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    Effect of Fluctuating surface heat and mass flux on natural convection flow along a vertical flat plate
    (© 2015 Hindawi Publishing Corporation, 2015) Hussain, Sharmina; Roy, Nepal Chandra; Hossain, Md. Anwar; Saha, Suvash Chandra; Department of Mathematics and Natural Sciences, BRAC University
    An investigation has been carried on double diffusive effect on boundary layer flow due to small amplitude oscillation in surface heat and mass flux. Extensive parametric simulations were performed in order to elucidate the effects of some important parameters, that is, Prandtl number, Schmidt number, and Buoyancy ratio parameter on flow field in conjunction with heat and mass transfer. Asymptotic solutions for low and high frequencies are obtained for the conveniently transformed governing coupled equations. Solutions are also obtained for wide ranged value of the frequency parameters. Comparisons between the asymptotic and wide ranged values are made in terms of the amplitudes and phases of the shear stress, surface heat transfer, and surface mass transfer. It has been found that the amplitudes and phase angles obtained from asymptotic solutions are found in good agreement with the finite difference solutions obtained for wide ranged value of the frequency parameter.
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    Unsteady laminar mixed convection boundary layer flow near a vertical wedge due to oscillations in the free-stream and surface temperature
    (© 2016 De Gruyter Open Ltd., 2016) Roy, Nepal Chandra; Hossain, Md. Anwar; Hussain, Sharmina; Department of Mathematics and Natural Sciences, BRAC University
    The unsteady laminar boundary layer characteristics of mixed convection flow past a vertical wedge have been investigated numerically. The free-stream velocity and surface temperature are assumed to be oscillating in the magnitude but not in the direction of the oncoming flow velocity. The governing equations have been solved by two distinct methods, namely, the straightforward finite difference method for the entire frequency range, and the extended series solution for low frequency range and the asymptotic series expansion method for high frequency range. The results demonstrate the effects of the Richardson number, Ri, introduced to quantify the influence of mixed convection and the Prandtl number, Pr, on the amplitudes and phase angles of the skin friction and heat transfer. In addition, the effects of these parameters are examined in terms of the transient skin friction and heat transfer.