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Littérature scientifique sur le sujet « Bed roughness »

Auteur : Grafiati
Publié le 1 février 2025

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Articles de revues sur le sujet "Bed roughness"

1

Lang, Shinan, Ben Xu, Xiangbin Cui, Kun Luo, Jingxue Guo, Xueyuan Tang, Yiheng Cai, Bo Sun et Martin J. Siegert. « A self-adaptive two-parameter method for characterizing roughness of multi-scale subglacial topography ». Journal of Glaciology 67, no 263 (24 février 2021) : 560–68. http://dx.doi.org/10.1017/jog.2021.12.

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AbstractDuring the last few decades, bed-elevation profiles from radar sounders have been used to quantify bed roughness. Various methods have been employed, such as the ‘two-parameter’ technique that considers vertical and slope irregularities in topography, but they struggle to incorporate roughness at multiple spatial scales leading to a breakdown in their depiction of bed roughness where the relief is most complex. In this article, we describe a new algorithm, analogous to wavelet transformations, to quantify the bed roughness at multiple scales. The ‘Self-Adaptive Two-Parameter’ system calculates the roughness of a bed profile using a frequency-domain method, allowing the extraction of three characteristic factors: (1) slope, (2) skewness and (3) coefficient of variation. The multi-scale roughness is derived by weighted-summing of these frequency-related factors. We use idealized bed elevations to initially validate the algorithm, and then actual bed-elevation data are used to compare the new roughness index with other methods. We show the new technique is an effective tool for quantifying bed roughness from radar data, paving the way for improved continental-wide depictions of bed roughness and incorporation of this information into ice flow models.
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Faruque, Md Abdullah Al, et Ram Balachandar. « Roughness effects on turbulence characteristics in an open channel flow ». Canadian Journal of Civil Engineering 37, no 12 (décembre 2010) : 1600–1612. http://dx.doi.org/10.1139/l10-098.

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A comprehensive study was carried out to understand the effect of roughness on the turbulence characteristics of flow in an open channel. To this end, tests were conducted with four different types of bed surface conditions at two different Reynolds number (Re = 47 500 and 31 000). This includes the use of an impermeable smooth bed, impermeable rough bed, permeable sand bed, and an impermeable bed with distributed roughness. The roughness is generated using sand grains of median diameter 2.46 mm. The effect of bed roughness is seen to have penetrated through most of the flow depth, disputing the conventional "wall similarity" hypothesis. The results show that the distributed roughness generates the largest roughness effect. The differences in the characteristics as noted by the velocity triple products exceed 200% between the flow over the smooth and rough beds. Although the same sand grain is used to create the different rough bed conditions, there are differences in turbulence characteristics, which is an indication that specific geometry of the roughness has an influence. A quadrant analysis indicates that roughness increases the contribution of the extreme turbulent events that produce very large instantaneous Reynolds shear stress and consequently influence the flow.
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A.Merry, Marwa. « EXPERIMENTAL STUDY FOR DETERMINE MANNING'S COEFFICIENT WITH DIFFERENT SLOPES AND CHANNEL BED MATERIALS ». Kufa Journal of Engineering 8, no 3 (12 novembre 2017) : 76–88. http://dx.doi.org/10.30572/2018/kje/8031160.

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Water resources and hydraulic engineering projects have been upward rapidly in all over the world, accordingly the prediction of roughness coefficient is essential criteria to design open channels, and related hydraulic structures. The aims of this research are to find out the effect of changing beds materials and discharge on coefficient of roughness (n), the beds that used in the tests are smooth which represented by original channel bed (steel plate), rough bed material which is a gravel bed and waved bed .The experimental work was performed in a rectangular flume with dimension of (15 m* 0.3 m* 0.45 m) long, wide and deep, respectively with different value of slope (1:200 and 1:500) to analyze slope effect on coefficient of roughness in addition to the effect of channel bed material. The experimental work showed that The coefficient of roughness reduced when the discharge increases for specified slope and channel bed, The slope of the channel and bed roughness is the main factors affected on determining coefficient of roughness and when the channel slope increases the coefficient of roughness increases, the coefficient of roughness is decreased when using smooth bed and it is increased when channel bed is waved. The percentage change in the Manning coefficient due to changing in slope and channel bed is (112.6%) when slope equal to (1/200) and the channel bed changed from smooth to rough , (184%) when the bed changed from rough to waved, and (33.6%) when channel bed changed from rough to waved. And for (1/500) slope, the percentage change in the Manning coefficient equal to (33.5%) when the bed changed from smooth to rough, (80%) when changed from smooth to waved, and (33.1%) when changed from rough to waved.
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Irzooki, Raad Hoobi, et Ayad Saoud Najem. « Experimental Investigation for Free Overfall of Flow in Semi-circular Channels ». IOP Conference Series : Earth and Environmental Science 1120, no 1 (1 décembre 2022) : 012010. http://dx.doi.org/10.1088/1755-1315/1120/1/012010.

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Abstract In the present paper, the effects of diameter, bed slopes, and bed roughness on free overfall flow of semi-circular channels were investigated experimentally. For this purpose, three models of semi-circular channels with free overfall were built and installed in a 6m long laboratory flume. These three models were 250 cm long and had varying diameters 160, 200, and 250 mm. Four different bed slopes (S) were used in each of these models (0, 0.004, 0.008, and 0.012). For each bed slope, three sand particle sizes were used to roughen the bed (1.18mm, 2.36mm, and 4.75mm). For each model, the experimental testing program contained sixteen series of experiments. They were divided into two categories: four smooth beds and twelve rough beds. Different rates of discharge (Q) were examined in a total of 192 tests. According to the experimental results of all models, the Froude number (F r ) of flow decreases as the end depth ratio ( y b / y c ) increases for various bed roughnesses. For varying bed slopes and bottom roughness, a simple linear formula was developed to relate the brink depth ( y b ) with the critical depth ( y c ). For various bed slopes and roughness conditions, simple empirical equations for the flow over the free overfall in semi-circular channels were found. The results demonstrate a good level of agreement.
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Nikora, Vladimir I., Derek G. Goring et Barry J. F. Biggs. « On gravel-bed roughness characterization ». Water Resources Research 34, no 3 (mars 1998) : 517–27. http://dx.doi.org/10.1029/97wr02886.

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Majeed, Hayder Q., Ali M. Ghazal et Basheer Al-Hadeethi. « Experimental and Numerical Study of Open Channel Flow with T-Section Artificial Bed Roughness ». Mathematical Modelling of Engineering Problems 9, no 6 (31 décembre 2022) : 1589–95. http://dx.doi.org/10.18280/mmep.090619.

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Experimental and numerical studies have been conducted on the effects of bed roughness elements such as cubic and T-section elements that are regularly half-channel arrayed on one side of the river on turbulent flow characteristics and bed erosion downstream of the roughness elements. The experimental study has been done for two types of bed roughness elements (cubic and T-section shape) to study the effect of these elements on the velocity profile downstream the elements with respect to different water flow discharges and water depths. A comparison between the cubic and T-section artificial bed roughness showed that the velocity profile downstream the T-section increased in smooth side from the river and decrease in the rough side from it compared with the case when a cubic artificial bed roughness is used. By comparing the results for the element shapes, it can be notices that the T-section bed roughness element more effective compared to cubic shape for both sides of the channel. The numerical method has been done using Computational Fluid Dynamic (CFD) method. A validation for the CFD model with the experimental study have been carried out for a specific flow discharge and water depth. The results indicated that the velocity distribution profiles downstream the bed roughness elements in both sides shown very good agreement for manning coefficients between the numerical and experimental studies. The range of errors between the experimental and numerical study have been calculated using Root Mean Square Error (RMSE) approach, which is found that the RMSE is approximately equal to 1 in case of cubic bed roughness and the RMSE is about 1.5 in case of T-section bed roughness for both smooth and rough sides. Furthermore, the influence of the velocity profile and the bed erosion downstream of the T-section element under the effect of tides have been investigated using the CFD method, which is commonly happened in Shat al-Arab south of Iraq. The results show that the tide of the flow has a reverse effect on the velocity profiles for both sides. Since the velocity profile downstream of bed roughness region increase in the rough side and decrease in the smooth side compared with the normal flow of the river.
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FALCINI, FRANCESCA A. M., DAVID M. RIPPIN, MAARTEN KRABBENDAM et KATHERINE A. SELBY. « Quantifying bed roughness beneath contemporary and palaeo-ice streams ». Journal of Glaciology 64, no 247 (13 septembre 2018) : 822–34. http://dx.doi.org/10.1017/jog.2018.71.

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ABSTRACTBed roughness is an important control on ice-stream location and dynamics. The majority of previous bed roughness studies have been based on data derived from radio-echo sounding (RES) transects across Antarctica and Greenland. However, the wide spacing of RES transects means that the links between roughness and flow are poorly constrained. Here, we use Digital Terrain Model/bathymetry data from a well-preserved palaeo-ice stream to investigate basal controls on the behaviour of contemporary ice streams. Artificial transects were set up across the Minch Palaeo-Ice Stream (NW Scotland) to mimic RES flight lines over Institute and Möller Ice Streams (Antarctica). We then explored how different data-resolution, transect orientation and spacing, and different methods, impact roughness measurements. Our results show that fast palaeo-ice flow can occur over a rough, hard bed, not just a smooth, soft bed, as previous work has suggested. Smooth areas of the bed occur over both bedrock and sediment covered regions. Similar trends in bed roughness values were found using Fast Fourier Transform analysis and standard deviation methods. Smoothing of bed roughness results can hide important details. We propose that the typical spacing of RES transects is too wide to capture different landform assemblages and that transect orientation influences bed roughness measurements in both contemporary and palaeo-ice-stream setting.
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Fredsøe, J., B. M. Sumer, T. S. Laursen et C. Pedersen. « Experimental investigation of wave boundary layers with a sudden change in roughness ». Journal of Fluid Mechanics 252 (juillet 1993) : 117–45. http://dx.doi.org/10.1017/s0022112093003696.

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This study deals with turbulent oscillatory boundary-layer flows over a plane bed with a sudden spatial change in roughness. Two kinds of ‘change in the roughness’ were investigated: in one, the roughness changed from a smooth-wall roughness to a roughness equal to 4.8 mm, and in the other, it changed from a roughness equal to 0.35 mm to the same roughness as in the previous experiment (4.8 mm). The free-stream flow was a purely oscillating flow with sinusoidal velocity variation. Mean flow and turbulence properties were measured. The Reynolds number was 6 × 106 for the major part of the experiments, with a maximum velocity of approximately 2 m/s and the stroke of the motion about 6 m. The response of the boundary layer to the sudden change in roughness was found to occur over a transitional length of the flow. The bed shear stress over this transitional length attains a peak value over the bed section with the larger roughness. It was found that the amplification in the bed shear stress due to this peak could be up to 2.5 times its asymptotic value. Also, it was found that the turbulence is quantitatively different in the two half periods; a much stronger turbulence is experienced in the half period where the flow is towards the less-rough section. The present experiments further showed that a constant streaming occurs near the bed in the neighbourhood of the junction between the two bed sections. This streaming is directed towards the section with the larger roughness.
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Devi, Kalpana, Prashanth Reddy Hanmaiahgari, Ram Balachandar et Jaan H. Pu. « A Comparative Study between Sand- and Gravel-Bed Open Channel Flows in the Wake Region of a Bed-Mounted Horizontal Cylinder ». Fluids 6, no 7 (1 juillet 2021) : 239. http://dx.doi.org/10.3390/fluids6070239.

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In nature, environmental and geophysical flows frequently encounter submerged cylindrical bodies on a rough bed. The flows around the cylindrical bodies on the rough bed are very complicated as the flow field in these cases will be a function of bed roughness apart from the diameter of the cylinder and the flow velocity. In addition, the sand-bed roughness has different effects on the flow compared to the gravel-bed roughness due to differences in the roughness heights. Therefore, the main objective of this article is to compare the mean velocities and turbulent flow properties in the wake region of a horizontal bed-mounted cylinder over the sand-bed with that over the gravel-bed. Three experimental runs, two for the sand-bed and one for the gravel-bed with similar physical and hydraulic conditions, were recorded to fulfil this purpose. The Acoustic Doppler Velocimetry (ADV) probe was used for measuring the three-dimensional (3D) instantaneous velocity data. This comparative study shows that the magnitude of mean streamwise flow velocity, streamwise Reynolds normal stress, and Reynolds shear stress are reduced on the gravel-bed compared to the sand-bed. Conversely, the vertical velocities and vertical Reynolds normal stress are higher on the gravel-bed than the sand-bed.
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Kashefipour, Seyed Mahmood, Mehdi Daryaee et Mehdi Ghomeshi. « Effect of bed roughness on velocity profile and water entrainment in a sedimentary density current ». Canadian Journal of Civil Engineering 45, no 1 (janvier 2018) : 9–17. http://dx.doi.org/10.1139/cjce-2016-0490.

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In this study, the effect of bed roughness on velocity profile and water entrainment in a sedimentary density current for Richardson numbers of 1.2–7 (subcritical flow conditions) was investigated. Experiments were carried out in a tilting flume with four different bed slopes, four roughness heights, and two fluid densities of sedimentary density currents. The results showed that bed roughness significantly affects the general shapes of velocity profiles, especially in the wall region. Two empirical equations were developed as the functions of the relative roughness for the wall and jet regions of velocity profile using the measured velocities of density currents. Water entrainment was also affected by bed roughness and an empirical equation was developed describing the relationship of this phenomenon with the Richardson number and relative roughness. Sensitivity analysis of this equation by using elasticity coefficient method showed that the effectiveness of the Richardson number is 3.9 times more than the effect of relative roughness on water entrainment.
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Thèses sur le sujet "Bed roughness"

1

Robert, Andre. « Statistical modelling of sediment bed profiles and bed roughness properties in alluvial channels ». Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292244.

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Sorenson, Kent S. (Kent Soren). « Moveable bed roughness and sediment resuspension in the field ». Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/35047.

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Wilbers, Antoine. « The development and hydraulic roughness of subaqueous dunes / ». Utrecht : Koninklijk Nederlands Aardrijkskundig Genootschap, 2004. http://www.loc.gov/catdir/toc/fy0708/2004464077.html.

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Lefebvre, Alice. « Bed roughness over vegetated beds : sonar imaging techniques and effect on unidirectional currents ». Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/72139/.

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Small scale roughness of the seafloor is of direct relevance to a range of interests, including boundary layer hydrodynamics, sediment transport and high-frequency acoustic scattering. Despite its importance, only few studies have quantitatively resolved seafloor height at the relevant scales. In particular, characterisation of roughness over vegetated beds is needed to better understand hydrodynamics and sediment transport in the coastal zone. A new Benthic Roughness Acoustic Device (BRAD) has been developed to define microtopographical roughness through high-resolution imagery of the seabed. BRAD, composed of a profiling sonar – the Sediment Imager Sonar (SIS) – and a motor, both mounted on a frame, enables measurements of the seabed elevation over an area of 1.7 m2. A threshold method was established to detect the seabed from the SIS raw data. Laboratory deployments were carried out in order to assess the system accuracy over known targets and its ability to discriminate sediment sizes. Field deployments at 6 sites enabled the imaging of a variety of seabed types; in particular bioturbated fine sand and mud, seagrass canopies, gravelly sand and ripple fields. Spectral analysis applied on the seabed elevations was used to characterise roughness type. Seagrasses are flowering plants that have adapted to the submerged marine environment. They develop extensive underwater meadows in coastal areas around the world, forming complex, highly productive ecosystems. The SIS was used together with a towed video camera system to survey a seagrass (Zostera marina) bed in Calshot, UK. A method was developed to assess Z. marina presence from the SIS data and its results were tested against video data. The SIS proved to be a useful tool for seagrass surveying and the use of the SIS and the video yielded a preliminary map of the seagrass bed. Seagrass canopies exert strong effects on water flow inside and around them. The influence of Zostera marina canopies on flow, turbulence, roughness and sediment movement was evaluated through laboratory experiments. Numerous runs were carried out in an annular and a straight, recirculating flume using live Z. marina and a mobile sand layer. Flow was greatly decelerated inside the canopy while turbulence was increased. The Turbulent Kinetic Energy was observed to be maximal at the canopy/water interface. This was hypothesised to be related to the canopy ‘wavy’ motion. Sediment movement was observed within the canopy as scour around the stems. Ripples formed downstream of the canopy at velocities lower than the sediment threshold of motion. Intermittent turbulence associated with the burst phenomenon is thought to be responsible for this.
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Rahman, Shikha. « Effect of bed roughness on scalar mixing in turbulent boundary layers ». Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/32794.

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Batt, Rachel Louise. « The influence of bed roughness on the dynamics of gravity currents ». Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/11282/.

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To date the influence of bed roughness onl the propagation and dynamics of gravity currents has been largely neglected. A new physical modelling dataset has been compiled, which details the fundamental affects of several bed roughnesses on lock-release gravity currents. Five bed configurations were chosen encompassing 'grain' and 'form' type elements at a range of spacings. 1%, 5% and 10% initial density excesses were studied and the effect of removing the buoyant ambient fluid between the elements examined. Observations due to changing the current depth relative to the element height were also made. Ultrasonic Doppler velocimetry profiling (UDVP) and video capture techniques were used to analyse stream wise and vertical velocity structures and the affects on the front speed and distance travelled by the current. A 10 depth-averaged model solves modified 2-layer shallow water equations using the method of characteristics to obtain temporal velocity and depth evolution for a current under the influence of a general roughness quantity. 2D and 3D depth-resolved CFD simulations use the commercial software FLUENT to solve the RANS equations and transport of a scalar for the dense current with the RNG k - € turbulence model. The CFD predictions were well validated by the new experimental dataset and provide supplementary predictions of concentration, lateral motion and activity in the vicinity of the roughness elements. Comparison of 20 and 30 models resulted in the conclusion that the 3D model is vital for accurate simulation of internal dynamics of gravity current propagation over beam type bed roughness. In general general, the distance that the front travels decreases with any bed roughness present. This reduction increases with element spacing. The stream wise mean velocity profiles show a reduced velocity maximum further from the bed. Decreased entrainment results from breakdown of larger billows. Also observed is a thicker current, a rounder profile and a shorter, diluted head. Areas of increased vertical motion within the current. associated with decreased horizontal motion are observed, indicative of ejections of ambient fluid from between the elements. The presence of this fluid is found to contribute to ~ 50% of the current retardation. There are also similarities with the effects of bed roughness in open channel and pipe flows, most notably there is a critical element spacing (11'/ kr ~ 7) where the effects of roughness are greatest (where w is element spacing and kr is element height). The experimental and numerical results demonstrate that the application of existing models that rely on experimental validation with smooth beds to situations where a rough boundary is present may lead to significant errors.
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Hersberger, Daniel S. « Wall roughness effects on flow and scouring in curved channels with gravel bed / ». Lausanne, 2002. http://library.epfl.ch/theses/?display=detail&nr=2632.

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Thèse sciences techniques, EPF Lausanne, no 2632 (2002), Faculté Environnement naturel, architectural et construit ENAC, Domaine du génie civil. Directeur: A. Schleiss ; rapporteurs: M. Altinakar, G.-R. Bezzola, J. Gessler.
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Kendall, Robert L. « Sand bed roughness in the nearshore, COAST 3D experiment, Egmond aan Zee, the Netherlands ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA380327.

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Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, June 1998.
Thesis advisor(s): Gallagher, Edith L. ; Thornton, Edward B. "June 2000." Includes bibliographical references (p. 75-76). Also available online.
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Velioglu, Deniz. « Effects Of Different Bed Roughnesses On The Characteristics Of Hydraulic Jumps ». Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614018/index.pdf.

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In practice, baffle blocks and sills are commonly being used to stabilize the location of a hydraulic jump and shorten the length of a stilling basin. On the other hand, gravels, corrugations and rectangular prismatic roughnesses which cover the entire length of the basin or placed in a staggered manner may be an alternative. The objective of this study is to determine the effects of these roughness elements on the characteristics of hydraulic jumps such as conjugate depth, jump length and energy dissipation using experimental data collected from the previous studies. The investigations show that the roughness elements have positive effects on the characteristics of hydraulic jumps. The tailwater depth reduction compared to classical jump is 2-10%. The length of the jump is reduced about by 30-50% by prismatic roughness elements, 40% by corrugations, and 30% by gravels. The roughness elements induce 3-15% more energy dissipation than that of classical jump. Therefore, these types of bed roughness elements should be considered as an effective alternative of accessory devices such as baffle blocks and sills.
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Khan, Muhammad Ijaz. « The influence of two-dimensional bed roughness on the flow structure of a turbulent boundary layer ». Thesis, University College London (University of London), 2004. http://discovery.ucl.ac.uk/1446901/.

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Experiments have been performed to investigate the relationship between the geometry of an idealised bed roughness and the structure of the turbulent boundary layer above. This work has particular applications in relation to architecture and environmental health, designing comfort for pedestrians and managing environmental pollution. Experiments were carried out in a laboratory water flume to study the turbulence structure generated under both rough and smooth bed conditions. The relationship between small scale turbulent eddies formed between the elements of a two-dimensional bed roughness and the intermittent turbulent structure of the boundary layer was established in the form of roughness length scale and friction velocity using LDV measurements from the mean velocity profile. Turbulence production was also determined from measurements of the Reynolds stress and velocity gradient. This was compared with the diffusion characteristics of the flow. Spacing between the roughness slats was varied for different tests to produce isolated (k-type) bed roughness, skimming (d-type) flow, and wake interference flow for transitional roughness. Transition between these regimes was further investigated using flow visualisation, and a clear correlation established between the vortices at the bed and the turbulence characteristics of the boundary layer. The effect of sudden changes in bed geometry on the turbulence structure was investigated for flows aligned perpendicular to the roughness elements forming simulated urban environment. These results were compared for a similar model street canyon with and without a large scale upstream approach roughness. The turbulence generated as a result of the change in local bed geometry has a significant influence on the dispersion of dye tracer used to simulate pollutant. It was found that uniformity in height of buildings along parallel streets in an urban environment promotes shear at roof-level, thereby trapping fluid and pollution within the canyon. On the other hand, non-uniformity in building height and the presence of substantial upstream buildings promotes turbulence which helps in ventilation of street canyons.
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Livres sur le sujet "Bed roughness"

1

Wilbers, Antoine. The development and hydraulic roughness of subaqueous dunes. Utrecht : Royal Dutch Geographical Society/Utrecht University, 2004.

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2

Kendall, Robert L. Sand bed roughness in the nearshore, COAST 3D experiment, Egmond aan Zee, the Netherlands. Monterey, Calif : Naval Postgraduate School, 2000.

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3

Jong, Carmen De. Temporal and spatial interactions between river bed roughness, geometry, bedload transport and flow hydraulics in mountain streams : Examples from Squaw Creek (Montana, USA) and Lainbach/Schmiedlaine (Upper Bavaria, Germany). Berlin : Im Selbstverlag des Instituts für Geographische Wissenschaften der Freien Universität Berlin, 1995.

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4

Hey, Richard D., et C. R. Thorne. A Field Guide to Roughness Characteristics of Gravel-Bed Rivers : A Practical Approach. Wiley, 2001.

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Sand Bed Roughness in the Nearshore, COAST 3D Experiment, Egmond aan Zee, The Netherlands. Storming Media, 2000.

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6

McAdams, Stephen, et Bruno L. Giordano. The perception of musical timbre. Sous la direction de Susan Hallam, Ian Cross et Michael Thaut. Oxford University Press, 2012. http://dx.doi.org/10.1093/oxfordhb/9780199298457.013.0007.

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This article discusses musical-timbre perception. Musical timbre is a combination of continuous perceptual dimensions and discrete features to which listeners are differentially sensitive. The continuous dimensions often have quantifiable acoustic correlates. The timbre-space representation is a powerful psychological model that allows predictions to be made about timbre perception in situations beyond those used to derive the model in the first place. Timbre can play a role in larger-scale movements of tension and relaxation and thus contribute to the expression inherent in musical form. Under conditions of high blend among instruments composing a vertical sonority, timbral roughness is a major component of musical tension. However, it strongly depends on the way auditory grouping processes have parsed the incoming acoustic information into events and streams.
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Paeglīte, Ilze. Kustīgās slodzes dinamiskās iedarbes uz autoceļu tiltiem eksperimentāla izpēte un novērtējums. RTU Press, 2021. http://dx.doi.org/10.7250/9789934227028.

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Using data obtained from the dynamic load testing of bridges a method was developed to evaluate level of the dynamic performance without performing a dynamic load test. In this method a dynamic index of the bridge is calculated. Dynamic index allows to evaluate the dynamic performance level of existing and new structures taking into account such bridge parameters as span length / height ratio, natural frequency, vibration damping coefficient, relative deflection and international roughness index IRI. Dynamic index method can be used by bridge owners and maintainers to determine the dynamic potential of a particular bridge. The maximum allowable values of the dynamic amplification factor for standard prestressed concrete beam bridges were determined. These values were calculated for maximum allowed traffic load in Latvia. The obtained results can be used for the safety assessment of existing and reconstructed reinforced concrete beam bridges.
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Escudier, Marcel. Turbulent flow. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198719878.003.0018.

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In this chapter the principal characteristics of a turbulent flow are outlined and the way that Reynolds’ time-averaging procedure, applied to the Navier-Stokes equations, leads to a set of equations (RANS) similar to those governing laminar flow but including additional terms which arise from correlations between fluctuating velocity components and velocity-pressure correlations. The complex nature of turbulent motion has led to an empirical methodology based upon the RANS and turbulence-transport equations in which the correlations are modelled. An important aspect of turbulent flows is the wide range of scales involved. It is also shown that treating near-wall turbulent shear flow as a Couette flow leads to the Law of the Wall and the log law. The effect of surface roughness on both the velocity distribution and surface shear stress is discussed. It is shown that the distribution of mean velocity within a turbulent boundary layer can be represented by a linear combination of the near-wall log law and an outer-layer Law of the Wake.
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Chapitres de livres sur le sujet "Bed roughness"

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Kumar, Vijay. « Bed Roughness ». Dans Encyclopedia of Earth Sciences Series, 94. Dordrecht : Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-90-481-2642-2_40.

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Lan, Xinyu, Jingmei Zhang et Hang Wang. « Hydraulic Characteristics of Undular Hydraulic Jumps Over Different Bed Roughness ». Dans Lecture Notes in Civil Engineering, 453–62. Singapore : Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-4355-1_42.

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AbstractOccurrence of undular hydraulic jumps has impact on sediment transport and bank erosion in estuarine areas. The hydraulic properties vary when it forms on a rough bed, leading to modification of turbulent mixing processes. This paper reports on a study of undular hydraulic jumps generated with different types of bed roughness including smooth, rough rubber-matted and grated beds. The experiment was conducted with a flow rate of 241 m3/h using acoustic displacement meters (ADMs) and an acoustic Doppler velocimeter (ADV). The obtained results reveal a discernible descending order in the undulations of the first three waves: smooth, grated, and rough rubber mat. In instances where roughness deviates to either extreme—being excessively small or large—the undulation of the first three waves intensifies. Through both free surface wave and turbulent flow field evolution experiments, it was determined that the roughness of the bed primarily influences the first wave, exerting the most pronounced impact on the crest of the initial wave. As the wave progresses, this influence gradually diminishes. Therefore, this article further posits that heightened bed roughness corresponds to an increased fluctuation in velocity at the bottom of the first peak, resulting in a weakened impact of toe jump oscillation on the flow field. Consequently, this diminishes the likelihood of negative velocity occurrences.
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Armanini, Aronne. « Roughness in Fixed-Bed Streams ». Dans Principles of River Hydraulics, 1–31. Cham : Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-68101-6_1.

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Rauen, W. B., B. Lin et R. A. Falconer. « Modelling Dynamic Bed Roughness Associated with Bed Form Development ». Dans Advances in Water Resources and Hydraulic Engineering, 865–70. Berlin, Heidelberg : Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-89465-0_152.

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Zanke, Ulrich. « Turbulence and suspension related to different bed roughness ». Dans Transport of Suspended Solids in Open Channels, 157–60. London : Routledge, 2022. http://dx.doi.org/10.1201/9780203735152-24.

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Chung, S. W., Q. Luo et T. Stoesser. « Large-scale motion over spanwise heterogeneous bed roughness ». Dans River Flow 2022, 83–89. London : CRC Press, 2024. http://dx.doi.org/10.1201/9781003323037-12.

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Nicholas, A. P. « Roughness Parameterization in CFD Modelling of Gravel-Bed Rivers ». Dans Computational Fluid Dynamics, 329–55. Chichester, UK : John Wiley & Sons, Ltd, 2005. http://dx.doi.org/10.1002/0470015195.ch13.

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Wang, Di, Yongqiang Yang, Yang Liu, Yuchao Bai et Chaolin Tan. « Surface Characteristics and Roughness of Laser Powder Bed Fusion Processed Parts ». Dans Laser Powder Bed Fusion of Additive Manufacturing Technology, 179–222. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-5513-8_6.

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Mercurio, Vincenza, Flaviana Calignano, Giovanni Marchiandi et Luca Iuliano. « Surface Roughness Measurement in Laser Powder Bed Fusion Manufacturing Process ». Dans Flexible Automation and Intelligent Manufacturing : Establishing Bridges for More Sustainable Manufacturing Systems, 425–33. Cham : Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-38241-3_48.

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Kim, Jisung, Won Kim, Chanjoo Lee et Yong Jeon Kim. « Characteristic of Roughness Coefficient Associated with Discharge in Gravel-Bed River ». Dans Advances in Water Resources and Hydraulic Engineering, 963–68. Berlin, Heidelberg : Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-89465-0_169.

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Actes de conférences sur le sujet "Bed roughness"

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Kang, Ranbir Singh. « QUANTIFYING STREAM BED ROUGHNESS USING TERRESTRIAL LIDAR ». Dans GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-334652.

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RATHORE, Vijit, Nadia PENNA, Subhasish DEY et Roberto GAUDIO. « Computation of Bed Shear Stress from Velocity Measurements in a Gradually Varying Roughness Bed ». Dans 38th IAHR World Congress. The International Association for Hydro-Environment Engineering and Research (IAHR), 2019. http://dx.doi.org/10.3850/38wc092019-0473.

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Kaczmarek, L. M., J. M. Harris et B. A. O'Connor. « Modelling Moveable Bed Roughness and Friction for Spectral Waves ». Dans 24th International Conference on Coastal Engineering. New York, NY : American Society of Civil Engineers, 1995. http://dx.doi.org/10.1061/9780784400890.024.

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Elgohary, T., R. Elgohary et M. Hagrass. « Using sea bed roughness as a wave energy dissipater ». Dans ISLANDS 2012. Southampton, UK : WIT Press, 2012. http://dx.doi.org/10.2495/islands120171.

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Adhikari, Manjish, et Jilu Li. « Ice surface and bed roughness estimation of petermann Glacier ». Dans 2018 IEEE Radar Conference (RadarConf18). IEEE, 2018. http://dx.doi.org/10.1109/radar.2018.8378707.

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Luo, Qianyu, et Thorsten Stoesser. « Secondary currents and turbulence over spanwise heterogeneous bed roughness ». Dans Proceedings of the 39th IAHR World Congress From Snow to Sea. Spain : International Association for Hydro-Environment Engineering and Research (IAHR), 2022. http://dx.doi.org/10.3850/iahr-39wc252171192022131.

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You, Zai-Jin, et Peter Nielsen. « Movable Bed Roughness in the Flow of Irregular Waves and Currents over Movable Beds ». Dans 25th International Conference on Coastal Engineering. New York, NY : American Society of Civil Engineers, 1997. http://dx.doi.org/10.1061/9780784402429.270.

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Qiao, Changkai, Ruihua Nie, Xingnian Liu, Er Huang et Shuyou Cao. « Study on the roughness coefficient of mountain gravel-bed rivers ». Dans 2011 International Conference on Electric Technology and Civil Engineering (ICETCE). IEEE, 2011. http://dx.doi.org/10.1109/icetce.2011.5775995.

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Ghodke, Chaitanya D., et Sourabh V. Apte. « A Numerical Investigation to Study Roughness Effects in Oscillatory Flows ». Dans ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69066.

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Effects of roughness on the near-bed turbulence characteristics in oscillatory flows are studied by means of particle-resolved direct numerical simulations (DNS). Two particle sizes of diameter 375 and 125 in wall units corresponding to the large size gravel and the small size sand particle, respectively, in a very rough turbulent flow regime are reported. A double-averaging technique is employed to study the nature of the wake field, i.e., the spatial inhomogeneities at the roughness length scale. This introduced additional production and transport terms in double-averaged Reynolds stress budget, indicating alternate pathways of turbulent energy transfer mechanisms. Budgets of normal components of Reynolds stress reveal redistribution of energy from streamwise component to other two components and is attributed to the work of pressure in both flow cases. It is shown that the large diameter gravel particles significantly modulate the near-bed flow structures, leading to pronounced isotropization of the near-bed flow; while in the sand case, elongated horseshoe structures are found as a result of high shear rate. Effect of mean shear rate on the near-bed anisotropy is significant in the sand case, while it is minimal for the gravel-bed. Redistribution of energy in the gravel case showed reduced dependence on the flow oscillations, while for the sand particle it is more pronounced towards the end of an acceleration cycle.
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Dissanayake, D. M. P. K., J. A. Roelvink et M. van Ormondt. « EFFECT OF BED ROUGHNESS ON MORPHOLOGY MODEL WESTERN SCHELDT ESTUARY, NL ». Dans Proceedings of the 30th International Conference. World Scientific Publishing Company, 2007. http://dx.doi.org/10.1142/9789812709554_0276.

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Rapports d'organisations sur le sujet "Bed roughness"

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Ivakin, Anatoliy N., et Darrell R. Jackson. Multiple Scattering and Volume-Roughness Interactions in Sea Bed Acoustics. Fort Belvoir, VA : Defense Technical Information Center, septembre 1998. http://dx.doi.org/10.21236/ada537382.

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Ivakin, Anatoliy N., et Darrell R. Jackson. Multiple Scattering and Volume-Roughness Interactions in Sea Bed Acoustics. Fort Belvoir, VA : Defense Technical Information Center, septembre 1999. http://dx.doi.org/10.21236/ada629694.

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Styles, Richard, Scott Glenn et Mitchell Brown. An optimized combined wave and current bottom boundary layer model for arbitrary bed roughness. Coastal and Hydraulics Laboratory (U.S.), juillet 2017. http://dx.doi.org/10.21079/11681/22734.

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Docherty, Nicholas J., et Hubert Chanson. Characterisation of unsteady turbulence in breaking tidal bores including the effects of bed roughness. Brisbane, Australia : The University of Queensland, School of Civil Engineering, mars 2010. http://dx.doi.org/10.14264/205576.

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Slattery, Kevin. Unsettled Topics on Surface Finishing of Metallic Powder Bed Fusion Parts in the Mobility Industry. SAE International, janvier 2021. http://dx.doi.org/10.4271/epr2021001.

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Laser and electron-beam powder bed fusion (PBF) additive manufacturing (AM) technology has transitioned from prototypes and tooling to production components in demanding fields such as medicine and aerospace. Some of these components have geometries that can only be made using AM. Initial applications either take advantage of the relatively high surface roughness of metal PBF parts, or they are in fatigue, corrosion, or flow environments where surface roughness does not impose performance penalties. To move to the next levels of performance, the surfaces of laser and electron-beam PBF components will need to be smoother than the current as-printed surfaces. This will also have to be achieve on increasingly more complex geometries without significantly increasing the cost of the final component. Unsettled Topics on Surface Finishing of Metallic Powder Bed Fusion Parts in the Mobility Industry addresses the challenges and opportunities of this technology, and what remains to be agreed upon by the industry.
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Ziegler, Nancy, Nicholas Webb, Adrian Chappell et Sandra LeGrand. Scale invariance of albedo-based wind friction velocity. Engineer Research and Development Center (U.S.), mai 2021. http://dx.doi.org/10.21079/11681/40499.

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Obtaining reliable estimates of aerodynamic roughness is necessary to interpret and accurately predict aeolian sediment transport dynamics. However, inherent uncertainties in field measurements and models of surface aerodynamic properties continue to undermine aeolian research, monitoring, and dust modeling. A new relation between aerodynamic shelter and land surface shadow has been established at the wind tunnel scale, enabling the potential for estimates of wind erosion and dust emission to be obtained across scales from albedo data. Here, we compare estimates of wind friction velocity (u*) derived from traditional methods (wind speed profiles) with those derived from the albedo model at two separate scales using bare soil patch (via net radiometers) and landscape (via MODIS 500 m) datasets. Results show that profile-derived estimates of u* are highly variable in anisotropic surface roughness due to changes in wind direction and fetch. Wind speed profiles poorly estimate soil surface (bed) wind friction velocities necessary for aeolian sediment transport research and modeling. Albedo-based estimates of u* at both scales have small variability because the estimate is integrated over a defined, fixed area and resolves the partition of wind momentum be-tween roughness elements and the soil surface. We demonstrate that the wind tunnel-based calibration of albedo for predicting wind friction velocities at the soil surface (us*) is applicable across scales. The albedo-based approach enables consistent and reliable drag partition correction across scales for model and field estimates of us* necessary for wind erosion and dust emission modeling.
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Stache, Jeremiah. A dynamic aircraft response model for determining roughness limits. Engineer Research and Development Center (U.S.), mai 2024. http://dx.doi.org/10.21079/11681/48513.

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Runway roughness poses significant risks to aircraft and aircraft personnel. Roughness irregularities can be found in both civilian and military airfields, from rutting to bomb-damaged repairs. Various methods exist for determining roughness criteria, such as discrete surface deviation evaluation and dynamic response models. Although validated dynamic response models such as TAXI-G were used extensively in the HAVE BOUNCE program from the 1970s up to the late 1990s, modern military aircraft have not undergone the same formal analysis. This paper presents the mathematical formulation and validation of the WESTAX dynamic response model. The computer program is capable of simulating the responses of different critical aircraft components while trafficking over idealized runway profiles. The validation results showed that the numerical model was capable of closely matching field data over single- and double bump events. The findings suggest that the WESTAX dynamic response model is a capable candidate for establishing aircraft roughness limits.
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Grimley, Terry. PR-015-20606-R01 Practical Effects of Rough-Walled pipe in Gas Metering Applications. Chantilly, Virginia : Pipeline Research Council International, Inc. (PRCI), janvier 2021. http://dx.doi.org/10.55274/r0012016.

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The influence of upstream pipe roughness on the performance of multipath ultrasonic flow meters was examined through a set of experiments involving three different brands of ultrasonic flow meters. Tests were conducted with 16-inch meters with piping, having a wide variation in surface roughness values with and without a flow conditioner. These results, when combined with the earlier testing of 8-inch diameter meters, can be used to support changes in the practices currently recommended by industry standards.
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Grimley, Terry. PR-015-19603-R01 Practical Effects of Rough-Walled Pipe in Gas Metering Applications. Chantilly, Virginia : Pipeline Research Council International, Inc. (PRCI), août 2020. http://dx.doi.org/10.55274/r0011742.

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The influence of upstream pipe roughness on the performance of multipath ultrasonic flow meters was examined through a cursory literature review and an examination of experimental test data supplied by the natural gas industry. The results of these efforts were used to develop a recommendation for additional testing whereby the results of that testing can be combined with these results and potentially be used to support changes in the practices recommended by current industry standards.
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Ziegler, Nancy, Nicholas Webb, John Gillies, Brandon Edward, George Nikolich, Justin Van Zee, Brad Cooper, Dawn Browning, Ericha Courtright et Sandra LeGrand. Plant phenology drives seasonal changes in shear stress partitioning in a semi-arid rangeland. Engineer Research and Development Center (U.S.), septembre 2023. http://dx.doi.org/10.21079/11681/47680.

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Accurate representation of surface roughness in predictive models of aeolian sediment transport and dust emission is required for model accuracy. While past studies have examined roughness effects on drag partitioning, the spatial and temporal variability of surface shear velocity and the shear stress ratio remain poorly described. Here, we use a four-month dataset of total shear velocity (u*) and soil surface shear velocity (us*) measurements to examine the spatiotemporal variability of the shear stress ratio (R) before, during, and after vegetation green-up at a honey mesquite (Prosopis glandulosa Torr.) shrub-invaded grassland in the Chihuahuan Desert, New Mexico, USA. Results show that vegetation green-up, the emergence of leaves, led to increased drag and surface aerodynamic sheltering and a reduction in us* and R magnitude and variability. We found that us* decreased from 20% to 5% of u* as the vegetation form drag and its sheltering effect increased. Similarly, the spatiotemporal variability of R was found to be linked directly to plant phenological phases. We conclude that drag partition schemes should incorporate seasonal vegetation change, via dynamic drag coefficients and/or R, to accurately predict the timing and magnitude of seasonal aeolian sediment fluxes.
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