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2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Lujing Zheng ◽  
Lulin Zheng ◽  
Yujun Zuo ◽  
Hao Liu ◽  
Bin Chen ◽  
...  

To study the mesoscale damage evolution law of irregular sandstone particles, based on RFPA2D and digital image processing technology, a real mesostructure numerical model of irregular sandstone particles is established to simulate the breakage process of particles, the effects of loading conditions and mesoscale heterogeneity on irregular sandstone particle damage are studied, and the calculation method of fractal dimension of irregular rock particles mesoscale fracture is proposed. The results show that the fracture damage degree (ω) and fractal dimension (D) maximum values of the constrained particles are 0.733 and 1.466, respectively, and the unconstrained particles are 0.577 and 1.153, respectively. The final failure mode of constrained particles is more complicated than unconstrained particles, the damage is more serious, and the fracture is more complete. Thus, the larger values of D yield a more complicated final failure mode of the particles. Consequently, with the larger ω, the final damage is more serious, and the breakage effect is comparatively better. The study is of great significance for exploring the laws of rock particle breakage and energy consumption, rock breakage mechanism, and searching for efficient and energy-saving rock-breaking methods.


2021 ◽  
Author(s):  
Ian Delaney ◽  
Leif S. Anderson ◽  
Frédéric Herman

Abstract. In addition to ice and water, glaciers expel sediment. As a result, changing glacier dynamics and melt will result in changes to glacier erosion and sediment discharge, which can impact the landscape surrounding retreating glaciers, as well as communities and ecosystems downstream. To date, the available models of subglacial sediment transport on the sub-hourly to decadal-scale exist in one dimension, usually along a glacier's flow line. Such models have proven useful in describing the formation of landforms, the impact of sediment transport on glacier dynamics, the interactions between climate, glacier dynamics, and erosion. However, because of the large role of sediment connectivity in determining sediment discharge, the geoscience community needs modeling frameworks that describe subglacial sediment discharge in two spatial dimensions over time. Here, we present SUGSET_2D, a numerical model that evolves a two-dimensional subglacial till layer in response to the erosion of bedrock and changing sediment transport conditions below the glacier. Experiments employed on test cases of synthetic ice sheets and alpine glaciers demonstrate the heterogeneity in sediment transport across a glacier's bed. Furthermore, the experiments show the non-linear increase in sediment discharge following increased glacier melt. Lastly, we apply the model to Griesgletscher in the Swiss Alps where we use a parameter search to test model outputs against annual observations of sediment discharge measured from the glacier. The model captures the glacier's inter-annual variability and quantities of sediment discharge. Furthermore, the model's capacity to represent the data depends greatly on the grain size of sediment. Smaller sediment sizes allow sediment transport to occur in regions of the bed with reduced water flow and channel size, effectively increasing sediment connectivity into the main channels. Model outputs from the three test-cases together show the importance of considering heterogeneities in water discharge and sediment availability in two dimensions.


2021 ◽  
Vol 922 (2) ◽  
pp. 128
Author(s):  
Sherry Chhabra ◽  
James A. Klimchuk ◽  
Dale E. Gary

Abstract There is a wide consensus that the ubiquitous presence of magnetic reconnection events and the associated impulsive heating (nanoflares) are strong candidates for solving the solar coronal heating problem. Whether nanoflares accelerate particles to high energies like full-sized flares is unknown. We investigate this question by studying the type III radio bursts that the nanoflares may produce on closed loops. The characteristic frequency drifts that type III bursts exhibit can be detected using a novel application of the time-lag technique developed by Viall & Klimchuk (2012) even when there are multiple overlapping events. We present a simple numerical model that simulates the expected radio emission from nanoflares in an active region, which we use to test and calibrate the technique. We find that in the case of closed loops the frequency spectrum of type III bursts is expected to be extremely steep such that significant emission is produced at a given frequency only for a rather narrow range of loop lengths. We also find that the signature of bursts in the time-lag signal diminishes as: (1) the variety of participating loops within that range increases; (2) the occurrence rate of bursts increases; (3) the duration of bursts increases; and (4) the brightness of bursts decreases relative to noise. In addition, our model suggests a possible origin of type I bursts as a natural consequence of type III emission in a closed-loop geometry.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fares Redouane ◽  
Wasim Jamshed ◽  
S. Suriya Uma Devi ◽  
M. Prakash ◽  
Kottakkaran Sooppy Nisar ◽  
...  

AbstractFluidity and thermal transport across the triangular aperture with lower lateral inlet and apply placed at the vertical outlet of the chamber which filled with efficient TiO2–SiO2/water hybrid nanofluid under the parametrical influence. Several parameters are tested like the numbers of Hartmann ($$0 \le Ha \le 100$$ 0 ≤ H a ≤ 100 ), Richardson ($$0 \le Ri \le 5$$ 0 ≤ R i ≤ 5 ), and Reynolds ($$10 \le Re \le 1000$$ 10 ≤ R e ≤ 1000 ) were critiqued through streamlines, isotherms, and Nusselt number ($$Nu$$ Nu ). Numerical model has to be developed and solved through the Galerkin finite element method (GFEM) by discretized with 13,569 triangular elements optimized through grid-independent analysis. The Hartmann number ($$Ha$$ Ha ), exerts minimal impact over the flow and thermal aspects while the other parameters significantly manipulate the physical nature of the flowing and thermal aspects behaviors.


Nukleonika ◽  
2021 ◽  
Vol 66 (4) ◽  
pp. 133-138
Author(s):  
Mikołaj Oettingen ◽  
Jerzy Cetnar

Abstract The volumetric homogenization method for the simplified modelling of modular high-temperature gas-cooled reactor core with thorium-uranium fuel is presented in the paper. The method significantly reduces the complexity of the 3D numerical model. Hence, the computation time associated with the time-consuming Monte Carlo modelling of neutron transport is considerably reduced. Example results comprise the time evolutions of the effective neutron multiplication factor and fissionable isotopes (233U, 235U, 239Pu, 241Pu) for a few configurations of the initial reactor core.


Author(s):  
Mona Amer ◽  
Martin Paehr ◽  
Lars Panning-von Scheidt ◽  
Joerg R. Seume ◽  
Joachim Schmied

Abstract Casings of machinery and support structures have an influence on the rotordynamic behaviour which is commonly considered by simplified models (e.g. one degree of freedom models). These are in many cases insufficient. Hence, more accurate modelling approaches are required which can be used in the design process or the rotordynamic calculation to achieve a better representation of the overall vibrational behaviour. To study the effects of casing and supporting structures on rotordynamics, the casing modal parameters of an axial compressor are determined by an experimental modal analysis. In parallel, a numerical model is established. As experimental data are rarely found in the literature, this work focuses on the parameter identification of the casing structure. The results are subsequently incorporated into a model updating strategy, in order to tune and improve the numerical model. Experimental and numerical data are compared to assess the quality of the data and the results gained. The ultimate objective is a reduced order model, which can be integrated in existing rotordynamic tools via an interface while keeping the calculation time low.


Author(s):  
Jeong-Ho Bae ◽  
Ki-Hong Min

Radar observation data with high temporal and spatial resolution are used in the data assimilation experiment to improve precipitation forecast of a numerical model. The numerical model considered in this study is Weather Research and Forecasting (WRF) model with double-moment 6-class microphysics scheme (WDM6). We calculated radar equivalent reflectivity factor using higher resolution WRF and compared with radar observations in South Korea. To compare the precipitation forecast characteristics of three-dimensional variational (3D-Var) assimilation of radar data, four experiments are performed based on different precipitation types. Comparisons of the 24-h accumulated rainfall with Automatic Weather Station (AWS) data, Contoured Frequency by Altitude Diagram (CFAD), Time Height Cross Sections (THCS), and vertical hydrometeor profiles are used to evaluate and compare the accuracy. The model simulations are performed with and with-out 3D-VAR radar reflectivity, radial velocity and AWS assimilation for two mesoscale convective cases and two synoptic scale cases. The radar data assimilation experiment improved the location of precipitation area and rainfall intensity compared to the control run. Especially, for the two convective cases, simulating mesoscale convective system was greatly improved.


Author(s):  
Ke Wang ◽  
Mobin Salasi ◽  
Mariano Iannuzzi

Abstract A comprehensive mathematical model, including electrode kinetics, hydrolysis and complexation reactions, salt film precipitation and pit interface movement, was developed to investigate pit growth of stainless steels 316L under a salt film. The new mathematical framework incorporates activity coefficients into the hydrolysis and complexation reaction calculations for the first time, using experimental results to parametrize the electrode kinetics in a saturated pit solution. The model was validated by 1D pit experiments and results documented in the literature. It can successfully estimate the transition potentials, salt film thickness, pit stability product, saturated pit concentration, and the pH at the pit base during pit propagation under the presence of a salt film. Moreover, the model can predict the Cr enrichment and Fe depletion in the saturated solution at the pit base, attributed to the higher diffusion coefficient of Fe and the lower Cr diffusivity.


MAUSAM ◽  
2021 ◽  
Vol 48 (4) ◽  
pp. 531-540
Author(s):  
ANWAR ALI ◽  
HAFIZUR RAHMAN ◽  
SYED SAZZAD HAIDER CHOWDHURY

Interactions among river discharge, storm surges and tides in the Meghna river estuary in Bangladesh have been studied by using a two-dimensional vertically integrated numerical model of the northern Bay of Bengal. The study considers the interactions mostly in terms of flow across the river mouth under the three forcings, individually and in different combinations of them. River discharge and tidal flow across the river mouth act both positively and negatively depending on the tidal phase, positively during high tide and negatively during low tide. This is also true for the combination of all the three forces. On the other hand, in most of the cases, river discharge acts in opposition to the storm surges. Under certain conditions and on rare occasions they act positively. The interactions between river discharge and storm surges, however, depend on their relative magnitudes. In respect of total elevation in the estuarial region, river discharge tends to increase the surge height. However, away from the estuary, the effect of river discharge is hardly discernible.      


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