Abstract
Laminar two-dimensional unsteady mixed-convection boundary-layer flow of a viscous incompressible fluid past asymmetric wedge with variable surface temperature embedded in a porous medium saturated with a nanofluid has been studied. The employed mathematical model for the nanofluid takes into account the effects of Brownian motion and thermophoresis. The velocity in the potential flow is assumed to vary arbitrary with time. The non-Darcy effects including convective, boundary and inertial effects will be included in the analysis. The unsteadiness is due to the time-dependent free stream velocity. The governing boundary layer equations along with the boundary conditions are converted into dimensionless form by a non-similar transformation, and then resulting system of coupled non-linear partial differential equations are solved by perturbation solutions for small dimensionless time until the second order. Numerical solutions of the governing equations are obtained employing the implicit finite-difference scheme in combination with the quasi-linearization technique. To validating the method used, we compared our results with previous results in earlier papers on special cases of the problem and are found to be in agreement. Effects of various parameters on velocity, temperature and nanoparticle volume fraction profiles are graphically presented.
Highlights
The study of mixed convection flow finds applications in several industrial and technical processes such as nuclear reactors cooled during emergency shutdown, solar central receivers exposed to winds, electronic devices cooled by fans, heat exchanges placed in a low-velocity environment, etc
The aim of the present paper is to study the unsteady mixed convection flow along a symmetric wedge embedded in a porous medium saturated with a nanofluid in the presence of first and second orders resistances, which to the best of our knowledge have not been investigated yet
In order to see the physical insight, the numerical values of velocity f ′(η ), temperature θ (η ), and nanoparticle volume fraction φ (η ) within the boundary layer computed for different parameters as unsteadiness parameter τ, mixed convection parameter λ, nanofluid buoyancy ratio parameter Nr, thermophoresis parameter NT, Brownian motion parameter NB, first resistant parameter γ, second resistant parameter ∆, Prandtl number Pr and Schmidt number Sc
Summary
The study of mixed convection flow finds applications in several industrial and technical processes such as nuclear reactors cooled during emergency shutdown, solar central receivers exposed to winds, electronic devices cooled by fans, heat exchanges placed in a low-velocity environment, etc. Smith [1] initiated the study of the unsteady incompressible forced convection boundary-layer flow past a semi-infinite wedge impulsively set into motion. This problem subsequently solved numerically by Nanbu [2] using the method proposed by Hall [3] and that modified by Harris et al [4]. Watkins [9] has solved this problem numerically following a second order; he has studied the unsteady heat transfer aspects of the semi-infinite wedge started impulsively from rest to include solutions of the energy equation. A new set of scaled coordinates introduced by Williams and Rhyne [10]
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