Effect of rotational speed modulation on heat transport in a fluid layer with temperature dependent viscosity and internal heat source

Ain Shams Engineering Journal

2016

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This paper carried out a nonlinear thermal convection in a porous medium saturated with viscoelastic nanofluid under vibrations. The Darcy model has been used for the porous medium, while the nanofluid layer incorporates the effect of Brownian motion along with thermophoresis. An Oldroyd-B type constitutive equation was used to describe the rheological behavior of viscoelastic nanofluids. The non-uniform vertical vibrations of the system, which can be realized by oscillating the system vertically, is considered to vary sinusoidally with time. In order to find the heat and mass transports for unsteady state, a nonlinear analysis, using a minimal representation of the truncated Fourier series of two terms, has been performed. Effect of various parameters has been investigated on heat and mass transport and then presented graphically. It is found that gravity modulation can be used effectively to regulate either heat or mass transports in the system. Ó 2015 Production and hosting by Elsevier B.V. on behalf of Ain Shams University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Section: Resultssupporting

confidence: 81%

Nonlinear thermal convection in a viscoelastic nanofluid saturated porous medium under gravity modulation

Ain Shams Engineering Journal

2016

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“…while eliminating the pressure term, introducing the stream function  we obtain the following dimensionless governing system (Bhadauria et al [15,19]…”

Section: Mathematical Formulationmentioning

confidence: 99%

“…They found that the modulated rotation speed has a stabilizing effect on the onset of convection for different values of modulation frequency and the other physical parameters involved. Bhadauria and Kiran [15] performed a weakly nonlinear thermal instability in a rotating fluid layer under rotation speed modulation using the Landau model. They found that instabilities are dominant for low frequencies and for small amplitudes.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The Complex Ginzburg Landau Model for an Oscillatory Convection in a Rotating Fluid Layer

Manjula¹,

International Journal of Applied Mechanics and Engineering

Reddy

et al. 2020

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A weakly nonlinear thermal instability is investigated under rotation speed modulation. Using the perturbation analysis, a nonlinear physical model is simplified to determine the convective amplitude for oscillatory mode. A non-autonomous complex Ginzburg-Landau equation for the finite amplitude of convection is derived based on a small perturbed parameter. The effect of rotation is found either to stabilize or destabilize the system. The Nusselt number is obtained numerically to present the results of heat transfer. It is found that modulation has a significant effect on heat transport for lower values of ωf while no effect for higher values. It is also found that modulation can be used alternately to control the heat transfer in the system. Further, oscillatory mode enhances heat transfer rather than stationary mode.

“…The effect of amplitude and frequency of modulation is of similar effect under rotation speed modulation [53] which is originating idea from temperature modulation. The results in the case of lower boundary temperature modulation only were also obtained, but found to be qualitatively very similar to those obtain in OPM case, therefore not presented here.…”

Section: Nonlinear Throughflow Effects Under Modulationmentioning

confidence: 96%

Nonlinear throughflow effects on thermally modulated porous medium

Ain Shams Engineering Journal

Bhadauria

2016

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Effect of vertical throughflow on Darcy convection has been investigated subject to timeperiodic temperature modulation of the boundaries. The amplitudes of temperature modulation at the lower and upper surfaces are considered to be very small, and the disturbances are expanded in terms of power series of amplitude of convection. A weak nonlinear stability analysis has been performed for the stationary mode of convection, and heat transport in terms of the Nusselt number, which is governed by the non-autonomous Ginzburg-Landau equation, is calculated. The effect of vertical throughflow is found to be either to destabilize or stabilize the system for downward or upward throughflows in the case of impermeable boundary conditions. The effect of amplitude and frequency of modulation, Prandtl-Darcy number on heat transport has been analyzed and depicted graphically. Further, the study establishes that the heat transport can be controlled effectively by a mechanism that is external to the system. Ó 2015 Faculty of Engineering, Ain Shams University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).