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1

Mixed convective flow of unsteady hydromagnetic couple stress fluid through a vertical channel filled with porous medium

Makhalemele C. R., Rundora L., Adesanya S. O.

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 4

148--161

EN

In this paper, the mixed convective flow of an electrically conducting, viscous incompressible couple stress fluid through a vertical channel filled with a saturated porous medium has been investigated. The fluid is assumed to be driven by both buoyancy force and oscillatory pressure gradient parallel to the channel plates. A uniform magnetic field of strength 0B is imposed transverse to the channel boundaries. The temperature of the right channel plate is assumed to vary periodically, and the temperature difference between the plates is high enough to induce radiative heat transfer. Under these assumptions, the equations governing the two-dimensional couple stress fluid flow are formulated and exact solutions of the velocity and the temperature fields are obtained. The effects of radiation, Hall current, porous medium permeability and other various flow parameters on the flow and heat transfer are presented graphically and discussed extensively.

2

A new approach for study the electrohydrodynamic oscillatory flow through a porous medium in a heating compliant channel

Haroun M. H.

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 3

30--44

EN

The governing equations of an electrohydrodynamic oscillatory flow were simplified, using appropriate nondimensional quantities and the conversion relationships between fixed and moving frame coordinates. The obtained system of equations is solved analytically by using the regular perturbation method with a small wave number. In this study, modified non-dimensional quantities were used that made fluid pressure in the resulting equations dependent on both axial and vertical coordinates. The current study is more realistic and general than the previous studies in which the fluid pressure is considered functional only in the axial coordinate. A new approach enabled the author to find an analytical form of fluid pressure while previous studies have not been able to find it but have found only the pressure gradient. Analytical expressions for the stream function, electrical potential function and temperature distribution are obtained. The results show that the electrical potential function decreases by the increase of the Prandtl number, secondary wave amplitude ratio and width of the channel.

3

Study of Conjugate Heat Transfer in Electromagnetic Liquid Metal Dream Pipe

Puvaneswari P., Shailendhra K.

Archive of Mechanical Engineering

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2017

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Vol. LXIV, nr 3

375--399

EN

The combined effect of conjugation, external magnetic field and oscillation on the enhancement of heat transfer in the laminar flow of liquid metals between parallel plate channels is analyzed. In order to make our results useful to the design engineers, we have considered here only the wall materials that are widely employed in liquid metal heat exchangers. Indeed, all the results obtained through this mathematical investigation are in excellent agreement with the available experimental results. The effective thermal diffusivity κe is increased by 3 · 106 times due to oscillation and that the heat flux as high as 1.5 · 1010 (W/m2) can be achieved. Based on our investigation, we have recommended the best choice of liquid metal heat carrier, wall material and its optimum thickness along with the optimum value of the frequency to maximize the heat transfer rate. At the optimum frequency, by choosing a wall of high thermal conductivity and optimum thickness, an increase of 19.98% in κe can be achieved. Our results are directly relevant to the design of a heat transfer device known as electromagnetic dream pipe which is a very recent development.

4

Modelowanie oscylacyjnego przepływu cieczy przez przewody prostoosiowe

Sorko S. A.

Symulacja w Badaniach i Rozwoju

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2014

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Vol. 5, nr 1

29--42

PL

W opracowaniu przedstawiono algorytm rozwiązania zagadnienia przepływowego, laminarnego ruchu cieczy w prostoosiowym przewodzie o dowolnym kształcie przekroju poprzecznego w warunkach oscylacyjnego ruchu wzdłużnego przewodu. Przedstawiono matematyczny opis problemu przy użyciu metody brzegowych równań całkowych. Zaprezentowano rozwiązanie zagadnienia testowego wykazujące poprawność modelu matematycznego i algorytmu obliczeniowego. Przedstawiono przykład wyznaczenia pola prędkości przepływu przez prostoosiowy przewód o przekroju eliptycznym.

EN

In the elaboration was presented the algorithm of solution of the problem of laminar viscous flow through straight pipe of an arbitrary cross-section under conditions of the oscillatory movement of the pipe in longitudinal direction. The mathematical description and solution of the problem was formulated by using integral equations method. One presented solution of the test-problem demonstrative the correctness of the mathematical model and the computational algorithm. The example of the solution of the flow generated by the pressure gradient and the oscillations of the tube of an elliptic cross-section shape was presented.

5

Effects of hematocrit level on the oscillatory flow characteristic of blood in a stenosed artery

Poria S., De K. N., Mazumdar H. P.

International Journal of Applied Mechanics and Engineering

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2007

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Vol. 12, no 4

1103-1115

EN

In this paper, a simple model for the oscillatory flow of blood through a stenosed artery is considered. Blood is considered throughout the whole tube (arterial) to be a suspension mainly of red ceIls. A standard distribution of the red celIs is assumed which is based on the idea that the concentration of the red celIs and hence viscosity of blood is higher towards the center of the tube. In effect, viscosity as assumed to vary radialIy. Analytical expressions for the axial velocity, the volumetric flow rate, resistive impedance and phase lag are derived. Effects of hematocrit level on these flow characteristics are discussed.

6

Rheological properties of carbon fibre filled low-density polyethylene under the parallel steady and oscillatory shear flows

Hausnerowa B., Zdrazilova N., Kitano T., Saha P.

Polimery

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2006

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T. 51, nr 1

33-41

EN

Investigations of the flow properties of low-density polyethylene compounded with carbon fibre under the parallel superposed steady and oscillatory shear flows were performed. The effect of the steady shear on the viscoelastic properties as well as the effect of fibre content on the superposed flow properties were discussed. Overall, superposed flow conditions enhanced viscoelastic response (dynamic viscosity, storage modulus) of the filled systems. The critical angular frequency, where phase angle becomes 90° and storage modulus decreases sharply to zero, was found to be largely dependent on the volume fraction of fibre, regardless of the superposed shear rate. Whereas superposed flow properties of the pure PE melt changed monotonously, those of the composites showed peaks in corresponding dependencies, even if under simple shear flows they behaved in the similar manner as PE matrix.

PL

Badano właściwości reologiczne polietylenu małej gęstości napełnianego różnymi ilościami włókien węglowych (tabela 1) z zastosowaniem różnych szybkości ścinania. Stwierdzono, że zarówno składowa rzeczywista modułu zespolonego (G') jak i lepkość dynamiczna (h') napełnianych próbek osiągają większe wartości w warunkach superpozycji ustalonego i oscylacyjnego przepływu niż z zastosowaniem tylko oscylacyjnego przepływu, a stopień wzrostu zależy od złożonej szybkości ścinania (), prędkości kątowej (w) i zawartości włókien (Vr) (rys. 2, 3, 5-9). Maksymalne wartości składowej rzeczywistej modułu zespolonego (G'max) i lepkości dynamicznej (h'max) znormalizowane względem prostego przepływu oscylacyjnego generalnie rosną ze zwiększaniem wartości Vr i maleją ze wzrostem w (rys. 10). Wartość krytyczna prędkości kątowej (wc), w której kąt przesunięcia fazowego (d) osiąga 90° powodując gwałtowny spadek G', silnie zależy od Vf, a praktycznie nie zależy od (rys. 12).

7

Effects of free convection currents on the oscillatory flow of an electrically conducting fluid past a stationary or steadily moving vertical plate with variable suction and constant heat flux

Soundalgekar V. M., Wavre P. D., Takhar H. S.

International Journal of Applied Mechanics and Engineering

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2001

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Vol. 6, no 3

639-658

EN

An approximate analysis of a two-dimensional flow of an electrically conducting incompressible viscous fluid past an infinite porous plate, stationary or steadily moving in its own plane, is presented under the following conditions: i) suction velocity oscillates about a constant non-zero mean; ii) the free stream velocity oscillating in time about a constant mean; iii) constant heat flux at the plate; iv) presence of free convection currents due to the temperature difference; v) a uniform transverse magnetic field. Approximate solutions to coupled nonlinear equations governing the problem have been derived for the transient velocity, the transient temperature, the amplitude and the phase of the skin-friction and the Nusselt number. During the course of analysis, the effects of the Grashof number Gr, the magnetic field parameter M, the suction parameter A, the Eckert number E, the velocity of the plate V and the frequency 'omega' have been discussed.

8

Non-linear effects in spherical particle motion in oscillatory flowing gas

Dolata M., Michalski J.

Polish Journal of Chemistry

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1999

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vol. 73 nr 2

347-357

EN

Basing on the Tchen equation, the dynamic characteristics of a system consisted of a little sphere moving in an oscillatory flowing gas are developed. The conditions of appearance of steady points of solutions (node, focus, saddle) are formulated. Numerical solutions show that an additional attractor (asymptotic trajectory) can be found in this system.