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  • 1
    Electronic Resource
    Electronic Resource
    Free Convection from a Vertical Plate in a Porous Medium Subjected to a Porous Medium Subjected to a Sudden Change in Surface Heat Flux (1997)
    Springer
    Transport in porous media 26 (1997), S. 205-224 
    Details
    ISSN: 1573-1634
    Keywords: porous medium ; convection ; boundary layer ; transient ; heat flux.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract An analysis is made of the transient free convection from a vertical flat plate which is embedded in a fluid-saturated porous medium. It is assumed that for time $$\overline \tau 〈 0$$ a steady state temperature or velocity has been obtained in the boundary-layer which occurs due to a uniform flux dissipation rate $$q_1^{\prime \prime } $$ . Then at time $$\overline \tau = 0$$ the heat flux on the plate is suddenly changed to $$q_2^{\prime \prime } $$ and maintained at this value for $$\overline \tau 〉 0$$ . An analytical solution has been obtained for the temperature/velocity field for small times in which the transport effects are confined within an inner layer adjacent to the plate. These effects cause a new steady boundary layer. A numerical solution of the full boundary-layer equations is then obtained for the whole transient from $$\overline \tau = 0$$ to the steady state, firstly by means of a step-by-step method and then by a matching technique. The transition between the two distinct solution methods is always observed to occur very near to the turning point of the plate surface temperature, a time at which the fluid temperature is close to its steady state profile. The solution obtained using the step-by-step method shows excellent agreement with the small time analytical solution. Results are presented to illustrate the occurrence of transients from both small and large increases and decreases in the levels of existing energy inputs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006550510374
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Transient Free Convection from a Horizontal Surface in a Porous Medium Subjected to a Sudden Change in Surface Heat Flux (2000)
    Springer
    Transport in porous media 39 (2000), S. 97-117 
    Details
    ISSN: 1573-1634
    Keywords: free convection ; boundary-layer ; horizontal surface ; transient ; heat flux
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This paper presents an analytical and numerical study of transient free convection from a horizontal surface that is embedded in a fluid-saturated porous medium. It is assumed that for time $$\bar \tau 〈 0$$ steady state velocity and temperature fields are obtained in the boundary-layer which occurs due to a uniform flux dissipation rate q 1′′ on the surface. Then, at $$\bar \tau = 0$$ the heat flux on the surface is suddenly changed to q 2′′ and maintained at this value for $$\bar \tau 〉 0$$ . Firstly, solutions which are valid for small and large $$\bar \tau $$ are obtained. The full boundary-layer equations are then integrated step-by-step for the transient regime from the initial unsteady state ( $$\bar \tau = 0$$ ) until such times at which this forward marching approach is no longer well posed. Beyond this time no valid solutions could be obtained which matched the final solution from the forward integration to the steady state profiles at large times $$\bar \tau \to \infty $$ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006697816838
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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