scholarly journals Experiments and simulations on the possibility of radiative contraction/collapse in the PF-1000 plasma focus

Nukleonika ◽  
2016 ◽  
Vol 61 (2) ◽  
pp. 145-148 ◽  
Author(s):  
Mohamad Akel ◽  
Jakub Cikhardt ◽  
Pavel Kubes ◽  
Hans-Joachim Kunze ◽  
Sing Lee ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Plasma Focus ◽  
Experimental Studies ◽  
Radiative Losses

Abstract Experimental studies of discharges in the plasma focus facility with neon filling and respective numerical simulations employing the radiative Lee code are reported. The pinch currents exceed the Pease-Braginskii current, which indicates that radiative losses are larger than heating and that contraction of the formed plasma should occur. Both of these effects were indeed observed. Parallel numerical simulations were crucial for the identification of such an effect.

Vortex-Induced Vibrations of a Cylinder at Subcritical Reynolds Number

2011 ◽  
Author(s):  
Yoann Jus ◽  
Elisabeth Longatte ◽  
Jean-Camille Chassaing ◽  
Pierre Sagaut
Keyword(s):  
Reynolds Number ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Damping Ratio ◽  
Experimental Studies ◽  
Cross Flow ◽  
Physical Analysis ◽  
Arbitrary Lagrangian Eulerian ◽  
Vortex Induced Vibrations ◽  
Low Mass

The present work focusses on the numerical study of Vortex-Induced Vibrations (VIV) of an elastically mounted cylinder in a cross flow at moderate Reynolds numbers. Low mass-damping experimental studies show that the dynamic behavior of the cylinder exhibits a three-branch response model, depending on the range of the reduced velocity. However, few numerical simulations deal with accurate computations of the VIV amplitudes at the lock-in upper branch of the bifurcation diagram. In this work, the dynamic response of the cylinder is investigated by means of three-dimensional Large Eddy Simulation (LES). An Arbitrary Lagrangian Eulerian framework is employed to account for fluid solid interface boundary motion and grid deformation. Numerous numerical simulations are performed at a Reynolds number of 3900 for both no damping and low-mass damping ratio and various reduced velocities. A detailed physical analysis is conducted to show how the present methodology is able to capture the different VIV responses.

Crashworthiness Performance of Mass-Efficient Extruded Structures

2002 ◽  
Author(s):  
Robert R. Mayer ◽  
Weigang Chen ◽  
Anil Sachdev
Keyword(s):  
Numerical Simulations ◽  
Single Cell ◽  
Experimental Testing ◽  
Experimental Studies ◽  
Nonlinear Material ◽  
Dynamic Strain ◽  
Cell Design ◽  
Explicit Finite Element ◽  
The One ◽  
Crushing Behavior

Theoretical, numerical and experimental studies were conducted on the axial crushing behavior of traditional single-cell and innovative four-cell extrusions. Two commercial aluminum alloys, 6061 and 6063, both with two tempers (T4 and T6), were considered in the study. Testing coupons taken from the extrusions assessed the nonlinear material properties. A theoretical solution was available for the one-cell design, and was developed for the mean crushing force of the four-cell section. Numerical simulations were carried out using the explicit finite element code LS-DYNA. The aluminum alloy 6063T4 was found to absorb less energy than 6061T4, for both the one-cell and four-cell configurations. Both 6061 and 6063 in the T6 temper were found to have significant fracture in the experimental testing. Theoretical analysis and numerical simulations predicted a greater number of folds for the four-cell design, as compared to the one-cell design, and this was confirmed in the experiments. The theoretical improvement in energy absorption of 57% for the four-cell in comparison with the one-cell design was confirmed by experiment. The good agreement between the theoretical, numerical and experimental results allows confidence in the application of the theoretical and numerical tools for both single-cell and innovative four-cell extrusions. It was also demonstrated that these materials have very little dynamic strain rate effect.

Hysteretic effects of dry friction: modelling and experimental studies

2007 ◽  
Vol 366 (1866) ◽  
pp. 747-765 ◽  
Author(s):  
Jerzy Wojewoda ◽  
Andrzej Stefański ◽  
Marian Wiercigroch ◽  
Tomasz Kapitaniak
Keyword(s):  
Numerical Simulations ◽  
Dry Friction ◽  
Experimental Studies ◽  
Friction Model ◽  
Hysteretic Effect ◽  
Motion Characteristic ◽  
Friction Models ◽  
Theoretical Analyses ◽  
Friction Modelling

In this paper, the phenomena of hysteretic behaviour of friction force observed during experiments are discussed. On the basis of experimental and theoretical analyses, we argue that such behaviour can be considered as a representation of the system dynamics. According to this approach, a classification of friction models, with respect to their sensitivity on the system motion characteristic, is introduced. General friction modelling of the phenomena accompanying dry friction and a simple yet effective approach to capture the hysteretic effect are proposed. Finally, the experimental results are compared with the numerical simulations for the proposed friction model.

Experimental studies of al corona plasma created within the PF-100 plasma focus facility

2000 ◽  
Vol 50 (S3) ◽  
pp. 150-154 ◽  
Author(s):  
M. Scholz ◽  
L. Karpinski ◽  
K. Tomaszewski ◽  
M. Paduch ◽  
J. Kravárik ◽  
...  
Keyword(s):  
Plasma Focus ◽  
Experimental Studies ◽  
Corona Plasma

Numerical simulations of preliminary state of stress in bundles of metal sheets on the guillotine

2017 ◽  
Vol 85 (1) ◽  
pp. 14-23 ◽  
Author(s):  
J. Kaczmarczyk
Keyword(s):  
Numerical Simulations ◽  
Experimental Studies ◽  
Cutting Parameters ◽  
Cutting Process ◽  
Main Task ◽  
Force Loading ◽  
State Of Stress ◽  
Metal Sheets ◽  
Optimum Cutting ◽  
Selection Of

Purpose: The work is aimed at determination of the influence of selected technological parameters on the preliminary state of stress in bundles of metal sheets being compressed by the pressure beam and submitted to the cutting process on a guillotine. Design/methodology/approach: The numerical simulations concerning the preliminary state of stress in the bundle of sheets were conducted by means of the finite element method and the computer system MSC.Patran with the computational module MSC.Marc. The experimental studies concerning the influence of a force loading the pressure beam on the quality of metal sheets were carried out using scanning electron microscopy. Findings: Possibilities of finding the optimum cutting parameters to maximise the values of preliminary state of stress in the bundle of metal sheets subjected to cutting. Higher values of stresses in the bundle coming from loading the pressure beam on the one hand decrease the maximum values of cutting force and thereby facilitate the performance of the cutting process, however on the other hand too high values of stresses might damage the surface of the top sheet in a bundle. Research limitations/implications: The main task of the presented research concerns the reduction of the maximum force generated on a knife during the cutting process. It is possible by increasing the values of preliminary state of stress realized in practice by applying higher values of a force loading the pressure beam. The force should not be too high in order to avoid damaging of the top sheet in the bundle loading by the pressure beam. Practical implications: The appropriate selection of the cutting parameters on account of preliminary state of stress in the bundle of sheets is essential in terms of industrial economy. It enables reducing the amount of waste caused by defects in bundles of sheets and decreases wear of the cutting tool. The research has been conducted in order to reduce the number of randomly occurring defects during cutting of metal sheets on a guillotine. Originality/value: The results acquired from the research facilitate selection of the best parameter settings required for conducting the optimum cutting process on a guillotine. The optimum set of cutting parameters leads to the reduction of defects’ number occurring during the process.

scholarly journals Wear Processes in a Mechanical Friction Clutch: Theoretical, Numerical, and Experimental Studies

2015 ◽  
Vol 2015 ◽  
pp. 1-28 ◽  
Author(s):  
Dariusz Grzelczyk ◽  
Jan Awrejcewicz
Keyword(s):  
Mathematical Modeling ◽  
Experimental Data ◽  
Numerical Analysis ◽  
Numerical Simulations ◽  
Experimental Studies ◽  
Friction Torque ◽  
Wear Properties ◽  
Wear Model ◽  
Differential Model ◽  
Friction Clutch

Mathematical modeling, theoretical/numerical analysis, and experimental verification of wear processes occurring on the contact surface of friction linings of a mechanical friction clutch are studied. In contrast to many earlier papers we take into consideration wear properties and flexibility of friction materials being in friction contact. During mathematical modeling and numerical simulations we consider a general nonlinear differential model of wear (differential wear model) and a model of wear in the integral form (integral wear model). Equations governing contact pressure and wear distributions of individual friction linings, decrease of distance between clutch shields, and friction torque transmitted by the clutch are derived and compared with experimental data. Both analytical and numerical analyses are carried out with the qualitative and quantitative theories of differential and integral equations, including the Laplace transform approach to ODEs. We show that theoretical results and numerical simulations agree with the experimental data. Finally, a numerical analysis of the proposed mathematical models was carried out in a wider range of parameters of the considered system.

scholarly journals Measurements of fast electron beams and soft X-ray emission from plasma-focus experiments

Nukleonika ◽  
2016 ◽  
Vol 61 (2) ◽  
pp. 161-167 ◽  
Author(s):  
Władysław Surała ◽  
Marek J. Sadowski ◽  
Roch Kwiatkowski ◽  
Lech Jakubowski ◽  
Jarosław Żebrowski
Keyword(s):  
Plasma Focus ◽  
Fast Electron ◽  
Hot Spots ◽  
Electron Beams ◽  
Experimental Studies ◽  
Neutron Counter ◽  
X Rays ◽  
Strong Electron ◽  
Time Resolved ◽  
X Ray

Abstract The paper reports results of the recent experimental studies of pulsed electron beams and soft X-rays in plasma-focus (PF) experiments carried out within a modified PF-360U facility at the NCBJ, Poland. Particular attention was focused on time-resolved measurements of the fast electron beams by means of two different magnetic analyzers, which could record electrons of energy ranging from about 41 keV to about 715 keV in several (6 or 8) measuring channels. For discharges performed with the pure deuterium filling, many strong electron signals were recorded in all the measuring channels. Those signals were well correlated with the first hard X-ray pulse detected by an external scintillation neutron-counter. In some of the analyzer channels, electron spikes (lasting about dozens of nanoseconds) and appearing in different instants after the current peculiarity (so-called current dip) were also recorded. For several discharges, fast ion beams, which were emitted along the z-axis and recorded with nuclear track detectors, were also investigated. Those measurements confirmed a multibeam character of the ion emission. The time-integrated soft X-ray images, which were taken side-on by means of a pinhole camera and sensitive X-ray films, showed the appearance of some filamentary structures and so-called hot spots. The application of small amounts of admixtures of different heavy noble gases, i.e. of argon (4.8% volumetric), krypton (1.6% volumetric), or xenon (0.8% volumetric), decreased intensity of the recorded electron beams, but increased intensity of the soft X-ray emission and showed more distinct and numerous hot spots. The recorded electron spikes have been explained as signals produced by quasi-mono-energetic microbeams emitted from tiny sources (probably plasma diodes), which can be formed near the observed hot spots.

Redox Processes in Early Earth Accretion and in Terrestrial Bodies

Elements ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 161-166 ◽  
Author(s):  
Kevin Righter ◽  
Christopher D. K. Herd ◽  
Asmaa Boujibar
Keyword(s):  
Numerical Simulations ◽  
Liquid Water ◽  
Experimental Studies ◽  
Early Earth ◽  
Redox Processes ◽  
Natural Materials ◽  
The Earth

The Earth is a unique rocky planet with liquid water at the surface and an oxygen-rich atmosphere, consequences of its particular accretion history. The earliest accreting bodies were small and could be either differentiated and undifferentiated; later larger bodies had formed cores and mantles with distinct properties. In addition, there may have been an overall trend of early reduced and later oxidized material accreting to form the Earth. This paper provides an overview—based on natural materials in our Earthbound sample collections, experimental studies on those samples, and calculations and numerical simulations of differentiation processes—of planetary accretion, core–mantle equilibration, mantle redox processes, and redox variations in Earth, Mars, and other terrestrial bodies.

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