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Journal articles on the topic 'Relative roughness height'

Author: Grafiati

Published: 3 June 2025

Last updated: 31 July 2025

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1

Kalpana, Soni*1 &. Surendra Bharti2. "CFD ANALYSIS OF SOLAR AIR HEATER FOR ENHANCEMENT OF HEAT TRANSFER." INTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCH TECHNOLOGY 6, no. 6 (2017): 430–44. https://doi.org/10.5281/zenodo.814587.

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Energy is the basic ingredient to sustain life and development. Work means moving or lifting something, warming or lighting something. There are many sources of energy that help to run the various machines invented by man.A 3-dimensional CFD analysis has been carried out to study heat transfer and fluid flow behavior in a rectangular duct of a solar air heater with one roughened wall having combination of circularand square transverse wire rib roughness. The effect of Reynolds number, roughness height, roughness pitch, relative roughness pitch and relative roughness height on the heat transfer

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2

Wang, Hong Cai, and Yang Wang. "The Height Amplitudes of Surface Roughness Based on Area-Direction Character and Relative Assessed Indexes." Advanced Materials Research 482-484 (February 2012): 1150–54. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.1150.

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To study the relationship among the height amplitude of surface roughness , assessed area and assessed direction, the height amplitudes SRa, SRq, SRsk and SRku based on area-direction character are defined in the paper. And on the foundation of these parameters, relative assessed area indexes, assessed direction indexes and assessed total indexes are established. SRa, SRq, SRsk and SRku are the natural extension of 2D height amplitudes Ra, Rq, Rsk and Rku. They are different from 3D height amplitudes Sa, Sq, Ssk and Sku. They provide an evidence to study the quantitative relationship among sur

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3

Mishra, Arin, Aman Mehrotra, and S. Senthur Prabu. "Study on Performance Analysis of a Solar Air Heater with Aerofoil Shaped Rib Roughness Using CFD." ECS Transactions 107, no. 1 (2022): 16065–79. http://dx.doi.org/10.1149/10701.16065ecst.

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Present study investigates the heat transfer, friction factor and fluid flow characteristics of fully developed turbulent flow in a rectangular duct of solar air heater having aerofoil shaped rib-roughness on underside of absorber plate. ANSYS 14.5 has been used to simulate air flow through roughened air heater duct. Effect of relative roughness height and roughness pitch on Nusselt number and friction factor of roughened duct have been investigated and compared with that of smooth duct. It is found that the Nusselt number improves by attaching the roughness. Maximum enhancement in Nusselt num

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4

Ajay, Jain, and H. S. Sahu Prof. "CFD Analysis of Solar Air Heater for Enhancenment of Heat Transfer Through Inclined Rib Roughness." International Journal of Trend in Scientific Research and Development 3, no. 1 (2018): 662–67. https://doi.org/10.31142/ijtsrd19057.

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A 3 dimensional CFD analysis has been carried out of solar air heater to study heat transfer and fluid flow behavior in a rectangular duct of a solar air heater with one roughened wall having combination of circular and square transverse wire rib roughness. The effect of Reynolds number, roughness height, roughness pitch, relative roughness pitch and relative roughness height on the heat transfer coefficient and friction factor have been studied. In order to validate the present numerical model, results have been compared with available experimental results under similar flow conditions. CFD I

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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

Yadav, Anil Singh, and J. L. Bhagoria. "Modeling and Simulation of Turbulent Flows through a Solar Air Heater Having Square-Sectioned Transverse Rib Roughness on the Absorber Plate." Scientific World Journal 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/827131.

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Solar air heater is a type of heat exchanger which transforms solar radiation into heat energy. The thermal performance of conventional solar air heater has been found to be poor because of the low convective heat transfer coefficient from the absorber plate to the air. Use of artificial roughness on a surface is an effective technique to enhance the rate of heat transfer. A CFD-based investigation of turbulent flow through a solar air heater roughened with square-sectioned transverse rib roughness has been performed. Three different values of rib-pitch (P) and rib-height (e) have been taken s

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7

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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8

Hu, Yandong, Carsten Werner, and Dongqing Li. "Influence of Three-Dimensional Roughness on Pressure-Driven Flow Through Microchannels." Journal of Fluids Engineering 125, no. 5 (2003): 871–79. http://dx.doi.org/10.1115/1.1598993.

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Surface roughness is present in most of the microfluidic devices due to the microfabrication techniques or particle adhesion. It is highly desirable to understand the roughness effect on microscale flow. In this study, we developed a three-dimensional finite-volume-based numerical model to simulate pressure-driven liquid flow in microchannels with rectangular prism rough elements on the surfaces. Both symmetrical and asymmetric roughness element arrangements were considered, and the influence of the roughness on pressure drop was examined. The three-dimensional numerical solution shows signifi

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9

Behura, Aruna Kumar, Chinmaya Prasad Mohanty, Manas Ranjan Singh, Ashwini Kumar, Emanoil Linul, and Dipen Kumar Rajak. "Performance Analysis of Three Side Roughened Solar Air Heater: A Preliminary Investigation." Materials 15, no. 7 (2022): 2541. http://dx.doi.org/10.3390/ma15072541.

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In recent years, sunlight has been used in several fields such as photovoltaic cells, flat plate collectors, solar cookers, green buildings, and agricultural applications. Improved thermal performance has been seen which comes of three sides absorber plate with glass cover compared to the traditional one. This paper presents the Nusselt (Nu) number, collector efficiency factor (CEF), and collector heat removal factor (CHRF) for the optimal solution of three sides artificially roughened solar air heater. Five input variables such as Reynolds (Re) number, relative roughness pitch, relative rough

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10

HABIB, Saqib, Norio TANAKA, and Yuta YOSHIZAWA. "OPEN CHANNEL TURBULENCE CHARACTERISTICS IN A ROUGHNESS LAYER FOR SMALL WATER DEPTH RELATIVE TO ROUGHNESS ELEMENTS HEIGHT." Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 72, no. 4 (2016): I_511—I_516. http://dx.doi.org/10.2208/jscejhe.72.i_511.

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11

Benabid, Seyfeddine, Sonia Cherhabil, Abdelkader Ouakouak, and Ali Bedjaoui. "Characteristics of hydraulic jump in asymmetrical trapezoidal channel with rough beds: experimental investigations." STUDIES IN ENGINEERING AND EXACT SCIENCES 5, no. 2 (2024): e11610. https://doi.org/10.54021/seesv5n2-630.

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Understanding the dynamics of hydraulic jumps is crucial for optimizing the design of stilling basins in dams, enhancing energy dissipation efficiency, and reducing corrosion risks in hydraulic structures. This work aims to investigate the effect of bed geometry and roughness on the properties of hydraulic jump in an asymmetric trapezoidal channel, including parameters such as sequential depths, roller length and energy loss. Experiments were carried out under open channel flow conditions using three different bottom roughness element heights and mm. The channel's bottom is inclined transverse

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12

Chan, L., M. MacDonald, D. Chung, N. Hutchins, and A. Ooi. "A systematic investigation of roughness height and wavelength in turbulent pipe flow in the transitionally rough regime." Journal of Fluid Mechanics 771 (April 27, 2015): 743–77. http://dx.doi.org/10.1017/jfm.2015.172.

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Direct numerical simulations (DNS) are conducted for turbulent flow through pipes with three-dimensional sinusoidal roughnesses explicitly represented by body-conforming grids. The same viscous-scaled roughness geometry is first simulated at a range of different Reynolds numbers to investigate the effects of low Reynolds numbers and low $R_{0}/h$, where $R_{0}$ is the pipe radius and $h$ is the roughness height. Results for the present class of surfaces show that the Hama roughness function ${\rm\Delta}U^{+}$ is only marginally affected by low Reynolds numbers (or low $R_{0}/h$), and observati

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13

YANG, SHANSHAN, HUAHUA FU, and BOMING YU. "FRACTAL ANALYSIS OF FLOW RESISTANCE IN TREE-LIKE BRANCHING NETWORKS WITH ROUGHENED MICROCHANNELS." Fractals 25, no. 01 (2017): 1750008. http://dx.doi.org/10.1142/s0218348x17500086.

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In this work, the effective average height of the roughness elements, the relative increase of the pressure gradients, the relative decrease of the permeability are derived based on the fractal geometry theory and technique for laminar flow through tree-like branching networks with roughened channels. The relationships among the effective average height, the structural parameters and pressure drops as well as permeability are studied. It is found that the total pressure drop across a tree-like branching network with roughened channels is increased by a factor of [Formula: see text], and the pe

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14

Ajay, Jain, and S. Sahu H. "CFD Analysis of Solar Air Heater Provided with Discrete Inclined Rib Roughness on the Absorber Plate A Review." International Journal of Trend in Scientific Research and Development 2, no. 6 (2018): 703–6. https://doi.org/10.31142/ijtsrd18686.

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Heat transfer enhancement is a subject of considerable interest to researchers as it leads to saving in energy and cost. Because of the rapid increase in energy demand in all over The world, both reducing energy lost related with ineffective use and enhancement of energy in the meaning of heat have become an increasingly significance task for design and operation engineers for many system. A 3 dimensional CFD analysis has been carried out to study heat transfer and fluid flow behavior in a rectangular duct of a solar air heater with one roughened wall having discrete inclined rib roughness. Th

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15

Shiba, Shamiran Jargess, Naeema Thaher Aaref, and Shaker A. Jalil. "Properties of Hydraulic Jump on Horizontal Rough Beds." Zanin Journal of Science and Engineering 1, no. 2 (2025): 01–09. https://doi.org/10.64362/zjse.22.

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Hydraulic jumps are essential for dissipating the kinetic energy of high-velocity flows downstream of hydraulic structures such as spillways, drops, chutes, and gates. Effective energy dissipation is critical to prevent scouring and structural damage, and one of the most influential factors in enhancing this dissipation is the roughness of the stilling basin floor. This study investigates how varying bed roughness affects hydraulic jump characteristics in open channel flow. Five-bed conditions were tested, including a smooth surface and four different gravel bed roughness heights: 1.13 cm, 1.5

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16

Kiran Kumar. B et al.,, Kiran Kumar B. et al ,. "Study of Relative Roughness Pitch and Height on Heat Transfer Coefficient of Solar Air Heater with Artificial Roughness." International Journal of Mechanical and Production Engineering Research and Development 8, no. 5 (2018): 409–16. http://dx.doi.org/10.24247/ijmperdoct201846.

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17

Ding, Lei, and Qing-He Zhang. "LATTICE BOLTZMANN SIMULATION TO CHARACTERIZE ROUGHNESS EFFECTS OF OSCILLATORY BOUNDARY LAYER FLOW OVER A ROUGH BED." Coastal Engineering Proceedings 1, no. 32 (2011): 3. http://dx.doi.org/10.9753/icce.v32.sediment.3.

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The 3-D lattice Boltzmann method was applied to characterize roughness effects of oscillatory boundary layer flow over a rough bed. The direct numerical simulation was carried out and the flow resistance of the flat and fixed bed was investigated. The position of the theoretical bed, equivalent roughness height and the behavior of friction factor at small values of relative roughness were obtained using the log-fit method.

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18

Wang, Zhihui, Xuguang Yang, Xiaohua Gu, et al. "Investigating Enhanced Convection Heat Transfer in 3D Micro-Ribbed Tubes Using Inverse Problem Techniques." Energies 17, no. 20 (2024): 5102. http://dx.doi.org/10.3390/en17205102.

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The improved heat dissipation observed in 3D micro-ribbed tubes is primarily influenced by the intricate interplay of multiple structural parameters. Nevertheless, research into the coupling mechanisms of these multi-structural parameters remains constrained by the absence of effective methodology in numerical solutions. In the present work, a new 3D micro-rib structure based on discrete adjoint method is established. Firstly, the research examines the interplay of different parameters (such as arrangement, relative roughness height, angle of attack, and circumferential rows) on the thermo-hyd

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19

Hans, V. S., R. S. Gill, and Rupinderpal Singh. "Effect of rib roughness pitch on thermal and thermo-hydraulic performance of a solar air heater roughened artificially with arc rib having gap." Journal of Applied and Natural Science 8, no. 1 (2016): 251–56. http://dx.doi.org/10.31018/jans.v8i1.782.

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This experimental study on a solar air heater having absorber plate roughened artificially by providing roughness in the form of arc ribs having gap was carried out in the Department of Mechanical Engineering, Punjab Agricultural University, Ludhiana, India to study the effect of relative roughness pitch on thermal and thermohydraulic performance as well as to compare the performance of arc rib with gap roughened solar air heater with that of continuous arc rib roughened solar air heater. The roughness geometry parameters included relative roughness height of 0.043, angle of attack of 30 degre

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20

Dejam, Morteza, Hassan Hassanzadeh, and Zhangxin Chen. "Shear Dispersion in a Rough-Walled Fracture." SPE Journal 23, no. 05 (2018): 1669–88. http://dx.doi.org/10.2118/189994-pa.

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Summary An expression is analytically presented for the shear dispersion, or Taylor (1953) and Aris (1956) dispersion, of a solute transporting in a coupled system, which consists of a matrix and a rough-walled fracture. To derive a shear-dispersion coefficient in a fracture with rough and porous walls, the continuities of solute concentrations and their fluxes are imposed at the fracture walls. The dispersion coefficient for the coupled system is obtained as a function of the Péclet number and relative roughness, where the latter parameter is defined as the ratio of the maximum height of the

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21

Stalin, P. Michael Joseph, R. Lokanadham, Gaddam Naveen, et al. "Innovative cinque rib-roughened stimulators on performance improvement in triangular channel solar air heater." International Journal of Low-Carbon Technologies 19 (2024): 224–32. http://dx.doi.org/10.1093/ijlct/ctae002.

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Abstract Present study investigates application of cinque-faced rib roughening to improve the efficiency of solar air heaters (SAHs). Research focuses on a novel design, the cinque-faced rib-roughened triangular channel SAH (CFRTCSAH), which incorporates five-faced wire ribs on the absorber plate’s underside. By breaking down the laminar sublayer and enhancing flow separation and reattachment, - ribs significantly enhance heat transfer. It establishes a comprehensive theoretical model to analyze the thermal and hydraulic performance of the CFRTCSAH. The study considers the influence of paramet

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22

Yang, X., R. Y. Gu, D. Y. Xing, Z. D. Wang, and Jinming Dong. "Tunneling Magnetoresistance in Ferromagnet/Insulator/Ferromagnet Junctions." International Journal of Modern Physics B 11, no. 28 (1997): 3375–84. http://dx.doi.org/10.1142/s0217979297001659.

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A δ-type potential with complex prefactor is modeled on the tunneling barrier of a thin insulator (I) film separating two ferromagnetic (FM) films. By matching value and slope of wave functions across the tunneling barrier of a FM/I/FM junction, we obtain a general expression for tunneling conductance as a function of relative orientation θ between magnetizations of the two ferromagnets, barrier height and interface roughness. It is shown that the magnitude of tunneling magnetoresistance is strongly dependent on θ, but much less affected by the barrier height and the interface roughness.

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Ghaderi, Amir, Mehdi Dasineh, Francesco Aristodemo, and Ali Ghahramanzadeh. "Characteristics of free and submerged hydraulic jumps over different macroroughnesses." Journal of Hydroinformatics 22, no. 6 (2020): 1554–72. http://dx.doi.org/10.2166/hydro.2020.298.

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Abstract The present study deals with numerical simulations of the free and submerged hydraulic jumps over different shapes of roughness in various roughness arrangements and different Froude number conditions. The models were studied using three roughness shapes, i.e. triangular, square and semi-oval for 0.2 &lt; T/I &lt; 0.5, where T and I are height and distance of roughness, respectively. The results showed that the numerical model is fairly well able to simulate the free and submerged jump characteristics. The effect of roughness plays a role in the reduction of the relative maxim

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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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Sayyadi, Keikhosro, Manouchehr Heidarpour, and Zahra Ghadampour. "Effect of Bed Roughness and Negative Step on Characteristics of Hydraulic Jump in Rectangular Stilling Basin." Shock and Vibration 2022 (August 5, 2022): 1–9. http://dx.doi.org/10.1155/2022/1722065.

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Water flow often releases excess energy after passing through gates and spillways. This energy should be reduced to avoid the destruction of downstream structures. The hydraulic jump, a natural phenomenon, inevitably reduces incoming flow energy. The experiments were carried out in this study to investigate the effect of bed roughness and abrupt negative drops on the characteristics of the hydraulic jump. Also, to investigate the effect of geometric and hydraulic parameters on energy dissipation and location of the hydraulic jump, there was a change in the height of the abrupt drop and roughne

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Rana, Jitesh, Anshuman Silori, Rajesh Maithani, and Sunil Chamoli. "Computational fluid dynamics analysis of a V-rib with gap roughened solar air heater." Thermal Science 22, no. 2 (2018): 963–72. http://dx.doi.org/10.2298/tsci160831010r.

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A CFD analysis of a solar air heater has been carried out using V-shaped ribs as artificial roughness on the absorber plate. The relative roughness pitch, P/e = 6-12, Reynolds number of 3800-18000, relative roughness height, e/D = = 0.042, and angle of attack, ? = 30?-75?, have been selected as design variables of V-shaped rib for analysis. The ANSYS FLUENT 15.0 with renormalization group k-? turbulence model is selected for the analysis of computational domain of solar air heater. The enhancement of Nusselt number and friction factor with Reynolds number for different values of a relative rou

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27

Şevik, Seyfi, Özgür Özdilli, and Mesut Abuşka. "Experimental investigation of relative roughness height effect in solar air collector with convex dimples." Renewable Energy 194 (July 2022): 100–116. http://dx.doi.org/10.1016/j.renene.2022.05.088.

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Carvalho, Gabriel Ferraz Marcondes de, Marília Fernandes Vidille, Alex Mendonça Bimbato, and Luiz Antonio Alcântara Pereira. "Lagrangian Vortices Interactions Using Large-Eddy Simulation (LES) and Surface Roughness Model—Application for Aircraft Wake Vortices with Crosswind." Applied Sciences 13, no. 22 (2023): 12336. http://dx.doi.org/10.3390/app132212336.

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A new technique for two-dimensional vortex methods is presented. The vorticity field is discretized and represented by vortex blobs. Viscosity and roughness are incorporated into vortex simulations by means of the corrected core-spreading method with LES theory. A deterministic and efficient grid-free method simulates viscous effects by maintaining small vortex core sizes through a splitting algorithm that controls the consistency error. The LES theory also enables the implementation of the roughness model. The effectiveness of this method is shown in calculating vortex interactions and decay

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Saleh, Layla A. M., and Saleh I. Khassaf. "Evaluating the Hydraulic Performance of USBR II Stilling Basin with Rough Bed." Tikrit Journal of Engineering Sciences 31, no. 3 (2024): 93–104. http://dx.doi.org/10.25130/tjes.31.3.9.

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Stilling basins are built in conjunction with dams, weirs, and gates to dissipate the high kinetic energy of incoming flow and prevent severe scouring of the downstream riverbed. Dissipation of this high energy can be achieved through forming a hydraulic jump. The hydraulic jump features, including the relative length, ratio of sequent depth, and energy dissipation, are utilized as criteria to evaluate the efficiency of the stilling basin operation. The present study involved conducting experimental and numerical tests to evaluate the performance of the USBR II stilling basin downstream of an

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Prasad, Radha K., and Mukesh K. Sahu. "Entropy generation and thermodynamic analysis of solar air heaters with artificial roughness on absorber plate." Archives of Thermodynamics 38, no. 3 (2017): 23–48. http://dx.doi.org/10.1515/aoter-2017-0014.

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AbstractThis paper presents mathematical modelling and numerical analysis to evaluate entropy generation analysis (EGA) by considering pressure drop and second law efficiency based on thermodynamics for forced convection heat transfer in rectangular duct of a solar air heater with wire as artificial roughness in the form of arc shape geometry on the absorber plate. The investigation includes evaluations of entropy generation, entropy generation number, Bejan number and irreversibilities of roughened as well as smooth absorber plate solar air heaters to compare the relative performances. Furthe

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Kanda, M., M. Kanega, T. Kawai, R. Moriwaki, and H. Sugawara. "Roughness Lengths for Momentum and Heat Derived from Outdoor Urban Scale Models." Journal of Applied Meteorology and Climatology 46, no. 7 (2007): 1067–79. http://dx.doi.org/10.1175/jam2500.1.

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Abstract Urban climate experimental results from the Comprehensive Outdoor Scale Model (COSMO) were used to estimate roughness lengths for momentum and heat. Two different physical scale models were used to investigate the scale dependence of the roughness lengths; the large scale model included an aligned array of 1.5-m concrete cubes, and the small scale model had a geometrically similar array of 0.15-m concrete cubes. Only turbulent data from the unstable boundary layers were considered. The roughness length for momentum relative to the obstacle height was dependent on wind direction, but t

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Ogar, P. M., V. A. Tarasov, and D. B. Gorokhov. "The Influence of Coating Thickness on the Relative Area of Tribounits Contact." Advanced Materials Research 1061-1062 (December 2014): 614–18. http://dx.doi.org/10.4028/www.scientific.net/amr.1061-1062.614.

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The contact of a rigid rough surface and an elastic layered half-space which consists of coating with thickness δ1 and the substrate. To determine the dependence of the relative contact area on dimensionless the force elastic geometrical parameter , the discrete roughness model presented by microasperities in the form of equal spherical segments with the height distribution corresponding to the bearing profile curve of the real surface is used. By using the stiffness model of layered half-space, the elastic characteristics for every each contacting asperity are determined. The system of transc

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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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Ogar, Peter, Yurij Alpatov, and Denis Gorokhov. "Relative contact area in metal-polymer joints." MATEC Web of Conferences 224 (2018): 02051. http://dx.doi.org/10.1051/matecconf/201822402051.

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The paper is devoted to the specification of the parameters of Bartenev-Lavrentiev’s empirical dependence for the relative area of contact with taking into account the mutual influence of asperities. The relative contact area is determined using a discrete roughness model for a wide range of distributions of the peaks of the asperities in the rough layer. It is shown that when determining the relative contact area, the distribution of the asperities in height practically does not affect the final result, since the obtained dependences coincide. This fact allowed us to determine the parameters

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Akutina, Yulia, Frédéric Moulin, Maxime Rouzes, and Olivier Eiff. "Flow structures in a shallow channel with lateral bed-roughness variation." E3S Web of Conferences 40 (2018): 02051. http://dx.doi.org/10.1051/e3sconf/20184002051.

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Highly heterogeneous floodplains can give rise to secondary flow structures responsible for the bulk of lateral momentum exchange. Quantifying the redistribution of momentum is required to predict lateral profiles of flow velocity and the associated water level in a river. In the work herein, we focus on studying secondary flow structures and the momentum redistribution associated with a lateral bed-roughness variation in a channel with low relative submergence of the roughness elements, h=k = 3, 2 and 1.5, where h is the flow depth and k is the roughness height. A series of laboratory experim

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Li, Shuolin, Haoran Shi, Zhengwei Xiong, Wenxin Huai, and Niansheng Cheng. "New formulation for the effective relative roughness height of open channel flows with submerged vegetation." Advances in Water Resources 86 (December 2015): 46–57. http://dx.doi.org/10.1016/j.advwatres.2015.09.018.

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Mitsuya, Y. "Stokes Roughness Effects on Hydrodynamic Lubrication. Part II—Effects Under Slip Flow Boundary Conditions." Journal of Tribology 108, no. 2 (1986): 159–66. http://dx.doi.org/10.1115/1.3261154.

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Stokes roughness effects on hydrodynamic lubrication are studied in the slip flow regime. Slip flow boundary conditions for Navier-Stokes equations are derived, assuming that the fluid on a surface slips due to the molecular mean free path along the surface, even if the surface is rough. The perturbation method for Navier-Stokes equations, which was derived in Part I of this report, is then applied. Slip flow effects on load carrying capacity and frictional force are numerically clarified for both Stokes and Reynolds roughnesses. In the slip flow regime, second-order quantities induced by Stok

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Williams, H. H., A. K. Aiyer, L. Deike, and M. E. Mueller. "Examining relative impacts of atmospheric and oceanic factors on offshore wind farms." Journal of Physics: Conference Series 2767, no. 6 (2024): 062001. http://dx.doi.org/10.1088/1742-6596/2767/6/062001.

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Abstract Accurate understanding and prediction of how ocean waves affect offshore wind farms are critical to their siting, design, and operation. This study presents a computational framework for simulating finite offshore wind farms using Large Eddy Simulation (LES) and a Dynamic Wave Spectrum Model (Dyn-WaSp). Implementation of the Dyn-WaSp with and without a correction for swell modes is compared to a static roughness (wave phase-averaged) model, which has a similar computational cost. Impacts of the different wave models on the wind’s mean velocity and turbulent kinetic energy profiles in

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Tian, Hong, and Takeo Matsudaira. "The Role of Relative Humidity, Surface Roughness and Liquid Build-Up on Static Friction Behavior of the Head/Disk Interface." Journal of Tribology 115, no. 1 (1993): 28–35. http://dx.doi.org/10.1115/1.2920983.

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Stiction at the head/disk interface has become one of the major concerns as smoother surfaces are required to achieve lower flying heights of magnetic heads over magnetic disks. In this paper, static friction forces on three types of disk samples with different surface roughness values were measured at various relative humidities. It was found that static friction coefficients were well correlated with total thickness of liquid (lubricant and adsorbed water) at the head/disk interface. The experimental data also agreed fairly well with the calculated values based on a proposed stiction model.

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Hunt, Sherry L., Kem C. Kadavy, Tony L. Wahl, and Dana W. Moses. "Physical Modeling of Beveled-Face Stepped Chute." Water 14, no. 3 (2022): 365. http://dx.doi.org/10.3390/w14030365.

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New construction practices for roller compacted concrete (RCC) overlays and stepped chutes are changing the step geometry from a traditional square-edge, vertical face to a 45° beveled face. A large-scale 3(H):1(V) (i.e., θ = 18.4°) stepped chute model was tested with a 45° beveled face step with a height (h) of 152 mm. Results were compared to data on square-edge, vertical face steps previously obtained. The distance to the inception point of free-surface aeration normalized by the surface roughness was reduced approximately 25% for the same Froude number defined in terms of roughness height.

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Wang, Fengjiao, He Xu, Yikun Liu, and Chaoyang Hu. "A Simplified Lattice Boltzmann Boundary Conditions for Gas Transport in Self-Affine Microchannels with an Inherent Roughness of in a Tight Reservoir." Fractal and Fractional 7, no. 8 (2023): 596. http://dx.doi.org/10.3390/fractalfract7080596.

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A simplified method of determining lattice Boltzmann boundary conditions based on self-affine microchannels with an inherent roughness in a tight reservoir is presented in this paper to address nonlinear efficiency problems in fluid simulation. This approach effectively combines the influence of rough surfaces in the simulation of the flow field, the description of L-fractal theory applied to rough surfaces, and a generalized lattice Boltzmann method with equivalent composite slip boundary conditions for inherent roughness. The numerical simulations of gas slippage in a two-dimensional plate m

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Crawford, C. W., and O. A. Plumb. "The Influence of Surface Roughness on Resistance to Flow Through Packed Beds." Journal of Fluids Engineering 108, no. 3 (1986): 343–47. http://dx.doi.org/10.1115/1.3242584.

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Experiments were performed to determine the effect of roughness on flow through randomly packed beds of spheres. Three different packings were investigated, one of smooth spheres, and two others composed of spheres with roughness elements added to the surface. The relative roughness, defined as the height of the added elements divided by the diameter of the smooth spheres, was .012 and .026 for these two cases. The experiments covered a range of Reynolds numbers based on the sphere diameter from near unity where the flow is dominated by viscosity to 1600 where the flow is dominated by inertia.

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Ritter, Severin, Kaspar Staub, and Patrick Eppenberger. "Associations between relative body fat and areal body surface roughness characteristics in 3D photonic body scans—a proof of feasibility." International Journal of Obesity 45, no. 4 (2021): 906–13. http://dx.doi.org/10.1038/s41366-021-00758-w.

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Abstract Introduction A reliable and accurate estimate of the percentage and distribution of adipose tissue in the human body is essential for evaluating the risk of developing chronic and noncommunicable diseases. A precise and differentiated method, which at the same time is fast, noninvasive, and straightforward to perform, would, therefore, be desirable. We sought a new approach to this research area by linking a person’s relative body fat with their body surface’s areal roughness characteristics. Materials and methods For this feasibility study, we compared areal surface roughness charact

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Biswas, R., M. M. Rahman, A. Khanom, and M. A. Taher. "Heat transfer performance analysis through inline and staggered grooved microchannel using lattice Boltzmann method." Energy and Thermofluids Engineering 5 (September 22, 2024): 11–23. https://doi.org/10.38208/ete.v5.752.

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The D2Q9 Bhatnagar-Gross-Krook (BGK) model, utilizing the Thermal Lattice Boltzmann Method (TLBM) to examine the temperature and mass transfer numerically across inline and staggered grooved microchannels. The conditions are (a) cold fluid at inlet and outlet, (b) walls are heated (c) relative roughness height is rh=4%, 8% and 12% according to channel height and (d) parabolic velocity profile at inlet and outlet section with slip flow at the walls for different Knudsen numbers from Kn=0.02 to 0.10. The study goals to examine the impact of temperature profiles, Nusselt number, average friction

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Biswas, R., M. M. Rahman, A. Khanom, and M. A. Taher. "Heat transfer performance analysis through inline and staggered grooved microchannel using lattice Boltzmann method." Energy and Thermofluids Engineering 5 (September 22, 2024): 11–23. https://doi.org/10.38208/ete.v5.

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The D2Q9 Bhatnagar-Gross-Krook (BGK) model, utilizing the Thermal Lattice Boltzmann Method (TLBM) to examine the temperature and mass transfer numerically across inline and staggered grooved microchannels. The conditions are (a) cold fluid at inlet and outlet, (b) walls are heated (c) relative roughness height is rh=4%, 8% and 12% according to channel height and (d) parabolic velocity profile at inlet and outlet section with slip flow at the walls for different Knudsen numbers from Kn=0.02 to 0.10. The study goals to examine the impact of temperature profiles, Nusselt number, average friction

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Chen, Qianyong, Jinghua Xu, and Shuyou Zhang. "Volumetric adaptive slicing of manifold mesh for rapid prototyping based on relative volume error." Rapid Prototyping Journal 28, no. 3 (2021): 606–26. http://dx.doi.org/10.1108/rpj-08-2020-0194.

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Purpose Compared with cusp height and area deviation ratio, volume error (VE) caused by the layer height could represent the stair-case effect more comprehensively. The proposed relative volume error (RVE)-based adaptive slicing method takes VE rather than cusp height as slicing criteria, which can improve part surface quality for functionalized additive manufacturing. Design/methodology/approach This paper proposes a volumetric adaptive slicing method of manifold mesh for rapid prototyping based on RVE. The pre-height sequences of manifold mesh are first preset to reduce the SE by dividing th

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Mazzuoli, Marco, and Markus Uhlmann. "Direct numerical simulation of open-channel flow over a fully rough wall at moderate relative submergence." Journal of Fluid Mechanics 824 (July 11, 2017): 722–65. http://dx.doi.org/10.1017/jfm.2017.371.

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Direct numerical simulation of open-channel flow over a bed of spheres arranged in a regular pattern has been carried out at bulk Reynolds number and roughness Reynolds number (based on sphere diameter) of approximately 6900 and 120, respectively, for which the flow regime is fully rough. The open-channel height was approximately 5.5 times the diameter of the spheres. Extending the results obtained by Chan-Braun et al. (J. Fluid Mech., vol. 684, 2011, pp. 441–474) for an open-channel flow in the transitionally rough regime, the present purpose is to show how the flow structure changes as the f

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Lv, Jiaorong, Yongsheng Xie, and Han Luo. "Erosion Process and Temporal Variations in the Soil Surface Roughness of Spoil Heaps under Multi-Day Rainfall Simulation." Remote Sensing 12, no. 14 (2020): 2192. http://dx.doi.org/10.3390/rs12142192.

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The extensive artificially accelerated erosion of spoil heaps on newly engineered landforms is a key ecological management point requiring better understanding. Soil surface roughness is a crucial factor influencing erosion processes; however, study on spoil heap erosion with a view of surface roughness is lacking. This study investigated the erosion processes and the spatiotemporal variation of surface roughness on spoil heaps, and then, analyzed how the roughness affected the hydrological and sediment yield characteristics. Sequences of four artificial rainstorms with constant rainfall inten

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ACHOUR, Bachir. "Design of a Pressurized Rectangular Conduit With Triangular Bottom Using The Rough Model Method." Open Civil Engineering Journal 8, no. 1 (2014): 205–12. http://dx.doi.org/10.2174/1874149501408010205.

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A new theory is presented to design pressurized conduits, particularly rectangular shaped conduit with triangular bottom. This theory is based on a referential rough conduit model characterized by an arbitrarily assigned relative roughness taken in the rough turbulent flow regime. Thus, the geometric elements of the chosen model are well defined. In particular, the relative height of the rough model, which is expressed by an implicit relationship, has been resolved by an appropriate limited development. The obtained relationship is used to calculate the almost exact value of the relative heigh

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Dai, Meiling, Xirui Wang, Cheng Cheng, Zhuoli Chen, and Jiyu Deng. "Efficient Evaluation of Concrete Fracture Surface Roughness Using Fringe Projection Technology." Materials 16, no. 12 (2023): 4430. http://dx.doi.org/10.3390/ma16124430.

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The evaluation of concrete surface roughness is crucial in the field of civil engineering. The purpose of this study is to propose a no-contact and efficient method for the measurement of the roughness of concrete fracture surfaces based on fringe-projection technology. A simple phase-correction method using one additional strip image is presented for the phase unwrapping to improve the measurement efficiency and accuracy. The experimental results indicate that the measuring error for plane height is less than 0.1mm, and the relative accuracy for measuring a cylindrical object is about 0.1%, m

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