scholarly journals What Determines the Parameters of a Propagating Streamer: A Comparison of Outputs of the Streamer Parameter Model and of Hydrodynamic Simulations

2021 ◽  
Author(s):  
Nikolai G. Lehtinen ◽  
Robert Marskar
Keyword(s):  
Experimental Data ◽  
Electric Discharge ◽  
Propagation Velocity ◽  
Hydrodynamic Simulation ◽  
Hydrodynamic Simulations ◽  
Important Stage ◽  
Streamer Discharges

Electric streamer discharges (streamers) in air are a very important stage of lightning, taking place before formation of the leader discharge, and with which an electric discharge starts from conducting objects which enhance the background elecric field, such as airplanes. Despite years of research, it is still not well understood what mechanism determines the values of streamer parameters, such as its radius and propagation velocity. The Streamer Parameter Model (SPM) is aimed to understand this mechanism, as well as to provide a way to efficiently calculate streamer parameters. Previously, we demonstrated that SPM results compared well with a limited set of experimental data. In this Brief Report, we compare SPM predictions to the published hydrodynamic simulation (HDS) results.

scholarly journals What Determines the Parameters of a Propagating Streamer: A Comparison of Outputs of the Streamer Parameter Model and of Hydrodynamic Simulations

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1664
Author(s):  
Nikolai G. Lehtinen ◽  
Robert Marskar
Keyword(s):  
Experimental Data ◽  
Electric Field ◽  
Electric Discharge ◽  
Propagation Velocity ◽  
The Novel ◽  
Hydrodynamic Simulation ◽  
Hydrodynamic Simulations ◽  
Important Stage ◽  
Streamer Discharges

Electric streamer discharges (streamers) in the air are a very important stage of lightning, taking place before formation of the leader discharge, and with which an electric discharge starts from conducting objects which enhance the background electric field, such as airplanes. Despite years of research, it is still not well understood what mechanism determines the values of a streamer’s parameters, such as its radius and propagation velocity. The novel Streamer Parameter Model (SPM) was made to explain this mechanism, and to provide a way to efficiently calculate streamer parameters. Previously, we demonstrated that SPM results compared well with a limited set of experimental data. In this article, we compare SPM predictions to the published hydrodynamic simulation (HDS) results.

scholarly journals Study of the influence of initial-state fluctuations on hydrodynamic simulations

2020 ◽  
Vol 245 ◽  
pp. 06005
Author(s):  
Marcin Słodkowski ◽  
Patryk Gawryszewski ◽  
Dominik Setniewski
Keyword(s):  
Initial Conditions ◽  
Graphics Processing Unit ◽  
Heavy Ion ◽  
Processing Unit ◽  
Initial State ◽  
Final State ◽  
Hydrodynamic Simulation ◽  
Hydrodynamic Simulations ◽  
Cartesian Coordinate ◽  
Ion Collision

In this work, we are focusing on assessing the contribution of the initial-state fluctuations of heavy ion collision in the hydrodynamic simulations. We are trying to answer the question of whether the hydrodynamic simulation retains the same level of fluctuation in the final-state as for the initial stage. In another scenario, the hydrodynamic simulations of the fluctuation drowns in the final distribution of expanding matter. For this purpose, we prepared sufficient relativistic hydrodynamic program to study A+A interaction which allows analysing initial-state fluctuations in the bulk nuclear matter. For such an assumption, it is better to use high spatial resolution. Therefore, we applied the (3+1) dimensional Cartesian coordinate system. We implemented our program using parallel computing on graphics cards processors - Graphics Processing Unit (GPU). Simulations were carried out with various levels of fluctuation in initial conditions using the average method of events coming from UrQMD models. Energy density distributions were analysed and the contribution of fluctuations in initial conditions was assessed in the hydrodynamic simulation.

HYDRODYNAMIC SIMULATIONS OF 16O+208Pb COLLISIONS AT 200 GeV/N

1989 ◽  
Vol 04 (11) ◽  
pp. 983-993 ◽  
Author(s):  
T.L. McABEE ◽  
J.R. WILSON ◽  
J.A. ZINGMAN ◽  
C.T. ALONSO
Keyword(s):  
Experimental Data ◽  
Equations Of State ◽  
Recent Experimental Data ◽  
Baryonic Matter ◽  
Hydrodynamic Simulations ◽  
200 Gev ◽  
Rapidity Distributions ◽  
Target Rapidity ◽  
Bombarding Energy ◽  
Initial Target

We investigate collisions of 16 O with 208 Pb at a bombarding energy of 200 GeV /N in the lab frame. Our basis is an ideal, one-fluid 3-D hydrodynamics model. Several equations of state are used to study the qualitative relation between final baryon rapidity distributions and the stiffness of the EOS. We find that 75% of the baryonic matter lies within one unit of the initial target rapidity, in qualitative agreement with recent experimental data. In addition, our calculation is able to reproduce the integrated value of the dET/dy distribution that is observed experimentally.

scholarly journals Utilizing MIKE 21 Software to Create Simple Hydrodynamic Simulations

2021 ◽  
Vol 2 (1) ◽  
pp. 14-17
Author(s):  
Subiyanto Subiyanto ◽  
Sudradjat Supian
Keyword(s):  
Coastal Areas ◽  
Climatic Data ◽  
Coastal Morphology ◽  
Hydrodynamic Simulation ◽  
Hydrodynamic Simulations ◽  
Line Theory ◽  
Shoreline Dynamics ◽  
The Cross ◽  
Coastal Profile ◽  
Mike 21

This paper aim to create simple hydrodynamic simulation by using MIKE 21. The module used in MIKE 21 is LITPACK. LITPACK is one of the modules in MIKE 21 to solve hydraulic and sedimentation problems in coastal areas. Especially in this paper, the LITTLITE engine in LITPACK will be used. LITLINE determines the coastline position using a timeseries of wave climatic data. The model is based on a one-line theory, in which the cross-shore profile is expected to remain unaltered during erosion/accretion, with minor adjustments. Coastal morphology is thus only defined by coastline location (cross-shore direction) and coastal profile at a given long-shore position. The simulation used in this paper is the influence of groins on shoreline dynamics. The results of the simulation show that some areas will experience abrasion and some will experience accretion. 

scholarly journals Hybrid analytic and machine-learned baryonic property insertion into galactic dark matter haloes

2021 ◽  
Author(s):  
Ben Moews ◽  
Romeel Davé ◽  
Sourav Mitra ◽  
Sultan Hassan ◽  
Weiguang Cui
Keyword(s):  
Machine Learning ◽  
Dark Matter ◽  
High Speed ◽  
Hydrodynamic Simulation ◽  
Hydrodynamic Simulations ◽  
Learning Framework ◽  
Advantages And Disadvantages ◽  
Reasonable Degree ◽  
Galactic Dark Matter ◽  
Speed Advantage

Abstract While cosmological dark matter-only simulations relying solely on gravitational effects are comparably fast to compute, baryonic properties in simulated galaxies require complex hydrodynamic simulations that are computationally costly to run. We explore the merging of an extended version of the equilibrium model, an analytic formalism describing the evolution of the stellar, gas, and metal content of galaxies, into a machine learning framework. In doing so, we are able to recover more properties than the analytic formalism alone can provide, creating a high-speed hydrodynamic simulation emulator that populates galactic dark matter haloes in N-body simulations with baryonic properties. While there exists a trade-off between the reached accuracy and the speed advantage this approach offers, our results outperform an approach using only machine learning for a subset of baryonic properties. We demonstrate that this novel hybrid system enables the fast completion of dark matter-only information by mimicking the properties of a full hydrodynamic suite to a reasonable degree, and discuss the advantages and disadvantages of hybrid versus machine learning-only frameworks. In doing so, we offer an acceleration of commonly deployed simulations in cosmology.

Thermal and Mechanical Influence of Ultrasonically Aided Electrical Discharge Machining on Co-Cr Alloys

2020 ◽  
Vol 1157 ◽  
pp. 93-107
Author(s):  
Bogdan Ionuț Cristea ◽  
Daniel Ghiculescu ◽  
Dumitru Mnerie
Keyword(s):  
Experimental Data ◽  
Electric Discharge ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Comsol Multiphysics ◽  
Removal Mechanism ◽  
Electric Discharge Machining ◽  
Mechanical Influence

The paper reviews machining of CoCr alloys by electric discharge machining and ultrasonic aided discharge machining. The removal mechanism is discussed, modeled with Comsol Multiphysics and validated using experimental data.

scholarly journals Comparative Analysis of Methods for Mathematical Modeling of Specific Electrical Conductivity of Plasma in the Channel of an Electric Discharge in Water

2021 ◽  
Vol 57 (4) ◽  
pp. 24-34
Author(s):  
V.M. Kosenkov ◽  
Keyword(s):  
Mathematical Modeling ◽  
Experimental Data ◽  
Mathematical Model ◽  
Electrical Conductivity ◽  
Comparative Analysis ◽  
Electric Discharge ◽  
Specific Electrical Conductivity ◽  
Empirical Function ◽  
Electric Discharge In Water

In the present work, a comparative analysis of three methods for determining the specific electrical conductivity of the plasma formed in the channel of an electric discharge in water is carried out for its mathematical modeling. The parameters of the empirical function are determined, at which the results of mathematical modeling are consistent with the experimental data. The necessity of using empirical functions in calculating the specific electrical conductivity of plasma has been substantiated. The obtained ratios made it possible to significantly increase the adequacy of the previously developed mathematical model of the physical discharge processes in water and to expand the range of parameters in which it can be used.

scholarly journals Mathematical Modelling of Electric Discharge Machining of Al (6351)-SiC-B4C Hybrid Composite

2020 ◽  
Vol 8 (4S4) ◽  
pp. 163-166
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Surface Roughness ◽  
Mathematical Modelling ◽  
Electric Discharge ◽  
Electrode Wear ◽  
Electric Discharge Machining ◽  
Pulse On Time ◽  
The Mathematical Model ◽  
Time Pulse

The Electric Discharge Machining (EDM) has emerged as one of the major machining method for the machining of hard-to- machine materials and composites. This paper aims at creating a mathematical model for the machining of the Al(6351)-SiC-B4C composites based on the experimental data and compare the same to identify the level of errors between the mathematical model and the experimental results. This paper was aimed as an attempt to develop a mathematical model for the output parameters viz. Electrode Wear ratio and Surface roughness based on the input parameters viz. current, pulse-on-time, pulse duty-factor and gap voltage.

scholarly journals Reproducing sub-millimetre galaxy number counts with cosmological hydrodynamic simulations

2021 ◽  
Author(s):  
Christopher C Lovell ◽  
James E Geach ◽  
Romeel Davé ◽  
Desika Narayanan ◽  
Qi Li
Keyword(s):  
Galaxy Evolution ◽  
Galaxy Formation ◽  
Formation Rate ◽  
Small Contribution ◽  
Redshift Distribution ◽  
Hydrodynamic Simulation ◽  
Hydrodynamic Simulations ◽  
Multiple Components ◽  
Number Counts ◽  
Good Agreement

Abstract Matching the number counts of high-z sub-millimetre-selected galaxies (SMGs) has been a long standing problem for galaxy formation models. In this paper, we use 3D dust radiative transfer to model the sub-mm emission from galaxies in the Simba cosmological hydrodynamic simulations, and compare predictions to the latest single-dish observational constraints on the abundance of 850 μm-selected sources. We find good agreement with the shape of the integrated 850 μm luminosity function, and the normalisation is within 0.25 dex at >3 mJy, unprecedented for a fully cosmological hydrodynamic simulation, along with good agreement in the redshift distribution of bright SMGs. The agreement is driven primarily by Simba’s good match to infrared measures of the star formation rate (SFR) function between z = 2 − 4 at high SFRs. Also important is the self-consistent on-the-fly dust model in Simba, which predicts, on average, higher dust masses (by up to a factor of 2.5) compared to using a fixed dust-to-metals ratio of 0.3. We construct a lightcone to investigate the effect of far-field blending, and find that 52% of sources are blends of multiple components, which makes a small contribution to the normalisation of the bright-end of the number counts. We provide new fits to the 850 μm luminosity as a function of SFR and dust mass. Our results demonstrate that solutions to the discrepancy between sub-mm counts in simulations and observations, such as a top-heavy IMF, are unnecessary, and that sub-millimetre-bright phases are a natural consequence of massive galaxy evolution.

scholarly journals Effects of radiation pressure on the evaporative wind of HD 209458b

2020 ◽  
Vol 493 (1) ◽  
pp. 1292-1305 ◽  
Author(s):  
Alex Debrecht ◽  
Jonathan Carroll-Nellenback ◽  
Adam Frank ◽  
Eric G Blackman ◽  
Luca Fossati ◽  
...  
Keyword(s):  
Radiation Pressure ◽  
High Energy ◽  
Line Of Sight ◽  
Hydrodynamic Simulation ◽  
High Energy Radiation ◽  
Hydrodynamic Simulations ◽  
Cometary Tail ◽  
Effects Of Radiation ◽  
Simplified Calculation

ABSTRACT The role of radiation pressure in shaping exoplanet photoevaporation remains a topic of contention. Radiation pressure from the exoplanet’s host star has been proposed as a mechanism to drive the escaping atmosphere into a ‘cometary’ tail and explain the high velocities observed in systems where mass-loss is occurring. In this paper, we present results from high-resolution 3D hydrodynamic simulations of a planet similar to HD 209458b. We self-consistently launch a wind flowing outwards from the planet by calculating the ionization and heating resulting from incident high-energy radiation, and account for radiation pressure. We first present a simplified calculation, setting a limit on the Lyman-α flux required to drive the photoevaporated planetary material to larger radii and line-of-sight velocities. We then present the results of our simulations, which confirm the limits determined by our analytic calculation. We thus demonstrate that, within the limits of our hydrodynamic simulation and for the Lyman-α fluxes expected for HD 209458, radiation pressure is unlikely to significantly affect photoevaporative winds or to explain the high velocities at which wind material is observed, though further possibilities remain to be investigated.

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