10.21236/ada581869.

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