scholarly journals MagmaFOAM-1.0: a modular framework for the simulation of magmatic systems

2021 ◽  
Author(s):  
Federico Brogi ◽  
Simone Colucci ◽  
Jacopo Matrone ◽  
Chiara Paola Montagna ◽  
Mattia De' Michieli Vitturi ◽  
...  
Keyword(s):  
Model Development ◽  
Equilibrium Phase ◽  
Solution Technique ◽  
Computer Performance ◽  
Community Model ◽  
Volcanic Processes ◽  
Rayleigh Taylor Instability ◽  
Basaltic Melts ◽  
Time Selection ◽  
Selection Of

Abstract. Numerical simulations of volcanic processes play a fundamental role in understanding the dynamics of magma storage, ascent and eruption. The recent extraordinary progress in computer performance and improvements in numerical modeling techniques allow simulating multiphase systems in mechanical and thermodynamical disequilibrium. Nonetheless, the growing complexity of these simulations requires the development of flexible computational tools that can easily switch between sub-models and solution techniques. In this work we present MagmaFOAM, a library based on the open source computational fluid dynamics software OpenFOAM, that incorporates models for solving the dynamics of multiphase, multicomponent magmatic systems. Retaining the modular structure of OpenFOAM, MagmaFOAM allows run-time selection of the solution technique depending on the physics of the specific process, and sets a solid framework for in-house and community model development, testing and comparison. MagmaFOAM models thermo-mechanical non-equilibrium phase coupling and phase change, and implements state-of-the-art multiple volatile saturation models and constitutive equations with composition-dependent and space-time local computation of thermodynamic and transport properties. Code testing is performed using different multiphase modeling approches for processes relevant to magmatic systems: Rayleigh-Taylor instability, for buyoancy-driven magmatic processes; multiphase shock tube simulations, propedeutical to conduit dynamics studies; bubble growth and breakage in basaltic melts. Benchmark simulations illustrate the capabilities and potential of MagmaFOAM to account for the variety of non-linear physical and thermodynamical processes characterizing the dynamics of volcanic systems.

Stability of a tokamak plasma with diffuse toroidal rotation

2020 ◽  
Vol 86 (5) ◽  
Author(s):  
O. E. López ◽  
L. Guazzotto
Keyword(s):  
Shooting Method ◽  
Tokamak Plasma ◽  
Solution Technique ◽  
Large Aspect Ratio ◽  
Internal Resonances ◽  
Flow Shear ◽  
Magnetic Shear ◽  
The Stability ◽  
External Kink ◽  
Selection Of

The present work considers the stability of a high- $\beta$ , large aspect ratio, circular plasma with diffuse profiles for the safety factor and the angular toroidal frequency (López & Guazzotto, Phys. Plasmas, vol. 24, 032501). An application of the Frieman–Rotenberg formalism results in a system of scalar eigenmode equations whose coupling is retained at the plasma–vacuum transition but is disregarded across the plasma column, which is a standard practice. The solution technique consists of a multidimensional shooting method for the poloidal harmonics; robust initial guesses are constructed by solving the dispersion relation in the static scenario with vanishing magnetic shear. Flow shear appears as a high- $\beta$ toroidal contribution, and we illustrate its destabilizing influence on $n=1$ external kink modes in the presence of ideal and resistive walls. Internal resonances are avoided by means of the selection of appropriate equilibrium parameters. The stabilizing influence of a finite positive average magnetic shear is also exemplified.

scholarly journals Selection of hexagonal buckling patterns by the elastic Rayleigh-Taylor instability

2018 ◽  
Vol 121 ◽  
pp. 234-257 ◽  
Author(s):  
Aditi Chakrabarti ◽  
Serge Mora ◽  
Franck Richard ◽  
Ty Phou ◽  
Jean-Marc Fromental ◽  
...  
Keyword(s):  
Taylor Instability ◽  
Rayleigh Taylor Instability ◽  
Selection Of

Robustness of Parametric and Nonparametric Fitting Procedures of Tree-Stem Taper with Alternative Definitions for Validation Data

2020 ◽  
Vol 118 (6) ◽  
pp. 576-583
Author(s):  
Sheng-I Yang ◽  
Harold E Burkhart
Keyword(s):  
Loblolly Pine ◽  
Model Development ◽  
Data Partitioning ◽  
Parametric Models ◽  
Validation Data ◽  
Data Set ◽  
Stem Taper ◽  
Computationally Intensive ◽  
Tree Stem ◽  
Selection Of

Abstract This study aims to evaluate the robustness of parametric and nonparametric procedures using alternative definitions of validation data for loblolly pine. Specifically, four data division strategies were implemented: random selection of one-third of the trees in the data set, selection of the smallest one-third of the trees by diameter at breast height (DBH), selection of the middle third of the trees by DBH, and selection of the largest third of the trees by DBH. Results indicate that tree taper was predicted reasonably well by both procedures when the smallest, medium-sized, or randomly selected trees were withheld for validation. However, when the largest trees were withheld for validation, diameters predicted by the nonparametric random forest algorithm were considerably less accurate than those predicted by the parametric models, especially for diameters near the tree top. When extrapolation is anticipated, a carefully designed data-partitioning strategy should provide some protection against poor results for given prediction objectives. Study Implications Parametric tree-stem taper models have been widely applied in forestry. Recently, nonparametric methods with computationally intensive algorithms were proposed for estimating tree taper, but reliability of the methods has not been explicitly examined. In practice, models are commonly applied to predict unknown populations, which may vary from the observations used in model development. This study provides insights for natural resource and forest managers to select appropriate validation procedures when developing models for predicting tree-stem taper and examining robustness of parametric and nonparametric fitting of tree-stem taper under varying levels of interpolation/extrapolation from fitting to validation of data.

scholarly journals Procurement Selection Model: Development of a Conceptual Model Based on Transaction Costs

2014 ◽  
Vol 2 (2) ◽  
pp. 56 ◽  
Author(s):  
Mohammed A Rajeh ◽  
John Tookey ◽  
James Rotimi
Keyword(s):  
Transaction Costs ◽  
Construction Projects ◽  
Negative Impact ◽  
Selection Process ◽  
Model Development ◽  
Evaluation Criteria ◽  
Analytical Form ◽  
Model Based ◽  
Suitable Combination ◽  
Selection Of

Procurement is a major improvement area and a crucial element contributing to project success, and the selection of an optimal procurement system is an important and difficult step in project execution. The criteria for choosing suitable procurement methods are based on client’s objectives and priorities, and influenced by project constraints. The procurement path determination chart has largely dominated research in procurement selection process in construction. Eight factors need to be considered by the client when developing procurement selection criteria. At the procurement strategy the focus should be on factors such as cost, quality, and time, while at the procurement route the consideration should focus on complexity, certainty, risk, responsibility, and degree of control by the client. However, including certain criteria and ignoring the magnitude of transaction costs (TCs) associated with uncertainties in the transaction environment simplifies this process. This study addresses this shortcoming by combining evaluation criteria with TCs incurred because of external and internal environmental uncertainties in a theoretical model on procurement selection. This is achieved by developing a conceptual framework model based on TCs. Uncertainties in the transaction environment have a positive or negative impact on the magnitude of TCs such as information, procurement, administration, and enforcement. The model represents an analytical form of a suitable combination of factors influencing procurement systems, which guide procurement decisions. The model will increase understanding of how efficient procurement selection of construction projects can be achieved through appropriate procurement procedures, which could positively impact project performance.Keywords: Construction, Procurement systems, Transaction costs

The Use of Magnetostrictive Cores for the Vibrations Generation and Energy Harvesting from Vibration, in the Selected Frequencies of Work

2014 ◽  
Vol 598 ◽  
pp. 75-80 ◽  
Author(s):  
Jerzy Kaleta ◽  
Krzysztof Kot ◽  
Rafał Mech ◽  
Przemyslaw Wiewiorski
Keyword(s):  
Energy Transfer ◽  
Information Transfer ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Mechanical Vibrations ◽  
Energy Transportation ◽  
To Receive ◽  
Low Power Electronics ◽  
Time Selection ◽  
Selection Of

The paper presents research on use of magnetostrictive cores for the recovery of energy from vibrations and its use to power low-power electronics. To achieve this goal a test stand was constructed to generate and to receive the vibrations in the measurement system at the same time. Selection of an appropriate magnetomechanical parameters of the system was an important element influencing end results. The most important were values of the prestress and magnetising field for actuators and harvesters. As a result of the investigation the device operating in a wide frequency range (up to 40 KHz) and a system for energy transportation through mechanical vibrations were developed. Moreover it was shown that the proposed solution allow information transfer in a short bursts over the same system as energy transfer.

Sign in / Sign up

Export Citation Format

Share Document