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Journal articles on the topic 'Wall roughness'

Author: Grafiati

Published: 4 June 2021

Last updated: 25 July 2025

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1

HERWIG, H., D. GLOSS, and T. WENTERODT. "A new approach to understanding and modelling the influence of wall roughness on friction factors for pipe and channel flows." Journal of Fluid Mechanics 613 (October 1, 2008): 35–53. http://dx.doi.org/10.1017/s0022112008003534.

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In this study, it is shown how the equivalent sand roughness required in the Moody chart can be calculated for arbitrarily shaped wall roughnesses. After a discussion of how to define the wall location and roughness height in the most reasonable way, a numerical approach based on the determination of entropy production in rough pipes and channels is presented. As test cases, three different two-dimensional roughness types have been chosen which are representative of regular roughnesses on machined surfaces. In the turbulent range, skin friction results with these test roughnesses can be linked

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2

Afzal, Noor. "Power Law Velocity Profile in the Turbulent Boundary Layer on Transitional Rough Surfaces." Journal of Fluids Engineering 129, no. 8 (2007): 1083–100. http://dx.doi.org/10.1115/1.2746902.

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A new approach to scaling of transitional wall roughness in turbulent flow is introduced by a new nondimensional roughness scale ϕ. This scale gives rise to an inner viscous length scale ϕν∕uτ, inner wall transitional variable, roughness friction Reynolds number, and roughness Reynolds number. The velocity distribution, just above the roughness level, turns out to be a universal relationship for all kinds of roughness (transitional, fully smooth, and fully rough surfaces), but depends implicitly on roughness scale. The open turbulent boundary layer equations, without any closure model, have be

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3

Anderson, William. "Amplitude modulation of streamwise velocity fluctuations in the roughness sublayer: evidence from large-eddy simulations." Journal of Fluid Mechanics 789 (January 26, 2016): 567–88. http://dx.doi.org/10.1017/jfm.2015.744.

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Recent studies have demonstrated that large- and very-large-scale motions in the logarithmic region of turbulent boundary layers ‘amplitude modulate’ dynamics of the near-wall region (Marusicet al.,Science, vol. 329, 2010, pp. 193–196; Mathiset al.,J. Fluid Mech., vol. 628, 2009a, pp. 311–337). These contributions prompted development of a predictive model for near-wall dynamics (Mathiset al.,J. Fluid Mech., vol. 681, 2011, pp. 537–566) that has promising implications for large-eddy simulations of wall turbulence at high Reynolds numbers (owing to the presence of smaller scales as the wall is

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4

Keirsbulck, L., L. Labraga, A. Mazouz, and C. Tournier. "Surface Roughness Effects on Turbulent Boundary Layer Structures." Journal of Fluids Engineering 124, no. 1 (2001): 127–35. http://dx.doi.org/10.1115/1.1445141.

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A turbulent boundary layer structure which develop over a k-type rough wall displays several differences with those found on a smooth surface. The magnitude of the wake strength depends on the wall roughness. In the near-wall region, the contribution to the Reynolds shear stress fraction, corresponding to each event, strongly depends on the wall roughness. In the wall region, the diffusion factors are influenced by the wall roughness where the sweep events largely dominate the ejection events. This trend is reversed for the smooth-wall. Particle Image Velocimetry technique (PIV) is used to obt

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5

Liu, Yanming, Jiahe Li, and Alexander J. Smits. "Roughness effects in laminar channel flow." Journal of Fluid Mechanics 876 (August 15, 2019): 1129–45. http://dx.doi.org/10.1017/jfm.2019.603.

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The effects of roughness on the frictional drag and pressure drop in laminar channel flow are investigated numerically. The inflow is fully developed smooth wall flow, and square rib roughness, aligned normal to the bulk flow direction, is introduced as a step change. The roughness height and spacing are systematically varied, and the flow is examined as it develops over the rough wall and becomes fully developed. The length of the development region depends primarily on the roughness height, although the effects of spacing become more important as the height decreases. In the fully developed

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6

NAPOLI, E., V. ARMENIO, and M. DE MARCHIS. "The effect of the slope of irregularly distributed roughness elements on turbulent wall-bounded flows." Journal of Fluid Mechanics 613 (October 1, 2008): 385–94. http://dx.doi.org/10.1017/s0022112008003571.

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Wall roughness produces a downward shift of the mean streamwise velocity profile in the log region, known as the roughness function. The dependence of the roughness function on the height and arrangement of roughness elements has been confirmed in several studies where regular rough walls were analysed; less attention has been paid to non-regular rough walls. Here, a numerical analysis of turbulent flows over irregularly shaped rough walls is performed, clearly identifying the importance of a parameter, called the effective slope (ES) of the wall corrugations, in characterizing the geometry of

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7

Meng, Han, Jing Zhang, Xinfeng Ge, and Jinwei Huang. "Research on the influence of needle roughness of Pelton turbine on flow characteristics." Journal of Physics: Conference Series 2707, no. 1 (2024): 012072. http://dx.doi.org/10.1088/1742-6596/2707/1/012072.

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Abstract The needle in the jetting mechanism of Pelton turbine may be uneven on the surface of the needle due to the knife marks in the cutting process or the erosion of the sediment in the water flow, resulting in the surface roughness of the needle, which affects the flow at the wall. In order to study the influence of the surface roughness of the needle on the jet flow characteristics, the jet flow characteristics and sediment characteristics of the jetting mechanism under different roughnesses were analyzed in this paper. The results show that the flow characteristics of the smooth wall an

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8

Mehdi, Faraz, J. C. Klewicki, and C. M. White. "Mean force structure and its scaling in rough-wall turbulent boundary layers." Journal of Fluid Mechanics 731 (August 28, 2013): 682–712. http://dx.doi.org/10.1017/jfm.2013.385.

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AbstractThe combined roughness/Reynolds number problem is explored. Existing and newly acquired data from zero pressure gradient rough-wall turbulent boundary layers are used to clarify the leading order balances of terms in the mean dynamical equation. For the variety of roughnesses examined, it is revealed that the mean viscous force retains dominant order above (and often well above) the roughness crests. Mean force balance data are shown to be usefully organized relative to the characteristic length scale, which is equal or proportional to the width of the region from the wall to where the

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9

Raupach, M. R., R. A. Antonia, and S. Rajagopalan. "Rough-Wall Turbulent Boundary Layers." Applied Mechanics Reviews 44, no. 1 (1991): 1–25. http://dx.doi.org/10.1115/1.3119492.

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This review considers theoretical and experimental knowledge of rough-wall turbulent boundary layers, drawing from both laboratory and atmospheric data. The former apply mainly to the region above the roughness sublayer (in which the roughness has a direct dynamical influence) whereas the latter resolve the structure of the roughness sublayer in some detail. Topics considered include the drag properties of rough surfaces as functions of the roughness geometry, the mean and turbulent velocity fields above the roughness sublayer, the properties of the flow close to and within the roughness canop

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10

Afzal, Noor, Abu Seena, and Afzal Bushra. "Power Law Turbulent Velocity Profile in Transitional Rough Pipes." Journal of Fluids Engineering 128, no. 3 (2005): 548–58. http://dx.doi.org/10.1115/1.2175161.

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Alternate power law velocity profile u+=Aζα in transitional rough pipe fully turbulent flow, has been proposed, in terms of new appropriate inner rough wall variables (ζ=Z+∕ϕ, uϕ=u∕ϕ), and new parameters Rϕ=Rτ∕ϕ termed as the roughness friction Reynolds number, Reϕ=Re∕ϕ termed as the roughness Reynolds number and ϕ termed as roughness scale (along with normal wall coordinate Z=y+ϵr where ϵr is the shift of the origin of boundary layer due to the rough wall, Z+=Zuτ∕ν and u+=u∕uτ). The envelope of the power law shows that the power law constants α and A depend on the parameter Rϕ (i.e., α=α(Rϕ)

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11

Leonardi, S., P. Orlandi, L. Djenidi, and R. A. Antonia. "Heat transfer in a turbulent channel flow with square bars or circular rods on one wall." Journal of Fluid Mechanics 776 (July 13, 2015): 512–30. http://dx.doi.org/10.1017/jfm.2015.344.

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Direct numerical simulations (DNS) are carried out to study the passive heat transport in a turbulent channel flow with either square bars or circular rods on one wall. Several values of the pitch (${\it\lambda}$) to height ($k$) ratio and two Reynolds numbers are considered. The roughness increases the heat transfer by inducing ejections at the leading edge of the roughness elements. The amounts of heat transfer and mixing depend on the separation between the roughness elements, an increase in heat transfer accompanying an increase in drag. The ratio of non-dimensional heat flux to the non-di

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12

He, Xiaoke, Yingchong Zhang, Chuan Wang, et al. "Influence of Critical Wall Roughness on the Performance of Double-Channel Sewage Pump." Energies 13, no. 2 (2020): 464. http://dx.doi.org/10.3390/en13020464.

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The numerical method on a double-channel sewage pump was studied, while the corresponding experimental result was also provided. On this basis, the influence of wall roughness on the pump performance was deeply studied. The results showed that there was a critical value of wall roughness. When the wall roughness was less than the critical value, it had a great influence on the pump performance, including the head, efficiency, and shaft power. As the wall roughness increased, the head and efficiency were continuously reduced, while the shaft power was continuously increased. Otherwise, the oppo

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13

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

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

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14

Gre´goire, G., M. Favre-Marinet, and F. Julien Saint Amand. "Modeling of Turbulent Fluid Flow Over a Rough Wall With or Without Suction." Journal of Fluids Engineering 125, no. 4 (2003): 636–42. http://dx.doi.org/10.1115/1.1593705.

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The turbulent flow close to a wall with two-dimensional roughness is computed with a two-layer zonal model. For an impermeable wall, the classical logarithmic law compares well with the numerical results if the location of the fictitious wall modeling the surface is considered at the top of the rough boundary. The model developed by Wilcox for smooth walls is modified to account for the surface roughness and gives satisfactory results, especially for the friction coefficient, for the case of boundary layer suction.

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15

Ortloff, Charles R. "Supercritical Froude Number Flow through Ducts with Statistically Roughened Walls." Water 15, no. 15 (2023): 2849. http://dx.doi.org/10.3390/w15152849.

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High-speed fluid flows over roughened surfaces occur in many engineering applications; one important application involves high velocity water flows in pipelines with roughened interior walls where the wall roughness affects head loss estimates necessary for engineering design purposes. The present analysis provides an analytical solution of the fluid physics underlying the induced static pressure profile resulting from high Froude number supercritical velocity through duct with random wall roughness. The analytic solution of the hyperbolic governing small perturbation velocity potential equati

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16

Abu Rowin, W., M. Abdelkader, A. Ramani, P. Manovski, and N. Hutchins. "Suppression Of Wall Reflection In PIV Images Over Rough Walls." Proceedings of the International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics 20 (July 11, 2022): 1–19. http://dx.doi.org/10.55037/lxlaser.20th.203.

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Wall reflections in particle image velocimetry (PIV) measurements is one of the limiting factors in obtaining velocity information in the vicinity of rough walls. This work tests two different techniques to suppress wall reflections for time-resolved, two-dimensional particle tracking velocimetry (2D-PTV) and stereoscopic-PIV (stereo-PIV). The 2D-PTV was performed for a turbulent boundary layer developed on a rough wall in a water towing tank facility. To measure velocity in the vicinity of the rough wall, the near-wall region on the viewing window was covered with tinted papers to mitigate th

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17

Zheng, Yu, Piaopiao Gao, Lianqiong Jiang, Xiaochao Kai, and Ji’an Duan. "Surface Morphology of Silicon Waveguide after Reactive Ion Etching (RIE)." Coatings 9, no. 8 (2019): 478. http://dx.doi.org/10.3390/coatings9080478.

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The side wall profile roughness of the silicon waveguide prepared by electron beam lithography and reactive ion etching is extracted by using the boundary tracing method. The maximum, minimum, and average roughness values are extracted from the side wall boundary, and the changes of the side wall boundary of waveguide after electron beam exposure and reactive ion etching were compared. The roughness variation of the waveguide side wall is similar with the same length. And roughness from the bottom of the waveguide etched region is measured directly by laser confocal microscope and roughness co

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18

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

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

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19

Glegg, Stewart, and William Devenport. "The far-field sound from rough-wall boundary layers." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 465, no. 2106 (2009): 1717–34. http://dx.doi.org/10.1098/rspa.2008.0318.

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The noise radiated by a turbulent boundary layer over a rough wall is shown to be characterized by a dipole surface source that, if the surface pressure is spatially homogeneous, can be specified by a convolution integral combining the surface pressure wavenumber spectrum and the wavenumber spectrum of the surface roughness slope. For random roughness elements with almost vertical sides, the surface slope has a wavenumber white spectrum and the radiated sound is directly proportional to the surface pressure spectrum multiplied by an acoustic efficiency factor ( k o h ) 2 , where k o is the aco

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20

Ma, Guo-Zhen, Chun-Xiao Xu, Hyung Jin Sung, and Wei-Xi Huang. "Scaling of rough-wall turbulence in a transitionally rough regime." Physics of Fluids 34, no. 3 (2022): 031701. http://dx.doi.org/10.1063/5.0084646.

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In this Letter, we propose a roughness scaling method based on the direct numerical simulation of turbulent channel flow over three-dimensional sinusoidal rough walls in a transitionally rough regime. A new coupling scale [Formula: see text] is defined by combining the Reynolds number [Formula: see text] and the roughness parameter [Formula: see text], where [Formula: see text] is the mean roughness height, S is the roughness steepness, and n is the scaling exponent—which depends on the roughness type. The relationships between [Formula: see text], the roughness function, the friction factor,

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21

Li, Shilong, Xiaolei Yang, and Yu Lv. "Predictive capability of the logarithmic law for roughness-modeled large-eddy simulation of turbulent channel flows with rough walls." Physics of Fluids 34, no. 8 (2022): 085112. http://dx.doi.org/10.1063/5.0098611.

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Direct numerical simulation (DNS) and large-eddy simulation (LES) resolving roughness elements are computationally expensive. LES employing the logarithmic law as the wall model, without the need to resolve the flow at the roughness element scale, provides an efficient alternative for simulating turbulent flows over rough walls. In this work, we evaluate the predictive capability of the roughness-modeled LES by comparing its predictions with those from the roughness-resolved DNS for turbulent channel flows with rough walls. A good agreement is observed for the mean streamwise velocity. The Rey

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22

Yao, Zhifeng, Min Yang, Ruofu Xiao, and Fujun Wang. "Influence of wall roughness on the static performance and pressure fluctuation characteristics of a double-suction centrifugal pump." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 7 (2018): 826–40. http://dx.doi.org/10.1177/0957650918757246.

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The unsteady flow field and pressure fluctuations in double-suction centrifugal pumps are greatly affected by the wall roughness of internal surfaces. To determine the wall roughness effect, numerical and experimental investigations were carried out. Three impeller schemes for different wall roughness were solved using detached eddy simulation, and the performance and pressure fluctuations resolved by detached eddy simulation were compared with the experimental data. The results show that the effects of wall roughness on the static performance of a pump are remarkable. The head and efficiency

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23

Liu, Zhaoxia, Wenhui Bian, Gang Pan, Pengcheng Li, and Wenxin Li. "Influences on Shotcrete Rebound from Walls with Random Roughness." Advances in Materials Science and Engineering 2018 (October 23, 2018): 1–12. http://dx.doi.org/10.1155/2018/7401358.

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Concrete slurry can be sprayed on walls for reinforcement; however, there is a certain amount of rebound which is hazardous, lowers production quality, and wastes material. To investigate this problem, we studied single slurry droplets at the mesoscopic level. We deduced the factors influencing droplet spreading and wall adhesion to create models of shotcrete rebound. Then, a numerical simulation orthogonal experiment investigating droplet-wall impacts was performed. The relationship between the spreading coefficient and each influencing factor is discussed, and numerical models are presented.

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24

LEE, SEUNG-HYUN, and HYUNG JIN SUNG. "Direct numerical simulation of the turbulent boundary layer over a rod-roughened wall." Journal of Fluid Mechanics 584 (July 25, 2007): 125–46. http://dx.doi.org/10.1017/s0022112007006465.

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The effects of surface roughness on a spatially developing turbulent boundary layer (TBL) are investigated by performing direct numerical simulations of TBLs over rough and smooth walls. The Reynolds number based on the momentum thickness was varied in the range Reθ = 300 ∼ 1400. The roughness elements were periodically arranged two-dimensional spanwise rods, and the roughness height was k = 1.5θin, where θin is the momentum thickness at the inlet, which corresponds to k/δ = 0.045 ∼ 0.125, δ being the boundary layer thickness. To avoid generating a rough-wall inflow, which is prohibitively dif

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25

Pan, Chong, Jianjie Wang, Ning Zhou, and Jinjun Wang. "Regularization of Wall-wall Turbulence by Discrete Roughness Element." Procedia Engineering 126 (2015): 98–102. http://dx.doi.org/10.1016/j.proeng.2015.11.186.

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26

LEE, JAE HWA, HYUNG JIN SUNG, and PER-ÅGE KROGSTAD. "Direct numerical simulation of the turbulent boundary layer over a cube-roughened wall." Journal of Fluid Mechanics 669 (January 12, 2011): 397–431. http://dx.doi.org/10.1017/s0022112010005082.

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Direct numerical simulation (DNS) of a spatially developing turbulent boundary layer (TBL) over a wall roughened with regularly arrayed cubes was performed to investigate the effects of three-dimensional (3-D) surface elements on the properties of the TBL. The cubes were staggered in the downstream direction and periodically arranged in the streamwise and spanwise directions with pitches of px/k = 8 and pz/k = 2, where px and pz are the streamwise and spanwise spacings of the cubes and k is the roughness height. The Reynolds number based on the momentum thickness was varied in the range Reθ =

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27

Han, Bingfu, Lei Tan, and Yadong Han. "Role of wall roughness on the energy performance for a mixed flow pump with tip clearance." Journal of Physics: Conference Series 2854, no. 1 (2024): 012029. http://dx.doi.org/10.1088/1742-6596/2854/1/012029.

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Abstract This study delves into the intricate influence of wall roughness on the mixed flow pump energy performance, particularly focusing on the simultaneous presence of tip clearance. Utilizing a well-performing mixed flow pump with a tip clearance of 0.8 mm as the subject of investigation, the research employs numerical simulation at different roughness to comprehensively analyse the effects of wall roughness on pump head, efficiency, and cavitation performance. The numerical simulation employs the SST k-ω model and the equivalent sand-gain roughness model to simulate the turbulent flow acc

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28

SCHULTZ, M. P., and K. A. FLACK. "The rough-wall turbulent boundary layer from the hydraulically smooth to the fully rough regime." Journal of Fluid Mechanics 580 (May 21, 2007): 381–405. http://dx.doi.org/10.1017/s0022112007005502.

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Turbulence measurements for rough-wall boundary layers are presented and compared to those for a smooth wall. The rough-wall experiments were made on a three-dimensional rough surface geometrically similar to the honed pipe roughness used by Shockling, Allen & Smits (J. Fluid Mech. vol. 564, 2006, p. 267). The present work covers a wide Reynolds-number range (Reθ = 2180–27 100), spanning the hydraulically smooth to the fully rough flow regimes for a single surface, while maintaining a roughness height that is a small fraction of the boundary-layer thickness. In this investigation, the root

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29

Ivanov, Martin, and Sergey Mijorski. "Development of thermal bridge numerical model, based on conjugate heat transfer and indoor and outdoor environment parameters." E3S Web of Conferences 180 (2020): 04011. http://dx.doi.org/10.1051/e3sconf/202018004011.

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The presented study reveals the development of a 3D numerical model for thermal bridge assessment, based on conjugate heat transfer and CFD methods. With the developed model, thermal simulations are performed, in order to analyse the interaction between different ambient conditions and material properties. The results show that the wall boundary layer profiles are depended on the attached air flow velocity magnitude and implemented wall roughness. The parametric analysis, of the varying ambient air temperatures, confirm the linear dependence to the internal wall surface temperatures. The demon

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30

Wu, Sicong, Kenneth T. Christensen, and Carlos Pantano. "Modelling smooth- and transitionally rough-wall turbulent channel flow by leveraging inner–outer interactions and principal component analysis." Journal of Fluid Mechanics 863 (January 29, 2019): 407–53. http://dx.doi.org/10.1017/jfm.2018.899.

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Direct numerical simulations (DNS) of turbulent channel flow over rough surfaces, formed from hexagonally packed arrays of hemispheres on both walls, were performed at friction Reynolds numbers $Re_{\unicode[STIX]{x1D70F}}=200$, $400$ and $600$. The inner normalized roughness height $k^{+}=20$ was maintained for all Reynolds numbers, meaning all flows were classified as transitionally rough. The spacing between hemispheres was varied within $d/k=2$–$4$. The statistical properties of the rough-wall flows were contrasted against a complementary smooth-wall DNS at $Re_{\unicode[STIX]{x1D70F}}=400

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31

VARNIK, FATHOLLAH, DOROTHÉE DORNER, and DIERK RAABE. "Roughness-induced flow instability: a lattice Boltzmann study." Journal of Fluid Mechanics 573 (February 2007): 191–209. http://dx.doi.org/10.1017/s0022112006003715.

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Effects of wall roughness/topography on flows in strongly confined (micro-)channels are studied by means of lattice Boltzmann simulations. Whereas wall roughness in macroscopic channels is considered to be relevant only for high-Reynolds-number turbulent flows (where the flow is turbulent even for smooth walls), it is shown in this paper that, in micro-channels, surface roughness may even modify qualitative features of the flow. In particular, a transition from laminar to unsteady flow is observed. It is found that this roughness-induced transition is strongly enhanced as the channel width is

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32

Zhu, Xiaojue, Ruben A. Verschoof, Dennis Bakhuis, et al. "Wall roughness induces asymptotic ultimate turbulence." Nature Physics 14, no. 4 (2018): 417–23. http://dx.doi.org/10.1038/s41567-017-0026-3.

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33

Bottaro, Alessandro, and Abdelfattah Zebib. "Görtler vortices promoted by wall roughness." Fluid Dynamics Research 19, no. 6 (1997): 343–62. http://dx.doi.org/10.1016/s0169-5983(96)00055-x.

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34

Chedevergne, F. "Analytical wall function including roughness corrections." International Journal of Heat and Fluid Flow 73 (October 2018): 258–69. http://dx.doi.org/10.1016/j.ijheatfluidflow.2018.08.001.

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35

Bo, Zheng, Qi Zhao, Xiaorui Shuai, Jianhua Yan, and Kefa Cen. "Numerical study on the pressure drop of fluid flow in rough microchannels via the lattice Boltzmann method." International Journal of Numerical Methods for Heat & Fluid Flow 25, no. 8 (2015): 2022–31. http://dx.doi.org/10.1108/hff-12-2014-0379.

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Purpose – The purpose of this paper is to provide a quantitative assessment on the effect of wall roughness on the pressure drop of fluid flow in microchannels. Design/methodology/approach – The wall roughness is generated by the method of random midpoint displacement (RMD) and the lattice Boltzmann BGK model is applied. The influences of Reynolds number, relative roughness and the Hurst exponent of roughness profile on the Poiseuille number are investigated. Findings – Unlike the smooth channel flow, Reynolds number, relative roughness and the Hurst exponent of roughness profiles play critica

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36

Sakaguchi, Hayate, Takuma Kishimoto, Saki Suematsu, et al. "Change in Surface Roughness on the Inner and Outer Surfaces of the Microtube during Hollow Sinking." Materials 17, no. 17 (2024): 4320. http://dx.doi.org/10.3390/ma17174320.

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Hollow sinking experiments and tensile tests were conducted to clarify the evolution of surface roughness during hollow sinking. Stainless steel tubes (outer diameter: 1.5 mm; wall thickness: 0.045 mm) featuring a single grain spanning the wall thickness achieved via annealing as the starting material. The tube was drawn without an internal tool using a draw bench by controlling the tube drawing speed ratio of the die entrance and exit sides. The surface roughnesses of the inner and outer surfaces at the die entrance and exit sides of the drawn tube were compared with the surface roughnesses o

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37

WU, Y., and K. T. CHRISTENSEN. "Spatial structure of a turbulent boundary layer with irregular surface roughness." Journal of Fluid Mechanics 655 (May 19, 2010): 380–418. http://dx.doi.org/10.1017/s0022112010000960.

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Particle image velocimetry experiments were performed to study the impact of realistic roughness on the spatial structure of wall turbulence at moderate Reynolds number. This roughness was replicated from an actual turbine blade damaged by deposition of foreign materials and its features are quite distinct from most roughness characterizations previously considered as it is highly irregular and embodies a broad range of topographical scales. The spatial structure of flow over this rough surface near the outer edge of the roughness sublayer is contrasted with that of smooth-wall flow to identif

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38

Kan, Kan, Qingying Zhang, Yuan Zheng, et al. "Investigation into Influence of Wall Roughness on the Hydraulic Characteristics of an Axial Flow Pump as Turbine." Sustainability 14, no. 14 (2022): 8459. http://dx.doi.org/10.3390/su14148459.

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Pump as turbine (PAT) is a factual alternative for electricity generation in rural and remote areas where insufficient or inconsistent water flows pose a threat to local energy demand satisfaction. Recent studies on PAT hydrodynamics have shown that its continuous operations lead to a progressive deterioration of inner surface smoothness, serving the source of near-wall turbulence build-up, which itself depends on the level of roughness. The associated boundary layer flow incites significant friction losses that eventually deteriorate the performance. In order to study the influence of wall ro

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39

Attenborough, Keith. "Influence of Periodically Varying Slit Widths on Sound Absorption by a Slit Pore Medium." Materials 18, no. 1 (2024): 54. https://doi.org/10.3390/ma18010054.

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A simple pore microstructure of parallel, identical, and inclined smooth-walled slits in a rigid solid, for which prediction of its geometrical and acoustic properties is straightforward, can yield useful sound absorption. This microstructure should be relatively amenable to 3D printing. Discrepancies between measurements and predictions of normal incidence sound absorption spectra of 3D printed vertical and slanted slit pore samples have been attributed to the rough surfaces of the slit walls and uneven slit cross-sections perpendicular to the printing direction. Theories of the influence of

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Seddighi, M., S. He, D. Pokrajac, T. O’Donoghue, and A. E. Vardy. "Turbulence in a transient channel flow with a wall of pyramid roughness." Journal of Fluid Mechanics 781 (September 16, 2015): 226–60. http://dx.doi.org/10.1017/jfm.2015.488.

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A direct numerical simulation investigation of a transient flow in a channel with a smooth top wall and a roughened bottom wall made of close-packed pyramids is presented. An initially stationary turbulent flow is accelerated rapidly to a new flow rate and the transient flow behaviour after the acceleration is studied. The equivalent roughness heights of the initial and final flows are $k_{s}^{+}=14.5$ and 41.5, respectively. Immediately after the acceleration ends, the induced change behaves in a ‘plug-flow’ manner. Above the roughness crests, the additional velocity due to the perturbation f

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Zhu, Xiaojue, Roberto Verzicco, and Detlef Lohse. "Disentangling the origins of torque enhancement through wall roughness in Taylor–Couette turbulence." Journal of Fluid Mechanics 812 (December 22, 2016): 279–93. http://dx.doi.org/10.1017/jfm.2016.815.

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Direct numerical simulations (DNS) are performed to analyse the global transport properties of turbulent Taylor–Couette flow with inner rough wall up to Taylor number$Ta=10^{10}$. The dimensionless torque $Nu_{\unicode[STIX]{x1D714}}$ shows an effective scaling of $Nu_{\unicode[STIX]{x1D714}}\propto Ta^{0.42\pm 0.01}$, which is steeper than the ultimate regime effective scaling $Nu_{\unicode[STIX]{x1D714}}\propto Ta^{0.38}$ seen for smooth inner and outer walls. It is found that at the inner rough wall, the dominant contribution to the torque comes from the pressure forces on the radial faces

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IKEDA, TOMOAKI, and PAUL A. DURBIN. "Direct simulations of a rough-wall channel flow." Journal of Fluid Mechanics 571 (January 4, 2007): 235–63. http://dx.doi.org/10.1017/s002211200600334x.

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In this study, we performed simulations of turbulent flow over rectangular ribs transversely mounted on one side of a plane in a channel, with the other side being smooth. The separation between ribs is large enough to avoid forming stable vortices in the spacing, which exhibits k-type, or sand-grain roughness. The Reynolds number Reτ of our representative direct numerical simulation case is 460 based on the smooth-wall friction velocity and the channel half-width. The roughness height h is estimated as 110 wall units based on the rough-wall friction velocity. The velocity profile and kinetic

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Lai, Chutao, Xiaokai Zhou, Yizhao Hu, Yitong Guo, Kunyi Li, and Panjie Wang. "Experimental study on spray impingement during diesel engine starting." Thermal Science, no. 00 (2024): 43. http://dx.doi.org/10.2298/tsci230515043l.

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A lot of research has been carried out in the field of improving combustion efficiency and reducing exhaust gas, but the phenomenon of engine fuel spray hitting the wall cannot be solved well all the time, thus the phenomenon will increase exhaust gas emissions and reduce combustion efficiency. Based on oil pump test bench of diesel engine, we designed spray-wall impingement?s test, did high speed camera shooting to capture the relevant motion characteristics of fuel spraing-hitting the wall by mosquito-rope method, under the starting process, the influence of different working condition on sp

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Wu, Beibei, Zengtian Xu, Shiquan Feng, Changqing Li, and Jia Yao. "Effect of different roughness on oil film formation in a diesel engine." Journal of Physics: Conference Series 2528, no. 1 (2023): 012014. http://dx.doi.org/10.1088/1742-6596/2528/1/012014.

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Abstract After diesel fuel injection, when the spray droplets in the air hit the wall, an oil film may be formed on the wall, and the surface roughness is the key parameter. To analyze the influence of roughness on the formation of oil film, a combustion model of the engine cylinder is built in this paper. The main part of the model is the simulation of diesel injection, and a related fuel injection model is built. The influence of cylinder wall roughness on the oil film formation in the diesel engine cylinder is analyzed through a wall-droplet interaction model.

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Yuan, J., and U. Piomelli. "Numerical simulation of a spatially developing accelerating boundary layer over roughness." Journal of Fluid Mechanics 780 (September 3, 2015): 192–214. http://dx.doi.org/10.1017/jfm.2015.437.

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The direct numerical simulation of an accelerating boundary layer over a rough wall has been carried out to investigate the coupling between the effects of roughness and strong free-stream acceleration. While the favourable pressure gradient is sufficient to achieve quasi-laminarization on a smooth wall, the flow reversion is prevented on a rough wall, and a higher friction coefficient, a faster increase of turbulence intensity compared to the free-stream velocity and more isotropic turbulence near the wall are observed. The logarithmic region of the mean-velocity profile presents an initial d

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Богомолов, Дмитрий, Dmitriy Bogomolov, Валерий Порошин, Valeriy Poroshin, Валентин Нижник, and Valentin Nizhnik. "Mathematical model of heat flux in continuous media in thin 2d channel with moving rough wall." Bulletin of Bryansk state technical university 2014, no. 4 (2014): 100–108. http://dx.doi.org/10.12737/23096.

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The mathematical model of heat flux in continuous media in thin channel with moving rough wall in 2D approach is described.. The results of the comparisons of flow factors and Mussel numbers in channels with smooth walls and channels with real stochastic wall roughness are shown. Both static and dynamic cases were investigated.

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Lu, Yuhan, Zaijie Liu, Teng Zhou, and Chao Yan. "Stability analysis of roughness-disturbed boundary layer controlled by wall-blowing." Physics of Fluids 34, no. 10 (2022): 104114. http://dx.doi.org/10.1063/5.0117405.

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Roughness-induced transition control is of considerable importance for high-speed vehicles. In this paper, the instability of a roughness-disturbed boundary layer controlled by spanwise-uniform wall-blowing is investigated through BiGlobal and three-dimensional parabolized stability equation (PSE-3D) analysis. Without wall-blowing, symmetric and antisymmetric unstable modes are observed when using BiGlobal analysis, with PSE-3D analysis suggesting that the symmetric mode is the dominant instability. Both modes are associated with the instability of the entire separated shear layer behind the r

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Cen, Zhoutao, Yuxin Wu, Jingyu Wang, et al. "Investigation of the Dominant Effects of Non-Spherical Particles on Particle–Wall Collisions." Processes 12, no. 6 (2024): 1234. http://dx.doi.org/10.3390/pr12061234.

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A deep understanding of the particle–wall collision (PWC) behaviors of non-spherical particles is important for managing gas–solid flows in industrial applications. It is important to identify the dominant parameters and to develop the common PWC prediction models for typical non-spherical particles. In this paper, different types of non-spherical particles were used to conduct the fundamental experiments. The effects of key parameters such as particle size, non-sphericity, wall roughness, and impact angle were analyzed. The results show that the trends of the collision coefficients with the i

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Abderrahaman-Elena, Nabil, Chris T. Fairhall, and Ricardo García-Mayoral. "Modulation of near-wall turbulence in the transitionally rough regime." Journal of Fluid Mechanics 865 (March 1, 2019): 1042–71. http://dx.doi.org/10.1017/jfm.2019.41.

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Direct numerical simulations of turbulent channels with rough walls are conducted in the transitionally rough regime. The effect that roughness produces on the overlying turbulence is studied using a modified triple decomposition of the flow. This decomposition separates the roughness-induced contribution from the background turbulence, with the latter essentially free of any texture footprint. For small roughness, the background turbulence is not significantly altered, but merely displaced closer to the roughness crests, with the change in drag being proportional to this displacement. As the

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Durbin, P. A., G. Medic, J. M. Seo, J. K. Eaton та S. Song. "Rough Wall Modification of Two-Layer k−ε". Journal of Fluids Engineering 123, № 1 (2000): 16–21. http://dx.doi.org/10.1115/1.1343086.

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A formulation is developed to apply the two-layer k−ε model to rough surfaces. The approach involves modifying the lν formula and the boundary condition on k. A hydrodynamic roughness length is introduced and related to the geometrical roughness through a calibration procedure. An experiment has been conducted to test the model. It provides data on flow over a ramp with and without surface roughness.

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