scholarly journals Slow magnetoacoustic waves in gravitationally stratified two-fluid plasmas in strongly ionized limit

2020 ◽  
Vol 501 (2) ◽  
pp. 1940-1950
Author(s):  
A Alharbi ◽  
I Ballai ◽  
V Fedun ◽  
G Verth
Keyword(s):  
Acoustic Waves ◽  
Fluid Model ◽  
Density Ratio ◽  
Charged Particles ◽  
Evolutionary Equation ◽  
Plasma Dynamics ◽  
Value Analysis ◽  
Strongly Coupled ◽  
Two Fluid Model ◽  
Two Fluid

ABSTRACT The plasma dynamics at frequencies comparable with collisional frequency between various species has to be described in multifluid framework, where collisional interaction between particles is an important ingredient. In our study, we will assume that charged particles are strongly coupled, meaning that they form a single fluid that interacts with neutrals, therefore we will employ a two-fluid model. Here, we aim to investigate the evolutionary equation of slow sausage waves propagating in a gravitationally stratified flux tube in the two-fluid solar atmosphere in a strongly ionized limit using an initial value analysis. Due to the collisional interaction between massive particles (ions and neutrals), the governing equations are coupled. Solutions are sought in the strongly ionized limit and the density ratio between neutrals and charged particles is a small parameter. This limit is relevant to the upper part of the chromosphere. Our results show that slow sausage waves associated with charged particles propagate such that their possible frequency is affected by a cut-off due to the gravitational stratification. In contrast, for neutral acoustic waves the cut-off value applies on their wavelength and only small wavelength waves are able to propagate. Slow modes associated with neutrals are driven by the collisional coupling with ions.

Assessment of Components of the Subcooled Boiling Model for CFD Simulations

2010 ◽  
Author(s):  
Deoras Prabhudharwadkar ◽  
Martin A. Lopez de Bertodano ◽  
John Buchanan ◽  
Avinash Vaidheeswaran
Keyword(s):  
Fluid Model ◽  
Constitutive Relations ◽  
Bubble Diameter ◽  
Density Ratio ◽  
Data Sets ◽  
Vapor Generation ◽  
Wide Range ◽  
Two Fluid Model ◽  
Bubble Sizes ◽  
Two Fluid

This paper describes the details of validation of heat and mass transfer models used for subcooled boiling simulation with a CFD two-fluid model. This research was focused on assessment of the wall heat flux partitioning model using the state-of-the-art multidimensional experimental data available in the literature. Various constitutive relations used to close the vapor generation rate at the heated wall were studied and the best suited combination of these was obtained. The current study was restricted to vertical flows through pipe and annulus geometries. Three data sets from the literature were considered: first with R12 at about 26 bar pressure, second with water at atmospheric pressure and third with R113 at 2.69 bar pressure. In these data sets, the bubble diameter distribution across the ducts was measured. Bubble diameter estimation brings in the largest uncertainty in the two-fluid model predictions and hence using the data with known bubble sizes allowed to focus on assessment of other parameters which use constitutive relations to model vapor generation rate, e.g. bubble nucleation site density and bubble departure frequency at the wall. The simulations were carried out using the CFD code CFX-12. The R12 data used here corresponds to fluid-vapor density ratio which is equivalent to that of water-steam at 150 bar. Therefore the density ratio varies over two orders of magnitude. The surface tension also varies over a wide range from 0.0017 to 0.057 N/m. The ratio of the flow channel hydraulic diameter to the bubble diameter in these simulations varied between 4 and 40. The two-fluid model was modified, for cases involving bubble sizes too large to be represented using the continuum assumption, in order to obtain satisfactory results. Hence, the model that has been developed for this study is applicable for a wide range of physical conditions and bubble sizes.

scholarly journals Natural modes of the two-fluid model of two-phase flow

2021 ◽  
Vol 33 (3) ◽  
pp. 033324
Author(s):  
Alejandro Clausse ◽  
Martín López de Bertodano
Keyword(s):  
Two Phase Flow ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Phase ◽  
Natural Modes ◽  
Two Fluid Model ◽  
Two Fluid

Self-consistent hydrodynamic two-fluid model of vortex plasma

2021 ◽  
Vol 33 (3) ◽  
pp. 037116
Author(s):  
Victor L. Mironov
Keyword(s):  
Fluid Model ◽  
Self Consistent ◽  
Two Fluid Model ◽  
Two Fluid

scholarly journals Mathematical study on two-fluid model for flow of K–L fluid in a stenosed artery with porous wall

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
R. Ponalagusamy ◽  
Ramakrishna Manchi
Keyword(s):  
Theoretical Study ◽  
Fluid Model ◽  
Porous Wall ◽  
Governing Equations ◽  
Rate Of Increase ◽  
Special Cases ◽  
Stenosed Artery ◽  
Flow Through ◽  
Two Fluid Model ◽  
Two Fluid

AbstractThe present communication presents a theoretical study of blood flow through a stenotic artery with a porous wall comprising Brinkman and Darcy layers. The governing equations describing the flow subjected to the boundary conditions have been solved analytically under the low Reynolds number and mild stenosis assumptions. Some special cases of the problem are also presented mathematically. The significant effects of the rheology of blood and porous wall of the artery on physiological flow quantities have been investigated. The results reveal that the wall shear stress at the stenotic throat increases dramatically for the thinner porous wall (i.e. smaller values of the Brinkman and Darcy regions) and the rate of increase is found to be 18.46% while it decreases for the thicker porous wall (i.e. higher values of the Brinkman and Darcy regions) and the rate of decrease is found to be 10.21%. Further, the streamline pattern in the stenotic region has been plotted and discussed.

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