Analysis of small-scale gravel bed topography during armoring

2003 ◽  
Vol 39 (12) ◽  
Author(s):  
Andrea Marion ◽  
Simon J. Tait ◽  
Ian K. McEwan
Keyword(s):  
Small Scale ◽  
Gravel Bed ◽  
Bed Topography

scholarly journals A new bedrock and surface elevation dataset for modelling the Greenland ice sheet

2003 ◽  
Vol 37 ◽  
pp. 351-356 ◽  
Author(s):  
Jonathan L. Bamber ◽  
Duncan J. Baldwin ◽  
S. Prasad Gogineni
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Detailed Comparison ◽  
Radar Data ◽  
The Arctic ◽  
Small Scale ◽  
Surface Model ◽  
Rock Outcrops ◽  
Bed Topography ◽  
Elevation Model

AbstractA new digital elevation model of the surface of the Greenland ice sheet and surrounding rock outcrops has been produced from a comprehensive suite of satellite and airborne remote-sensing and cartographic datasets. The surface model has been regridded to a resolution of 5 km, and combined with a new ice-thickness grid derived from ice-penetrating radar data collected in the 1970s and 1990s. A further dataset, the International Bathymetric Chart of the Arctic Ocean, was used to extend the bed elevations to include the continental shelf. The new bed topography was compared with a previous version used for ice-sheet modelling. Near the margins of the ice sheet and, in particular, in the vicinity of small-scale features associated with outlet glaciers and rapid ice motion, significant differences were noted. This was highlighted by a detailed comparison of the bed topography around the northeast Greenland ice stream.

scholarly journals Conditional simulation of Thwaites Glacier (Antarctica) bed topography for flow models: Incorporating inhomogeneous statistics and channelized morphology

2014 ◽  
Vol 60 (222) ◽  
pp. 635-646 ◽  
Author(s):  
John A. Goff ◽  
Evelyn M. Powell ◽  
Duncan A. Young ◽  
Donald D. Blankenship
Keyword(s):  
Conditional Simulation ◽  
Rapid Change ◽  
Radar Data ◽  
Small Scale ◽  
Flow Models ◽  
Bed Topography ◽  
Error Characterization ◽  
Glacier Flow ◽  
Global Sea Level ◽  
Scale Roughness

AbstractThwaites Glacier, Antarctica, is experiencing rapid change and its mass could, if disgorged into the ocean, lead to ∼1 m of global sea-level rise. Efforts to model flow for Thwaites Glacier are strongly dependent on an accurate model of bed topography. Airborne radar data collected in 2004/05 provide 35 000 line km of bed topography measurements sampled every 20 m along track. At ∼15 km track spacing, this extensive dataset nevertheless misses considerable important detail, particularly: (1) resolution of mesoscale channelized morphology that can guide glacier flow; and (2) resolution of small-scale roughness between the track lines that is critical for determining topographic resistance to flow. Both issues are addressed using a conditional simulation that merges a stochastic realization (an unconditional simulation) with a deterministic surface. A conditional simulation is a non-unique interpolation that reproduces observed statistical behavior without affecting data values. Channels are resolved in the deterministic surface using an interpolation algorithm designed for sinuous channels. Small-scale roughness is resolved using a statistical analysis that accounts for heterogeneity, including an abrupt transition between ‘lowland’ and ‘highland’ morphology. Multiple realizations of the unconditional simulation can be generated to sample the probability space and allow error characterization in flow modeling.

scholarly journals Thermal refraction: implications for subglacial heat flux

2021 ◽  
pp. 1-10
Author(s):  
Simon Willcocks ◽  
Derrick Hasterok ◽  
Samuel Jennings
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Small Scale ◽  
Geothermal Heat ◽  
Temperature Anomalies ◽  
Bed Topography ◽  
Subglacial Topography ◽  
State Models ◽  
Typical Range ◽  
Conductivity Contrast

Abstract In this study, we explore small-scale (~1 to 20 km) thermal-refractive effects on basal geothermal heat flux (BGHF) at subglacial boundaries resulting from lateral thermal conductivity contrasts associated with subglacial topography and geologic contacts. We construct a series of two-dimensional, conductive, steady-state models that exclude many of the complexities of ice sheets in order to demonstrate the effect of thermal refraction. We show that heat can preferentially flow into or around a subglacial valley depending on the thermal conductivity contrast with underlying bedrock, with anomalies of local BGHF at the ice–bedrock interface between 80 and 120% of regional BGHF and temperature anomalies on the order of ±15% for the typical range of bedrock conductivities. In the absence of bed topography, subglacial contacts can produce significant heat flux and temperature anomalies that are locally extensive (>10 km). Thermal refraction can result in either an increase or decrease in the likelihood of melting and ice-sheet stability depending on the conductivity contrast and bed topography. While our models exclude many of the physical complexities of ice behavior, they illustrate the need to include refractive effects created by realistic geology into future glacial models to improve the prediction of subglacial melting and ice viscosity.

Performance Evaluation of a Solar Greenhouse Dryer at Different Bed Conditions Under Passive Mode

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Asim Ahmad ◽  
Om Prakash
Keyword(s):  
Performance Evaluation ◽  
Heat Storage ◽  
Superior Performance ◽  
Small Scale ◽  
Passive Mode ◽  
Maximum Heat ◽  
Gravel Bed ◽  
Drying Efficiency ◽  
Small Scale Industries ◽  
Drying Chamber

Greenhouse drying shows a significant role in the bulk level of drying. In the present setup, a greenhouse dryer operating under natural convection mode was designed and fabricated. The sensible heat storage concept was applied to the bed of the drying chamber. Four different beds, namely, gravel bed, ground bed, concrete bed, and black painted gravel bed was being selected for the comparative heat transfer analyses of the proposed setup. The maximum heat gain takes place at the black painted gravel bed conditions, i.e., 53%, while for concrete bed, gravel bed, and ground bed, it is 33%, 49%, and 29%, respectively. Hence, black painted gravel bed condition is strongly recommended for maximum heat storage. The proposed setup was used for drying of tomato flakes in black painted gravel bed condition. It has been found that the moisture content in the tomato flakes has been removed from 96% to 9.10% in 13 h. The average drying efficiency of the proposed greenhouse dryer is found to be 23.49%. The comparative analysis of the performance evaluation has been done with other investigators, and it was found that the drying rate of the proposed setup shows superior performance as compared with others. The design of the proposed greenhouse setup with black painted gravel bed condition is strongly recommended for small-scale industries and farmers.

Sampling Interval Analysis and CDF Generation for Grain-Scale Gravel Bed Topography

2018 ◽  
Vol 144 (10) ◽  
pp. 04018065 ◽  
Author(s):  
Daniel G. Wren ◽  
James R. Rigby ◽  
Eddy J. Langendoen ◽  
Roger A. Kuhnle
Keyword(s):  
Interval Analysis ◽  
Sampling Interval ◽  
Gravel Bed ◽  
Bed Topography

scholarly journals Turbulent kinetic energy flux and budget in a water-worked gravel bed

2018 ◽  
Vol 40 ◽  
pp. 05006
Author(s):  
Ellora Padhi ◽  
Nadia Penna ◽  
Roberto Gaudio ◽  
V. R. Desai ◽  
Subhasish Dey
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Flow Measurements ◽  
Gravel Bed ◽  
Bed Topography ◽  
Flow Parameters ◽  
Turbulent Characteristics ◽  
Image Velocimetry ◽  
Double Averaging ◽  
Water Work

Turbulent flow over a water-worked gravel bed (WGB) was investigated using the double-averaging methodology (DAM). The flow measurements were carried out by the particle image velocimetry (PIV) technique. The double-averaged (DA) turbulent characteristics (DA Turbulent kinetic energy (TKE) components, form-induced TKE components, DA TKE fluxes, form-induced TKE fluxes, DA TKE budget) were analyzed for the WGB. To understand the effect of changed bed topography on the turbulent characteristics, the flow measurements were carried out over a screeded gravel bed (SGB), keeping the flow Froude number same as in case of WGB. Owing to water work, the bed topography of WGB was dissimilar to that of SGB, resulting in higher roughness size for the former than that for the latter. Comparative study of the DA turbulent characteristics of both the beds infers that especially in the near-bed flow zone, the flow parameters of the WGB are attaining higher values than those of the SGB. However, they are almost alike for both the beds in the flow outer layer.

scholarly journals Bar dynamics and sediment transport pulses in gravel-bed channels

2018 ◽  
Vol 40 ◽  
pp. 05047
Author(s):  
Blaise Dhont ◽  
Christophe Ancey ◽  
Patricio Bohorquez
Keyword(s):  
Sediment Transport ◽  
Laser Sheet ◽  
Water Discharge ◽  
Bedload Transport ◽  
Transport Rate ◽  
Experimental Conditions ◽  
Gravel Bed ◽  
Bed Topography ◽  
Sediment Transport Rate ◽  
Alternate Bars

Mountain rivers exhibit sediment transport rate fluctuations that often cover more than two orders of magnitude. Bedform migration is often cited as the key process that causes giant fluctuations in the sediment transport rate. To quantify the effect of bedform migration on transport rate, we ran laboratory experiments in a 19-m long 60-cm wide flume with well-sorted gravel bed. At the flume inlet, the water discharge and the particle flux were kept constant. Experiments were conducted over long times (typically > 500 h). Sediment transport rate was monitored at the flume outlet using accelerometers. Bed topography was scanned at high spatial resolution using a laser sheet. Water depth was measured using ultrasonic probes mounted on an automated rolling carriage. We observed that, under steady state experimental conditions, bed morphology played a key part in the generation of bedload transport fluctuations. The bars migrated downstream intermittently, producing the most important pulses. When the bar position was stable for a few hours, additional pulses resulted from sediment transfer from pool to pool, in the form of sediment waves (bedload sheets). Thus, in our experiments, alternate bars formed a two-entity system (bar + pool) with two distinctive functions: the bars contributed to fix and stabilize the bed whereas the pools were the preferential zones of short-term storage and transfer of sediment.

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