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1
Content available Effective interfacial tension effect on the instability of streaming Rivlin-Ericksen elastico-viscous fluid flow through a porous medium
Singh M.
International Journal of Applied Mechanics and Engineering
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2016
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Vol. 21, no. 1
221--229
EN
The instability of the plane interface between two uniform, superposed and streaming Rivlin-Ericksen elastico-viscous fluids through porous media, including the ‘effective interfacial tension’ effect, is considered. In the absence of the ‘effective interfacial tension’ stability/instability of the system as well as perturbations transverse to the direction of streaming are found to be unaffected by the presence of streaming if perturbations in the direction of streaming are ignored, whereas for perturbation in all other directions, there exists instability for a certain wave number range. The ‘effective interfacial tension’ is able to suppress this Kelvin-Helmholtz instability for small wavelength perturbations, the medium porosity reduces the stability range given in terms of a difference in streaming velocities.
2
Content available Physical and Numerical Investigations of Mould Flux Entrainment into Liquid Steel
Jowsa J., Bielnicki M., Cwudziński A.
Archives of Metallurgy and Materials
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2016
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Vol. 61, iss. 4
2043--2050
EN
This paper presents results of model tests, performed in order to analyze phenomenon of slag droplets entrainment into steel in mould, during continuous casting process. The carried out studies took the form of laboratory experiments using physical model, in which – using similarity criteria – the behaviour of interfacial boundary liquid steel-liquid slag has been simulated using water and silicon oils, differing in physicochemical properties. Additionally, based on PIV (Particle Image Velocimetry) measurements and numerical simulations, vector flow field and values of critical velocities, at which observed the occurrence of interfacial boundary silicon oil-water instability have been identified. Based on the carried out investigations, results, that illustrate relationship between critical entrainment velocity and physicochemical properties of oils have been presented.
3
Content available remote The instability of streaming viscous-viscoelastic fluids in a porous medium
Kumar P., Singh G. J.
International Journal of Applied Mechanics and Engineering
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2012
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Vol. 17, no. 1
191-201
EN
The Kelvin-Helmholtz instability of a Newtonian viscous fluid overlying a viscoelastic fluid in a porous medium is considered separately for Walters B' and Rivlin-Ericksen viscoelastic fluids. It is found that for the special case when perturbations in the directions of streaming are ignored, the system is unstable for a potentially unstable configuration and the system is stable for a potentially stable configuration for Rivlin-Ericksen viscoelastic fluids, which is in contrast to the case of the Walters B' viscoelastic fluid, where the system can be stable or unstable depending upon kinematic viscoelasticity, medium porosity, relative density of the viscoelastic fluid and medium permeability, for both potentially unstable and potentially stable configurations. In every other direction, a minimum value of wave-number has been found. The system is unstable for all wave-numbers greater than this minimum wave number.
4
Content available remote Kelvin - Helmholtz instability of two superposed Oldroydian viscoelastic fluid layers in a horizontal magnetic field
Khan A., Tak S. S., Patni P.
International Journal of Applied Mechanics and Engineering
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2010
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Vol. 15, no 4
1129-1142
EN
The Kelvin-Helmholtz instability of the plane interface separating two superposed viscous electrically conducting streaming Oldroydian fluids permeated with surface tension and magnetic field in a porous medium is considered. The stability motion is also assumed to have uniform two dimensional streaming velocity. The stability analysis has been carried out for two highly viscous fluids. By applying the normal mode technique to the linearized perturbation equations, the dispersion relation has been derived. As in the case of superposed Newtonian fluids, the system is stable in the potentially stable case and unstable in the potentially unstable case, that holds also for the present case. The behavior of growth rate with respect to kinematic viscosity, elasticity, permeability of porous medium, surface tension and streaming velocity are examined numerically and discussed in detail in section 5.
5
Content available remote The instability of streaming Walters B' viscoelastic fluids in hydromagnetics through porous media
Kumar P., Sharma P.
International Journal of Applied Mechanics and Engineering
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2005
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Vol. 10, no 1
123-131
EN
The instability of streaming Walters B' elastico-viscous fluids in hydromagnetics through porous medium is considered. The case of two uniform streaming fluids separated by a common horizontal interface is considered. It is found that for the special case when perturbations in the direction of streaming are ignored, the system can be stable or unstable, depending upon kinematic viscoelasticity, medium porosity and medium permeability, for both potentially unstable and stable configurations. In all other directions, a minimum value of wave-number has been found and the system is unstable for all wave-numbers greater than this minimum wave number and the instability of the system is found to be postponed due to the presence of the magnetic field.
6
Content available remote Kelvin-Helmholtz instability of Walters' (model B') viscoelastic fluid in porous medium in hydromagnetics
Sunil Y. D., Sharma P. K., Bharti, Sharma R. C.
Studia Geotechnica et Mechanica
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2003
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Vol. 25, nr 3-4
53--63
EN
The instability of streaming Walters' B' viscoelastic fluid in porous medium in the presence of magnetic field in the direction of streaming and also transverse with respect to the direction of streaming is considered. The case of two uniform streaming fluids separated by a horizontal boundary is studied. It is observed that for the special case where perturbations in the direction of streaming are ignored, the system is unstable for unstable configuration, i.e. heavier fluid overlying lighter fluid. However for potentially stable configuration, the system can be stable or unstable, depending on kinematic viscoelasticity which is smaller or greater than the medium permeability divided by medium porosity. In every other direction, a minimum value of wave number has been found and the system is unstable for all wave numbers greater than this minimum wave number. It is also found that the development of the Kelvin-Helmholtz instability in the direction of streaming remains uninfluenced by the presence of magnetic field in the transverse direction.
PL
W polu magnetycznym badano niestateczność przepływu lepkosprężystej cieczy B' Waltersa w ośrodku porowatym w kierunku przepływu, a także w kierunku do niego poprzecznym. Rozważano przypadek dwóch jednorodnych cieczy, które oddziela pozioma granica. Zaobserwowano, że w szczególnym przypadku, gdy zakłócenia w kierunku przepływu zostaną pominięte, układ jest niestateczny w niestatecznej konfiguracji, co oznacza, że cięższa ciecz nakłada się na lżejszą. Jednakże dla potencjalnie statecznej konfiguracji układ może być stateczny lub niestateczny w zależności od tego, czy kinematyczna lepkosprężystość jest większa, czy mniejsza niż przepuszczalność ośrodka podzielona przez jego porowatość. Dla każdego innego kierunku określa się minimalną liczbę falową i układ jest niestateczny, jeśli wszystkie liczby falowe są od niej większe. Ustalono też, że rozwijanie się niestateczności Kelvina-Helmholtza w poprzecznym kierunku nie podlega wpływowi pola magnetycznego.
7
Content available remote Instability of the interface between fluids of different densities flowing through a complex vertical hydraulic system
Grygoriev A., Jeżowiecka-Kabsch K., Szewczyk H.
International Journal of Applied Mechanics and Engineering
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2003
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Vol. 8, no 3
403-411
EN
The impact of the gas density difference on formation of flow patterns of fluids of different density was analysed. Physical modelling of a non-isothermal laminar flow of a gas mixture in a vertical epitaxial reactor chamber was carried out and the model flow was visualised. Visualisation studies, performed using a smoke method, confirmed that the stability of a gas interface determines the flow pattern in the chamber. The Rayleigh-Taylor instability occurs in the flow through a reactor, which, together with the Kelvin-Helmholtz instability and with the superposition of convection flows on the principal flow, shapes the flow pattern in the whole reactor chamber. On the basis of results of visualisation studies, the possibility of making the flow through a vertical reactor stable was indicated if the inlet guide apparatus is applied and the flow direction is reversed.
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