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Weakly nonlinear oscillatory convection in a viscoelastic fluid saturated porous medium with throughflow and temperature modulation

Kiran P., Narasimhulu Y., Manjula S. H.

International Journal of Applied Mechanics and Engineering

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2018

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Vol. 23, no. 3

635--653

EN

The effect of vertical throughfow and temperature modulation on a viscoelastic fluid saturated porous medium has been investigated. 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 oscillatory mode of convection, and heat transport in terms of the Nusselt number, which is governed by the non autonomous complex Ginzburg- Landau equation, is calculated. The effect of vertical through flow is found to stabilize the system irrespective of the direction of through flow in the case of permeable boundary conditions. The time relaxation has a destabilizing effect, while the time retardation parameter has a stabilizing effect on the system. The effects of amplitude and frequency of modulation on heat transport have been analyzed and depicted graphically. The study shows that the heat transport can be controlled effectively by a mechanism that is external to the system. Further, it is also found that heat transfer is more in oscillatory mode of convection rather than in stationary mode of convection.

2

Biogeochemical multifunctionality of wetland ecotones in lakeland agricultural landscape

Kruk M.

Polish Journal of Ecology

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2003

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Vol. 51, nr 2

247-254

EN

The study was focused on the analysis of the effect of the nutrient loads from cultivated and fertilized watershed on the ion balance in wetland ecotones. The investigations were carried out in Masurian Lakeland (NE Poland) in small (0.2 ha) fens dominated by cattail association. Wetland ecotones constitute an effective biogeochemical barrier in respect to nitrates. However, they do not protect lakes against other eutrophication factors arising as the result of multifunctional character of biogeochemical processes in the wetland environment under pression of nutrients of fertilizing origin. The eutrophication of waters can be enhanced by increased amounts of potassium, phosphates, and dissolved organic nitrogen moving out from wetland ecotones.

3

On Bénard convection in a porous medium in the presence of throughflow and rotation in hydromagnetics

Sunil, Bharti P. K., Sharma R. C.

Archives of Mechanics

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2003

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Vol. 55, nr 3

257-274

EN

The effect of throughflow on a layer of a rotating fluid heated from below in porous medium in the presence of vertical magnetic field is considered. For the case of stationary convection, the rotation has always a stabilizing effect. The medium permeability has always a destabilizing effect whereas the magnetic field and the throughflow have always a stabilizing effects in the absence of rotation. But in the presence of rotation, the medium permeability is found to have a destabilizing effect whereas the magnetic field and the throughflow have a stabilizing effects under certain conditions. Graphs have been plotted by giving numerical values to the parameters, to depict the stability characteristics. The magnetic field and rotation introduce oscillatory modes in the system, which were nonexistent in their absence. The sufficient conditions for non-existence of the overstability are also obtained.

4

Onset of convection in a sparsely packed porous layer with throughflow

Shivakumara I. S., Nanjundappa C. E.

Archives of Mechanics

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2001

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Vol. 53, nr 3

219-241

EN

The onset of Rayleigh-Bénard convection in a sparsely packed porous layer with vertical throughflow is investigated using Brinkman's modification of the Darcy flow model with fluid viscosity different from effective viscosity. The critical Rayleigh numbers are obtained for free-free, rigid-rigid and rigid-free boundaries which are insulated to temperature perturbations. It is noted that an increase in the value of viscosity ratio is to delay the onset of convection. Further, it is observed that the throughflow can be used either to suppress or augment convection, depending on the nature of boundaries and also on the values of physical parameters.