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1

Double - diffusive electro-convection in aqueous solutions of polymeric liquids

Siddheshwar P. G., Srikrishna C. V.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 2

543-555

EN

The linear stability analysis of double-diffusive electroconvection in an aqueous- solution of a polymeric liquid is performed when a uniform DC electric field is applied. The polymeric liquid is assumed to be viscoelastic and the viscoelastic correction to the momentum equation is effected by considering the Jeffry constitutive equation. The eigenvalue at the onset of convection is obtained by employing the Rayleigh-Ritz technique for isothermal and isohaline boundary combination. The results of the study reveal that the strengths of the electric field and salinity delay the onset of convection. The classical results of the effect of the viscoelastic parameter on the onset of convection are found to be unaltered by the inducted electric field. The problem has industrial applications.

2

Effect of time - periodic modulation on convection in solutions of dilute polymeric liquids in a porous medium

Siddheshwar P. G., Srikrishna C. V.

International Journal of Applied Mechanics and Engineering

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2008

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Vol. 13, no 3

753-780

EN

The thermal instability in a layer of dilute polymeric liquid when boundaries are subjected to imposed time - periodic boundary temperatures (ITBT) is investigated. The critical Rayleigh and wave numbers for small amplitudes of ITBT are obtained for synchronous and asynchronous cases by following the Venezian approach. For small frequency modulation the Floquet theory adopted by Rosenblat and Herbert is employed and the periodicity and amplitude criterion is determined for thermal stability. The qualitative effects of various governing parameters on convective system are discussed. The problem has applications in solidification process of polymeric solutions and melts.

3

Przepływ nienewtonowskich roztworów polimerowych w zakrzywionych rurach o przekroju eliptycznym

Matras Z.

Inżynieria Chemiczna i Procesowa

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2002

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T. 23, z. 4

549-563

PL

Podjęto próbę obliczania strat ciśnienia występujących w laminarnym i turbulentnym przepływie dowolnie zdefiniowanych, reostabilnych cieczy nienewtonowskich w zakrzywionych kołowo przewodach o przekroju eliptycznym. Zaproponowano drugi wariant metody wielokrotnej transformacji zmiennych. W rezultacie tego otrzymano nowe, bezwymiarowe równania opisujące zarówno przepływ nienewtonowski jak również jego pseudonewtonowski analogon. Uzyskane przez autora dane doświadczalne w pełni potwierdzają przedstawione w pracy rezultaty rozważań teoretycznych.

EN

An attempt is made to calculate pressure drops in the laminar and the turbulent flow of generalised, purely-viscous, non-newtonian liquids in curved conducts of elliptic cross-section. Second variant of the several-stage transformation method is proposed. New dimensionless equations describing both the non-newtonian flow and its pseudo-newtonian analogue have been found. The experimental data obtained by the author shows good agreement with theory.

4

Pressure waves in elastic tube with polymeric liquid

Levitsky S., Bergman R., Levi O., Haddad J.

Applied Mechanics and Engineering

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1999

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Vol. 4, no 3

561-574

EN

Propagation of acoustic waves in an elastic tube with compressible polymeric liquid is investigated. A dispersion equation is derived that accounts for viscoelastic effects in the fluid in coupling with inertia, radial and longitudinal deformations of the tube's wall. The equation is valid in the frequency range where sound wave length is greater from the tube radius and includes the Korteweg- Joukowski speed of water hammer as a limiting case. Analysis of the dispersion relation has shown a strong influence of the rheological properties of the liquid on dispersion and attenuation of pressure signals. The results indicate also that the model developed could give means to characterize the rheological parameters of a polymeric liquid with sufficiently simple acoustic technique.