scholarly journals Vadasz Number Effects on Convection in a Horizontal Porous Layer Subjected to Internal Heat Generation and G-Jitter

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 124
Author(s):  
Saneshan Govender
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Porous Layer ◽  
Heat Generation ◽  
Critical Rayleigh Number ◽  
Internal Heat ◽  
Internal Heat Generation ◽  
Onset Of Convection ◽  
Vadasz Number ◽  
The Impact

Flow and heat transfer in a horizontal porous layer subjected to internal heat generation and g-jitter is considered for the Dirichlet thermal boundary condition. A linear stability analysis is used to determine the convection threshold in terms of the critical Rayleigh number. For the low amplitude, high frequency approximation, the results show that vibration has a stabilizing effect on the onset of convection when the porous layer is heated from below. When the porous layer is cooled from below and heated from above, the vibration has a destabilizing effect in the presence of internal heat generation. It is also demonstrated that when the top and bottoms walls are cooled and rigid/impermeable, the critical Rayleigh number is infinitely large and conduction is the only possible mode of heat transfer. The impact of increasing the Vadasz number is to stabilize the convection, in addition to reducing the transition point from synchronous to subharmonic solutions.

scholarly journals Vadasz Number Effects on Convection in a Vertical Rotating Porous Layer, Placed Far from Axis of Rotation, and Subjected to Internal Heat Generation and Centrifugal Jitter

Physics ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 728-738
Author(s):  
Saneshan Govender
Keyword(s):  
Porous Layer ◽  
Heat Generation ◽  
Critical Rayleigh Number ◽  
Time Derivative ◽  
Internal Heat ◽  
Internal Heat Generation ◽  
Stability Criteria ◽  
Axis Of Rotation ◽  
Vadasz Number ◽  
The Impact

The flow and heat transfer in a rotating vertical porous layer, placed far from the axis of rotation, and subjected to internal heat generation and centrifugal jitter, is considered. The linear stability theory is used to determine the convection threshold, in terms of the critical Rayleigh number. Typical liquids used in engineering applications and heavy liquid metals are used to demonstrate conditions at which the Vadasz number is sufficiently small to warrant the retention of the time derivative in the momentum equation. When considering low amplitude and high frequency approximation, the results show that vibration has a stabilizing effect on the onset of convection. The impact of increasing the Vadasz number is to stabilize the convection, in addition to reducing the transition point from synchronous to subharmonic solutions. In summary, when the Vadasz number is large, centrifugal jitter has no impact on the convection stability criteria. In contrast, when the Vadasz number is small, centrifugal jitter impacts the convection stability criteria.

scholarly journals Onset of Convection in an Inclined Anisotropic Porous Layer with Internal Heat Generation

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 75 ◽  
Author(s):  
Leiv Storesletten ◽  
D. Andrew S. Rees
Keyword(s):  
Porous Layer ◽  
Heat Generation ◽  
Internal Heat ◽  
Convective Motion ◽  
Linear Instability ◽  
Internal Heat Generation ◽  
Anisotropy Ratio ◽  
Heat Sources ◽  
Onset Of Convection ◽  
Set Up

The onset of convection in an inclined porous layer which is heated internally by a uniform distribution of heat sources is considered. We investigate the combined effects of inclination, anisotropy and internal heat generation on the linear instability of the basic parallel flow. When the Rayleigh number is sufficiently large, instability occurs and a convective motion is set up. It turns out that the preferred motion at convection onset depends quite strongly on the anisotropy ratio, ξ , and the inclination angle. When ξ < 1 the preferred motion is in the form of longitudinal rolls for all inclinations. When ξ > 1 transverse rolls are preferred for small inclinations but, at high inclinations, longitudinal rolls are preferred. At intermediate inclinations the preferred roll orientation varies smoothly between these two extremes.

Thermal exploration of radial porous fin fully wetted with SWCNTs and MWCNTs along with temperature-dependent internal heat generation

2020 ◽  
Vol 234 (24) ◽  
pp. 4945-4952
Author(s):  
G Sowmya ◽  
BJ Gireesha ◽  
S Sindhu
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Heat Generation ◽  
Internal Heat ◽  
Internal Heat Generation ◽  
Multiwalled Carbon ◽  
Single Walled Carbon ◽  
Swcnts And Mwcnts ◽  
The Impact

The numerical examination of radiation and natural convection in a porous radial fin along with varying internal heat generation with respect to temperature is carried out in the current study. The aim of this study is to scrutinize the heat transfer phenomenon in fin wetted with water-based carbon nanotubes like single-walled carbon nanotubes and multiwalled carbon nanotubes. In the proposed work, the Darcy’s model is employed for the analysis. The modeled equations are nondimensionalized and solved by utilizing Runge–Kutta–Fehlberg method. The impact of relevant parameters on the heat transfer rate is comprehensively explored with an aid of graphs. Here, multiwalled carbon nanotube–water shows better heat transfer from surface of fin compared to single-walled carbon nanotube–water.

Numerical Study of Natural Convection in a Ferrofluid-Filled Corrugated Cavity With Internal Heat Generation

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Öztop
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Magnetic Dipole ◽  
Heat Generation ◽  
Internal Heat ◽  
Internal Heat Generation ◽  
Dipole Source ◽  
Internal Heating ◽  
Dipole Strength

In this paper, numerical simulations for the natural convection in a ferrofluid-filled corrugated cavity with internal heat generation under the influence of a magnetic dipole source were performed. The cavity is heated from below and cooled from above while vertical side walls are assumed to be adiabatic. A magnetic dipole source was located under the bottom heated wall. The governing equations were solved by Galerkin weighted residual finite-element formulation. The influence of external Rayleigh number (between 104 and 5 × 105), internal Rayleigh number (between 104 and 5 × 106), magnetic dipole strength (between 0 and 4), horizontal (between 0.2 and 0.8) and vertical (between −5 and −2) locations of the magnetic dipole source on fluid flow, and heat transfer are numerically investigated. It was observed that depending on heating mechanism (the external or internal heating), the presence of corrugation of the bottom wall either enhances or deteriorates the absolute value of the averaged heat transfer. The strength and locations of the magnetic dipole source affect the distribution of the flow and thermal patterns within the cavity for both flat and corrugated wall cavity. The net effect of the complicated interaction of the internal heating, external heating, and ferroconvection of magnetic source results in heat transfer enhancement with increasing values of magnetic dipole strength. Wall corrugation causes more enhancement of averaged heat transfer and this is more pronounced for low values of vertical location of magnetic source.

Heat Transfer on Nanofluid Flow With Homogeneous–Heterogeneous Reactions and Internal Heat Generation

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Raj Nandkeolyar ◽  
Peri K. Kameswaran ◽  
Sachin Shaw ◽  
Precious Sibanda
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Generation ◽  
Internal Heat ◽  
Internal Heat Generation ◽  
Heterogeneous Reactions ◽  
Transfer Coefficients ◽  
Transfer Characteristics ◽  
Fluid Properties

We investigated heat and mass transfer on water based nanofluid due to the combined effects of homogeneous–heterogeneous reactions, an external magnetic field and internal heat generation. The flow is generated by the movement of a linearly stretched surface, and the nanofluid contains nanoparticles of copper and gold. Exact solutions of the transformed model equations were obtained in terms of hypergeometric functions. To gain more insights regarding subtle impact of fluid and material parameters on the heat and mass transfer characteristics, and the fluid properties, the equations were further solved numerically using the matlab bvp4c solver. The similarities and differences in the behavior, including the heat and mass transfer characteristics, of the copper–water and gold–water nanofluids with respect to changes in the flow parameters were investigated. Finally, we obtained the numerical values of the skin friction and heat transfer coefficients.

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