Bibliographies thématiques / Shear stress bed

Sommaire

Articles de revues
Thèses
Livres
Chapitres de livres
Actes de conférences
Rapports d'organisations

Littérature scientifique sur le sujet « Shear stress bed »

Auteur : Grafiati

Publié le 10 mars 2023

Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres

Choisissez une source :

Consultez les listes thématiques d’articles de revues, de livres, de thèses, de rapports de conférences et d’autres sources académiques sur le sujet « Shear stress bed ».

À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.

Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.

Articles de revues sur le sujet "Shear stress bed"

Guard, Paul Andrew, Peter Nielsen et Tom E. Baldock. « BED SHEAR STRESS IN UNSTEADY FLOW ». Coastal Engineering Proceedings 1, n^o 32 (31 janvier 2011) : 8. http://dx.doi.org/10.9753/icce.v32.sediment.8.

Texte intégral

Résumé :

Standard engineering methods of estimating bed shear stress using friction factors can fail spectacularly in unsteady hydrodynamic conditions. This paper demonstrates this fact using direct measurements of bed shear stresses under irregular waves using a shear plate apparatus. The measurements are explained in terms of the influence of the horizontal pressure gradient and the shear stresses acting on the surface of the plate. The horizontal fluid velocity at the edge of the boundary layer and the water surface elevation and slope were also measured. The paper demonstrates that the water surface measurements can be used to obtain accurate estimates of the forces on the bed, by employing Fourier analysis techniques or an innovative convolution integral method. The experimental results indicate that an offshore bed shear stress may be recorded while the free stream velocity remains onshore at all times. This demonstrates the failure of the standard engineering friction factor method in this scenario, since negative friction factors would be required. Important questions are raised regarding the appropriate definition for the bed shear stress when the vertical gradient of the shear stress is large. It is shown that it is problematic to define a single value for a “bed” shear stress in the presence of a strong horizontal pressure gradient. It is also argued that the natural driver for any model used to predict bed shear stress is the pressure gradient (or its proxy the free stream acceleration), rather than the velocity. This allows for accurate calculation of both acceleration effects (more rapid acceleration leads to a thinner boundary layer and higher shear stress) and also the direct action of the horizontal pressure gradient.

Styles APA, Harvard, Vancouver, ISO, etc.

Schönfeldt, Hans-Jürgen. « On the aeolian saltation bed shear stress and saltation roughness length ». Meteorologische Zeitschrift 15, n^o 3 (10 juillet 2006) : 307–15. http://dx.doi.org/10.1127/0941-2948/2006/0126.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Cheng, Nian-Sheng, et Adrian Wing-Keung Law. « Fluctuations of Turbulent Bed Shear Stress ». Journal of Engineering Mechanics 129, n^o 1 (janvier 2003) : 126–30. http://dx.doi.org/10.1061/(asce)0733-9399(2003)129:1(126).

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Papa, M., S. Egashira et T. Itoh. « Critical conditions of bed sediment entrainment due to debris flow ». Natural Hazards and Earth System Sciences 4, n^o 3 (2 août 2004) : 469–74. http://dx.doi.org/10.5194/nhess-4-469-2004.

Texte intégral

Résumé :

Abstract. The present study describes entrainment characteristics of bed material into debris flow, based on flume tests, numerical and dimensional analyses. Flume tests are conducted to investigate influences of bed sediment size on erosion rate by supplying debris flows having unsaturated sediment concentration over erodible beds. Experimental results show that the erosion rate decreases monotonically with increase of sediment size, although erosion rate changes with sediment concentration of debris flow body. In order to evaluate critical condition of bed sediment entrainment, a length scale which measures an effective bed shear stress is introduced. The effective bed shear stress is defined as total shear stress minus yield stress on the bed surface. The results show that critical entrainment conditions can be evaluated well in terms of Shields curve using the effective bed shear stress instead of a usual bed shear stress.

Styles APA, Harvard, Vancouver, ISO, etc.

Seelam, Jaya Kumar, et Tom E. Baldock. « MEASUREMENT AND MODELING OF SOLITARY WAVE INDUCED BED SHEAR STRESS OVER A ROUGH BED ». Coastal Engineering Proceedings 1, n^o 33 (11 octobre 2012) : 21. http://dx.doi.org/10.9753/icce.v33.waves.21.

Texte intégral

Résumé :

Bed shear stresses generated by solitary waves were measured using a shear cell apparatus over a rough bed in laminar and transitional flow regimes (~7600 < Re < ~60200). Modeling of bed shear stress was carried out using analytical models employing convolution integration methods forced with the free stream velocity and three eddy viscosity models. The measured wave height to water depth (h/d) ratio varied between 0.13 and 0.65; maximum near- bed velocity varied between 0.16 and 0.47 m/s and the maximum total shear stress (sum of form drag and bed shear) varied between 0.565 and 3.29 Pa. Wave friction factors estimated from the bed shear stresses at the maximum bed shear stress using both maximum and instantaneous velocities showed that there is an increase in friction factors estimated using instantaneous velocities, for non-breaking waves. Maximum positive total stress was approximately 2.2 times larger than maximum negative total stress for non-breaking waves. Modeled and measured positive total stresses are well correlated using the convolution model with an eddy viscosity model analogous to steady flow conditions (nu_t=0.45u* z1; where nu_t is eddy viscosity, u* is shear velocity and z1 is the elevation parameter related to relative roughness). The bed shear stress leads the free stream fluid velocity by approximately 30° for non-breaking waves and by 48° for breaking waves, which is under-predicted by 27% by the convolution model with above mentioned eddy viscosity model.

Styles APA, Harvard, Vancouver, ISO, etc.

Zhang, Liyuan, Faxing Zhang, Ailing Cai, Zhaoming Song et Shilin Tong. « Comparison of Methods for Bed Shear Stress Estimation in Complex Flow Field of Bend ». Water 12, n^o 10 (2 octobre 2020) : 2753. http://dx.doi.org/10.3390/w12102753.

Texte intégral

Résumé :

Bed shear stress is closely related to sediment transport in rivers. Bed shear stress estimation is very difficult, especially for complex flow fields. In this study, complex flow field measurement experiments in a 60° bend with a groyne were performed. The feasibility and reliability of bed shear stress estimations using the log-law method in a complex flow field were analyzed and compared with those associated with the Reynolds, Turbulent Kinetic Energy (TKE), and TKE-w′ methods. The results show that the TKE, Reynolds, and log-law methods produced similar bed shear stress estimates, while the TKE-w′ method produced larger estimates than the other methods. The TKE-w′ method was found to be more suitable for bed shear stress estimation than the TKE method, but the value of its constant C2 needed to be re-estimated. In a complex, strong, three-dimensional flow field, the height of the measurement point (relative or absolute) should be re-estimated when a single point measurement is used to estimate the bed shear stress. The results of this study provide guidance for experimental measurement of bed shear stress in a complex flow field.

Styles APA, Harvard, Vancouver, ISO, etc.

Golpira, Amir, Fengbin Huang et Abul B. M. Baki. « The Effect of Habitat Structure Boulder Spacing on Near-Bed Shear Stress and Turbulent Events in a Gravel Bed Channel ». Water 12, n^o 5 (16 mai 2020) : 1423. http://dx.doi.org/10.3390/w12051423.

Texte intégral

Résumé :

This study experimentally investigated the effect of boulder spacing and boulder submergence ratio on the near-bed shear stress in a single array of boulders in a gravel bed open channel flume. An acoustic Doppler velocimeter (ADV) was used to measure the instantaneous three-dimensional velocity components. Four methods of estimating near-bed shear stress were compared. The results suggested a significant effect of boulder spacing and boulder submergence ratio on the near-bed shear stress estimations and their spatial distributions. It was found that at unsubmerged condition, the turbulent kinetic energy (TKE) and modified TKE methods can be used interchangeably to estimate the near-bed shear stress. At both submerged and unsubmerged conditions, the Reynolds method performed differently from the other point-methods. Moreover, a quadrant analysis was performed to examine the turbulent events and their contribution to the near-bed Reynolds shear stress with the effect of boulder spacing. Generally, the burst events (ejections and sweeps) were reduced in the presence of boulders. This study may improve the understanding of the effect of the boulder spacing and boulder submergence ratio on the near-bed shear stress estimations of stream restoration practices.

Styles APA, Harvard, Vancouver, ISO, etc.

Iverson, Neal R., Christian Helanow et Lucas K. Zoet. « Debris-bed friction during glacier sliding with ice–bed separation ». Annals of Glaciology 60, n^o 80 (décembre 2019) : 30–36. http://dx.doi.org/10.1017/aog.2019.46.

Texte intégral

Résumé :

AbstractTheory and experiments indicate that ice–bed separation during glacier slip over 2-D hard beds causes basal shear stress to reach a maximum at a particular slip velocity and decrease at higher velocities. We use the sliding theory of Lliboutry (1968) to explore how friction between debris particles in sliding ice and a rock bed affects this relationship between shear stress and slip velocity. Particle–bed contact forces and associated debris friction increase with increasing slip velocity, owing to increased rates of ice convergence with up-glacier facing surfaces. However, debris friction on diminished areas of the bed counteracts this effect as cavities grow. Thus, friction from debris alone increases only slightly with slip velocity, and for sediment particles larger than ~60 mm in diameter, debris friction peaks and decreases with increasing slip velocity. The effect on the sliding relationship is to steepen its rising limb and shift its shear stress peak to a slightly higher velocity. These results, which exclude the effect of debris friction on cavity size and debris concentrations above ~15%, indicate that the effect of debris in ice is to increase basal shear stress but not significantly change the form of the sliding relationship.

Styles APA, Harvard, Vancouver, ISO, etc.

Kiraga et Popek. « Bed Shear Stress Influence on Local Scour Geometry Properties in Various Flume Development Conditions ». Water 11, n^o 11 (8 novembre 2019) : 2346. http://dx.doi.org/10.3390/w11112346.

Texte intégral

Résumé :

Numerous approaches in sediment mobility studies highlighted the key meaning of channel roughness, which results not only from bed material granulation but also from various bed forms presence, caused by continuous sediment transport. Those forms are strictly connected with the intensity of particle transport, and they eventuate from bed shear stress. The present paper comprised of local scours geometric dimensions research in three variants of lengthwise development of laboratory flume in various hydraulic properties, both in “clear-water” and “live-bed” conditions of sediment movement. Lots of measurements of the bed conformation were executed using the LiDAR device, marked by a very precise three-dimensional shape description. The influence of the bed shear stress downstream model on scours hole dimensions of water structure was investigated as one of the key factors that impact the sediment transport intensity. A significant database of 39 experimental series, lasting averagely 8 hours, was a foundation for delineating functional correlations between bed shear stress-and-critical shear stress ratio and geometry properties of local scours in various flume development cases. In the scope of mutual influence of bed shear stress and water depth, high correlation coefficients were attained, indicating very good and good functional correlations. Also, the influence of bed shear stress and the total length of the scour demonstrated a high correlation coefficient.

Styles APA, Harvard, Vancouver, ISO, etc.

Maclean, Alastair G. « Bed Shear Stress and Scour over Bed‐Type River Intake ». Journal of Hydraulic Engineering 117, n^o 4 (avril 1991) : 436–51. http://dx.doi.org/10.1061/(asce)0733-9429(1991)117:4(436).

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Plus de sources

Thèses sur le sujet "Shear stress bed"

Su, Yan. « An annular fluidized-bed experiment for inter-granular shear stress ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0008/MQ31257.pdf.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Yang, Qingjun (Judy Qingjun). « Estimation of the bed shear stress in vegetated and bare channels ». Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99580.

Texte intégral

Résumé :

Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 69-77).
The shear stress at the bed of a channel influences important benthic processes such as sediment transport. Several methods exist to estimate the bed shear stress in bare channels without vegetation, but most of these are not appropriate for vegetated channels due to the impact of vegetation on the velocity profile and turbulence production. This study proposes a new model to estimate the bed shear stress in both vegetated and bare channels with smooth beds. The model, which is supported by measurements, indicates that for both bare and vegetated channels with smooth beds, within a viscous sub-layer at the bed, the viscous stress decreases linearly with increasing distance from the bed, resulting in a parabolic velocity profile at the bed. For bare channels, the model describes the velocity profile in the overlap region of the Law of the Wall. For emergent canopies of sufficient density (frontal area per unit canopy volume a >/= 4.3m⁻¹ ), the thickness of the linear-stress layer is set by the stem diameter, leading to a simple estimate for bed shear stress.
by Qingjun (Judy) Yang.
S.M.

Styles APA, Harvard, Vancouver, ISO, etc.

Yaeger, Mary A. « MEAN FLOW AND TURBULENCE AROUND TWO SERIES OF EXPERIMENTAL DIKES ». Thesis, The University of Arizona, 2009. http://hdl.handle.net/10150/193453.

Texte intégral

Résumé :

Scour around various structures obstructing flow in an open channel is a common problem; therefore a better understanding of how turbulent flow affects sediment transport is needed. Additionally, is it the mean flow or the turbulence properties that are more important in contributing to bed shear stress? To this end, an experimental study was conducted in a fixed-bed flume containing a series of dikes. Turbulence intensities and Reynold's stresses were calculated from 3-D velocity measurements gathered with a microADV. Results showed that the maximum shear stress was nearly 12-20 times that of the approach flow, while maximum turbulence intensities were about 3-5 times those of the incoming flow. Highest magnitudes of both were seen at the tip of the second dike in the three-dike series. The mean velocity appeared to have no relation to the formation of scour near the tips of the dikes but the turbulence intensities did.

Styles APA, Harvard, Vancouver, ISO, etc.

Emerson, Samuel D. « The role of bed shear stress in sediment sorting patterns in a reconstructed, gravel bed river ». Thesis, San Jose State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10128515.

Texte intégral

Résumé :

The role of bed shear stress in bed surface grain size sorting was investigated on a reconstructed reach of the Merced River in the Central Valley of California. Pebble count data were collected at the inside, middle, and outside of ten bends in April 2015 and compared to data from pebble counts conducted in previous years. Output from a previously developed 2D flow model (FaSTMECH) was compared to critical shear stresses calculated from median grain-size data. Comparison of pebble count results from 2002 through 2015 showed that there was no temporally consistent pattern of coarsening or fining along the study reach; however, the bed surface coarsened between 2002 and 2015. Pebble count data from April 2015 revealed a distinct spatial distribution of grain sizes with a larger median grain size (D₅₀) at the outside of bends and a smaller D₅₀ at the inside of bends. Regression analyses performed on pebble count data from point bars revealed statistically significant downstream changes in surface grain size on two of the seven bars. Analysis of shear stress data showed a weak relationship between the modeled bed shear stress (τ_b) and the calculated critical shear stress (τ_cr). The weak relationship between τ_b and τ_cr indicated that bed shear stress was not solely responsible for the grain size sorting in the study reach. It is likely that the observed grain size sorting patterns resulted from helical secondary flows at the bends.

Styles APA, Harvard, Vancouver, ISO, etc.

Sarra, Angela M. « Particle-wall shear stress measurements within the standpipe of a circulating fluidized bed ». Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2078.

Texte intégral

Résumé :

Thesis (M.S.)--West Virginia University, 2001.
Title from document title page. Document formatted into pages; contains xi, 137 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 136-137).

Styles APA, Harvard, Vancouver, ISO, etc.

Perret, Emeline. « Transport of moderately sorted gravels at low bed shear stress : impact of bed arrangement and fine sediment infiltration ». Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1223/document.

Texte intégral

Résumé :

Le but de cette thèse est de comprendre la dynamique des graviers au sein des rivières alpines à faible contrainte en utilisant des expériences en laboratoire. Ces rivières sont souvent composées d’une large gamme de sédiments, allant des argiles aux galets. Ces différentes classes sédimentaires peuvent interagir entre elles, ce qui peut rendre difficile l’estimation du transport solide. Des expériences en laboratoire ont été conduites en écoulements instationnaires dans un canal de 18m de long et 1m de large. Deux types de lits ont été étudiés : lits unimodaux et bimodaux. Une attention particulière a été portée sur la réalisation des lits de graviers dans notre canal. Ils ont été créés dans le but d’approcher au mieux la configuration des lits de rivières alpines, c’est-à-dire avec différents arrangements et degrés de colmatage du lit par des sédiments fins. Les lits unimodaux sont composés de graviers peu triés avec divers arrangements de surface. Les lits bimodaux sont composés d’une matrice de graviers peu triés dans laquelle des sédiments fins se sont infiltrés (sables ou limons). Les processus régissant le transport de graviers ont été mis en avant. Le transport de graviers est impacté par l’arrangement du lit, la concentration de sédiments fins dans la couche de charriage, et par le changement de propriétés du lit due à la présence de sédiments fins (cohésion, perméabilité du lit). Plus le lit est arrangé, plus le transport est difficile. Plus la couche de charriage est concentrée en sédiments fins, plus le transport est facile. La forme des sédiments fins est aussi un facteur important pouvant modifier le transport des graviers. La présence de sédiments fins cohésifs dans la matrice peut considérablement réduire le taux de graviers transportés. Un modèle conceptuel a été développé pour résumer les différents processus contrôlant le transport de graviers. Il décrit le comportement des graviers dans les différentes configurations étudiées. L’outil proposé peut aider à comprendre, estimer et interpréter le transport de graviers. Il a été appliqué et discuté sur un cas de terrain sur la rivière de l’Arc. Basé sur ce modèle, nous avons proposé une nouvelle analyse dimensionnelle pour la construction d’un modèle de prédiction de transport solide prenant en compte des paramètres décrivant l’arrangement du lit, les propriétés géotechniques du lit et la présence de sédiments fins
This PhD thesis aims to understand gravel dynamics in Alpine rivers at low bed shear stress using laboratory experiments. Alpine river beds are often poorly sorted and composed of sediments ranging from clay to pebble. To understand interactions between these classes is an issue for predicting bedload rate. Laboratory experiments were performed in a 18m long and 1m wide flume, under unsteady flows. Two types of bed were investigated: unimodal and bimodal beds. A particular attention was paid to the bed construction, which was conducted in order to obtain a nature-like bed 12with different bed arrangements and degrees of clogging. Unimodal beds were made of moderately sorted gravels with different bed surface arrangements. Bimodal beds were made of moderately sorted gravels in which fine sediments (sand or silt) were infiltrated. Gravel rate was found to be impacted by the bed arrangement degree, the fine sediment concentration within the bedload layer and the changes in bed properties due to fine sediment presence (bed cohesion, bed permeability). The more packed the bed is; the more difficult it is to move gravels. The more concentrated in fine sediment the bedload layer is; the easier the transport of gravels is. The shape of fine sediments can also be an important factor for modifying the gravel rate. The presence of cohesive fine sediments within the bed matrix reduces significantly the gravel rate. A conceptual model was developed to recap the different processes controlling gravel transport. It provides a phenomenological description of the overall bed responses to a hydrograph. This tool is designed to help understanding, estimating or interpreting gravel transport in Alpine rivers. The conceptual model was discussed and applied to a field case made on the Arc River. Using the model, we also suggest a new dimensionless analysis for the construction of a bedload predicting model involving parameters describing bed arrangement, bed properties and fine sediment presence

Styles APA, Harvard, Vancouver, ISO, etc.

Thompson, Charlotte E. L. « The role of the solid-transmitted bed shear stress of mobile granular material on cohesive bed erosion by unidirectional flow ». Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398824.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Sime, Louise C. « Reach-scale spatial variation of grain-size, shear stress, and bedload transport in gravel-bed rivers ». Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401128.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Valentine, Kendall. « Characterization of the bed, critical boundary shear stress, roughness, and bedload transport in the Connecticut River Estuary ». Thesis, Boston College, 2015. http://hdl.handle.net/2345/bc-ir:104550.

Texte intégral

Résumé :

Thesis advisor: Gail C. Kineke
This study characterizes the bed of the Connecticut River estuary in terms of grain size and bedforms, and relates these to river discharge, tidal currents, and sediment transport. Over four field excursions, sediment cores were collected, in addition to bathymetry surveys, and water column measurements. A three-dimensional circulation and sediment transport model calculated boundary shear stress over the same time. The bed of the estuary is composed mostly of sand, with small amounts of fine sediments. Deposition of fine sediments is limited by the landward extent of the salt intrusion. Large bedforms are oriented seaward. The critical shear stress for the median grain size is exceeded each tidal cycle. Bedload transport is dominantly seaward during high discharge conditions, but varies during low discharge. Bathymetry surveys from previous studies and this study show consistent bedform fields over 25 years. Bedforms observed in the field reflect typical conditions rather than extreme events
Thesis (MS) — Boston College, 2015
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Earth and Environmental Sciences

Styles APA, Harvard, Vancouver, ISO, etc.

Mayoral, Helen. « Particle Size, Critical Shear Stress, and Benthic Invertebrate Distribution and Abundance in a Gravel-bed River of the Southern Appalachians ». Digital Archive @ GSU, 2011. http://digitalarchive.gsu.edu/geosciences_theses/31.

Texte intégral

Résumé :

To determine the relationship between the abundance and density of benthic invertebrates, and the critical shear stress of individual grain sizes, a reach along Smith Creek, was divided into ten 2m x 2m quadrants. Within each quadrant, five randomly selected clasts for each grain size ranging from 2.26 to 25.6 cm were cleaned for benthic invertebrates. Wolman pebble counts for each quadrant were also conducted and used to determine the critical Shields stress per grain size fraction from the model given by Wiberg and Smith (1987) that explicitly accounts for particle hiding/sheltering effects in mixed-bed rivers. Particle entrainment values were then compared with estimated bankfull Shields stress values to determine sediment transport potential during bankfull flow. Invertebrate abundance was strongly positively correlated with critical Shields stress up to the 18.0 cm grain size, indicating a preference for certain grain sizes; while density was positively correlated with all grain sizes present.

Styles APA, Harvard, Vancouver, ISO, etc.

Plus de sources

Livres sur le sujet "Shear stress bed"

Sturm, Terry W. Estimating critical shear stress of bed sediment for improved prediction of bridge contraction scour in Georgia : Final report. Forest Park, Ga.] : Dept. of Transportation, Office of Materials and Research, 2008.

Trouver le texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Furst, Eric M., et Todd M. Squires. Magnetic bead microrheology. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199655205.003.0008.

Texte intégral

Résumé :

Magnetism is a convenient force for actively pulling colloidal particles in a material. Many materials of interest in a microrheology experiment have a negligible magnetic susceptibility, and so embedded magnetic particles can be subject to relatively strong forces by fields imposed from outside of the sample. These are usually generated by electromagnets, but can also include the use of permanent magnets, or a combination of both. Such “magnetic tweezers” are used as sensitive force probes, capable of generating forces ranging from femtonewtons to nanonewtons. Magnetic forces and magnetic materials are reviewed and magnetic tweezer designs discussed. Linear and non-linear measurements using magnetic tweezers are presented, including studies yield stress and shear thinning. The operating regime of magnetic tweezer microrheology is presented, which enables microrheology experiments to access stiffer materials.

Styles APA, Harvard, Vancouver, ISO, etc.

Escudier, Marcel. Basic equations of viscous-fluid flow. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198719878.003.0015.

Texte intégral

Résumé :

In this chapter it is shown that application of the momentum-conservation equation (Newton’s second law of motion) to an infinitesimal cube of fluid leads to Cauchy’s partial differential equations, which govern the flow of any fluid satisfying the continuum hypothesis. Any fluid flow must also satisfy the continuity equation, another partial differential equation, which is derived from the mass-conservation equation. It is shown that distortion of a flowing fluid can be split into elongational distortion and angular distortion or shear strain. For a Newtonian fluid, the normal and shear stresses in Cauchy’s equations are related to the elongational and shear-strain rates through Stokes’ constitutive equations. Substitution of these constitutive equations into Cauchy’s equations leads to the Navier-Stokes equations, which govern steady or unsteady flow of a fluid. A minor modification of the constitutive equations for a Newtonian fluid allows consideration of generalised Newtonian fluids, for which the viscosity depends upon the shear-strain rates. The boundary conditions for the tangential and normal velocity components are discussed briefly.

Styles APA, Harvard, Vancouver, ISO, etc.

Kiss, Thomas, et Paolo Pelosi. Lung recruitment techniques in the ICU. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0120.

Texte intégral

Résumé :

Lung recruitment manoeuvres (RMs) have been suggested as a means of homogenizing the lung structure and distribution of the mechanical stress across the lungs. Such effects can be achieved provided enough pressure is applied for enough time at the airways, and maintained if adequate levels of positive end-expiratory pressure (PEEP) are used. When RMs effectively open atelectatic tissue, shear stress, and cyclic collapse/reopening are importantly reduced. The lung response to RMs is mainly determined by cause and severity of lung injury, and the position of the lungs with respect to the gravity gradient. RMs can be performed in several different ways, the most relevant RMs in terms of clinical applicability are sustained inflation manoeuvres, high pressure controlled ventilation, incremental PEEP, and intermittent sighs.

Styles APA, Harvard, Vancouver, ISO, etc.

Escudier, Marcel. Turbulent flow. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198719878.003.0018.

Texte intégral

Résumé :

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.

Styles APA, Harvard, Vancouver, ISO, etc.

Escudier, Marcel. Fluids and fluid properties. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198719878.003.0002.

Texte intégral

Résumé :

In this chapter it is shown that the differences between solids, liquids, and gases have to be explained at the level of the molecular structure. The continuum hypothesis makes it possible to characterise any fluid and ultimately analyse its response to pressure difference Δ‎p and shear stress τ‎ through macroscopic physical properties, dependent only upon absolute temperature T and pressure p, which can be defined at any point in a fluid. The most important of these physical properties are density ρ‎ and viscosity μ‎, while some problems are also influenced by compressibility, vapour pressure pV, and surface tension σ‎. It is also shown that the bulk modulus of elasticity Ks is a measure of fluid compressibility which determines the speed at which sound propagates through a fluid. The perfect-gas law is introduced and an equation derived for the soundspeed c.

Styles APA, Harvard, Vancouver, ISO, etc.

Cates, M. Complex fluids : the physics of emulsions. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198789352.003.0010.

Texte intégral

Résumé :

These lectures start with the mean field theory for a symmetric binary fluid mixture, addressing interfacial tension, the stress tensor, and the equations of motion (Model H). We then consider the phase separation kinetics of such a mixture: coalescence, Ostwald ripening, its prevention by trapped species, coarsening of bicontinuous states, and the role of shear flow. The third topic addressed is the stabilization of emulsions by using surfactants to reduce or even eliminate the interfacial tension between phases; the physics of bending energy, which becomes relevant in the latter case, is then presented briefly. The final topic is the creation of long-lived metastable emulsions by adsorption of colloidal particles or nanoparticles at the fluid–fluid interface; alongside spherical droplets, these methods can be used to create a range of unconventional structures with potentially interesting properties that are only now being explored.

Styles APA, Harvard, Vancouver, ISO, etc.

Escudier, Marcel. Linear momentum equation and hydrodynamic forces. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198719878.003.0009.

Texte intégral

Résumé :

In this chapter a method is shown for calculating the external reaction force which must be applied to a duct to counteract the hydrodynamic forces generated by a fluid flowing through it. Newton’s second law of motion applied to fluid flow through a duct of arbitrary shape leads to the linear momentum equation for fluid flow. This shows that the change in the momentum flowrate of the fluid is equal to the net force exerted on the fluid. The individual forces which contribute to the net force are the pressure forces at inlet and outlet, and the forces which arise due to the static pressure and shear stress distributed over the wetted interior surface of the duct. The condition of static equilibrium for the duct is used to relate the external restraining force to the force exerted by the flowing fluid on the wetted surface, which is termed the fluid-structure interaction force.

Styles APA, Harvard, Vancouver, ISO, etc.

Woźniak, Monika, et Maria Wyke, dir. The Novel of Neronian Rome and its Multimedial Transformations. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198867531.001.0001.

Texte intégral

Résumé :

When in 1905 the Polish writer Henryk Sienkiewicz was awarded the Nobel Prize for Literature ‘for outstanding services as an epic writer’, it was his novel Quo vadis. A Narrative of the Time of Nero that motivated the committee to bestow this notable honour. The extraordinary international success of Quo vadis catapulted the author into literary stardom, placing him at the top of international league tables for the sheer quantity of his readers. But, before long, the historical novel began to detach itself from the person of its author and to become a multimedial, mass–culture phenomenon. In the West and East, Quo vadis was adapted for the stage and screen, provided the inspiration for works of music and other genres of literature, was transformed into comic strips and illustrated children’s books, and was cited in advertising and referenced in everyday objects of material culture. No work in English to date has explored in depth the mechanisms that released Quo vadis into mass circulation and the influence that its diverse spin-off forms exercised on other areas of culture—even on the reception and interpretation of the literary text itself. In the context of a robust scholarly interest in the processes of literary adaptation and classical reception, and set alongside the recent emergence of interest in the ‘Ben-Hur tradition’, this volume provides a coherent forum for a much-needed exploration, from various disciplinary and national perspectives, of the multimedial transformations of Quo vadis. Uniquely, also, for its English-speaking readers this collection of essays renders more visible the cultural conquests achieved by Poland on the world map of classical reception.

Styles APA, Harvard, Vancouver, ISO, etc.

Chapitres de livres sur le sujet "Shear stress bed"

Maa, Jerome P. Y. « The Bed Shear Stress of an Annular Sea-Bed Flume ». Dans Estuarine Water Quality Management, 271–75. Berlin, Heidelberg : Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-75413-5_41.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Maa, Jerome P. Y. « The bed shear stress of an annular sea-bed flume ». Dans Estuarine Water Quality Management Monitoring, Modelling and Research, 271–75. Washington, D. C. : American Geophysical Union, 1990. http://dx.doi.org/10.1029/ce036p0271.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Visuvamithiran, Nandakumar, V. Sriram et Jaya Kumar Seelam. « Numerical Modelling of Bed Shear Stress in OpenFOAM ». Dans Lecture Notes in Civil Engineering, 637–45. Singapore : Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-3119-0_41.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Xia, Y. F., Hua Xu et S. Z. Zhang. « Measurement and Primary Study on Bed Shear Stress Under Complex Hydrodynamic Environment ». Dans APAC 2019, 529–33. Singapore : Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-15-0291-0_73.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Sharma, Anurag, et Bimlesh Kumar. « Higher Order Statistics of Reynolds Shear Stress in Nonuniform Sand Bed Channel ». Dans GeoPlanet : Earth and Planetary Sciences, 401–13. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-70914-7_27.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Yao, Zishun, Lidi Shi, Shoupeng Xie, Peng Li et Dawei Guan. « Experimental Study on Flow Characteristics Around a Submerged Half-Buried Pipeline ». Dans Lecture Notes in Civil Engineering, 74–81. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-6138-0_7.

Texte intégral

Résumé :

AbstractThis paper describes the flow characteristics around a half-buried pipeline exposed to different current conditions by flume experiment. Particle Imaging Velocimetry (PIV) technique was used in the experiment to reveal the flow structure. The experiment results indicate that the hydrodynamic parameters, including average kinetic energy, vorticities, Reynolds shear stress, and kinetic turbulence energy, increased with the Renolds numbers. Furthermore, it is found that the vortex at the upstream side of the half-buried pipeline vanishes gradually with increasing Renolds numbers. However, the two vortices at the locations downstream of the half-buried pipeline exist all the time, in which the vortex closed to the downstream of the pipeline becomes unstable, the vortex at the pipeline wake remains unchanged. In the meantime, the turbulence intensity at the upstream side of the half-buried pipe near the bed surface strengthens significantly under Reynolds number conditions, which may accelerate the potential scour process in front of the pipeline.

Styles APA, Harvard, Vancouver, ISO, etc.

Daniels, Melinda D., et Bruce L. Rhoads. « Spatial pattern of turbulence kinetic energy and shear stress in a meander bend with large woody debris ». Dans Riparian Vegetation and Fluvial Geomorphology, 87–97. Washington, D. C. : American Geophysical Union, 2004. http://dx.doi.org/10.1029/008wsa07.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

« critical (bed) shear(ing) stress ». Dans Dictionary Geotechnical Engineering/Wörterbuch GeoTechnik, 307. Berlin, Heidelberg : Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-41714-6_35444.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Horst, U. Oebius. « Laboratory and insitu bed shear stress measurements ». Dans Mechanics of Sediment Transport, 243–54. CRC Press, 2020. http://dx.doi.org/10.1201/9781003079019-32.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Gopichand, Malasani, Tapas Kumar Pradhan, K. Murali et Venu Chandra. « Numerical study of ship induced bed shear stress ». Dans River Flow 2020, 2338–42. CRC Press, 2020. http://dx.doi.org/10.1201/b22619-326.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Actes de conférences sur le sujet "Shear stress bed"

Tavouktsoglou, Nicholas S., John M. Harris, Richard R. Simons et Richard J. S. Whitehouse. « Bed Shear Stress Distribution Around Offshore Gravity Foundations ». Dans ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41966.

Texte intégral

Résumé :

Offshore gravity foundations are often designed with complex geometries. Such structures interact with the local hydrodynamics and generate enhanced bed shear stresses and flow turbulence capable of scouring the seabed or destabilizing bed armour where deployed. In the present study a novel bed shear stress measurement method has been developed from the camera and laser components of a Particle Image Velocimetry (PIV) system. The bed shear stress amplification was mapped out around six models of gravity foundations with different geometries. Tests were repeated for two bed roughness conditions. The structures tested included uniform cylinders, cylindrical base structures and conical base structures. The flow field around the models was also measured using PIV. The results of this study reveal that the conical base structures generate a different hydrodynamic response compared to the other structures. For uniform cylinders the maximum bed shear stress amplification occurs upstream, at an angle of 45° relative to the flow direction, and measurements were found to agree well with numerical results obtained by Roulund et al. (2005). In the case of the cylindrical base structure the maximum amplification occurs upstream at a similar location to the uniform cylinder case. For the conical base structures the maximum amplification of the bed shear stress occurs on the lee side of the structure, with the magnitude dependent on the side slope of the cone. The bed shear stress results were validated against stresses derived from analysis of the flow fields obtained by the PIV measurements performed under the same test conditions. Conclusions from the study are that the structure with the cylindrical base foundation produces the lowest bed shear stress amplification and that an increase in the bed roughness results in an increase in the amplification of the bed shear stress. These findings have direct implications for design of scour protection. In addition the flow reattachment point behind the foundation is dependent on pile Reynolds number (ReD). This suggests that the results of this study may be extrapolated for higher pile Reynolds using the method described in Roulund et al. (2006).

Styles APA, Harvard, Vancouver, ISO, etc.

Sumer, B. M., J. Fredsøe, N. Christiansen et S. B. Hansen. « Bed Shear Stress and Scour Around Coastal Structures ». Dans 24th International Conference on Coastal Engineering. New York, NY : American Society of Civil Engineers, 1995. http://dx.doi.org/10.1061/9780784400890.116.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Rankin, Kelly L., Michael S. Bruno et Richard I. Hires. « Measurement of Shear Stress on a Moveable Bed ». Dans 26th International Conference on Coastal Engineering. Reston, VA : American Society of Civil Engineers, 1999. http://dx.doi.org/10.1061/9780784404119.199.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Oms, C., M. C. Gromaire-Mertz, R. DeSutter et G. Chebbo. « Measurement of Local Bed Shear Stress in Combined Sewers ». Dans Specialty Symposium on Urban Drainage Modeling at the World Water and Environmental Resources Congress 2001. Reston, VA : American Society of Civil Engineers, 2001. http://dx.doi.org/10.1061/40583(275)48.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Myrhaug, Dag, et Lars Erik Holmedal. « Seabed Shear Stress Spectrum for Very Rough Beds ». Dans ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57144.

Texte intégral

Résumé :

The spectrum of seabed shear stresses at beds with large roughness beneath ocean surface waves in finite water depth is derived by using the wave friction factor for large roughness. It is expressed in terms of the transfer function between the waves at the surface and the shear stress at the bed, and the wave spectrum in finite water depth, which is obtained by multiplying the deep water wave spectrum with a depth correction factor. The seabed shear stress spectrum for laminar flow, which is of practical interest for flow over muds, is also given as a reference case. Examples are included to illustrate the applicability of the seabed shear stress spectrum for practical purposes using data typical for field conditions, both for very rough beds and mud beds.

Styles APA, Harvard, Vancouver, ISO, etc.

Yilmaz, L. « Bed Shear Stress of a Flowing Meandering Fluid-Structure Interaction ». Dans ASME 2005 Pressure Vessels and Piping Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/pvp2005-71530.

Texte intégral

Résumé :

An analytical model is developed for free-surface flow over an erodible bed and is used to investigate the stability of the fluid-bed interface and the characteristics of the bed features by measuring the shear stress distribution with hot-film sensors. The model is based on the potential flow over a two-dimensional, moving, wavy bed with a sinusoidal profile of varying amplitude, and a sediment transport relation in which the transported rate is proportional to the power of the fluid velocity at the level of the meandering bed. Consideration is given to the factors involved in determining the shear stress distribution at the flow boundary layer. The experimental results are presented in two parts. Experimental observations of meander evolution described qualitatively. The most important parameter is the shear stress distribution, because of the inhomogeneous distribution of boundary layer meander features. At the wavy boundary layer, the shear stress distribution, measured with WTG-50 hot-film-anemometer is given graphically and theoretically.

Styles APA, Harvard, Vancouver, ISO, etc.

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.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

MUNAR-MARTINEZ, MATEO, ANDRÉS VARGAS-LUNA et ANDRÉS TORRES. « LABORATORY INVESTIGATION ON BED-SHEAR STRESS PARTITIONING IN VEGETATED FLOWS ». Dans 38th IAHR World Congress. The International Association for Hydro-Environment Engineering and Research (IAHR), 2019. http://dx.doi.org/10.3850/38wc092019-0438.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Matousˇek, Va´clav. « Solids Shear Stress in Sheet Flow Above Eroded Plane Bed ». Dans ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-09009.

Texte intégral

Résumé :

Solids shear stress at the bottom of a shear layer is described and quantified on a basis of characteristic shapes of concentration- and velocity profiles across a thickness of the layer. A comparison with experimental data shows that the bed friction coefficient associated with the solids shear stress correlates with the Shields number, relative height of the discharge area and the delivered concentration of solids in the sheet flow.

Styles APA, Harvard, Vancouver, ISO, etc.

Zordan, Jessica, Anton Schleiss et Mário J. Franca. « Bed shear stress estimation for gravity currents performed in laboratory ». Dans The International Conference On Fluvial Hydraulics (River Flow 2016). Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742 : CRC Press, 2016. http://dx.doi.org/10.1201/9781315644479-136.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Rapports d'organisations sur le sujet "Shear stress bed"

Pullammanappallil, Pratap, Haim Kalman et Jennifer Curtis. Investigation of particulate flow behavior in a continuous, high solids, leach-bed biogasification system. United States Department of Agriculture, janvier 2015. http://dx.doi.org/10.32747/2015.7600038.bard.

Texte intégral

Résumé :

Recent concerns regarding global warming and energy security have accelerated research and developmental efforts to produce biofuels from agricultural and forestry residues, and energy crops. Anaerobic digestion is a promising process for producing biogas-biofuel from biomass feedstocks. However, there is a need for new reactor designs and operating considerations to process fibrous biomass feedstocks. In this research project, the multiphase flow behavior of biomass particles was investigated. The objective was accomplished through both simulation and experimentation. The simulations included both particle-level and bulk flow simulations. Successful computational fluid dynamics (CFD) simulation of multiphase flow in the digester is dependent on the accuracy of constitutive models which describe (1) the particle phase stress due to particle interactions, (2) the particle phase dissipation due to inelastic interactions between particles and (3) the drag force between the fibres and the digester fluid. Discrete Element Method (DEM) simulations of Homogeneous Cooling Systems (HCS) were used to develop a particle phase dissipation rate model for non-spherical particle systems that was incorporated in a two-fluid CFDmultiphase flow model framework. Two types of frictionless, elongated particle models were compared in the HCS simulations: glued-sphere and true cylinder. A new model for drag for elongated fibres was developed which depends on Reynolds number, solids fraction, and fibre aspect ratio. Schulze shear test results could be used to calibrate particle-particle friction for DEM simulations. Several experimental measurements were taken for biomass particles like olive pulp, orange peels, wheat straw, semolina, and wheat grains. Using a compression tester, the breakage force, breakage energy, yield force, elastic stiffness and Young’s modulus were measured. Measurements were made in a shear tester to determine unconfined yield stress, major principal stress, effective angle of internal friction and internal friction angle. A liquid fludized bed system was used to determine critical velocity of fluidization for these materials. Transport measurements for pneumatic conveying were also assessed. Anaerobic digestion experiments were conducted using orange peel waste, olive pulp and wheat straw. Orange peel waste and olive pulp could be anaerobically digested to produce high methane yields. Wheat straw was not digestible. In a packed bed reactor, anaerobic digestion was not initiated above bulk densities of 100 kg/m³ for peel waste and 75 kg/m³ for olive pulp. Interestingly, after the digestion has been initiated and balanced methanogenesis established, the decomposing biomass could be packed to higher densities and successfully digested. These observations provided useful insights for high throughput reactor designs. Another outcome from this project was the development of low cost devices to measure methane content of biogas for off-line (US$37), field (US$50), and online (US$107) applications.

Styles APA, Harvard, Vancouver, ISO, etc.

Hammack, E. A., David S. Smith et Richard L. Stockstill. Modeling Vessel-Generated Currents and Bed Shear Stresses. Fort Belvoir, VA : Defense Technical Information Center, juin 2008. http://dx.doi.org/10.21236/ada482693.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Tarpley, Danielle, et David Perkey. Impacts of Granular Activated Carbon (GAC) on erosion behavior of muddy sediment. Engineer Research and Development Center (U.S.), juillet 2022. http://dx.doi.org/10.21079/11681/44841.

Texte intégral

Résumé :

Recent policy changes regarding the placement of dredged material have encouraged the USACE to increase its beneficial use (BU) of the sediments dredged from the nation’s navigation channels. A good portion of this material is fine grained (<63 μm), which traditionally has limited use in BU applications, in part due to its dispersive nature. A need exists to evaluate the potential of stabilizing and using fine-grained sediment (FGS) in BU projects. Previous studies have shown the addition of granular sand to FGS reduces the mobility of the bed. The potential of using Granular Activated Carbon (GAC), an amendment commonly used in environmental capping involving FGS, as a similar bed stabilizing material was explored in this study. A series of laboratory erosion tests using Sedflume were performed on FGS-GAC mixtures that ranged from 5% to 20% GAC by mass. Results suggested that GAC content ≤10% had no influence on the stability of the bed while GAC content ≥15% appeared to reduce both critical shear stress (τcr) and erosion rate (n). However, when compared to control cores, those without GAC, clear evidence of bed stabilization of FGS from the addition of GAC was not observed.

Styles APA, Harvard, Vancouver, ISO, etc.

Kinikles, Dellena, et John McCartney. Hyperbolic Hydro-mechanical Model for Seismic Compression Prediction of Unsaturated Soils in the Funicular Regime. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, décembre 2022. http://dx.doi.org/10.55461/yunw7668.

Texte intégral

Résumé :

A semi-empirical elasto-plastic constitutive model with a hyperbolic stress-strain curve was developed with the goal of predicting the seismic compression of unsaturated sands in the funicular regime of the soil-water retention curve (SWRC) during undrained cyclic shearing. Using a flow rule derived from energy considerations, the evolution in plastic volumetric strain (seismic compression) was predicted from the plastic shear strains of the hysteretic hyperbolic stress-strain curve. The plastic volumetric strains are used to predict the changes in degree of saturation from phase relationships and changes in pore air pressure from Boyle’s and Henry’s laws. The degree of saturation was used to estimate changes in matric suction from the transient scanning paths of the SWRC. Changes in small-strain shear modulus estimated from changes in mean effective stress computed from the constant total stress and changes in pore air pressure, degree of saturation and matric suction, in turn affect the hyperbolic stress-strain curve’s shape and the evolution in plastic volumetric strain. The model was calibrated using experimental shear stress-strain backbone curves from drained cyclic simple shear tests and transient SWRC scanning path measurements from undrained cyclic simple shear tests. Then the model predictions were validated using experimental data from undrained cyclic simple shear tests on unsaturated sand specimens with different initial degrees of saturation in the funicular regime. While the model captured the coupled evolution in hydro-mechanical variables (pore air pressure, pore water pressure, matric suction, degree of saturation, volumetric strain, effective stress, shear modulus) well over the first 15 cycles of shearing, the predictions were less accurate after continued cyclic shearing up to 200 cycles. After large numbers of cycles of undrained shearing, a linear decreasing trend between seismic compression and initial degree of saturation was predicted from the model while a nonlinear increasing-decreasing trend was observed in the cyclic simple shear experiments. This discrepancy may be due to not considering post shearing reconsolidation in the model, calibration of model parameters, or experimental issues including a drift in the position of the hysteretic shear-stress strain curve. Nonetheless, the trend from the model is consistent with predictions from previously- developed empirical models in the funicular regime of the SWRC. The developments of the new mechanistic model developed in this study will play a key role in the future development of a holistic model for predicting the seismic compression across all regimes of the SWRC.

Styles APA, Harvard, Vancouver, ISO, etc.

Hammack, E., et Morgan Johnston. Three-dimensional numerical model study of flow near a scour hole in Isle of Wight Bay near Ocean City, Maryland. Engineer Research and Development Center (U.S.), avril 2022. http://dx.doi.org/10.21079/11681/43921.

Texte intégral

Résumé :

A scour hole has developed in Isle of Wight Bay near Ocean City, MD. This hole could grow to the point that nearby land developments are threatened, so channel-bed protection measures may be implemented near this scour hole. Appropriately designing those bed protection measures requires knowledge of the flow behavior in the scour hole, so a three-dimensional model study has been conducted to determine the flow behavior at the extreme flood and ebb tides present during a pre-selected month of tide cycles. Steady-state simulations of the flows during those two tide conditions have been completed. Contour plots of the flow velocity near the bed and the corresponding bed shear stresses are provided as input for the design of the bed protection measures.

Styles APA, Harvard, Vancouver, ISO, etc.

Wibowo, Johannes, et Jamie López-Soto. Field Jet Erosion Tests on Benbrook Dam, Texas. Engineer Research and Development Center (U.S.), décembre 2021. http://dx.doi.org/10.21079/11681/42545.

Texte intégral

Résumé :

This report summarizes the results of eight field Jet Erosion Tests (JETs) performed on Benbrook Dam, TX. The results from these tests will be used by the U.S. Army Corps of Engineers, Fort Worth District, in assessments of the erosion resistance of the Benbrook Dam with regards to possible overtopping by extreme flooding. The JETs were performed at four different locations, i.e., two locations at the lowest crest elevation and two locations at the mid-slope face of the downstream embankment. Variations in estimated critical hydraulic shear stress and erosion rate values may have been caused by differences in soil composition, i.e., when the material changed from silt/sand to clay. The resulting values of the Erodibility Coefficient, Kd, and Critical Stress, τc, are very useful information in assessing the stability of Benbrook Dam during an overtopping event. Because of the observed natural variability of the materials, combining the erosion parameters presented in this report with the drilling logs and local geology will be imperative for assessing erosion-related failure modes of Benbrook Dam.

Styles APA, Harvard, Vancouver, ISO, etc.

Perkey, David, et Danielle Tarpley. Using geophysical and erosion properties to identify potential beneficial use applications for Atlantic Intracoastal Waterway sediments. Engineer Research and Development Center (U.S.), juillet 2022. http://dx.doi.org/10.21079/11681/44825.

Texte intégral

Résumé :

In an effort to identify alternative and beneficial use placement strategies for dredged sediments from the Atlantic Intracoastal Waterway (AIWW), the US Army Corps of Engineers, Savannah District (SAS), and the US Army Engineer Research and Development Center (ERDC) performed a series of physical property tests of 34 core borings from the SAS AIWW. Physical property testing found that 14 of the borings were non-cohesive sandy materials that may be suitable for potential beach renourishment or berm construction. The remaining 20 borings had mud contents sufficient enough to result in cohesive behavior. A subset of six of these materials from across the geographic region were further evaluated to characterize their erosion behavior. Following a self-weight consolidation period of 30 days, erosion testing showed that the tested cohesive sediments had critical shear stress values that ranged from 1.7 Pa to 2.9 Pa, suggesting that these sediments would likely be resistant to erosion in most wetland environments after placement. Additionally, the cohesive sediments were found to produce gravel-sized mud clasts. These clasts could account for 20% or more of the eroded mass and significantly reduce the amount of silts and clays incorporated in suspended plumes during and immediately following placement.

Styles APA, Harvard, Vancouver, ISO, etc.

Perkey, David W., Danielle R. N. Tarpley et Renée M. Styles. Using Geophysical and Erosion Properties to Identify Potential Beneficial Use Applications for Atlantic Intracoastal Waterway Sediments. U.S. Army Engineer Research and Development Center, juillet 2022. http://dx.doi.org/10.21079/11681/44906.

Texte intégral

Résumé :

Styles APA, Harvard, Vancouver, ISO, etc.

ELASTIC BUCKLING OF OUTSTAND STAINLESS-CLAD BIMETALLIC STEEL PLATES SUBJECTED TO UNIAXIAL COMPRESSION. The Hong Kong Institute of Steel Construction, août 2022. http://dx.doi.org/10.18057/icass2020.p.274.

Texte intégral

Résumé :

The application of stainless-clad (SC) bimetallic steel in various conditions such as offshore and marine environment requires members designed in different cross-sectional shapes, which consist of both internal and outstand elements. To form a comprehensive understanding of buckling behaviour of the SC bimetallic steel members, the behaviour of outstand compression plates needs to be investigated. In this study, the theoretical elastic buckling stress of outstand SC bimetallic steel plates subjected to uniformly distributed uniaxial compression is derived. Considering the position of neutral surface, the energy method and Ritz formulation are used to solve the buckling stress. Adaptation of the first-order shear deformation plate theory (FSDT) is used to modify the solution, which is further compared with finite element analyses. The influence of different parameters such as cladding configuration, clad ratio, elastic modulus ratio, aspect ratio and width-to-thickness ratio on the elastic buckling behaviour of SC bimetallic plates is analysed. The simplified design formulae and design requirements are summarized to form a comprehensive design method.

Styles APA, Harvard, Vancouver, ISO, etc.

ELASTIC BUCKLING OF OUTSTAND STAINLESS-CLAD BIMETALLIC STEEL PLATES. The Hong Kong Institute of Steel Construction, mars 2023. http://dx.doi.org/10.18057/ijasc.2023.19.1.5.

Texte intégral

Résumé :

The application of stainless-clad (SC) bimetallic steel in various conditions such as offshore and marine environment requires members designed in different cross-sectional shapes, which consist of both internal and outstand elements. To form a comprehensive understanding of buckling behaviour of the SC bimetallic steel members, the behaviour of outstand compression plates needs to be investigated. In this study, the theoretical elastic buckling stress of outstand SC bimetallic steel plates subjected to uniformly distributed uniaxial compression is derived. Considering the position of neutral surface, the energy method and Ritz formulation are used to solve the buckling stress. Adaptation of the first-order shear deformation plate theory (FSDT) is used to modify the solution, which is further compared with finite element analyses. The influence of different parameters such as cladding configuration, clad ratio, elastic modulus ratio, aspect ratio and width-to-thickness ratio on the elastic buckling behaviour of the SC bimetallic plates is analysed. The simplified design formulae and design requirements are summarized to form a comprehensive design method.

Styles APA, Harvard, Vancouver, ISO, etc.

Nous offrons des réductions sur tous les plans premium pour les auteurs dont les œuvres sont incluses dans des sélections littéraires thématiques. Contactez-nous pour obtenir un code promo unique!