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MHD effects on non-Newtonian power-law fluid past a continuously moving porous flat plate with heat flux and viscous dissipation

Kishan N., Shashidar Reddy B.

International Journal of Applied Mechanics and Engineering

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2013

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Vol. 18, no. 2

425--445

EN

The problem of a magneto-hydro dynamic flow and heat transfer to a non-Newtonian power-law fluid flow past a continuously moving flat porous plate in the presence of sucion/injection with heat flux by taking into consideration the viscous dissipation is analysed. The non-linear partial differential equations governing the flow and heat transfer are transformed into non-linear ordinary differential equations using appropriate transformations and then solved numerically by an implicit finite difference scheme. The solution is found to be dependent on various governing parameters including the magnetic field parameter M, power-law index n, suction/injection parameter ƒw, Prandtl number Pr and Eckert number Ec. A systematical study is carried out to illustrate the effects of these major parameters on the velocity profiles, temperature profile, skin friction coefficient and rate of heat transfer and the local Nusslet number.

2

Ocena liczby Reynoldsa w pomiarach reometrycznych polietylenu

Kloziński A.

Polimery

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2010

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T. 55, nr 7-8

575-581

PL

Przedstawiono wyniki badań dotyczących oceny liczby Reynoldsa, przeprowadzonych w rzeczywistych warunkach procesu wytłaczania, za pomocą reometru wytłaczarkowe-go, przy użyciu dysz cylindrycznych o przekroju kołowym i różnym stosunku L/D. W badaniach zastosowano polietylen małej gęstości (PE-LD FABS 23-D 022), polietylen średniej gęstości (PE-MD HF513) oraz ich równowagową mieszaninę (PE-LD/PE-MD). Oceniono wpływ wymiarów kanału dyszy oraz właściwości przetwarzanych polimerów na wartość liczby Reynoldsa. Charakter przepływu określono na podstawie wartości liczby Reynoldsa (Re), którą wyznaczono opierając się na średniej liniowej prędkości przepływu. Pomimo dużych prędkości przepływu polimerów wynoszących nawet 0,30 m/s (PE-LD, dysza: L = 20 mm, D = 2 mm), przepływ miał zawsze charakter laminarny. Analiza porównawcza wykazała istotne zmiany liczby Reynoldsa wynikające ze zróżnicowania wartości wykładnika płynięcia (n) oraz współczynnika konsystencji (k). Wyznaczenie przebiegów krzywych płynięcia umożliwiło również określenie zależności pomiędzy wartością Re, a lepkością η zastosowanych polimerów.

EN

The determination of the Reynolds number from experiments performed under real extrusion conditions with an extrusion Rheometer equipped with special cylindrical heads and exchangeable dies of varying L/D ratios has been presented. Low density (PE-LD FABS 23-D 022), middle density (PE-MD HF513) polyethylene and a blend of equal amounts of both were chosen for the rheological studies. The influence of the die dimensions and the properties of the extruded polymers on the Reynolds number was evaluated. The flow parameters were determined on the basis of the Reynolds number (Re) which was estimated on the basis of the average linear flow velocity. In spite of the high flow velocity of the polymer, attaining even 0.30 m/s for PE-LD through a die 20 mm in length and 2 mm in diameter, a laminar flow was maintained. A comparative analysis revealed significant changes of the Reynolds number resulting from the different values of the power flow index (n) and the consistency index (k). The determination of the flow curves also allowed for the evaluation of the dependence between the Re values and the viscosity η of the studied polymers.

3

Numerical study of non-Darcy forced convective heat transfer in a power law fluid over a stretching sheet

Prasad K. V., Datti P. S.

International Journal of Applied Mechanics and Engineering

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2009

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Vol. 14, no 2

473-488

EN

An analysis has been carried out to study the non-Darcy flow behavior and heat transfer characteristics of a non-Newtonian power law fluid over a non-isothermal stretching sheet with variable thermal conductivity and internal heat generation/absorption. Thermal conductivity is assumed to vary as a linear function of temperature. The partial differential equations governing the flow and heat transfer are converted into ordinary differential equations by a similarity transformation. The presence of non-Darcy forced convection and power law index leads to coupling and non-linearity in the boundary value problem. Because of the coupling and non-linearity, the problem has been solved numerically by the Keller box method. The computed values of horizontal velocity and temperature, boundary layer thickness are shown graphically in tables and figures. Several reported works on the problem are obtained as limiting cases of the present study. The results of the study have implications in extrusion processes and in other applications with porous media.