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Imre Ferenc Barna

Publications and source records attributed to Imre Ferenc Barna.

27 records · Page 2Linked to original sources
arXiv2014

Theoretical Study of Steam Condensation Induced Water Hammer Phenomena in Horizontal Pipeline

We investigate steam condensation induced water hammer (CIWH) phenomena and present new theoretical results. We use the WAHA3 model based on two-phase flow six first-order partial differential equations that present one dimensional, surface averaged mass, momentum and energy balances. A second order accurate high-resolution shock-capturing numerical scheme was applied with different kind of limiters in the numerical calculations. The applied two-fluid model shows some similarities to Relap5 which is widely used in the nuclear industry to simulate nuclear power plant accidents. This model was validated with different CIWH experiments which were performed in the PMK-2 facility, which is a full-pressure thermo-hydraulic model of the nuclear power plant of VVER-440/312 type in the Energy Research Center of the Hungarian Academy of Sciences in Budapest and in the Rosa facility in Japan. In our recent study we show the first part of a planned large database which will give us the upper and lower flooding mass flow rates for various pipe geometries where CIWH can happen. Such a reliable database would be a great help for future reactor constructions and scheming.

physics.flu-dyn↗
arXiv2012

Analytic solutions for the one-dimensional compressible Euler equation with heat conduction closed with different kind of equation of states

We present analytic self-similar or traveling wave solutions for a one-dimensional coupled system of continuity, compressible Euler and heat conduction equations. Different kind of equation of states are investigated. In certain forms of the equation of state one can arrive to a picture regarding the long time behavior of density and pressure. The impact of these quantities on the evolution of temperature is also discussed.

math-ph↗
arXiv2012

Heat conduction: hyperbolic self-similar shock-waves in solids

Analytic solutions for cylindrical thermal waves in solid medium is given based on the nonlinear hyperbolic system of heat flux relaxation and energy conservation equations. The Fourier-Cattaneo phenomenological law is generalized where the relaxation time and heat propagation coefficient have a general power law temperature dependence. From such laws one cannot form a second order parabolic or telegraph-type equation. We consider the original non-linear hyperbolic system itself with the self-similar Ansatz for the temperature distribution and for the heat flux. As results continuous and shock-wave solutions are presented. For physical establishment numerous materials with various temperature dependent heat conduction coefficients are mentioned.

math-ph↗
arXiv2011

Self-similar solutions for the Kardar-Parisi-Zhang interface dynamic equation

In this article we will present a study of the well-known Kardar-Parisi-Zhang(KPZ) model. Under certain conditions we have found analytic self-similar solutions for the underlying equation. The results are strongly related to the error functions. One and two spatial dimensions are considered with different kind of self-similar Ansaetze.

nlin.AO↗
arXiv2010

Homogeneous bubble nucleation limit of mercury under the normal working conditions of the planned European Spallation Source

In spallation neutron sources, liquid mercury is the subject of big thermal and pressure shocks, upon adsorbing the proton beam. These changes can cause unstable bubbles in the liquid, which can damage the structural material. While there are methods to deal with the pressure shock, the local temperature shock cannot be avoided. In our paper we calculated the work of the critical cluster formation (i.e. for mercury micro-bubbles) together with the rate of their formation (nucleation rate). It is shown that the homogeneous nucleation rates are very low even after adsorbing several proton pulses, therefore the probability of temperature induced homogeneous bubble nucleation is negligible.

physics.flu-dyn↗
arXiv2010

Heat conduction: a telegraph-type model with self-similar behavior of solutions

For heat flux $q$ and temperature $T$ we introduce a modified Fourier--Cattaneo law $q_t+ l \frac{q}{t}= - kT_x .$ The consequence of it is a non-autonomous telegraph-type equation. % $εS_{tt} + \frac{a}{t} S_t = S_{xx}$ . This model already has a typical self-similar solution which may be written as product of two travelling waves modulo a time-dependent factor and might play a role of intermediate asymptotics.

math-ph↗
arXiv2008

Two-phase flow model for energetic proton beam induced pressure waves in mercury target systems in the planned European Spallation Source

Two-phase flow calculations are presented to investigate the thermo-hydraulical effects of the interaction between 300 kJ proton pulses (2 ms long, 1.3 GeV) with a closed mercury loop which can be considered as a model system of the target of the planned European Spallation Source(ESS) facility. The two-fluid model consists of six first-order partial differential equations that present one dimensional mass momentum and energy balances for mercury vapour and liquid phases are capable to describe quick transients like cavitation effects or shock waves. The absorption of the proton beam is represented as instantaneous heat source in the energy balance equations. Densities and internal energies of the mercury liquid-vapour system are calculated from van der Waals equation, and the general method how to obtain such properties is also presented. A second order accurate high-resolution shock-capturing numerical scheme is applied with different kinds of limiters in the numerical calculations. %Our two-fluid model is very similar to the RELAP5 thermo-hydraulical code %which is used in the nuclear industry to simulate nuclear power plant accidents. Our analysis show that even 75 degree temperature heat shocks cannot cause considerable cavitation effects in mercury in 2ms long pulses

cond-mat.other↗
arXiv2006

Searching for dark matter with helium atom

With the help of the boost operator we can model the interaction between a weakly interacting particle(WIMP) of dark matter(DAMA) and an atomic nuclei. Via this "kick" we calculate the total electronic excitation cross section of the helium atom. The bound spectrum of He is calculated through a diagonalization process with a configuration interaction (CI) wavefunction built up from Slater orbitals. All together 19 singly- and doubly-excited atomic sates were taken with total angular momenta of L=0,1 and 2. Our calculation may give a rude estimation about the magnitude of the total excitation cross section which could be measured in later scintillator experiments. The upper limit of the excitation cross section is $9.7\cdot 10^{-8}$ barn.

gr-qc↗