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1
Content available The effect of thermal modulation on double diffusive convection in the presence of applied magnetic field and internal heat source
Manjula S. H., Suresh P., Rao M. G.
International Journal of Applied Mechanics and Engineering
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2021
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Vol. 26, no. 1
135--155
EN
The investigation of thermal modulation on double-diffusive stationary convection in the presence of an applied magnetic field and internal heating is carried out. A weakly nonlinear stability analysis has been performed using the finite-amplitude Ginzburg-Landau model. This finite amplitude of convection is obtained at the third order of the system. The study considers three different forms of temperature modulations. OPM-out of phase modulation, LBMO-lower boundary modulation, IPM-in phase modulation. The finite-amplitude is a function of amplitude ,Tδ frequency ω and the phase differenceθ . The effects of Tδ and ω on heat/mass transports have been analyzed and depicted graphically. The study shows that heat/mass transports can be controlled effectively by thermal modulation. Further, it is found that the internal Rayleigh number iR enhances heat transfer and reduces the mass transfer in the system.
2
Content available Slowly vibrating axially symmetric bodies-transverse flow
Srivastava D. K.
International Journal of Applied Mechanics and Engineering
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2021
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Vol. 26, no. 1
226--250
EN
Stokes drag on axially symmetric bodies vibrating slowly along the axis of symmetry placed under a uniform transverse flow of the Newtonian fluid is calculated. The axially symmetric bodies of revolution are considered with the condition of continuously turning tangent. The results of drag on sphere, spheroid, deformed sphere, egg-shaped body, cycloidal body, Cassini oval, and hypocycloidal body are found to be new. The numerical values of frictional drag on a slowly vibrating needle shaped body and flat circular disk are calculated as particular cases of deformed sphere.
3
Content available Analytical solutions for a general mixed boundary value problem associated with motions of fluids with linear dependence of viscosity on the pressure
Vieru D., Fetecau C., Bridges C.
International Journal of Applied Mechanics and Engineering
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2020
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Vol. 25, no. 3
181--197
EN
An unsteady flow of incompressible Newtonian fluids with linear dependence of viscosity on the pressure between two infinite horizontal parallel plates is analytically studied. The fluid motion is induced by the upper plate that applies an arbitrary time-dependent shear stress to the fluid. General expressions for the dimensionless velocity and shear stress fields are established using a suitable change of independent variable and the finie Hankel transform. These expressions, that satisfy all imposed initial and boundary conditions, can generate exact solutions for any motion of this type of the respective fluids. For illustration, three special cases with technical relevance are considered and some important observations and graphical representations are provided. An interesting relationship is found between the solutions corresponding to motions induced by constant or ramptype shear stresses on the boundary. Furthermore, for validation of the results, the steady-state solutions corresponding to oscillatory motions are presented in different forms whose equivalence is graphically proved.
4
Content available remote Geometrical modifications of the anchor impeller to enhance the overall performances in stirred tanks
Ameur Houari, Kamla Youcef
Instal
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2020
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nr 6
42--45
EN
The performance of modified anchor impellers in stirred tanks is investigated. The classical anchor impeller is taken as a reference, then the upper part of the blade arm is curved at different degrees (α). Three geometrical configurations are explored, namely: α = 0° (which corresponds to the standard shape of anchor impellers), 45°, and 90°. The study is achieved numerically by using a finite volume method based CFD tool. The case of highly viscous Newtonian fluids under laminar flow conditions is considered. From the obtained results, the newly modified anchor impeller has allowed an enhancement in the axial circulation of liquid and a reduction in power requirements. The curved blade with 90° yielded a decrease in power number by about 2.5%, compared to the classical anchor impeller.
PL
W pracy przebadano działanie zmodyfikowanych mieszadeł kotwicowych w zbiornikach z mieszaniem. Jako element referencyjny przyjęto klasyczne mieszadło kotwicowe, w którym górną część ramienia łopatki zakrzywiono pod różnym kątem (α). Przebadano trzy konfiguracje geometryczne, a mianowicie: α = 0° (co odpowiada standardowemu kształtowi mieszadła kotwicowego), 45° i 90°. Badania realizowano numerycznie przy użyciu metody objętości skończonych CFD. Rozważany przypadek dotyczy wysoko lepkich płynów newtonowskich w warunkach przepływu laminarnego. Na podstawie uzyskanych wyników zmodyfikowane mieszadło kotwicowe umożliwiło zwiększenie osiowej cyrkulacji cieczy i zmniejszenie zapotrzebowania na moc. Zakrzywiona łopatka o kącie 90° spowodowała spadek liczby mocy o około 2,5% w porównaniu z klasycznym mieszadłem kotwicowym.
5
Content available Performance analysis of pumping viscous fluids with complex rheological properties using a screw conveyor
Miastkowski K., Bakier S.
Journal of Research and Applications in Agricultural Engineering
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2018
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Vol. 63, nr 4
117--120
EN
The work concerns analysis of a single screw feeder working in special conditions as a conveyor of fluids with high viscosity and pseudoplastic properties. The research was carried out on the transport of Newtonian and non-Newtonian pseudoplastic fluids using the original construction of the screw conveyor depending on the angular velocity of the screw and the rheological properties of the fluids being pumped. The testing material involved honey in its liquid i.e. non-Newtonian form and partially crystallized one (power-law fluid). The dynamic viscosity of the pumped medium (Newtonian fluid) was in the range η ∈ (1.66; 4.43) Pa s. The value of the non-Newtonian power-law fluid consistency coefficient was contained within m ∈(2.562; 9,422) Pa sn, and the flow index n∈(0.856; 0.975). As a result of comparative analysis, a significant difference between the performance of the conveyor was shown as a function of the rheological properties of the pumped medium. The special effect of the research concerns the determination of the impact of the angular velocity of the screw and the force of inertia on the actual performance of the feeder. It was found that each viscosity value of the medium has its corresponding minimum angular velocity of the screw at which the fluid transport is carried out. It was demonstrated that the screw feeder can act as a conveyor of high viscosity fluids.
PL
Praca dotyczy analizy działania przenośnika jednoślimakowego w nietypowych warunkach - jako transportera płynów o dużej lepkości i właściwościach pseudoplastycznych. Przeprowadzono badania transportu płynów newtonowskiegi i nienewtonowskiego pseudoplastycznego przy wykorzystaniu oryginalnej konstrukcji transportera ślimakowego w zależności od prędkości kątowej ślimaka i właściwości reologicznych przetłaczanych płynów. Jako materiał transportowany zastosowano miód w postaci płynnej (płyn newtonowski) oraz częściowo skrystalizowanej (płyn potęgowy). Lepkość dynamiczna przetłaczanego medium (płyn newtonowski) należała do przedziału η∈(1,66; 4,43) Pa s. Wartość współczynnika konsystencji płynu nienewtonowskiego (potęgowego) zawierała się w granicach m∈(2,562; 9,422) Pa sn, a wskaźnik płynięcia n∈(0,856;0,975). W wyniku analizy porównawczej wykazano istotne różnice pomiędzy wydajnością przenośnika w funkcji właściwości reologicznych przetłaczanych mediów. Różnice były tym większe im niższa była lepkość przetłaczanej cieczy. Szczególnym efektem pracy jest określenie wpływu prędkości kątowej ślimaka i siły bezwładności na wydajność tłoczenia. Wykazano, że każdej wartości lepkości medium odpowiada minimalna prędkość kątowa ślimaka, przy której następuje transport płynu. Dowiedziono tym samym, że przenośnik ślimakowy może pracować jako transporter cieczy o dużych lepkościach.
6
Content available remote Inertia effects in a curvilinear thrust hydrostatic bearing
Walicka A., Wojnarowski J.
International Journal of Applied Mechanics and Engineering
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2010
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Vol. 15, no 3
909-920
EN
The flow of a Newtonian lubricant in a clearance of a curvilinear thrust hydrostatic bearing with impermeable walls is considered. The flow in the bearing clearance is considered with inertia forces. The equations of motion are solved by an averaged inertia method. A step bearing and a spherical bearing are discussed as examples. It is shown that inertia effects influence the bearing performance considerably.
7
Content available remote Stability of superposed viscous - viscoelastic (couple-stress) fluids in the presence of variable magnetic field through porous medium
Kumar P., Sharma P.
International Journal of Applied Mechanics and Engineering
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2008
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Vol. 13, no 3
837-845
EN
The Rayleigh-Taylor instability of a Newtonian viscous fluid overlying a couple-stress viscoelastic fluid through a porous medium is considered in the presence of a variable horizontal magnetic field. The stability analysis is carried out, for mathematical simplicity, for two highly viscous fluids of equal kinematic viscosities. For the stable configuration, the system is found to be stable or unstable under certain conditions. However, for the unstable configuration, the magnetic field has got stabilizing effects.
8
Content available remote Effects of magnetic field on stokes flow due to an oscillating wall under the fluid slip condition
Poria S.
International Journal of Applied Mechanics and Engineering
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2008
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Vol. 13, no 3
847-853
EN
In this paper we have studied the motion of an incompressible viscous conducting fluid about an harmonically oscillating vertical wall under fluid slip boundary condition at the wall and subjected to a uniform weak transverse magnetic filed. Effects of variations of the magnetic field and the slip parameter on the evolution of the velocity filed and shear stress are determined and discussed.
9
Content available remote Rotational inertia effect in a curvilinear thrust bearing with porous layer lubricated by a Newtonian fluid
Jurczak P.
International Journal of Applied Mechanics and Engineering
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2007
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Vol. 12, no 1
37-45
EN
The flow of a Newtonian lubricant in a bearing clearance is discussed. The bearing is modelled by two rotational surfaces and the porous layer is adhered to the curved impermeable surface. The effects of rotational inertia forces on the pressure distribution are examined. The flow in the bearing clearance is considered with inertia and the Navier-Stokes and Poisson equations are uncoupled by using the Morgan-Cameron approximation. As an example the bearing modelled by two spherical surfaces was discussed in detail.
10
Content available remote Large eddy simulations of the newtonian fluid flow through a Kenics static mixer
Peryt S., Jaworski Z.
Chemical and Process Engineering
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2007
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Vol. 28, z. 3
435-444
EN
Results of large eddy simulations of Newtonian flows in a Kenics static mixer are presented. The computational fluid dynamics study was carried out using the Smagorinsky-Lilly model for Reynolds numbers of 640, 1280 and 2560. The CFD results were also compared with the LDA measurements and a good agreement between them was found.
PL
Przedstawiono wyniki symulacji numerycznych CFD przepływu płynu newtonowskiego przez mieszalnik statyczny Kenics. W badaniach numerycznych zastosowano model Smagorinskiego-Lilly dla liczb Reynoldsa Re równych 640, 1280, 2560. Wyniki modelowania CFD porównano z wynikami badań LDA. Stwierdzono dobrą zgodność wyników badań numerycznych z wynikami badań eksperymentalnych.
11
Newtonian flow instabilities inside an SMX static mixer
Peryt S., Jaworski Z.
Inżynieria Chemiczna i Procesowa
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2006
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T. 27, z. 4
1447-1453
EN
LDA measurements of the axial velocity of Newtonian fluid (starch syrup) flow inside an SMX static mixer have been presented. The experimental results were evaluated by means of the fast Fourier transform (FFT) and resulted in determining the critical Reynolds number.
PL
Przedstawiono wyniki pomiarów anemometrycznych LDA prędkości osiowej wewnątrz mieszalnika statycznego SMX podczas przepływu płynu newtonowskiego (syropu skrobiowego). Do opracowania wyników zastosowano szybką transformatę Fouriera (FFT), co umożliwiło wyznaczenie krytycznej wartości liczby Reynoldsa.
12
Content available remote Mixed convection heat transfer from a vertical heated plate embedded in a sparsely packed porous medium
Pal D., Shivakumara I. S.
International Journal of Applied Mechanics and Engineering
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2006
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Vol. 11, no 4
929-939
EN
An improved numerical study on mixed convection from a heated vertical plate embedded in a Newtonian fluid saturated sparsely packed porous medium is undertaken by considering the variation of permeability, porosity and thermal conductivity. The boundary layer flow in the porous medium is governed by the Lapwood-Forchheimer-Brinkman extended Darcy model. Similarity transformations are employed and the resulting ordinary differential equations are solved numerically by using a shooting algorithm with the Runge-Kutta-Fehlberg integration scheme to obtain velocity and temperature distributions. Besides, the skin friction and Nusselt number are also computed for various physical parameters governing the problem under consideration. It is found that the inertial parameter has a significant influence on decreasing the flow field, whereas its influence is reversed on the rate of heat transfer for all values of permeability parameter considered. Further, the results under the limiting conditions were found to be in good agreement with the existing ones.
13
Straty ciśnienia w przepływie przez łuki [pi]/2 wykonane z rur gładkich
Wojtkowiak J., Oleśkowicz-Popiel Cz.
Ciepłownictwo, Ogrzewnictwo, Wentylacja
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2006
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R. 37, nr 3
26-29
PL
Porównano wartości współczynników strat ciśnienia w łukach [pi]/2 obliczane z równań najczęściej polecanych w literaturze. Analizę przeprowadzono dla ustalonych przepływów turbulentnych, jednofazowych płynów newtonowskich przez łuki wykonane z rur o hydraulicznie gładkich ścianach. W wyniku selekcji danych literaturowych zaproponowano własne uśrednione równanie.
EN
The values of loss coefficients for [pi]/2 pipe bends, calculated from equations, recommended most frequently in professional literature, have been compared. The analysis was made for steady-state turbulent flows of single-phase Newton fluids through hydraulic smooth pipe bends. The authors suggest their own averaging equation as a result of literature data selection.
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