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Title:	Stability analysis of the dual solutions in the boundary layer flow over a stretching/shrinking and moving surfaces
Authors:	Siti Khuzaimah Soid (P72855)
Supervisor:	Anuar Mohd Ishak, Prof. Dr.
Keywords:	Boundary layer Fluid dynamics Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	26-Feb-2019
Description:	This thesis focuses on the stability of the dual solutions that appears in the boundary layer problems. The investigation concentrates on the boundary layer flow over a stretching/shrinking or moving surface in viscous fluid, nanofluid and micropolar fluid with different geometric shapes. The study involves unsteady and steady two- and three-dimensionals magnetohydrodynamic (MHD) stagnation flows with permeable/impermeable and slip/no-slip boundary conditions. The present problems are formulated in a simplified Navier-Stokes equations which are then transformed into a system of nonlinear ordinary differential equations using the appropriate similarity variables. The system is solved numerically using the boundary value problem solver in MATLAB software. The first three problems are applied on viscous fluid which related to the unsteady MHD stagnation flow towards a stretching/shrinking plate with viscous dissipation and ohmic heating in two-dimensional Cartesian coordinate, steady MHD flow over a radially stretching/shrinking disk in two-dimensional cylindrical coordinate and the mixed convention steady axisymmetric stagnation flow over a vertical stretching/shrinking plate with second order velocity slip in three-dimensional Cartesian coordinate. The fourth problem is associated to the nanofluid which specifically studies the steady boundary layer flow past a continuously moving thin needle in a nanofluid. The investigation applies the Tiwari and Das model that incorporates the effect of the volume fraction of the copper nanoparticles. The last problem deliberates the steady MHD stagnation flow over a stretching/shrinking plate in a micropolar fluid with partial slip. The pronounced results are observed for the shrinking case. It is concluded that the unsteadiness diminishes the skin friction and the rate of heat transfer for larger shrinking rate. Also, magnetic field and suction enable to increase the skin friction but decrease the rate of heat transfer. Both assisting and opposing flows are capable to decrease the skin friction coefficient and increase the rate of heat transfer as the slip velocity increases. Moreover, the existence of nanoparticles has been demonstrated to enhance the rate of heat transfer in the nanofluid especially when the plate is shrunk strongly. In a micropolar fluid, the micropolar parameter and slip velocity lead to decrease the skin friction coefficient and the couple stress for both the stretching and shrinking cases, but increase with increasing the magnetic parameter. The boundary layer thickness is significantly influenced by the existence of these prominent parameters. The range of solutions is wider in the existence of magnetic, suction, unsteadiness and slip parameters, but the range is narrower in the presence of nanoparticles as well as in the micropolar fluids. Dual solutions exist for the shrinking case and for the buoyancy opposing flow case. The stability analysis is performed to investigate whether the solutions are stable or not as time passes. It is found that only one of the solutions is stable., Certification of Master's/Doctoral Thesis is not available,Ph.D.
Pages:	315
Call Number:	QA913.S568 2019 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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