The Effect of Longitudinal Oscillations on Free Convection From Vertical Surfaces

1965 ◽  
Vol 32 (1) ◽  
pp. 183-191 ◽  
Author(s):  
Siavash Eshghy ◽  
V. S. Arpaci ◽  
J. A. Clark
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Shear Stress ◽  
Steady State ◽  
Free Convection ◽  
Classical Problem ◽  
Vertical Cylinder ◽  
Convection Flow ◽  
Fluid Temperature ◽  
Average Coefficient

The free-convection flow along a vertical plate oscillating in its own plane is given analytical treatment. The basic equations of boundary-layer flow and heat transfer are linearized and the first three approximations are considered. The first approximation, being the case of steady-state free convection, is the classical problem of Schmidt and Beckman extended by Ostrach. The second approximation is the frequency response of the fluid temperature and velocity for which limiting solutions are obtained in two regions; namely, the regions of small and large ω* = ωδ2/ν where ω is the circular frequency, δ the steady-state velocity boundary-layer thickness, and ν the fluid kinematic viscosity. The approximate range of validity of the asymptotic solution is estimated in terms of parameter ω0* which is a function only of Prandtl number. Part of the third approximation is time independent and gives rise to a net change in the steady values of the wall heat flux and shear stress. It is found that within the domain of laminar flow this net change is a decrease for the rate of heat transfer and an increase for the shear stress both evaluated for large values of ω0*. Heat-transfer measurements are made for a vertical cylinder in air. It is found that in the laminar regime the average coefficient of heat transfer experiences a slight decrease relative to its measured steady state value. For higher values of oscillatory velocity amplitude the average coefficient of heat transfer undergoes an increase over its measured steady-state value. This reversal in the behavior of average coefficient of heat transfer appears to be due to flow transition which is confirmed by smoke studies along a vertical cylinder.

scholarly journals Free convection flow of power law fluid in a vertical cylinder of finite height

1995 ◽  
Vol 17 (2) ◽  
pp. 34-39
Author(s):  
Nguyen Van Que
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Power Law ◽  
Average Velocity ◽  
Vertical Cylinder ◽  
Convection Flow ◽  
Power Law Fluid ◽  
Free Convection Flow ◽  
Finite Height ◽  
Good Agreement

A numerical solution has been presented for free convection flow of power law fluid in a vertical cylinder of finite height. The average velocity along the channel and the heat transfer have been calculated. Graphs of velocities and temperature are shown. The results show good agreement with analytic one in the asymptotic case.

scholarly journals The Effect of Plate Oscillations on Horizontal Free Convection Flow

1977 ◽  
Vol 30 (3) ◽  
pp. 335 ◽  
Author(s):  
RL Verma ◽  
Punyatma Singh
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Convection ◽  
Skin Friction ◽  
Low Frequency ◽  
Convection Flow ◽  
Phase Lag ◽  
Mean Flow ◽  
Free Convection Flow ◽  
Boundary Layer Equations

The free convection flow along a semi-infinite horizontal plate oscillating in its own plane is analysed The basic flow is purely buoyancy induced, while the oscillations in the plate cause a time-dependent boundary layer flow and heat transfer. The boundary layer equations are linearized and the first two approximations are considered. Two separate solutions valid for high and low frequency ranges are obtained by a series expansion in terms of frequency parameters. The skin friction and the rate of heat transfer are studied for both frequency ranges. For very high frequencies, the oscillatory flow pattern is of a 'shear-wave' type, unaffected by the mean flow. It is found that the phase of the skin friction at the plate lags that of the plate oscillations by in and the rate of heat transfer has a phase lag of 1/2n.

Laminar Boundary∼Layer Free Convection along an Inclined, Isothermal Surface

1972 ◽  
Vol 1 (4) ◽  
pp. 189-196 ◽  
Author(s):  
J.B. Lee ◽  
G.S.H. Lock
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Convection ◽  
Laminar Boundary Layer ◽  
Theoretical Consideration ◽  
Plane Surface ◽  
Convection Flow ◽  
Inclined Plane ◽  
Free Convection Flow ◽  
Boundary Layer Equations

This paper gives theoretical consideration to the problem of laminar, boundary-layer, free convection flow along a long, inclined, plane surface heated isothermally. Development of the appropriate boundary-layer equations is followed by their numerical solution for air. The effects of inclination and position on heat transfer and the temperature, pressure and velocity profiles are presented graphically for RaL ≤ 106.

MHD Double Diffusive Natural Convection Flow Over Exponentially Accelerated Inclined Plate

2016 ◽  
Vol 33 (01) ◽  
pp. 87-99 ◽  
Author(s):  
G. S. Seth ◽  
R. Tripathi ◽  
R. Sharma ◽  
A. J. Chamkha
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Shear Stress ◽  
Fluid Velocity ◽  
Convection Flow ◽  
Fluid Temperature ◽  
Inclined Plate ◽  
Natural Convection Flow ◽  
Species Concentration ◽  
Double Diffusive

AbstractAn investigation of unsteady MHD double diffusive natural convection flow of a viscous, incompressible, electrically conducting, heat absorbing, radiating and chemically-reactive fluid past an exponentially accelerated moving inclined plate in a fluid-saturated porous medium, when the temperature of the plate and the concentration at the surface of the plate have ramped profiles, is carried out. Exact solutions for the fluid velocity, fluid temperature and the species concentration, under Boussinesq approximation, are obtained in closed form by the Laplace transform technique. The expressions for the shear stress, rate of heat transfer and the rate of mass transfer at the plate are also derived. Numerical evaluations of the fluid velocity, fluid temperature and the species concentration are performed and displayed graphically whereas those of the shear stress, rate of heat transfer and the rate of mass transfer at the plate are presented in tabular form for various values of the pertinent flow parameters.

scholarly journals Theoretical Analysis of Radiative Effects on Transient Free Convection Heat Transfer past a Hot Vertical Surface in Porous Media

2008 ◽  
Vol 13 (4) ◽  
pp. 419-432 ◽  
Author(s):  
S. K. Ghosh ◽  
O. Anwar Beg
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Porous Medium ◽  
Shear Stress ◽  
Free Convection ◽  
Thermal Radiation ◽  
Stress Function ◽  
Dimensionless Time ◽  
Permeability Parameter ◽  
Shear Stress Function

The purpose of the present investigation deals with the unsteady free convective flow of a viscous incompressible gray, absorbing-emitting but non-scattering, optically-thick fluid occupying a semi-infinite porous regime adjacent to an infinite moving hot vertical plate with constant velocity. We employ a Darcian viscous flow model for the porous medium. The momentum and thermal boundary layer equations are non-dimensionalized using appropriate transformations and then solved subject to physically realistic boundary conditions using the Laplace transform technique. Thermal radiation effects are simulated via a radiation-conduction parameter, Kr, based on the Rosseland diffusion approximation. The influence of Grashof (free convection) number, radiation-conduction parameter (Kr), inverse permeability parameter (Kp) and dimensionless time (t) are studied graphically. We observe that increasing thermal radiation parameter causes a noticeable increase in the flow velocity, u. Temperature, θ, is significantly increased within the boundary layer with a rise in Kr since the latter represents the relative contribution of thermal radiation heat transfer to thermal conduction heat transfer. Increased radiation therefore augments heat transfer, heats the fluid and increases the thickness of the momentum and thermal boundary layers. Velocity is found to decrease with an increase in Kp (inverse permeability parameter) as are shear stress function ( ∂u/∂y | y=0) magnitudes owing to greater resistance of the porous medium for lower permeabilities, which decelerate the flow. An increase in Kr however boosts the shear stress function magnitudes i.e. serves to accelerate the flow. Temperature gradient, ∂θ/∂y | y=0 is also positively affected by an increase in thermal radiation (Kr) and with time. The present study has applications in geological convection, forest fire propagation, glass heat treatment processes at high temperature, metallurgical processing etc.

MHD Double Diffusive Natural Convection Flow Over Exponentially Accelerated Inclined Plate

2016 ◽  
Vol 33 (1) ◽  
pp. 87-99 ◽  
Author(s):  
G. S. Seth ◽  
R. Tripathi ◽  
R. Sharma ◽  
A. J. Chamkha
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Shear Stress ◽  
Fluid Velocity ◽  
Convection Flow ◽  
Fluid Temperature ◽  
Inclined Plate ◽  
Natural Convection Flow ◽  
Species Concentration ◽  
Double Diffusive

AbstractAn investigation of unsteady MHD double diffusive natural convection flow of a viscous, incompressible, electrically conducting, heat absorbing, radiating and chemically-reactive fluid past an exponentially accelerated moving inclined plate in a fluid-saturated porous medium, when the temperature of the plate and the concentration at the surface of the plate have ramped profiles, is carried out. Exact solutions for the fluid velocity, fluid temperature and the species concentration, under Boussinesq approximation, are obtained in closed form by the Laplace transform technique. The expressions for the shear stress, rate of heat transfer and the rate of mass transfer at the plate are also derived. Numerical evaluations of the fluid velocity, fluid temperature and the species concentration are performed and displayed graphically whereas those of the shear stress, rate of heat transfer and the rate of mass transfer at the plate are presented in tabular form for various values of the pertinent flow parameters.

Numerical Investigation of Unsteady Multiphase Nanofluid-Free Convection Flow About a Vertical Cylinder With Non-Uniform Temperature

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Marneni Narahari ◽  
S. Suresh Kumar Raju ◽  
Rajashekhar Pendyala ◽  
Suhaib Umer Ilyas
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Surface Temperature ◽  
Numerical Investigation ◽  
Power Law ◽  
Wall Temperature ◽  
Vertical Cylinder ◽  
Convection Flow ◽  
Free Convection Flow ◽  
Power Law Exponent

Abstract A numerical investigation on the transient-free convection flow of the multiphase nanofluid past a vertical cylinder, which has a power-law variation surface temperature along with the height, is presented. The problem has typical engineering applications involving cooling of vertical cylindrical rods in mechanical/manufacturing systems, cooling of nuclear reactors, and the design of other advanced cooling technologies. Buongiorno’s model is applied in this research, which incorporates thermophoresis and Brownian diffusion effects of nanoparticles. The zero-volume flux condition is implemented for nanoparticle concentration at the boundary to obtain realistic results. A robust second-order accurate finite-difference scheme of Crank–Nicolson type is applied to tackle the system of coupled non-linear partial differential equations numerically. The impacts of time, variable surface temperature power-law exponent, Brownian and thermophoresis parameters are investigated on nanofluid flow and heat transfer aspects. The decisive finding suggests that the effect of the power-law exponent of the variable wall temperature is to reduce the nanoparticle relocation, velocity, and temperature in the nanofluid boundary layer causing the heat transfer enhancement. The skin-friction decreased significantly with the rise of the power-law exponent of the wall temperature. The present numerical scheme is corroborated by comparing the average skin-friction results with the available literature for clear fluid.

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