Experimental and Theoretical Analyses of Small-Scale Radionuclide Migration Field Experiments

1981 ◽  
Vol 6 ◽  
Author(s):  
K. L. Erickson ◽  
D. R. Fortney
Keyword(s):  
Distribution Coefficient ◽  
Field Experiments ◽  
Fluid Velocity ◽  
Small Scale ◽  
Fracture Aperture ◽  
Radionuclide Migration ◽  
Experimental Conditions ◽  
Dissolved Species ◽  
Key Variables ◽  
Aperture Distribution

ABSTRACTAnalyses have been completed which provide guidance for conducting radionuclide migration field experiments. Characterization of nonwelded tuffs and laboratory experiments defining dominant chemical phenomena were used to develop a model for describing migration in fractured porous rock. Criteria for obtaining optimum experimental conditions were developed in terms of the key variables dominating migration in a given rock type, namely the fracture aperture, distribution coefficient, and average fluid velocity. For simple dissolved species, which are reversibly sorbed, variations in fracture aperture and fluid velocity affect experiment results much more than variations in distribution coefficient. Therefore, the experiment should be designed to optimize hydrogeologic conditions rather than sorption properties.

Effects of magnetic field on the turbulent wake of a cylinder in free-surface magnetohydrodynamic channel flow

2014 ◽  
Vol 742 ◽  
pp. 446-465 ◽  
Author(s):  
John R. Rhoads ◽  
Eric M. Edlund ◽  
Hantao Ji
Keyword(s):  
Magnetic Field ◽  
Free Surface ◽  
Power Law ◽  
Applied Magnetic Field ◽  
Effective Viscosity ◽  
Field Experiments ◽  
Fluid Velocity ◽  
Mhd Flow ◽  
Small Scale ◽  
Ir Camera

AbstractResults from a free-surface magnetohydrodynamic (MHD) flow experiment are presented detailing the modification of vortices in the wake of a circular cylinder with its axis parallel to the applied magnetic field. Experiments were performed at Reynolds numbers of the order of ${\mathit{Re}}\sim 10^4$ as the interaction parameter ${\mathit{N}}$, representing the ratio of electromagnetic forces to inertial forces, was increased through unity. The von Kármán vortex street in the wake of the cylinder was observed by simultaneously sampling the gradient of the induced electric potential, $ \boldsymbol {\nabla }{\phi }$, at 16 cross-stream locations as a proxy for the streamwise fluid velocity. An ensemble of vortex velocity profiles was measured as a function of the applied magnetic field strength. Results indicate a significant change in the circulation of vortices and the deviations from the average profile as ${\mathit{N}}$ was increased. By sampling the fluctuations in $\boldsymbol {\nabla }{\phi }$ at three locations in the wake, the decay of the vortices was examined and the effective viscosity was found to decrease as ${\mathit{N}}^{-0.49 \pm 0.04}$. Using temperature as a passive tracer, qualitative observations were made with an infrared (IR) camera that showed significant changes in the wake, including the absence of small-scale structures at high magnetic field strengths. Collectively, the results suggest that the reduction in effective viscosity was due to the suppression of the small-scale eddies by the magnetic field. The slope of the power spectrum was observed to change from a $k^{-1.8}$ power law at low ${\mathit{N}}$ to a $k^{-3.5}$ power law for ${\mathit{N}}> 1$. Together, these results suggest the flow smoothly transitioned from a hydrodynamic state to a magnetohydrodynamic regime over the range of $0 < {\mathit{N}}< 1$.

Nuclide Migration Field Experiments in Tuff, G Tunnel, Nevada Test Site

1981 ◽  
Vol 6 ◽  
Author(s):  
B. R. Erdal ◽  
R. S. Rundberg ◽  
W. R. Daniels ◽  
K. Wolfsberg ◽  
A. M. Friedman ◽  
...  
Keyword(s):  
Field Experiments ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Test Site ◽  
Current Status ◽  
Real Field ◽  
Small Scale ◽  
Single Fracture ◽  
Radionuclide Migration ◽  
Porous Rock

ABSTRACTA project to begin to address the phenomena of flow and element migration in fractured porous rock has recently been started by the Los Alamos National Laboratory, Sandia National Laboratories, and Argonne National Laboratory. The work has three objectives: 1) to develop the experimental, instrumental, and safety techniques necessary to conduct controlled, small-scale, radionuclide migration, field experiments; 2) to use these techniques to define radionuclide migration through rock by performing generic, at-depth experiments under closely controlled conditions in a single fracture in porous rock; and 3) to determine whether available lithologic, geochemical, and hydraulic properties together with existing or developed transport models are sufficient and appropriate to describe real field conditions (i.e., to scale from small-scale laboratory studies to bench-size studies to field studies). The detailed scope of this project and its current status are described.

scholarly journals Applications of Chemically Modified Clay Minerals and Clays to Water Purification and Slow Release Formulations of Herbicides

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 9
Author(s):  
Tomas Undabeytia ◽  
Uri Shuali ◽  
Shlomo Nir ◽  
Baruch Rubin
Keyword(s):  
Clay Minerals ◽  
Field Experiments ◽  
Slow Release ◽  
Freeze Fracture ◽  
Nano Particles ◽  
Organic Cations ◽  
Small Scale ◽  
High Exposure ◽  
Model Calculations ◽  
Slow Release Formulations

This review deals with modification of montmorillonite and other clay-minerals and clays by interacting them with organic cations, for producing slow release formulations of herbicides, and efficient removal of pollutants from water by filtration. Elaboration is on incorporating initially the organic cations in micelles and liposomes, then producing complexes denoted micelle- or liposome-clay nano-particles. The material characteristics (XRD, Freeze-fracture electron microscopy, adsorption) of the micelle– or liposome–clay complexes are different from those of a complex of the same composition (organo-clay), which is formed by interaction of monomers of the surfactant with the clay-mineral, or clay. The resulting complexes have a large surface area per weight; they include large hydrophobic parts and (in many cases) have excess of a positive charge. The organo-clays formed by preadsorbing organic cations with long alkyl chains were also addressed for adsorption and slow release of herbicides. Another examined approach includes “adsorptive” clays modified by small quaternary cations, in which the adsorbed organic cation may open the clay layers, and consequently yield a high exposure of the siloxane surface for adsorption of organic compounds. Small scale and field experiments demonstrated that slow release formulations of herbicides prepared by the new complexes enabled reduced contamination of ground water due to leaching, and exhibited enhanced herbicidal activity. Pollutants removed efficiently from water by the new complexes include (i) hydrophobic and anionic organic molecules, such as herbicides, dissolved organic matter; pharmaceuticals, such as antibiotics and non-steroidal drugs; (ii) inorganic anions, e.g., perchlorate and (iii) microorganisms, such as bacteria, including cyanobacteria (and their toxins). Model calculations of adsorption and kinetics of filtration, and estimation of capacities accompany the survey of results and their discussion.

scholarly journals Formation conditions and mechanical properties of aggregates produced in tephra–water–snow flows

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Hirofumi Niiya ◽  
Kenichi Oda ◽  
Daisuke Tsuji ◽  
Hiroaki Katsuragi
Keyword(s):  
Mechanical Properties ◽  
Mixing Time ◽  
Testing Machine ◽  
Small Scale ◽  
Scaling Analysis ◽  
Compression Tests ◽  
Ice Slurry ◽  
Experimental Conditions ◽  
Formation Conditions ◽  
Snow And Ice

Abstract The formation of aggregates consisting of snow, water, and tephra has been reported in small-scale experiments on three-phase flows containing tephra, water, and snow, representing lahars triggered by snowmelt. Such aggregates reduce the mobility of mud flow. However, the formation mechanism of such aggregates under various conditions has not been investigated. To elucidate the formation conditions and mechanical properties of the aggregates, we performed mixing experiments with materials on a rotating table and compression tests on the resulting aggregates with a universal testing machine in a low-temperature room at $$0\,^{\circ }\text {C}$$ 0 ∘ C . From experiments with varying component ratios of the mixture and tephra diameter, the following results were obtained: (i) the aggregate grew rapidly and reached maturity after a mixing time of 5 min; (ii) the mass of aggregates increased with snow concentration, exhibiting an approximately linear relationship; (iii) single aggregates with large mass formed at lower and higher tephra concentrations, whereas multiple aggregates with smaller mass were observed at intermediate concentrations; (iv) the shape of the aggregate satisfied the similarity law for an ellipsoid; (v) the compressive mechanical behavior could be modeled by an empirical nonlinear model. The obtained mechanical properties of the aggregates were independent of the experimental conditions; (vi) scaling analysis based on the Reynolds number and the strength of the aggregates showed that the aggregates cannot form in ice-slurry lahars. Our findings suggest that low-speed lahars containing snow and ice are likely to generate aggregates, but snow and ice in the ice-slurry lahars are dispersed without such aggregates.

scholarly journals Fabrication of freestanding Pt nanowires for use as thermal anemometry probes in turbulence measurements

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Hai Le-The ◽  
Christian Küchler ◽  
Albert van den Berg ◽  
Eberhard Bodenschatz ◽  
Detlef Lohse ◽  
...  
Keyword(s):  
Room Temperature ◽  
Fluid Velocity ◽  
Current Mode ◽  
Constant Current ◽  
Small Scale ◽  
Turbulence Measurements ◽  
High Dynamic ◽  
Scale Turbulence ◽  
Constant Current Mode ◽  
Pt Nanowires

AbstractWe report a robust fabrication method for patterning freestanding Pt nanowires for use as thermal anemometry probes for small-scale turbulence measurements. Using e-beam lithography, high aspect ratio Pt nanowires (~300 nm width, ~70 µm length, ~100 nm thickness) were patterned on the surface of oxidized silicon (Si) wafers. Combining wet etching processes with dry etching processes, these Pt nanowires were successfully released, rendering them freestanding between two silicon dioxide (SiO2) beams supported on Si cantilevers. Moreover, the unique design of the bridge holding the device allowed gentle release of the device without damaging the Pt nanowires. The total fabrication time was minimized by restricting the use of e-beam lithography to the patterning of the Pt nanowires, while standard photolithography was employed for other parts of the devices. We demonstrate that the fabricated sensors are suitable for turbulence measurements when operated in constant-current mode. A robust calibration between the output voltage and the fluid velocity was established over the velocity range from 0.5 to 5 m s−1 in a SF6 atmosphere at a pressure of 2 bar and a temperature of 21 °C. The sensing signal from the nanowires showed negligible drift over a period of several hours. Moreover, we confirmed that the nanowires can withstand high dynamic pressures by testing them in air at room temperature for velocities up to 55 m s−1.

scholarly journals Flow topologies in bubble-induced turbulence: a direct numerical simulation analysis

2018 ◽  
Vol 857 ◽  
pp. 270-290 ◽  
Author(s):  
Josef Hasslberger ◽  
Markus Klein ◽  
Nilanjan Chakraborty
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Volume Fraction ◽  
Fluid Velocity ◽  
Small Scale ◽  
Flow Topology ◽  
Two Phase ◽  
Local Flow ◽  
Interface Curvature

This paper presents a detailed investigation of flow topologies in bubble-induced two-phase turbulence. Two freely moving and deforming air bubbles that have been suspended in liquid water under counterflow conditions have been considered for this analysis. The direct numerical simulation data considered here are based on the one-fluid formulation of the two-phase flow governing equations. To study the development of coherent structures, a local flow topology analysis is performed. Using the invariants of the velocity gradient tensor, all possible small-scale flow structures can be categorized into two nodal and two focal topologies for incompressible turbulent flows. The volume fraction of focal topologies in the gaseous phase is consistently higher than in the surrounding liquid phase. This observation has been argued to be linked to a strong vorticity production at the regions of simultaneous high fluid velocity and high interface curvature. Depending on the regime (steady/laminar or unsteady/turbulent), additional effects related to the density and viscosity jump at the interface influence the behaviour. The analysis also points to a specific term of the vorticity transport equation as being responsible for the induction of vortical motion at the interface. Besides the known mechanisms, this term, related to surface tension and gradients of interface curvature, represents another potential source of turbulence production that lends itself to further investigation.

Scale-dependent alignment, tumbling and stretching of slender rods in isotropic turbulence

2018 ◽  
Vol 860 ◽  
pp. 465-486 ◽  
Author(s):  
Nimish Pujara ◽  
Greg A. Voth ◽  
Evan A. Variano
Keyword(s):  
Isotropic Turbulence ◽  
Fluid Velocity ◽  
Inertial Range ◽  
Small Scale ◽  
Strain Rate Tensor ◽  
Scaling Exponents ◽  
Slender Body Theory ◽  
Velocity Statistics ◽  
Rigid Rods ◽  
Dissipation Range

We examine the dynamics of slender, rigid rods in direct numerical simulation of isotropic turbulence. The focus is on the statistics of three quantities and how they vary as rod length increases from the dissipation range to the inertial range. These quantities are (i) the steady-state rod alignment with respect to the perceived velocity gradients in the surrounding flow, (ii) the rate of rod reorientation (tumbling) and (iii) the rate at which the rod end points move apart (stretching). Under the approximations of slender-body theory, the rod inertia is neglected and rods are modelled as passive particles in the flow that do not affect the fluid velocity field. We find that the average rod alignment changes qualitatively as rod length increases from the dissipation range to the inertial range. While rods in the dissipation range align most strongly with fluid vorticity, rods in the inertial range align most strongly with the most extensional eigenvector of the perceived strain-rate tensor. For rods in the inertial range, we find that the variance of rod stretching and the variance of rod tumbling both scale as $l^{-4/3}$, where $l$ is the rod length. However, when rod dynamics are compared to two-point fluid velocity statistics (structure functions), we see non-monotonic behaviour in the variance of rod tumbling due to the influence of small-scale fluid motions. Additionally, we find that the skewness of rod stretching does not show scale invariance in the inertial range, in contrast to the skewness of longitudinal fluid velocity increments as predicted by Kolmogorov’s $4/5$ law. Finally, we examine the power-law scaling exponents of higher-order moments of rod tumbling and rod stretching for rods with lengths in the inertial range and find that they show anomalous scaling. We compare these scaling exponents to predictions from Kolmogorov’s refined similarity hypotheses.

scholarly journals Short Circuit Recognition for Metal Electrorefining Using an Improved Faster R-CNN With Synthetic Infrared Images

2021 ◽  
Vol 15 ◽  
Author(s):  
Xin Li ◽  
Yonggang Li ◽  
Renchao Wu ◽  
Can Zhou ◽  
Hongqiu Zhu
Keyword(s):  
Detection System ◽  
Short Circuit ◽  
Infrared Image ◽  
Parameter Tuning ◽  
Recall Rate ◽  
Synthetic Methods ◽  
Synthetic Dataset ◽  
Small Scale ◽  
Infrared Images ◽  
Key Variables

This paper is concerned with the problem of short circuit detection in infrared image for metal electrorefining with an improved Faster Region-based Convolutional Neural Network (Faster R-CNN). To address the problem of insufficient label data, a framework for automatically generating labeled infrared images is proposed. After discussing factors that affect sample diversity, background, object shape, and gray scale distribution are established as three key variables for synthesis. Raw infrared images without fault are used as backgrounds. By simulating the other two key variables on the background, different classes of objects are synthesized. To improve the detection rate of small scale targets, an attention module is introduced in the network to fuse the semantic segment results of U-Net and the synthetic dataset. In this way, the Faster R-CNN can obtain rich representation ability about small scale object on the infrared images. Strategies of parameter tuning and transfer learning are also applied to improve the detection precision. The detection system trains on only synthetic dataset and tests on actual images. Extensive experiments on different infrared datasets demonstrate the effectiveness of the synthetic methods. The synthetically trained network obtains a mAP of 0.826, and the recall rate of small latent short circuit is superior to that of Faster R-CNN and U-Net, effectively avoiding short-circuit missed detection.

Experimental Testing and Numerical Modeling of Small-Scale Boat With Drag-Reducing Air-Cavity System

2021 ◽  
Author(s):  
Jeffrey M. Collins ◽  
Phillip R. Whitworth ◽  
Konstantin I. Matveev
Keyword(s):  
Adaptive Mesh Refinement ◽  
Experimental Testing ◽  
Hydrodynamic Performance ◽  
Small Scale ◽  
Video Monitor ◽  
Data Logger ◽  
Time Step ◽  
Experimental Conditions ◽  
Air Cavity ◽  
Air Supply

Abstract Hydrodynamic performance of ships can be greatly improved by the formation of air cavities under ship bottom with the purpose to decrease water friction on the hull surface. The air-cavity ships using this type of drag reduction are usually designed for and typically effective only in a relatively narrow range of speeds and hull attitudes and sufficient rates of air supply to the cavity. To investigate the behavior of a small-scale air-cavity boat operating under both favorable and detrimental loading and speed conditions, a remotely controlled model hull was equipped with a data acquisition system, video camera and onboard sensors to measure air-cavity characteristics, air supply rate and the boat speed, thrust and trim in operations on open-water reservoirs. These measurements were captured by a data logger and also wirelessly transmitted to a ground station and video monitor. The experimental air-cavity boat was tested in a range of speeds corresponding to length Froude numbers between 0.17 and 0.5 under three loading conditions, resulting in near zero trim and significant bow-up and bow-down trim angles at rest. Reduced cavity size and significantly increased drag occurred when operating at higher speeds, especially in the bow-up trim condition. The other objective of this study was to determine whether computational fluid dynamics simulations can adequately capture the recorded behavior of the boat and air cavity. A computational software Star-CCM+ was utilized with the VOF method employed for multi-phase flow, RANS approach for turbulence modeling, and economical mesh settings with refinements in the cavity region and near free surface. Upon conducting the mesh verification study, several experimental conditions were simulated, and approximate agreement with measured test data was found. Adaptive mesh refinement and time step controls were also applied to compare results with those obtained on the user-generated mesh. Adaptive controls improved resolution of complex shedding patterns from the air cavity but had little impact on overall results. The presented here experimental approach and obtained results indicate that both outdoor experimentation and computationally inexpensive modeling can be used in the process of developing air-cavity systems for ship hulls.

Progress towards small-scale field trials of coastal enhanced weathering of olivine

2021 ◽  
Author(s):  
Stephen Romaniello ◽  
Shanee Stopnitzky ◽  
Tom Green ◽  
Francesc Montserrat ◽  
Eric Matzner ◽  
...  
Keyword(s):  
Real World ◽  
Field Experiments ◽  
Ecological Impact ◽  
Field Trials ◽  
Research Strategy ◽  
Unintended Consequences ◽  
Ecological Impacts ◽  
Small Scale ◽  
Climate Mitigation ◽  
Stage Of Development

&lt;p&gt;Slow progress towards achieving global greenhouse gas emissions targets significantly increases the likelihood that future climate efforts may require not only emissions cuts but also direct climate mitigation via negative emissions technologies (IPCC AR5). Currently, such technologies exist at only a nascent stage of development, with significant uncertainties regarding their feasibility, cost, and potential unintended consequences and/or co-benefits.&lt;/p&gt;&lt;p&gt;Coastal enhanced weathering of olivine (CEWO) has been suggested as one potential pathway for achieving net negative CO&lt;sub&gt;2&lt;/sub&gt; emissions at scale. CEWO involves the mining of olivine-rich ultramafic rocks (such as dunite) for incorporation during beach augmentation and restoration work. While grinding this rock into increasingly fine particle sizes is essential for increasing its surface area and reactivity, this step is also costly and energetically expensive. CEWO attempts to minimize this cost and energy penalty by relying on wave and tidal action to provide ongoing physical weathering of olivine grains once distributed on beaches. Laboratory experiments and carbon emissions assessments of CEWO suggest that these approaches may be technically feasible and carbon negative, but significant uncertainties remain regarding the real-world kinetics of coastal olivine dissolution. Furthermore, concerns about the fate and ecological impact of nickel (Ni) and chromium (Cr)&amp;#8212;potentially toxic trace metals found in olivine&amp;#8212;require careful evaluation.&lt;/p&gt;&lt;p&gt;In 2019, Project Vesta was established as a nonprofit, philanthropically funded effort to evaluate the technical feasibility and ecological impacts of CEWO through a dedicated research program ultimately culminating in small-scale, real-world field trials of CEWO. This presentation will provide an overview and discussion of our overall research strategy, share insights from interim modeling and mesocosm experiments designed to ensure the practicality and safety of future field experiments, and explain our approach for ensuring transparent, responsible, and ethical research oversight and governance.&lt;/p&gt;

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