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Journal articles on the topic 'Wall roughness model'

Author: Grafiati

Published: 4 June 2021

Last updated: 13 February 2022

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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

Keirsbulck, L., L. Labraga, A. Mazouz, and C. Tournier. "Surface Roughness Effects on Turbulent Boundary Layer Structures." Journal of Fluids Engineering 124, no. 1 (October 15, 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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3

Afzal, Noor. "Power Law Velocity Profile in the Turbulent Boundary Layer on Transitional Rough Surfaces." Journal of Fluids Engineering 129, no. 8 (March 4, 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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4

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 (July 1, 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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5

Aupoix, B. "A General Strategy to Extend Turbulence Models to Rough Surfaces: Application to Smith’s k-L Model." Journal of Fluids Engineering 129, no. 10 (April 27, 2007): 1245–54. http://dx.doi.org/10.1115/1.2776960.

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A general procedure to extend turbulence models to account for wall roughness, in the framework of the equivalent sand grain approach, is proposed. It is based on the prescription of the turbulent quantities at the wall to reproduce the shift of the logarithmic profile and hence provide the right increase in wall friction. This approach was previously applied to Spalart and Allmaras one equation (1992, “A One-Equation Turbulence Model for Aerodynamic. Flows,” 30th Aerospace Sciences Meeting and Exhibit, Reno, NV, AIAA paper No. 92-0439;1994, ibid, Rech. Aerosp. 1, pp. 5–21). Here, the strategy

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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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7

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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8

Lin, Xiaohui, Fu-bing Bao, Xiaoyan Gao, and Jiemin Chen. "Molecular Dynamics Simulation of Nanoscale Channel Flows with Rough Wall Using the Virtual-Wall Model." Journal of Nanotechnology 2018 (June 24, 2018): 1–7. http://dx.doi.org/10.1155/2018/4631253.

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Molecular dynamics simulation is adopted in the present study to investigate the nanoscale gas flow characteristics in rough channels. The virtual-wall model for the rough wall is proposed and validated. The computational efficiency can be improved greatly by using this model, especially for the low-density gas flow in nanoscale channels. The effect of roughness element geometry on flow behaviors is then studied in detail. The fluid velocity decreases with the increase of roughness element height, while it increases with the increases of element width and spacing.

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9

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 (17 листопада 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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10

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 (December 5, 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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11

Zhang, Xia, and Lixing Zhou. "A second-order moment particle–wall collision model accounting for the wall roughness." Powder Technology 159, no. 2 (November 2005): 111–20. http://dx.doi.org/10.1016/j.powtec.2005.07.005.

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12

Naimi, M., and F. B. Gessner. "Calculation of Fully-Developed Turbulent Flow in Rectangular Ducts With Nonuniform Wall Roughness." Journal of Fluids Engineering 119, no. 3 (September 1, 1997): 550–58. http://dx.doi.org/10.1115/1.2819279.

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The predictive capabilities of four transport-type turbulence models are analyzed by comparing predictions with experimental data for fully-developed flow in (1) a rectangular duct with a step change in roughness on one wall (Case 1), and (2) a square duct with one rib-roughened wall (Case 2). The models include the Demuren-Rodi (DR) k-ε model, the Sugiyama et al. (S) k-ε model, the Launder-Li (LL) Reynolds stress transport equation model, and the differential stress (DS) model proposed recently by the authors. For the first flow situation (Case 1), the results show that the DS model yields im

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13

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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14

GAMRAT, G., M. FAVRE-MARINET, S. LE PERSON, R. BAVIÈRE, and F. AYELA. "An experimental study and modelling of roughness effects on laminar flow in microchannels." Journal of Fluid Mechanics 594 (December 14, 2007): 399–423. http://dx.doi.org/10.1017/s0022112007009111.

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Three different approaches were used in the present study to predict the influence of roughness on laminar flow in microchannels. Experimental investigations were conducted with rough microchannels 100 to 300μm in height (H). The pressure drop was measured in test-sections prepared with well-controlled wall roughness (periodically distributed blocks, relative roughness k* =k/0.5H≈0.15) and in test-sections with randomly distributed particles anchored on the channel walls (k* ≈0.04–0.13). Three-dimensional numerical simulations were conducted with the same geometry as in the test-section with p

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15

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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16

Taylor, R. P., H. W. Coleman, and B. K. Hodge. "Prediction of Turbulent Rough-Wall Skin Friction Using a Discrete Element Approach." Journal of Fluids Engineering 107, no. 2 (June 1, 1985): 251–57. http://dx.doi.org/10.1115/1.3242469.

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

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17

Annus, Ivar, Anatoli Vassiljev, Nils Kändler, and Katrin Kaur. "Determination of the corresponding roughness height in a WDS model containing old rough pipes." Journal of Water Supply: Research and Technology-Aqua 69, no. 3 (October 1, 2019): 201–9. http://dx.doi.org/10.2166/aqua.2019.080.

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Abstract The aim of the paper was to determine the influence of irregular pipe wall roughness on the flow velocity in a water distribution system (WDS) containing old pipes. Field studies have shown that due to pipe wall build-up, the shape of the inner pipe surface can vary temporally and spatially. This will lead to unrealistic pipe roughness values when calibrating the WDS model using nominal pipe diameters. Therefore, in this study, three types of pipe wall build-up were investigated using EPANET2 and computational fluid dynamics (CFD) to estimate the velocity correction coefficients for E

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18

Yang, Xiang I. A., Jasim Sadique, Rajat Mittal, and Charles Meneveau. "Exponential roughness layer and analytical model for turbulent boundary layer flow over rectangular-prism roughness elements." Journal of Fluid Mechanics 789 (January 18, 2016): 127–65. http://dx.doi.org/10.1017/jfm.2015.687.

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We conduct a series of large-eddy simulations (LES) to examine the mean flow behaviour within the roughness layer of turbulent boundary layer flow over rough surfaces. We consider several configurations consisting of arrays of rectangular-prism roughness elements with various spacings, aspect ratios and height distributions. The results provide clear evidence for exponential behaviour of the mean flow with respect to the wall normal distance. Such behaviour has been proposed before (see, e.g., Cionco, 1966 Tech. Rep. DTIC document), and is represented as $U(z)/U_{h}=\exp [a(z/h-1)]$, where $U(

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19

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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20

Mitchell, R. J. "Model studies on the stability of confined fills." Canadian Geotechnical Journal 26, no. 2 (May 1, 1989): 210–16. http://dx.doi.org/10.1139/t89-030.

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Stabilized backfills are used extensively for ground control in most bulk underground mining operations. The stability of the fill face during pillar ore removal is of prime concern and has been the subject of considerable research because of many factors, including the effects of wall interaction and the high costs of stabilization. Centrifuge modelling data presented in this paper clearly show that fill confined between sloped walls, which is the most common prototype condition, is much more stable than fill between vertical rock walls, a condition previously studied. This study also shows t

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21

García-López, Erika, Juansethi Ibarra-Medina, Hector Siller, Jan Lammel-Lindemann, and Ciro Rodriguez. "Surface Finish and Back-Wall Dross Behavior during the Fiber Laser Cutting of AZ31 Magnesium Alloy." Micromachines 9, no. 10 (September 24, 2018): 485. http://dx.doi.org/10.3390/mi9100485.

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Magnesium alloys are of increasing interest in the medical industry due to their biodegradability properties and better mechanical properties as compared to biodegradable polymers. Fiber laser cutting of AZ31 magnesium alloy tubes was carried out to study the effect of cutting conditions on wall surface roughness and back-wall dross. During the experiments, an argon gas chamber was adapted in order to avoid material reactivity with oxygen and thus better control the part quality. A surface response methodology was applied to identify the significance of pulse overlapping and pulse energy. Our

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22

Scaggs, W. F., R. P. Taylor, and H. W. Coleman. "Measurement and Prediction of Rough Wall Effects on Friction Factor—Uniform Roughness Results." Journal of Fluids Engineering 110, no. 4 (December 1, 1988): 385–91. http://dx.doi.org/10.1115/1.3243568.

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The results of an experimental investigation of the effects of surface roughness on turbulent pipe flow friction factors are presented and compared with predictions from a previously published discrete element roughness model. Friction factor data were acquired over a pipe Reynolds number range from 10,000 to 600,000 for nine different uniformly rough surfaces. These surfaces covered a range of roughness element sizes, spacings and shapes. Predictions from the discrete element roughness model were in very good agreement with the data.

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23

Straka, Petr, and Jaromír Příhoda. "Extension of the algebraic transition model for the wall roughness effect." EPJ Web of Conferences 114 (2016): 02114. http://dx.doi.org/10.1051/epjconf/201611402114.

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24

Wang, Haoli, Yuan Wang, and Jiazhong Zhang. "Influence of Ribbon Structure Rough Wall on the Microscale Poiseuille Flow." Journal of Fluids Engineering 127, no. 6 (June 25, 2005): 1140–45. http://dx.doi.org/10.1115/1.2060733.

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The regular perturbation method is introduced to investigate the influence of two-dimensional roughness on laminar flow in microchannels between two parallel plates. By superimposing a series of harmonic functions with identical dimensional amplitude as well as the same fundamental wave number, the wall roughness functions are obtained and the relative roughness can be determined as the maximal value of the product between the normalized roughness functions and a small parameter. Through modifying the fundamental wave number, the dimensionless roughness spacing is changed. Under this roughness

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25

Tang, Feng, Yue Zhong Li, and Xiao Ming Guan. "A Study of Velocity Distribution Impact of Wall Roughness on Ultrasonic Gas Flowmeter." Advanced Materials Research 433-440 (January 2012): 349–52. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.349.

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In order to study the effects of velocity distribution of ultrasonic gas flow meter based on wall roughness, , a full developed turbulence model is established based on the theory of prandtl mixing length and flow loss coefficent λ has been calculated by using Colebrook friction correlation formula after analyzing time interval difference measuring method of ultrasonic flow meter. Through Matlab calculating and simulating velocity distribution in different conditions of wall roughness about the model shows and through Fluent simulating, velocity vector and pressure distribution in smooth and r

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26

Gu¨lich, J. F. "Effect of Reynolds Number and Surface Roughness on the Efficiency of Centrifugal Pumps." Journal of Fluids Engineering 125, no. 4 (July 1, 2003): 670–79. http://dx.doi.org/10.1115/1.1593711.

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A procedure has been developed to predict the effects of roughness and Reynolds number on the change in efficiency from a model or baseline to a prototype pump (“efficiency scaling”). The analysis of individual losses takes into account different roughnesses of impeller, diffuser/volute, impeller side disks, and casing walls in the impeller side rooms. The method also allows to predict the effect of roughness and Reynolds number on the hydraulic efficiency. The calculations are based on physical models but the weighting of impeller versus diffuser/volute roughness and the fraction of scalable

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27

Shishkina, Olga, and Claus Wagner. "Modelling the influence of wall roughness on heat transfer in thermal convection." Journal of Fluid Mechanics 686 (September 27, 2011): 568–82. http://dx.doi.org/10.1017/jfm.2011.348.

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AbstractThe objective of this study is to approximate heat transport in thermal convection enhanced by the roughness of heated/cooled horizontal plates. The roughness is introduced by a set of rectangular heated/cooled obstacles located at the corresponding plates. An analytical model to estimate the Nusselt number deviations caused by the wall roughness is developed. It is based on the two-dimensional Prandtl–Blasius boundary layer equations and therefore is valid for moderate Rayleigh numbers and regular wall roughness, for which the height of the obstacles and the distances between them are

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28

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 (November 2, 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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29

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 mo

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Jun, Li, Chunyuan Ma, Wang Tao, Jingcai Chang, and Xiqiang Zhao. "Effects of roughness on the performance of axial flow cyclone separators using numerical simulation method." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 233, no. 7 (February 26, 2019): 914–27. http://dx.doi.org/10.1177/0957650919831892.

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An axial flow cyclone is a separator with high efficiency and low resistance. Researchers have extensively studied the structure and parameters that have the greatest influence on its performance. However, the influence of wall roughness on the performance of axial flow cyclones has been neglected for a long time. The wall roughness height can be changed by the manufacturing process and the effect of particles on the wall. Thus, in this study, the effects of roughness on an axial flow cyclone are investigated using a numerical simulation method. The Reynolds stress model and discrete phase mod

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Li, Lei, Yuliang Su, Han Wang, Guanglong Sheng, and Wendong Wang. "A New Slip Length Model for Enhanced Water Flow Coupling Molecular Interaction, Pore Dimension, Wall Roughness, and Temperature." Advances in Polymer Technology 2019 (December 17, 2019): 1–12. http://dx.doi.org/10.1155/2019/6424012.

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In this paper, a slip length model is proposed to analyze the enhanced flow based on the Hagen–Poiseuille equation. The model considers the multimechanisms including wall-water molecular interactions, pore dimensions, fractal roughness, and temperature. The increasing wall-water interactions result in the greater slip length and flow enhancement factor. The increased temperature enhances the kinetic energy of water molecules that leads to great surface diffusion coefficient and small work of adhesion. The wall roughness can decrease the slip length and flow enhancement factor in hydrophilic na

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32

Lambeth, Christopher, Ziyu Wang, Kristina Kairaitis, Abouzar Moshfegh, Ahmad Jabbarzadeh, and Terence Amis. "Modelling mucosal surface roughness in the human velopharynx: a computational fluid dynamics study of healthy and obstructive sleep apnea airways." Journal of Applied Physiology 125, no. 6 (December 1, 2018): 1821–31. http://dx.doi.org/10.1152/japplphysiol.00233.2018.

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We previously published a unique methodology for quantifying human velopharyngeal mucosal surface topography and found increased mucosal surface roughness in patients with obstructive sleep apnea (OSA). In fluid mechanics, surface roughness is associated with increased frictional pressure losses and resistance. This study used computational fluid dynamics (CFD) to analyze the mechanistic effect of different levels of mucosal surface roughness on velopharyngeal airflow. Reconstructed velopharyngeal models from OSA and control subjects were modified, giving each model three levels of roughness,

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Effendy, Marwan, Yu Feng Yao, and Jun Yao. "Effect of Mesh Topologies on Wall Heat Transfer and Pressure Loss Prediction of a Blade Coolant Passage." Applied Mechanics and Materials 315 (April 2013): 216–20. http://dx.doi.org/10.4028/www.scientific.net/amm.315.216.

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This paper studies the effect of mesh topologies such as hybrid and structured meshes on the evaluation of wall heat transfer coefficient (HTC) and pressure loss of a blade cooling passage. An experimental model is chosen; it has five-row of stream wise staggered elliptical pin-fin fitted inside a 10owedge-shape duct and one-row of fillet circular pin-fin in the exit region. Simulations consider two types; i.e. warm test with isothermal wall condition and cold test with adiabatic wall condition respectively, in order to evaluate flow and thermal characteristics such as HTC and pressure loss. F

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34

Boulle, A., I. C. Infante, and N. Lemée. "Diffuse X-ray scattering from 180° ferroelectric stripe domains: polarization-induced strain, period disorder and wall roughness." Journal of Applied Crystallography 49, no. 3 (May 4, 2016): 845–55. http://dx.doi.org/10.1107/s1600576716005331.

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A key element in ferroic materials is the presence of walls separating domains with different orientations of the order parameter. It is demonstrated that 180° stripe domains in ferroelectric films give rise to very distinct features in their diffuse X-ray scattering (DXS) intensity distributions. A model is developed that allows the determination of not only the domain period but also the period disorder, the thickness and roughness of the domain walls, and the strain induced by the rotation of the polarization. As an example, the model is applied to ferroelectric/paraelectric superlattices.

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35

Lin, Jian-Hung, and Keh-Chin Chang. "A Modeling Study on Particle Dispersion in Wall-Bounded Turbulent Flows." Advances in Applied Mathematics and Mechanics 6, no. 06 (December 2014): 764–82. http://dx.doi.org/10.4208/aamm.2014.m533.

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AbstractThree physical mechanisms which may affect dispersion of particle’s motion in wall-bounded turbulent flows, including the effects of turbulence, wall roughness in particle-wall collisions, and inter-particle collisions, are numerically investigated in this study. Parametric studies with different wall roughness extents and with different mass loading ratios of particles are performed in fully developed channel flows with the Eulerian-Lagrangian approach. A low-Reynolds-numberk–εturbulence model is applied for the solution of the carrier-flow field, while the deterministic Lagrangian me

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Aupoix, B., and P. R. Spalart. "Extensions of the Spalart–Allmaras turbulence model to account for wall roughness." International Journal of Heat and Fluid Flow 24, no. 4 (August 2003): 454–62. http://dx.doi.org/10.1016/s0142-727x(03)00043-2.

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Hu, Ya Lun, Zheng Li, and Zhong Xu. "Simulation of Microbubbles Drag Reduction on Nonsmooth Surface with Hydrophobic Property." Applied Mechanics and Materials 300-301 (February 2013): 3–9. http://dx.doi.org/10.4028/www.scientific.net/amm.300-301.3.

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The friction resistance accounts for a large proportion of the total resistance, during the navigation of ships and underwater vehicles. Drag reduction techniques can significantly reduce the friction resistance of the wall and improve the speed of navigation. This paper combine microbubbles drag reduction technology and nonsmooth and hydrophobic surface technology. Building different analysis models, considering the dimples size of nonsmooth surface , the contact angle of surface and wall roughness, study the law between drag reduction and parameters of the wall by gas-liquid two-phase flow m

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Kleinstreuer, C., and J. Koo. "Computational Analysis of Wall Roughness Effects for Liquid Flow in Micro-Conduits." Journal of Fluids Engineering 126, no. 1 (January 1, 2004): 1–9. http://dx.doi.org/10.1115/1.1637633.

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Fluid flow in microchannels or microtubes may differ in terms of wall frictional effects, and hence flow rates, when compared to macrochannels. Focusing on steady laminar fully developed flow of a liquid in different micro-conduits, relative surface roughness is captured in terms of a porous medium layer (PML) model. The new approach allows the evaluation of microfluidics variables as a function of PML characteristics, i.e., layer thickness and porosity, uncertainties in measuring hydraulic diameters as well as the inlet Reynolds number. Specifically, realistic values for the PML Darcy number,

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Li, Mingzhong, Chunting Liu, and Guodong Zhang. "Calibration of the Interaction Parameters between the Proppant and Fracture Wall and the Effects of These Parameters on Proppant Distribution." Energies 13, no. 8 (April 23, 2020): 2099. http://dx.doi.org/10.3390/en13082099.

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Saltation and reputation (creep) dominate proppant transport rather than suspension during slickwater fracturing, due to the low sand-carrying capacity of the slickwater. Thus, the interaction parameters between proppants and fracture walls, which affect saltation and reputation, play a more critical role in proppant transport. In this paper, a calibration method for the interaction parameters between proppants and walls is built. A three-dimensional coupled computational fluid dynamics–discrete element method (CFD–DEM) model is established to study the effects of the interaction parameters on

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Singh, Kalyan Kumar, and Dhiraj Kumar. "Experimental investigation and modelling of drilling on multi-wall carbon nanotube–embedded epoxy/glass fabric polymeric nanocomposites." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 232, no. 11 (December 20, 2016): 1943–59. http://dx.doi.org/10.1177/0954405416682277.

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The primary objective of this research is to investigate the effect of multi-wall carbon nanotubes on drilling of multi-wall carbon nanotube–embedded epoxy/glass fabric polymeric nanocomposites. The experiments were conducted on composites with varying the weight percentage of multi-wall carbon nanotubes content to analyse drilling-induced delamination and surface roughness, which affect the quality and property of the drilled holes. The drilling parameters considered are spindle speed, feed rate and drill diameter. The microstructure of the holes was characterized using field emission scannin

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Cui, Jie, Virendra C. Patel, and Ching-Long Lin. "Prediction of Turbulent Flow Over Rough Surfaces Using a Force Field in Large Eddy Simulation." Journal of Fluids Engineering 125, no. 1 (January 1, 2003): 2–9. http://dx.doi.org/10.1115/1.1524587.

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A force field model to simulate turbulent flow over a surface with arbitrary roughness is described. A given roughness is decomposed into resolved and subgrid-scale roughness, conceptually similar to the flow decomposition in large eddy simulation (LES). For a given flow and Reynolds number, a Cartesian grid is selected to satisfy LES requirements. This grid determines the geometric features of the roughness that are formally resolved. The force field used to represent this resolved roughness is determined during the LES solution process, without any empirical input. The subgrid roughness that

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Cavar, Dalibor, Pierre-Elouan Réthoré, Andreas Bechmann, Niels N. Sørensen, Benjamin Martinez, Frederik Zahle, Jacob Berg, and Mark C. Kelly. "Comparison of OpenFOAM and EllipSys3D for neutral atmospheric flow over complex terrain." Wind Energy Science 1, no. 1 (May 20, 2016): 55–70. http://dx.doi.org/10.5194/wes-1-55-2016.

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Abstract. The flow solvers OpenFOAM and EllipSys3D are compared in the case of neutral atmospheric flow over terrain using the test cases of Askervein and Bolund hills. Both solvers are run using the steady-state Reynolds-averaged Navier–Stokes k–ϵ turbulence model. One of the main modeling differences between the two solvers is the wall-function approach. The OpenFOAM v.1.7.1 uses a Nikuradse's sand roughness model, while EllipSys3D uses a model based on the atmospheric roughness length. It is found that Nikuradse's model introduces an error dependent on the near-wall cell height. To mitigate

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Robertson, Iain, Adrien Becot, Adrian Gaylard, and Ben Thornber. "Automotive Drag Reduction through Distributed Base Roughness Elements." Applied Mechanics and Materials 553 (May 2014): 267–72. http://dx.doi.org/10.4028/www.scientific.net/amm.553.267.

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This paper focuses on the effect of base roughness added to the rear of an automotive reference model, the Windsor model. This roughness addition was found to reduce both the drag and the lift of the model. RANS CFD simulations presented here replicate the experimentally observed drag reduction and enable a detailed examination of the mechanisms behind this effect. Investigations into the wake structure of the configurations with base roughness and the baseline case without base roughness showed the main changes to the wake to include a reduction in the overall size of the wake with base rough

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Bavière, R., G. Gamrat, M. Favre-Marinet, and S. Le Person. "Modeling of Laminar Flows in Rough-Wall Microchannels." Journal of Fluids Engineering 128, no. 4 (November 22, 2005): 734–41. http://dx.doi.org/10.1115/1.2201635.

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Numerical modeling and analytical approach were used to compute laminar flows in rough-wall microchannels. Both models considered the same arrangements of rectangular prism rough elements in periodical arrays. The numerical results confirmed that the flow is independent of the Reynolds number in the range 1–200. The analytical model needs only one constant for most geometrical arrangements. It compares well with the numerical results. Moreover, both models are consistent with experimental data. They show that the rough elements drag is mainly responsible for the pressure drop across the channe

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Bou-Zeid, Elie, Marc B. Parlange, and Charles Meneveau. "On the Parameterization of Surface Roughness at Regional Scales." Journal of the Atmospheric Sciences 64, no. 1 (January 1, 2007): 216–27. http://dx.doi.org/10.1175/jas3826.1.

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Abstract A parameterization for surface roughness and blending height at regional scales, under neutral atmospheric stability, is studied and tested. The analysis is based on a suite of large-eddy simulations (LES) over surfaces with varying roughness height and multiple variability scales. The LES are based on the scale-dependent Lagrangian dynamic subgrid-scale model, and the surface roughnesses at the ground are imposed using the rough-wall logarithmic law. Several patterns of roughness distribution are considered, including random tiling of patches with a wide distribution of length scales

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MacDonald, M., D. Chung, N. Hutchins, L. Chan, A. Ooi, and R. García-Mayoral. "The minimal-span channel for rough-wall turbulent flows." Journal of Fluid Mechanics 816 (February 28, 2017): 5–42. http://dx.doi.org/10.1017/jfm.2017.69.

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Roughness predominantly alters the near-wall region of turbulent flow while the outer layer remains similar with respect to the wall shear stress. This makes it a prime candidate for the minimal-span channel, which only captures the near-wall flow by restricting the spanwise channel width to be of the order of a few hundred viscous units. Recently, Chung et al. (J. Fluid Mech., vol. 773, 2015, pp. 418–431) showed that a minimal-span channel can accurately characterise the hydraulic behaviour of roughness. Following this, we aim to investigate the fundamental dynamics of the minimal-span channe

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Lin, J. H., and K. C. Chang. "Particle Dispersion Simulation in Turbulent Flow Due to Particle-Particle and Particle-Wall Collisions." Journal of Mechanics 32, no. 2 (August 19, 2015): 237–44. http://dx.doi.org/10.1017/jmech.2015.63.

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AbstractSimulation of the 3-D, fully developed turbulent channel flows laden with various mass loading ratios of particles is made using an Eulerian-Lagrangian approach in which the carrier-fluid flow field is solved with a low-Reynolds-number k-ε turbulence model while the deterministic Lagrangian method together with binary-collision hard-sphere model is applied for the solution of particle motion. Effects of inter-particle collisions and particle-wall collisions under different extents of wall roughness on particle dispersion are addressed in the study. A cost-effective searching algorithm

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Shukla, R., S. S. Bhatt, A. Medhavi, and R. Kumar. "Effect of Surface Roughness during Peristaltic Movement in a Nonuniform Channel." Mathematical Problems in Engineering 2020 (July 15, 2020): 1–8. http://dx.doi.org/10.1155/2020/9643425.

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In this study, the effect of the roughness parameter during the peristaltic transport of a Newtonian fluid in a nonuniform channel has been explored. The motivation of this study comes from various research studies in the area of life sciences and engineering, which reveal that the wall of living beings’ arteries and all other surfaces have roughness to some extent. As peristalsis is a major mode of transporting biological fluids in various organs, the effect of surface roughness during peristaltic flow becomes very significant. The problem of peristaltic motion of a Newtonian fluid through a

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He, Ning, and Bin Qin. "Influence Analysis of Roadway Friction on Shock Wave Attenuation." Applied Mechanics and Materials 178-181 (May 2012): 1619–22. http://dx.doi.org/10.4028/www.scientific.net/amm.178-181.1619.

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Friction is the extremely important factor when considering the interaction between the shock wave and the tunnel wall. But so far, the impact of wall friction on the shock wave is mainly measured by experimental methods. This paper mainly discusses the effect of wall friction on the shock wave attenuation, without considering roughness, roughness elements, the viscosity of air, and the complex relationship between them; the numerical simulation calculation model is established with DYNA calculation software; the influence law of friction coefficient on tunnel shock wave propagation and attenu

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Bons, Jeffrey P., and Stephen T. McClain. "The Effect of Real Turbine Roughness With Pressure Gradient on Heat Transfer." Journal of Turbomachinery 126, no. 3 (July 1, 2004): 385–94. http://dx.doi.org/10.1115/1.1738120.

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Experimental measurements of heat transfer (St) are reported for low speed flow over scaled turbine roughness models at three different freestream pressure gradients: adverse, zero (nominally), and favorable. The roughness models were scaled from surface measurements taken on actual, in-service land-based turbine hardware and include samples of fuel deposits, TBC spallation, erosion, and pitting as well as a smooth control surface. All St measurements were made in a developing turbulent boundary layer at the same value of Reynolds number Rex≅900,000. An integral boundary layer method used to e

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