Artykuły w czasopismach: „HORIZONTAL BED”

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Zhang, Zhenxiang, Jin Yang, Shengnan Chen, Qibin Ou, Yichi Zhang, Ximo Qu i Yafei Guo. "Numerical Simulation of Pulsed Gravel Packing Completion in Horizontal Wells". Energies 14, nr 2 (7.01.2021): 292. http://dx.doi.org/10.3390/en14020292.

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The gravel packing completion method for horizontal wells has the advantages of maintaining high oil production for a long time, maintaining wellbore stability, and preventing sand production, so it has become the preferred completion method for horizontal wells. At present, this technology still faces the problems of high sand bed height and poor gravel migration. In order to improve the efficiency of gravel packing in horizontal wells, pulsed gravel packing technology for horizontal wells is proposed for the first time. Based on the mechanism of hydraulic pulse, the Eulerian–Eulerian model, k-ε model based on the renormalization group theory (RNG k-ε model), and Fluent are used to simulate the solid-liquid two-phase flow. By optimizing the parameters such as frequency and amplitude of pulse waveform, the optimal pulse waveform of pulsed gravel packing in horizontal wells is determined. The effects of parameters such as sand-carrying fluid displacement, sand-carrying fluid viscosity, sand-carrying ratio, gravel particle size, and string eccentricity on pulsed gravel packing in horizontal wells are studied, and the distribution law of gravel migration velocity and volume fraction in horizontal wells is obtained. According to the results, it can be seen that with the increase of displacement and viscosity of carrier fluid, the volume fraction of fixed bed and moving bed decreases gradually, while that of suspension bed increases gradually. With the increase of sand-carrying ratio, gravel particle size, and string eccentricity, the volume fraction of fixed bed and moving bed increases gradually, while that of suspended bed decreases gradually. Comparing the effects of conventional gravel packing and pulsed gravel packing in horizontal wells, it can be concluded that the efficiency of pulsed gravel packing in horizontal wells is higher. The volume fraction of fixed bed and moving bed decreased by 30% and 40% respectively, while the volume fraction of suspended bed increased by 20%. The migration velocity of moving bed and suspended bed increased by 40% and 25%, respectively, and the migration ability of gravel improved obviously.

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Zhang, Zhenxiang, Jin Yang, Shengnan Chen, Qibin Ou, Yichi Zhang, Ximo Qu i Yafei Guo. "Numerical Simulation of Pulsed Gravel Packing Completion in Horizontal Wells". Energies 14, nr 2 (7.01.2021): 292. http://dx.doi.org/10.3390/en14020292.

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The gravel packing completion method for horizontal wells has the advantages of maintaining high oil production for a long time, maintaining wellbore stability, and preventing sand production, so it has become the preferred completion method for horizontal wells. At present, this technology still faces the problems of high sand bed height and poor gravel migration. In order to improve the efficiency of gravel packing in horizontal wells, pulsed gravel packing technology for horizontal wells is proposed for the first time. Based on the mechanism of hydraulic pulse, the Eulerian–Eulerian model, k-ε model based on the renormalization group theory (RNG k-ε model), and Fluent are used to simulate the solid-liquid two-phase flow. By optimizing the parameters such as frequency and amplitude of pulse waveform, the optimal pulse waveform of pulsed gravel packing in horizontal wells is determined. The effects of parameters such as sand-carrying fluid displacement, sand-carrying fluid viscosity, sand-carrying ratio, gravel particle size, and string eccentricity on pulsed gravel packing in horizontal wells are studied, and the distribution law of gravel migration velocity and volume fraction in horizontal wells is obtained. According to the results, it can be seen that with the increase of displacement and viscosity of carrier fluid, the volume fraction of fixed bed and moving bed decreases gradually, while that of suspension bed increases gradually. With the increase of sand-carrying ratio, gravel particle size, and string eccentricity, the volume fraction of fixed bed and moving bed increases gradually, while that of suspended bed decreases gradually. Comparing the effects of conventional gravel packing and pulsed gravel packing in horizontal wells, it can be concluded that the efficiency of pulsed gravel packing in horizontal wells is higher. The volume fraction of fixed bed and moving bed decreased by 30% and 40% respectively, while the volume fraction of suspended bed increased by 20%. The migration velocity of moving bed and suspended bed increased by 40% and 25%, respectively, and the migration ability of gravel improved obviously.

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Berni, C., H. Michallet i E. Barthélemy. "Effects of horizontal pressure gradients on bed destabilization under waves". Journal of Fluid Mechanics 812 (5.01.2017): 721–51. http://dx.doi.org/10.1017/jfm.2016.805.

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We report on new experiments designed to investigate bed destabilization processes in a two-dimensional wave flume physical model of a beach. The mobile bed consists of non-cohesive granular material of low density. The wave conditions are provided by repeating a cycle of waves made of two bichromatic groups of different period. The horizontal and vertical velocities are acoustically profiled vertically from free-stream elevation down to the still bed level in the surf zone. Additional measurements of the fluid pressure at positions closely aligned horizontally and vertically in and slightly above the sediment bed are undertaken. Mobile bed interfaces, still bed and top interface, are detected via acoustic and optical methods. Both methods are cross-compared and give similar results. Flow turbulence over the bed is analysed, the Reynolds turbulent shear stress is found negligible compared to the orbital flow induced momentum diffusion. The shear stress and the horizontal pressure gradient are computed at near-bed elevation and used in the bed incipient plug flow model of Sleath (Cont. Shelf Res., vol. 19 (13), 1999, pp. 1643–1664). Both the model and the measurements confirm that destabilization occurs when the non-dimensional pressure gradient (or Sleath number) exceeds the threshold value of 0.3 which is simultaneous with strong flow acceleration. The near-bottom fluid shear stress detected during these flow accelerations at steep wave fronts is found experimentally to be negative, which is retrieved with an unsteady plug flow model. This is suggesting that the fluid above the bed resists the sediment layer motion at these particular phases.

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Termini, Donatella. "Experimental Analysis of Horizontal Turbulence of Flow over Flat and Deformed Beds". Archives of Hydro-Engineering and Environmental Mechanics 62, nr 3-4 (1.12.2015): 77–99. http://dx.doi.org/10.1515/heem-2015-0021.

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AbstractLaboratory experiments in a straight flume were carried out to examine the evolution of large-scale horizontal turbulent structures under flat-bed and deformed-bed conditions. In this paper, the horizontal turbulence of flow under these conditions is analyzed and compared. The conditioned quadrant method is applied to verify the occurrence of turbulent events. The distributions of horizontal Reynolds shear stress and turbulent kinetic energy are also presented and discussed. Results show the occurrence of an “initial” sequence of horizontal vortices whose average spatial length scales with the channel width. Under deformed-bed conditions, this spatial length does not change.

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Woods, J. A., R. B. Thorpe i S. E. Johnson. "Horizontal pneumatic conveying from a fluidized bed". Chemical Engineering Science 63, nr 7 (kwiecień 2008): 1741–60. http://dx.doi.org/10.1016/j.ces.2007.11.040.

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Caws, Mary Ann. "On the Horizontal: Women Writing on Writing Women". PMLA/Publications of the Modern Language Association of America 122, nr 2 (marzec 2007): 549–57. http://dx.doi.org/10.1632/pmla.2007.122.2.549.

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Writing in bed: I have always loved Edith Wharton's habit of doing just that, as well as Cynthia Ozick's discussion of it (look how neat the desk at which Wharton is photographed in her stays; imagine how much more comfortable she is in bed with her stays undone). I remember learning, during my first studies of philosophy at Bryn Mawr, that René Descartes wrote in bed, by the heat of a stove supplied by Queen Christina, to say nothing of Winston Churchill's similar custom.

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Laishram, K., P. A. Kumar i T. T. Devi. "Effect of channel slope and roughness on hydraulic jump in open channel flow". IOP Conference Series: Earth and Environmental Science 958, nr 1 (1.12.2021): 012014. http://dx.doi.org/10.1088/1755-1315/958/1/012014.

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Abstract An experimental study is conducted on hydraulic jump characteristics for understanding the impact of slope in an open channel flume. Hydraulic jump on different channel characteristics (horizontal smooth & rough and sloping smooth & rough) were analysed. The measured characteristics of hydraulic jump with different channel roughness and different slope were compared. The results showed that the sequent depth ratio (y2/y1 ) increases with the increase in Froude number (Fr1 ) for smooth horizontal bed and horizontal rough bed. It was also observed that with an increase in Fr1 , a decrease in y2/y1 in smooth sloping bed condition and decreases for rough sloping bed. New empirical relationships were also developed with the experimental data and results were found similar with the observed hydraulic characteristics data.

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Lu, Zongyu, Baocheng Wu, Jiangang Shi, Chuanming Xi i Kai Wei. "A Multiparameter Coupled Prediction Model for Annular Cuttings Bed Height in Horizontal Wells". Geofluids 2022 (23.06.2022): 1–9. http://dx.doi.org/10.1155/2022/9938546.

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Cuttings accumulation in horizontal drilling is one of the main reasons for high drilling torque and drag and serious backing pressure and consequently influencing the rate of penetration (ROP), so inhibiting the generation of cuttings bed and keeping the hole clean is an important prerequisite to ensure the smooth and safe drilling of horizontal section. In order to master the formation mechanism of cuttings bed and reveal the influence law of influencing factors, based on the three-layer cuttings bed migration model and the two-phase solid-liquid flow theory, this paper establishes a numerical simulation method for cuttings migration characteristics in the annulus of horizontal wells, reveals the cuttings concentration distribution law and migration characteristics in the horizontal well section, and fits the engineering prediction model of cuttings bed height considering many factors such as geology, engineering, and fluid body according to the simulation results. The analysis of sensitive factors shows that the rate of penetrating, cuttings density, and drill pipe eccentricity is not conducive to borehole cleaning, and cuttings are easy to accumulate to form cuttings bed; increasing the drilling fluid density, displacement, and drill pipe speed is conducive to borehole cleaning and reducing the height of cuttings bed. The research shows that within the range of normal construction parameters, the error of the horizontal cuttings height prediction model is less than 10%, which can meet the needs of engineering analysis. The model provides convenience for engineering applications.

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Merazka, M., i M. S. Kim. "The Effect of a Ground Brace with a Spacer on the Displacement and Bearing Capacity of a Horizontally Loaded Single Pile". Russian Journal of Building Construction and Architecture, nr 3(59) (12.07.2023): 6–15. http://dx.doi.org/10.36622/vstu.2023.3.59.001.

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Statement of the problem. The influence of a ground brace with a spacer attached to the pile trunk on the movement and bearing capacity of piles under horizontal loads is investigated and the results obtained during the experiment are compared with the test results of a single pile. Results. A noticeable effect of the presence of a bed on the movement of the pile foundation has been established. With equal loads, piles with a bed have horizontal movement and the angle of rotation of the pile head is up to 2÷3 times less than those without a bed. An increase in the length of the strut leads to a decrease in the horizontal movement of the pile head up to 1.6 times and the angle of rotation up to 1.9 times compared to that with a bed, but without a strut. The bearing capacity of a pile with a bed increases up to 1.66 times with an increase in the length of the spacer from 0 to 3d, where d is the diameter of the cross-section of the pile. Conclusions. The dependence of the increase in the bearing capacity of the pile on the presence of a bed with a spacer was experimentally verified. The test results demonstrate a considerable ffect of the presence of a bed with a spacer on the horizontal and vertical movements of the pile, as well as on the decrease in the angle of rotation of the pile head.

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Tennakoon, S. G. K., L. Kondic i R. P. Behringer. "Onset of flow in a horizontally vibrated granular bed: Convection by horizontal shearing". Europhysics Letters (EPL) 45, nr 4 (15.02.1999): 470–75. http://dx.doi.org/10.1209/epl/i1999-00190-3.

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Li, Xiaoming, Yuyue Fan, Jiahua Li, Xinghua Su, Sheng Zhan, Gang Hu, Yiqing He i Ming Zhang. "Research on the Influence of a Cuttings Bed on Drill String Friction Torque in Horizontal Well Sections". Processes 10, nr 10 (12.10.2022): 2061. http://dx.doi.org/10.3390/pr10102061.

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Horizontal well drills are difficult to operate and require high borehole cleaning operations. The impact of cuttings accumulation on friction and torque cannot be ignored. In the process of horizontal well drilling, it is very easy to form a cuttings bed in the highly inclined eccentric annulus. The formation of the cuttings bed will not only increase the friction torque but also have a greater impact on the annulus flow. Based on the application of gas drilling in horizontal wells, this paper uses laboratory experiments to study the influence of cuttings with different particle sizes and lithology on the friction coefficient between the drill string and the borehole wall of the horizontal well section. In addition, in view of the difficulty in the migration of cuttings in gas drilling horizontal wells and the formation of cuttings deposits, this paper carries out an experimental study on the effect of the cuttings bed on drill pipe coating height and cuttings bed thickness on friction coefficient. Experimental results show that the friction coefficient of gas drilling horizontal wells is about 0.44–0.58. When the coating height of the cuttings on the drill pipe exceeds a certain value (26 mm), the friction coefficient tends to be stable, but its value is as high as about 0.55. When the thickness of the accumulation of cuttings exceeds a certain value (10 mm), the subsidence hindering effect between the particles in the cuttings bed is weakened, so the friction coefficient of the casing section and the open hole section tends to be stable, about 0.53.

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Kantawanichkul, S., S. Somprasert, U. Aekasin i R. B. E. Shutes. "Treatment of agricultural wastewater in two experimental combined constructed wetland systems in a tropical climate". Water Science and Technology 48, nr 5 (1.09.2003): 199–205. http://dx.doi.org/10.2166/wst.2003.0319.

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Two designs of experimental combined constructed wetland systems were constructed: vegetated (Scirpus grossus Linn) subsurface horizontal flow bed followed by a vegetated vertical flow bed and a vegetated vertical flow bed over an unvegetated horizontal flow sand bed. The systems were used to compare the nitrification/denitrification efficiency in a tropical climate which has temperatures above an average of 25°C throughout the year. The effluent from a biogas digester of pig farm wastewater with TKN and COD concentrations of approximately 400 and 1,000 mg/L was fed every 4 hours intermittently. The effluent was recycled to the system with the ratio of 1:1 and the hydraulic loading rate was increased from 3 to 6 and 12 cm/d including recycled water. At higher hydraulic loading rates, nitrogen COD and BOD removal efficiencies were lower. The SS, TP and fecal coliform bacteria removal efficiencies were not clearly affected by the high hydraulic loading or the different layout of the system. Nitrogen uptake by plants was very low in relation to the nitrogen loading of the systems. In general, the removal efficiencies of both types were comparable but the system with a vertical flow over horizontal flow sand bed is more suitable for sites with limited land area, although its construction can be more difficult than the system with horizontal flow followed by a vertical flow bed.

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Holmes, Vicky. "What We Did in Bed: A Horizontal History". Cultural and Social History 18, nr 1 (1.01.2021): 126–27. http://dx.doi.org/10.1080/14780038.2020.1862343.

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FONG, DEREK A., i MARK T. STACEY. "Horizontal dispersion of a near-bed coastal plume". Journal of Fluid Mechanics 489 (25.07.2003): 239–67. http://dx.doi.org/10.1017/s002211200300510x.

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Toyama, Shigeki, Hidetoshi Mori i Yoshiteru Mizutani. "Performance of horizontal gas flow granular bed filters." KAGAKU KOGAKU RONBUNSHU 13, nr 5 (1987): 621–26. http://dx.doi.org/10.1252/kakoronbunshu.13.621.

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Beeckmans, J. M., i K. Macwilliam. "Stabilization of a fluidized bed by horizontal vibrations". Powder Technology 45, nr 2 (styczeń 1986): 177–81. http://dx.doi.org/10.1016/0032-5910(66)80011-6.

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Guard, Paul Andrew, Peter Nielsen i Tom E. Baldock. "BED SHEAR STRESS IN UNSTEADY FLOW". Coastal Engineering Proceedings 1, nr 32 (31.01.2011): 8. http://dx.doi.org/10.9753/icce.v32.sediment.8.

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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.

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Bizhani, M., i E. Kuru. "Particle Removal From Sandbed Deposits in Horizontal Annuli Using Viscoelastic Fluids". SPE Journal 23, nr 02 (19.12.2017): 256–73. http://dx.doi.org/10.2118/189443-pa.

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Summary This paper presents results of an experimental study on how fluid viscoelastic properties would influence the particle removal from the sandbed deposited in horizontal annuli. Water and two different viscoelastic fluids were used for bed-erosion experiments. The particle-image-velocimetry (PIV) technique was used to measure the local fluid velocity at the fluid/sandbed interface, allowing for accurate estimation of the fluid-drag forces and the turbulence stresses. It was found that polymer fluids needed to exert higher level drag forces (than those of water) on the sandbed to start movement of the particles. Results have also shown that, at the critical flow rate of bed erosion, the polymer fluids yielded higher local fluid velocities and turbulent stresses than those of water. Moreover, the local velocity measurements by means of the PIV technique and the resultant bed-shear-stress calculations indicated that enhancing polymer concentration under the constant flow rate should also enhance the drag forces acting on the sandbed. However, these improved fluid hydrodynamic forces did not result in any improvement in the bed erosion. Therefore, the mechanism causing the delay in the bed erosion by polymer additives could not be explained by any decrease in the local fluid velocity and the turbulence. The primary reason for the delayed bed erosion by the polymer fluids was suggested to be linked to their viscoelastic properties. Two possible mechanisms arising from the elastic properties of the polymer fluids that hinder bed erosion were further discussed in the paper. The stress tensor of the viscoelastic-fluid flow was analyzed to determine the normal stress differences and the resultant normal fluid force acting on the particles at the fluid/sandbed interface. The normal force induced by the normal stress differences of the viscoelastic fluid was identified as one of the possible causes of the delayed bed erosion by these types of fluids.

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Sergaliev, N. Kh, i K. M. Akhmedenov. "Dynamics of river bed processes of the Ural River in Western Kazakhstan". Water Practice and Technology 9, nr 4 (1.12.2014): 457–63. http://dx.doi.org/10.2166/wpt.2014.050.

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A retrospective analysis of river bed deformation over a 34-year period has been carried out for the first time for the Ural River in West Kazakhstan, in different environmental conditions. Horizontal shifts of the Ural riverbed have been defined according to space shots made in 2012. Erosion risk, as a result of horizontal displacement of the river bed has been determined in West Kazakhstan. A geomorphologic description of the Ural River bed and floodplain, and the dynamics of channel processes in the river within West Kazakhstan are given. The probable pattern of channel realignments for the Ural River has been determined. The paper describes the results of map compilation and related data consolidation with respect to the horizontal river bed shifts in West Kazakhstan, and includes a review of characteristics of the hydrologic and hydrochemical regimes of the river. The main river bed types, which are typical of flat terrain, are also discussed. West Kazakhstan is a region where there is medium-level ecologic stress on the river beds and floodplains.

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Wu, Xuning, Qian Li, Hu Yin, Zaoyuan Li, Jianhua Jiang, Menghan Si i Yangyang Zhang. "Real-Time Intelligent Recognition Method for Horizontal Well Marker Bed". Mathematical Problems in Engineering 2020 (17.06.2020): 1–8. http://dx.doi.org/10.1155/2020/8583943.

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The accurate identification of the horizontal well marker bed is to guarantee the soft landing of the well trajectory. With the intelligent development of the petroleum industry, it is feasible to apply computers to identify the marker bed automatically. In case-based reasoning technology, the data of well logging while drilling (LWD) as characteristic parameters are compared with those of adjacent well. By taking the depth sequence of LWD data as time series and using Dynamic Time Warping (DTW) similarity measure algorithm, the similarity index of each drilling depth is calculated corresponding to the marker bed in the adjacent well. The total similarity curve is obtained by giving different weights of different feature parameters. Selecting natural gamma, deep resistivity, and shallow resistivity LWD curves as characteristic parameters, two horizontal wells in JL block of Junggar basin are analysed by this method. The result of similarity curve indicates the location of the marker bed and the total similarity value reaches 78%. The research shows that the method based on case-based reasoning can identify the marker bed of the horizontal well accurately and effectively, assist the geologist to carry out formation correlation of multiple wells at the same time, reduce the cost of human labour force, and improve work efficiency.

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Arai, Y., K. Sugiyama i T. Narabayashi. "ICONE15-10776 COOLABILITY OF OXIDIZED PARTICULATE DEBRIS BED ACCUMULATED IN HORIZONTAL NARROW GAPS". Proceedings of the International Conference on Nuclear Engineering (ICONE) 2007.15 (2007): _ICONE1510. http://dx.doi.org/10.1299/jsmeicone.2007.15._icone1510_399.

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Nagel, Tim, Julien Chauchat, Cyrille Bonamy, Antoine Mathieu, Xiaofeng Liu, Zhen Cheng i Tian-Jian Hsu. "TWO-PHASE FLOW SIMULATIONS OF SCOUR AROUND VERTICAL AND HORIZONTAL CYLINDERS". Coastal Engineering Proceedings, nr 36 (30.12.2018): 22. http://dx.doi.org/10.9753/icce.v36.sediment.22.

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Scour around structures is a major engineering issue that requires a detailed description of the flow field as well as sediment transport processes. Due to enhanced suspended load associated with vortices generated around structures, sediment transport cannot be solely related to bed shear stress, such as Shields parameter based formula. In order to address this issue, we used a multi-dimensional two-phase flow solver, sedFoam-2.0 (Chauchat et al., GMD 2017) implemented under the open-source CFD toolbox OpenFOAM. Three configurations are studied and compared with experimental and numerical data from the literature. First, the 2D configurations of an horizontal cylinder lying on a sediment bed (Mao, 1986; Sumer et al., 2001) are investigated. Then, the 3D configuration of the scour around a vertical cylindrical pile reported by Roulund et al. (2005) for rigid-bed and live bed cases is investigated.

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Faraci, Carla, Pietro Scandura, Carmelo Petrotta i Enrico Foti. "Wave-Induced Oscillatory Flow Over a Sloping Rippled Bed". Water 11, nr 8 (5.08.2019): 1618. http://dx.doi.org/10.3390/w11081618.

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In this paper, the findings of an experimental analysis aimed at investigating the flow generated by waves propagating over a fixed rippled bed within a wave flume are reported. The bottom of the wave flume was constituted by horizontal part followed by a 1:10 sloping beach. Bedforms were generated in a previous campaign performed with loose sand, and then hardened by means of thin layers of concrete. The flow was acquired through a Vectrino Profiler along two different ripples, one located in the horizontal part of the bed and the second over the sloping beach. It was observed that, on the horizontal bed, near the bottom, ripple lee side triggered the appearance of an onshore directed steady streaming, whereas ripple stoss side gave rise to an offshore directed steady streaming. On the sloping bed, a strong return current appears at all positions, interacting with the rippled bottom. The turbulence is non-negligible within the investigated water depth, particularly when velocities were onshore directed, due to flow asymmetry. Turbulence caused a considerable flow stirring which, above a non-cohesive bed, could lift the sediment up in the water column and give rise to a strong sediment transport.

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Penna, Nadia, Francesco Coscarella i Roberto Gaudio. "Turbulent Flow Field around Horizontal Cylinders with Scour Hole". Water 12, nr 1 (2.01.2020): 143. http://dx.doi.org/10.3390/w12010143.

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This study presents the results of an experimental investigation on the flow-structure interactions at scoured horizontal cylinders, varying the gap between the cylinder and the bed surface. A 2D Particle Image Velocimetry (PIV) system was used to measure the flow field in a vertical plane at the end of the scouring process. Instantaneous and ensemble-averaged velocity and vorticity fields, viscous and Reynolds stresses, and ensemble-averaged turbulence indicators were calculated. Longitudinal bed profiles were measured at the equilibrium. The results revealed that suspended and laid on cylinders behave differently from half-buried cylinders if subjected to the same hydraulic conditions. In the latter case, vortex shedding downstream of the cylinder is suppressed by the presence of the bed surface that causes an asymmetry in the development of the vortices. This implies that strong turbulent mixing processes occur downstream of the uncovered cylinders, whereas in the case of half-buried cylinders they are confined within the scour hole.

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Ma, Yongqian, Chunxu Yang i Xiaolan Liu. "On Hole Cleaning Evaluation Method in Highly Deviated / Horizontal Well Sections". Journal of Physics: Conference Series 2442, nr 1 (1.02.2023): 012037. http://dx.doi.org/10.1088/1742-6596/2442/1/012037.

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Abstract To solve the problem of hole cleaning quantitative evaluation in highly deviated / horizontal well sections, experiments are made on the experimental system of highly deviated / horizontal well sections, the influence laws of annulus return speed, pipe speed, drill tool eccentricity, well deviation angle, drilling fluid density and viscosity, cuttings size and other parameters on cuttings bed thickness are studied, and the calculation models of steady-state dimensionless cuttings bed thickness in horizontal well and highly deviated well are established, the calculation error is controlled within ±5%, which provides an accurate method for hydraulic parameter optimization and design.

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Verbeek, Merel C., Robert J. Labeur i Wim S. J. Uijttewaal. "Estimating the stability of a bed protection of a weir-mounted tidal turbine". International Marine Energy Journal 3, nr 1 (13.05.2020): 21–24. http://dx.doi.org/10.36688/imej.3.21-24.

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Coastal infrastructure, such as bridges and storm surge barriers with weirs, provides an attractive location for harvesting renewable energy using tidal turbines. Often stone layers are applied downstream of coastal infrastructure to protect the sea bed from erosion. However, little is known about the potential effect of tidal energy extraction on the stability of this granular bed protection. This paper describes a study of the flow conditions influencing the stability of the bed protection downstream of a weir-mounted tidal turbine, using hydrodynamic data of an experimental test. The analysis indicates that the flow recirculation zone downstream of a weir may become shorter and flatter due to the presence of a horizontal-axis turbine. As a result, energetic turbulence eddies can transport more horizontal momentum towards the bed – hence the reason a heavier bed protection may be required for granular beds downstream of weirs when a turbine is installed. This information is essential when designing safe bed protections for coastal infrastructure with tidal turbines.

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Amri, A. El, i J. L. Verrette. "Variations des efforts hydrodynamiques sur radiers horizontal et affouillé en aval d'un dissipateur d'énergie de type auge". Canadian Journal of Civil Engineering 34, nr 7 (1.07.2007): 890–94. http://dx.doi.org/10.1139/l07-065.

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The distribution of the hydrodynamic efforts under solid horizontal or scoured bed downstream of a roller bucket spillway can be represented by two typical distributions: type A and B for pressure and type I and II for pressure fluctuation. However, the scoured bed presents a pressure distribution that is closer to the equilibrium pressure compared with that of the horizontal bed and a much lower pressure fluctuation distribution. This could be due to the bed scour in the vicinity of the bucket that carries an effective value for the height of the bucket lip, which decreases the suction effect, and the fact that the eroded shape of the bed corresponds with reduced pressure efforts, which translates into weaker turbulence and therefore a more stable flow. These results show the advantage of a scoured bed that could be more secure when the bucket lip height of the roller bucket spillway is well chosen.Key words: hydrodynamic efforts, pressure, pressure fluctuation, hydraulic energy dissipation, roller bucket.

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Song, Xianzhi, Zhaoyu Pang, Zhengming Xu, Gensheng Li, Baojiang Sun, Zhaopeng Zhu, Ruiyue Yang i Zehao Lyu. "Experimental Study on the Sliding Friction for Coiled Tubing and High-Pressure Hose in a Cuttings Bed During Microhole-Horizontal-Well Drilling". SPE Journal 24, nr 05 (31.12.2018): 2010–19. http://dx.doi.org/10.2118/194192-pa.

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Summary Microhole–horizontal–well–drilling technology is a high–efficiency and low–cost technology that has developed rapidly in recent years. However, during microhole–horizontal–well drilling, cuttings deposit easily at the bottom of the wellbore because of gravity and nonrotation of the pipe. The pipe sliding on the cuttings bed will cause extremely serious friction between the pipe and cuttings bed, which is an important limiting factor on the extended length of the microhole horizontal wellbore. Therefore, it is necessary to study the influencing factors and establish a model for evaluating the friction between the pipe and cuttings bed. In this study, laboratory experiments on the sliding friction between pipe and cuttings bed were conducted. By analyzing the comprehensive sliding–friction coefficient (CSFC) between the pipe and cuttings bed, the effects of dimensionless buried depth (0.2 to 1.0) and average cuttings size (0.249 to 2.667 mm) on the CSFC between the pipe and cuttings bed were obtained. CSFC is a function of dimensionless buried depth and relative roughness in the developed model. The results suggest that the sliding–friction resistance between the pipe and cuttings bed increases as the buried depth of pipe increases or the average cuttings size decreases. We propose a model for estimating the CSFC using experimental data and the least–squares method. The predictions show good agreement with the experimental data within suitable ranges of models. This work is expected to provide the basis for predicting the friction resistance between the pipe and cuttings bed.

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Kantawanichkul, S., P. Neamkam i R. B. E. Shutes. "Nitrogen removal in a combined system: vertical vegetated bed over horizontal flow sand bed". Water Science and Technology 44, nr 11-12 (1.12.2001): 137–42. http://dx.doi.org/10.2166/wst.2001.0820.

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Pig farm wastewater creates various problems in many areas throughout Thailand. Constructed wetland systems are an appropriate, low cost treatment option for tropical countries such as Thailand. In this study, a combined system (a vertical flow bed planted with Cyperus flabelliformis over a horizontal flow sand bed without plants) was used to treat settled pig farm wastewater . This system is suitable for using in farms where land is limited. The average COD and nitrogen loading rate of the vegetated vertical flow bed were 105 g/m2.d and 11 g/m2.d respectively. The wastewater was fed intermittently at intervals of 4 hours with a hydraulic loading rate of 3.7 cm/d. The recirculation of the effluent increased total nitrogen (TN) removal efficiency from 71% to 85%. The chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) removal efficiencies were 95% and 98%. Nitrification was significant in vertical flow Cyperus bed, and the concentration of nitrate increased by a factor of 140. The horizontal flow sand bed enhanced COD removal and nitrate reduction was 60%. Plant uptake of nitrogen was 1.1 g N/m2.d or dry biomass production was 2.8 kg/m2 over 100 days.

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Xiao, Ping, Guizhang Yan i Dasan Wang. "Investigation on horizontal mixing of particles in dense bed in Circulating Fluidized Bed (CFB)". Journal of Thermal Science 7, nr 2 (czerwiec 1998): 78–84. http://dx.doi.org/10.1007/s11630-998-0002-4.

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Itoh, Shingo, Keigo Tsujita, Taiki Morishige i Toshihide Takenaka. "The Effect of Vibration Condition for Magnesium Dry Gravity Sorting by Vibrating Particulate Bed". Materials Science Forum 941 (grudzień 2018): 1535–39. http://dx.doi.org/10.4028/www.scientific.net/msf.941.1535.

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Recycling Mg alloys has been demanded as the demand of Mg alloys has been increased. It is difficult to separate Mg with Al because the properties are similar except for the density. In this study, gravity sorting by vibrating particulate bed ajusted the density to intermediate between Mg and Al was applied for Mg separation with Al. The relationship the vibrating condition and the sorting accuracy was investigated by applying different vibration acceleration and by applying the vertical and horizontal vibration. Turbulent flow was observed and the recovery rate was improved when vertical vibration with high acceleration was applied to the bed. Higher recovery rate was achieved when horizontal vibration was applied to the bed. This result suggested that the horizontal movement of particle affected the behavior of sorting materials and high recovery ratio was achieved by optimizing vibrational condition such as vibration acceleration and the direction of vibration.

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FUKUSAKO, Shoichiro, Nobuhiro SEKI, Seigo ISHIGURO i Norio EGUCHI. "Heat transfer from horizontal immersed tube in particles bed." Transactions of the Japan Society of Mechanical Engineers Series B 51, nr 463 (1985): 989–95. http://dx.doi.org/10.1299/kikaib.51.989.

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Fyhr, Christian, Ian C. Kemp i Roland Wimmerstedt. "Mathematical modelling of fluidised bed dryers with horizontal dispersion". Chemical Engineering and Processing: Process Intensification 38, nr 2 (marzec 1999): 89–94. http://dx.doi.org/10.1016/s0255-2701(98)00063-4.

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Lu, Ping, Yan Cao, Wei-Ping Pan i Chengguo Ma. "Heat transfer characteristics in a horizontal swirling fluidized bed". Experimental Thermal and Fluid Science 35, nr 6 (wrzesień 2011): 1127–34. http://dx.doi.org/10.1016/j.expthermflusci.2011.03.007.

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Chen, Libin, i Herbert Weinstein. "Temperature distribution around heated horizontal jet in fluidized bed". AIChE Journal 43, nr 9 (wrzesień 1997): 2373–75. http://dx.doi.org/10.1002/aic.690430923.

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Swart, D. H., i J. B. Crowley. "GENERALIZED WAVE THEORY FOR A SLOPING BED". Coastal Engineering Proceedings 1, nr 21 (29.01.1988): 12. http://dx.doi.org/10.9753/icce.v21.12.

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This paper discusses the development from first principles of a first-order solution for non-breaking waves on a gently sloping bottom. The theory is derived in a similar fashion as was done by Swart and Loubser (1978) for vocoidal waves on a horizontal bottom. The resulting covocoidal theory was compared to an extensive data set for waves over a sloping bottom (Nelson, 1981) and is tested for analytical validity. It adheres exactly to continuity and the kinematic free surface boundary condition, and shows comparable errors in the dynamic free surface boundary condition to that found for the better, general horizontal bed wave theories.

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Arifjanov, Aybek, Maqsud Otaxonov, Luqmon Samiev i Shamshodbek Akmalov. "Hydraulic calculation of horizontal open drainages". E3S Web of Conferences 97 (2019): 05039. http://dx.doi.org/10.1051/e3sconf/20199705039.

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In article analysed the factors influencing the hydraulic processes which arise in the open horizontal drainage systems. Open drainages plays important role in order to improve the ameliorative condition of the agricultural area, salt washing on the soil. It is emphasized that the deep drainage in our region has a good effect on the soil condition and salt removing. At present, efforts are being made to improve the productivity of the collectors to clean and built. As example the collector drainage systems in Syrdarya region are listed. It is observed that the motion mode of open drainage flows is physically identical. Due to the complexity of equations in the unstable motion mode, the drainage water flow scheme in the collectors reflects the hydraulic calculation of the movement. Researches were provided in open agricultural drainage system of Syrdarya region and analysis have been done in natural field conditions. It has been noted when slope of the drainage bed is equal to i<0,0005 intensity of deformation were very high, when slope was between 0,0005<i<0,0011 intensity of deformation of collector bed was equal to the minimum level. In this article provided hydraulic calculation for Syrdarya region drainage system for choosing dynamical stable shape of bed. Those hydraulic calculations and projections ensure collectors with long time period of exploitation condition. Calculation and analyses were done with taking account trapezoidal capacity of the stream in drainage system, and the results of studies on increasing the flow efficiency are reflected. Analysed that when slope will increase until 20% discharge capacity will increase because of high average flow velocity increased by 7-8 times and discussed difference of them. As a result of the hydraulic calculation, the slope of the drainage increased from i-0,00048 to i-0,0006, the fact that the flow capacity increased by 25% due to the increase because of flow velocity.

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Wang, Peng, Yan Rui Zuo, Li Na Ren i Dong Dong Song. "Finite Element Analysis of Static and Dynamic Characteristics of High-Speed Horizontal Machining Center Bed". Advanced Materials Research 889-890 (luty 2014): 58–61. http://dx.doi.org/10.4028/www.scientific.net/amr.889-890.58.

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Based on the theory of finite element and modal analysis theory, analysis of static and dynamic characteristics of the lathe bed has been done. The static displacement contours and mode natural frequency and displacement contours have been given to realize the structure optimization of lathe bed of high-speed horizontal machining center. It is shown that the bed has good static stiffness and natural frequency and the deformation of lathe bed mainly occurred in the tray conversion mechanism and the cutter location. The deformation of processing work area is small and has certain light weight space, which lay the foundation for the lightweight design of the bed.

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Han, Yaotu, Xiaocheng Zhang, Zhengming Xu, Xianzhi Song, Weijie Zhao i Qilong Zhang. "Cuttings Bed Height Prediction in Microhole Horizontal Wells with Artificial Intelligence Models". Energies 15, nr 22 (10.11.2022): 8389. http://dx.doi.org/10.3390/en15228389.

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Inadequate drill cuttings removal can cause costly problems such as excessive drag, lower rate of penetration, and even mechanical pipe sticking. Cuttings bed height is usually used to evaluate hole-cleaning efficiency in horizontal wells. In this study, artificial intelligence models, including artificial neural network (ANN), support vector regression (SVR), recurrent neural network (RNN), and long short-term memory (LSTM), were employed to predict cuttings bed height in the well-bore. A total of 136 different tests were conducted, and cuttings bed height under different conditions were measured in our previous study. By training four different artificial intelligence models with the experiment data, it was found that the ANN model performed best among other artificial intelligence models. The ANN model outperformed the dimensionless cuttings bed height model proposed in our previous study. Due to the amount of data points, the memory ability of RNN and LSTM models has not been entirely played compared with the ANN model.

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Kuila, Asim, Subhasish Das i Asis Mazumdar. "A Comparative Analysis of Flow Fields around a Composite Hydrokinetic Device". Applied Mechanics and Materials 897 (kwiecień 2020): 173–78. http://dx.doi.org/10.4028/www.scientific.net/amm.897.173.

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. The flow pattern on the combined effect of a horizontal cylinder and a vertical plate is observed and analysed in this experimental study. The experiment was conducted with a 4 cm outer diameter cylinder arranged horizontally across flow above 2 cm from the bed and a vertical plate of 5 cm placed 9 cm downstream from cylinder surface reference as tilting flume bed surface. The water depth was maintained at 17 cm through a constant discharge of 35 lps in a re-circulating flume. Acoustic Doppler Velocimeter (ADV) was used to store the velocity fluctuation of velocity components and further used as a pictorial frame to understand the turbulence and the turbulent kinetic energy around the cylinder, plate and in between the cylinder - vertical plate. From the pictorial contour diagrams drawn, the velocity vector represents the flow feature over the cylinder and it is found that a horseshoe vortex, developed upstream of the plate, does effect on turbulent kinetic energy formed in between cylinder and vertical plate. The observation and obtained results from present study is compared with a 5 cm horizontal cylinder above 2 cm from the bed and a plate situated on 5.5 cm from cylinder curvature towards downstream.

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41

Wang, Lihua, Zemin Zhao, Jiongli Wang, Xianzeng Li, Yayu Huang i Tingqiang Yao. "Mechanical Characteristics of Ballast Bed under Dynamic Stabilization Operation Based on Discrete Element and Experimental Approaches". Shock and Vibration 2021 (17.03.2021): 1–11. http://dx.doi.org/10.1155/2021/6627612.

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To study the mechanical characteristics of ballasted bed under dynamic stability, a three-dimensional discrete element model of ballasted bed with 1000 mm × 700 mm × 550 mm is established based on the discrete element method. Meanwhile, a simulation test bench with the same size is built for simulation analysis and experimental research. The variation law and trend of settlement, lateral resistance, and compactness of ballasted bed under different excitation frequencies are analyzed comprehensively. The results show that when the excitation frequency is constant, the lateral resistance of sleeper, the settlement of sleeper, and the compactness of track bed under sleeper increase first and then tend to be stable. With the increase in horizontal excitation frequency, lateral resistance of ballast bed, sleeper settlement, and compactness first increase and then decrease after stable operation. The values of these parameters are maximized when the excitation frequency is 36 Hz which is the relative optimal horizontal excitation frequency of this model.

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42

Laber, Johannes, Raimund Haberl i Roshan Shrestha. "Two-Stage Constructed Wetland for Treating Hospital Wastewater in Nepal". Water Science and Technology 40, nr 3 (1.08.1999): 317–24. http://dx.doi.org/10.2166/wst.1999.0177.

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To treat the wastewater of a hospital at Dhulikhel/Nepal, a two-stage constructed wetland was built with a settlement tank, a horizontal flow bed as first stage and a vertical flow bed as second stage. The plant is operated without electric power. The aim was the elimination of organic compounds, nitrification and a significant reduction of indicator bacteria. Different phases of operation (high and low water level within the soil profile, serial operation, one stage operation) were investigated, of which the serial operation with high water level in the horizontal flow bed and low water level in the vertical flow bed showed the best elimination performance. The areal removal rate constants (k-values) turned out to be very high (especially of the vertical flow bed) compared with literature values of other subsurface flow constructed wetlands. For the vertical flow bed kCOD was 0.22 m/d and kNH4-N was 0.85 m/d during serial operation. For kNH4-N a strong correlation with the hydraulic loading rate and the COD inlet concentration was found.

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43

Chamberlain, P. G., i D. Porter. "Approximations to wave trapping by topography". Journal of Fluid Mechanics 325 (25.10.1996): 357–76. http://dx.doi.org/10.1017/s0022112096008154.

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The trapping of linear water waves over two-dimensional topography is investigated by using the mild-slope approximation. Two types of bed profile are considered: a local irregularity in a horizontal bed and a shelf joining two horizontal bed sections at different depths. A number of results are derived concerning the existence of trapped modes and their multiplicity. It is found, for example, that the maximum number of modes which can exist depends only on the gross properties of the topography and not on its precise shape. A range of problems is solved numerically, to inform and illustrate the analysis, using both the mild-slope equation and the recently derived modified mild-slope equation.

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44

Goshayeshi, A., J. R. Welty, R. L. Adams i N. Alavizadeh. "Local Heat Transfer Coefficients for Horizontal Tube Arrays in High-Temperature Large-Particle Fluidized Beds: An Experimental Study". Journal of Heat Transfer 108, nr 4 (1.11.1986): 907–12. http://dx.doi.org/10.1115/1.3247032.

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An experimental study is described in which time-averaged local heat transfer coefficients were obtained for arrays of horizontal tubes immersed in a hot fluidized bed. Bed temperatures up to 1005 K were achieved. Bed particle sizes of 2.14 mm and 3.23 mm nominal diameter were employed. An array of nine tubes arranged in three horizontal rows was used. The 50.8 mm (2 in.) diameter tubes were arranged in an equilateral triangular configuration with 15.24 cm (6 in.) spacing between centers. The center tube in each of the three rows in the array was instrumented providing data for local heat flux and surface temperature at intervals of 30 deg from the bottom to the top—a total of seven sets of values for each of the center tubes. The three sets of data are representative of the heat transfer behavior of tubes at the bottom, top, and in the interior of a typical array. Data were also obtained for a single horizontal tube to compare with the results of tube bundle performance. Superficial velocities of high-temperature air ranged from the packed-bed condition through approximately twice the minimum fluidization level. Comparisons with results for a single tube in a bubbling bed indicate only slight effects on local heat transfer resulting from the presence of adjacent tubes. Tubes in the bottom, top, and interior rows also exhibited different heat transfer performance.

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45

Wang, Alan L. T., John F. Stubington i Jiangang Xu. "Hydrodynamic Performance of a Novel Design of Pressurized Fluidized Bed Combustor". Journal of Energy Resources Technology 128, nr 2 (3.06.2005): 111–17. http://dx.doi.org/10.1115/1.2126987.

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A bench-scale fluidized bed combustor with a novel fluidizing gas injection manifold was successfully built for characterization of Australian black coals under PFBC conditions. Instead of the usual horizontal distributor plate to support the bed and distribute the fluidizing gas, the fluidizing gas was injected horizontally through 8 radial ports in the cylindrical wall of the combustor. To verify satisfactory hydrodynamic performance with the novel gas injection manifold, the fluidization was directly investigated by measuring differential pressure fluctuations under both ambient and PFBC conditions. In addition, a Perspex cold model was built to simulate the hydrodynamics of the hot bed in the PFBC facility. Under PFBC conditions, the bed operated in a stable bubbling regime and the solids were well mixed. The bubbles in the bed were effectively cloudless and no gas backmixing or slugging occurred; so the gas flow in the bed could be modeled by assuming two phases with plug flow through each phase. The ratio of Umf for the simulated bed to Umf for the hot PFBC bed matched the conditions proposed by Glicksman’s scaling laws. The bubbles rose along the bed with axial and lateral movements, and erupted from the bed surface evenly and randomly at different locations. Two patterns of particle movement were observed in the cold model bed: a circular pattern near the top section and a rising and falling pattern dominating in the lower section.

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Sadik Abbas, Ali. "The Effect of Infill Steel Plate Thickness on the Cycle Behavior of Steel Plate Shear Walls". DJES 11, nr 3 (1.09.2018): 7–13. http://dx.doi.org/10.24237/djes.2018.11302.

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The effect of changing in the bed slope of stilling basins produces changing in characteristics of the hydraulic jump such as sequent depth ratio, length of jump ratio, length of the roller and energy dissipation ratio, consequently the dimensions of stilling basin changed. In this study hydraulic jump investigated on smooth bed (without any appurtenances) for three adverse slopes (- 0.03, - 0.045, - 0.06) in addition to horizontal bed slope, the experiments were applied for the range of Froude number (Fr1) between 3.99 and 7.48. The results showed a reduction about10 % in sequent depth ratio, 22.1 % in length of jump ratio, 20.51 % in length of roller ratio and 13.87% in the energy dissipation ratio when the adverse slope (- 0.06) used instead of horizontal bed for the same Froude numbers. Empirical equations for the sequent depth ratio, length of roller ratio and the energy dissipation ratio were obtained from the experimental data

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47

Yadav, J. S., K. Kumar, R. K. Dutta i A. Garg. "Influence of positions of the geotextile on the load-settlement behaviour of circular footing resting on single stone column by 2D Plaxis software". Journal of Achievements in Materials and Manufacturing Engineering 2, nr 107 (1.08.2021): 59–74. http://dx.doi.org/10.5604/01.3001.0015.3584.

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Purpose: This study aims to study the load – settlement behaviour of circular footing rested on encased single stone column. Design/methodology/approach: The effect of vertical, horizontal and combined verticalhorizontal encasement of stone column on the load carrying capacity were examined numerically. The effect of stone column dimension (80 mm and 100 mm), length (400 mm and 500 mm), and spacing of reinforcement on the load carrying capacity and reinforcement ratio were assessed. Findings: The obtained results revealed that the load carrying capacity of geotextile encased stone columns are more than ordinary stone columns. For vertically encased stone columns as the diameter increases, the advantage of encasement decreases. Whereas, for horizontally encased stone column and combined vertical- horizontal encased stone column, the performance of encasement intensifies as the diameter of stone column increases. The improvement in the load carrying capacity of clay bed reinforced with combined verticalhorizontal encased stone columns are higher than vertical encased stone columns or horizontal encased stone column. The maximum performance of encasement was observed for VHESC1 of D = 80 mm. Research limitations/implications: For this study, the diameter of footing and stone column was kept same. The interface strength factor between stone column and clay bed was not considered. Practical implications: The encased stone column could be use improve the laod bearing capacity of weak soils. Originality/value: Many studies are available in literature regarding use of geosynthetic as vertical encasement and horizontal encasement of stone column. The study on combined effect of vertical and horizontal encasement of stone column on load carrying capacity of weak soil is very minimal. Keeping this in view, the present work was carried out.

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Cuzzone, Joshua K., Nicole-Jeanne Schlegel, Mathieu Morlighem, Eric Larour, Jason P. Briner, Helene Seroussi i Lambert Caron. "The impact of model resolution on the simulated Holocene retreat of the southwestern Greenland ice sheet using the Ice Sheet System Model (ISSM)". Cryosphere 13, nr 3 (14.03.2019): 879–93. http://dx.doi.org/10.5194/tc-13-879-2019.

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Abstract. Geologic archives constraining the variability of the Greenland ice sheet (GrIS) during the Holocene provide targets for ice sheet models to test sensitivities to variations in past climate and model formulation. Even as data–model comparisons are becoming more common, many models simulating the behavior of the GrIS during the past rely on meshes with coarse horizontal resolutions (≥10 km). In this study, we explore the impact of model resolution on the simulated nature of retreat across southwestern Greenland during the Holocene. Four simulations are performed using the Ice Sheet System Model (ISSM): three that use a uniform mesh and horizontal mesh resolutions of 20, 10, and 5 km, and one that uses a nonuniform mesh with a resolution ranging from 2 to 15 km. We find that the simulated retreat can vary significantly between models with different horizontal resolutions based on how well the bed topography is resolved. In areas of low topographic relief, the horizontal resolution plays a negligible role in simulated differences in retreat, with each model instead responding similarly to retreat driven by surface mass balance (SMB). Conversely, in areas where the bed topography is complex and high in relief, such as fjords, the lower-resolution models (10 and 20 km) simulate unrealistic retreat that occurs as ice surface lowering intersects bumps in the bed topography that would otherwise be resolved as troughs using the higher-resolution grids. Our results highlight the important role that high-resolution grids play in simulating retreat in areas of complex bed topography, but also suggest that models using nonuniform grids can save computational resources through coarsening the mesh in areas of noncomplex bed topography where the SMB predominantly drives retreat. Additionally, these results emphasize that care must be taken with ice sheet models when tuning model parameters to match reconstructed margins, particularly for lower-resolution models in regions where complex bed topography is poorly resolved.

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Ferreira da Silva, Ana Maria, i Habib Ahmari. "Size and effect on the mean flow of large-scale horizontal coherent structures in open-channel flows: an experimental studyThis paper is one of a selection of papers in this Special Issue in honour of Professor M. Selim Yalin (1925–2007)." Canadian Journal of Civil Engineering 36, nr 10 (październik 2009): 1643–55. http://dx.doi.org/10.1139/l09-093.

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The size of the largest horizontal coherent structures (HCSs) of turbulence in open-channel flows is investigated experimentally on the basis of three series of flow velocity measurements. These are further used to explore the dynamics and morphological consequences of HCSs. The flow velocity measurements were carried out in a 21 m long and 1 m wide channel, with a bed formed by sand with average grain size of 2 mm. The bed surface was flat. The turbulent and subcritical flow under investigation was uniform, with a flow depth of 4 cm. The bed slope of 0.0015 was such that, for the present flow depth, the bed shear stress acting on the bed was substantially below the threshold for initiation of motion, thus ensuring that the bed remained flat throughout the measurements. To the knowledge of the writers, this work is a first attempt to systematically investigate HCSs in open-channel flows. It should be viewed as an extension to the case of horizontal structures of work previously carried out by a number of authors on large-scale organized turbulence motion in open-channel flows, so far focusing exclusively on vertical coherent structures (VCSs). The horizontal burst length was found to be between five and seven times the flow width. A slight internal meandering of the flow caused by the superimposition of burst sequences on the mean flow was detectable. Both of these findings lend support to the longstanding belief expressed by many prominent researchers that the formation of large-scale river forms is directly related to the large-scale turbulence. In particular, the present measurements for the first time provide some direct evidence in support of hypotheses previously raised by Yalin and da Silva regarding the formation of alternate bars and meanders through the action of HCSs on the mean flow and the mobile bed and banks.

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Devi, Kalpana, Prashanth Reddy Hanmaiahgari, Ram Balachandar i 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, nr 7 (1.07.2021): 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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