Browsing by Author "Mwaonanji, John"

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    Boundary layer flow over a moving flat surface with temperature dependent viscosity
    (University of Dar es Salaam,, 2012) Mwaonanji, John
    Numerical investigation of two-dimensional laminar boundary layer flow over a moving flat surface with temperature dependent viscosity is studied.Viscosity of liquid decreases with increase in temperature while the viscosity of Jas increases with increase in temperature (Makinde and Kirundi, 1999). Using scaling vari-ables, we carry out non-dimensionalisation and order of magnitude analysis of the governing equations in our study. The surface or wall is assumed to move in the same direction as the free stream. The boundary layer equations are reduced to self-similarity form using the similarity variable n(x, y) and by assuming a power law variation on both the free stream and wall velocities i.e Ue(x) ~ (X) xn and Up(x) ~Xn In the case where vis-cous dissipation is taken into account, the boundary layer equations only admit to self-similarity solution when the pressure gradient parameter n = 0. When viscous dissipation is neglected, the flow is similar for all values of n. Effects of varying different parameters on the momentum boundary layer are either increasing or decreasing its thickness. For thermal boundary layer, an interesting result is obtained by varying the Eckert number in a small region ad-jacent to the wall where temperature exceeded its plate or surface temperature i.e temperature "overshoots" are obtained. This is because of the viscous dissipation effects which are stronger near the wall.(Mureithi and Mason. 2010) For the case when the free stream is moving faster than the wall, the skin friction coefficient is positive and decrease with increase in viscosity variation parameter E. The reverse occurs for the case when the wall is moving faster than the free stream. On the other hand, when the free stream is moving faster than the wall, the heat transfer coefficient increases with increase in viscosity variation parameter E The reverse occurs when the wall is moving faster than the free stream. Stability analysis on the steady boundary layer flow shows that at. high Reynolds number flow, the governing equations become the Rayleigh equation. The vis-cosity variation parameter E is found to stabilise the flow. For the case when the free stream is moving faster than the wall (0.5 < < 1), the flow becomes un-stable. The reverse occurs when the wall was moving faster than the, free stream (0 <, 4; < 0.5).
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    Boundary layer flow over a moving flat surface with temperature dependent viscosity
    (2012) Mwaonanji, John
    Numerical investigation of two-dimensional laminar boundary layer flow over a moving flat surface with temperature dependent viscosity is studied.Viscosity of liquid decreases with increase in temperature while the viscosity of Jas increases with increase in temperature (Makinde and Kirundi, 1999). Using scaling vari-ables, we carry out non-dimensionalisation and order of magnitude analysis of the governing equations in our study. The surface or wall is assumed to move in the same direction as the free stream. The boundary layer equations are reduced to self-similarity form using the similarity variable n(x, y) and by assuming a power law variation on both the free stream and wall velocities i.e Ue(x) ~ (X) xn and Up(x) ~Xn In the case where vis-cous dissipation is taken into account, the boundary layer equations only admit to self-similarity solution when the pressure gradient parameter n = 0. When viscous dissipation is neglected, the flow is similar for all values of n. Effects of varying different parameters on the momentum boundary layer are either increasing or decreasing its thickness. For thermal boundary layer, an interesting result is obtained by varying the Eckert number in a small region ad-jacent to the wall where temperature exceeded its plate or surface temperature i.e temperature "overshoots" are obtained. This is because of the viscous dissipation effects which are stronger near the wall.(Mureithi and Mason. 2010) For the case when the free stream is moving faster than the wall, the skin friction coefficient is positive and decrease with increase in viscosity variation parameter E. The reverse occurs for the case when the wall is moving faster than the free stream. On the other hand, when the free stream is moving faster than the wall, the heat transfer coefficient increases with increase in viscosity variation parameter E The reverse occurs when the wall is moving faster than the free stream. Stability analysis on the steady boundary layer flow shows that at. high Reynolds number flow, the governing equations become the Rayleigh equation. The vis-cosity variation parameter E is found to stabilise the flow. For the case when the free stream is moving faster than the wall (0.5 < < 1), the flow becomes un-stable. The reverse occurs when the wall was moving faster than the, free stream (0 <, 4; < 0.5).