Magneto-bioconvection flow of a Casson thin film with nanoparticles over an unsteady stretching sheet : HAM and GDQ computation

Purpose – To numerically investigate the two-dimensional unsteady laminar magnetohydrodynamic (MHD) bioconvection flow and heat transfer of an electrically-conducting non-Newtonian Casson thin film with uniform thickness over a horizontal elastic sheet emerging from a slit in the presence of viscous dissipation. The composite effects of variable heat, mass, nanoparticle volume fraction and gyrotactic micro-organism flux are considered as is hydrodynamic (wall) slip. The Buongiorno nanoscale model is deployed which features Brownian motion and thermophoretic effects. The model studies the manufacturing fluid dynamics of smart magnetic bio-nano-polymer coatings. Design/Methodology/Approach – The coupled non-linear partial differential boundary-layer equations governing the flow, heat and nano-particle and micro-organism mass transfer are reduced to a set of coupled non-dimensional equations using the appropriate transformations and then solved as an nonlinear boundary value problem with the semi-numerical Liao homotopy analysis method (HAM).Validation with a generalized differential quadrature (GDQ) numerical technique is included. Findings – An increase in velocity slip results in a significant decrement in skin friction coefficient and Sherwood number whereas it generates a substantial enhancement in Nusselt number and motile micro-organism number density. The computations reveal that the bioconvection Schmidt number decreases the micro-organism concentration and boundary-layer thickness which is attributable to a rise in viscous diffusion rate. Increasing bioconvection Péclet number substantially elevates the temperatures in the regime, thermal boundary layer thickness, nanoparticle concentration values and nano-particle species boundary layer thickness. The computations demonstrate the excellent versatility of HAM and GDQ in solving nonlinear multi-physical nanobioconvection flows in thermal sciences and furthermore are relevant to application in the synthesis of smart biopolymers, microbial fuel cell coatings etc. Originality/Value – The originality of the study is to address the simultaneous effects of unsteady and variable surface fluxes on Casson nanofluid transport of gyrotactic bio-convection thin film over a stretching sheet in the presence of a transverse magnetic field. Validation of HAM with a generalized differential quadrature (GDQ) numerical technique is included. Keywords – Magneto-hydrodynamics, Bioconvection, Nanofluid, Brownian motion, Homotopy analysis method (HAM), Generalized differential quadrature (GDQ

Hall current, viscous and Joule heating effects on steady radiative 2-D magneto-power-law polymer dynamics from an exponentially stretching sheet with power-law slip velocity : a numerical study

A mathematical model is developed for 2-D laminar, incompressible, electrically conducting non-Newtonian (Power-law) fluid boundary layer flow along an exponentially stretching sheet with power-law slip velocity conditions in the presence of Hall currents, transverse magnetic field and radiative flux. The secondary flow has been induced with appliance of Hall current. The distinguish features of Joule heating and viscous dissipation are included in the model since they are known to arise in thermal magnetic polymeric processing. Rosseland’s diffusion model is employed for radiation heat transfer. The non-linear partial differential equations describing the flow (mass, primary momentum, secondary momentum and energy conservation) are transformed into non-linear ordinary differential equations by employing local similarity transformations. The non-dimensional nonlinear formulated set of equations is numerically evaluated with famous shooting algorithm by using MATLAB software. The validation of simulated numerical results has been completed with generalized differential quadrature (GDQ). Extensive visualization of primary and secondary velocities and temperature distributions for the effects of the emerging parameters is presented for both pseudo-plastic fluids (n=0.8) and dilatant fluids (n=1.2). The study is relevant to the manufacturing transport phenomena in electro-conductive polymers (ECPs)

Structural, Magnetic, Dielectric, Electrical, Optical and Thermal Properties of Nanocrystalline Materials: Synthesis, Characterization and Application

This book is a collection of the research articles and review article, published in special issue "Structural, Magnetic, Dielectric, Electrical, Optical and Thermal Properties of Nanocrystalline Materials: Synthesis, Characterization and Application"

A numerical study of heat and mass transfer in non-Newtonian nanofluid models.

Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.A theoretical study of boundary layer flow, heat and mass transport in non-Newtonian nanofluids is presented. Because of the diversity in the physical structure and properties of non-Newtonian fluids, it is not possible to describe their behaviour using a single constitutive model. In the literature, several constitutive models have been proposed to predict the behaviour and rheological properties of non-Newtonian fluids. The question of interest is how the fluid physical parameters affect the boundary layer flow, and heat and mass transfer in various nanofluids. In this thesis, nanofluid models in various geometries and subject to different boundary conditions are constructed and analyzed. A range of fluid models from simple to complex are studied, leading to highly nonlinear and coupled differential equations, which require advanced numerical methods for their solution. This thesis is a conjoin between mathematical modeling of non-Newtonian nanofluid flows and numerical methods for solving differential equations. Some recent spectral techniques for finding numerical solutions of nonlinear systems of differential equations that model fluid flow problems are used. The numerical methods of primary interest are spectral quasilinearization, local linearization and bivariate local linearization methods. Consequently, one of the objectives of this thesis is to test the accuracy, robustness and general validity of these methods. The dependency of heat and mass transfer, and skin friction coefficients on the physical parameters is quantified and discussed. Results show that nanofluids and physical parameters have an important and significant impact on boundary layer flows, and on heat and mass transfer processes.The year on the title page reflects as 2019 on the thesis and differs from that on pages ii to iv which indicates the year 2020

Mechanical Engineering

The book substantially offers the latest progresses about the important topics of the "Mechanical Engineering" to readers. It includes twenty-eight excellent studies prepared using state-of-art methodologies by professional researchers from different countries. The sections in the book comprise of the following titles: power transmission system, manufacturing processes and system analysis, thermo-fluid systems, simulations and computer applications, and new approaches in mechanical engineering education and organization systems

Mass Transfer Across The Turbulent Gas-Liquid Interface

Ph.DDOCTOR OF PHILOSOPH

Mitigating fouling of heat exchangers with fluoropolymer coatings

Fouling is a chronic problem in many heat transfer systems and results in the need for frequent heat exchanger (HEX) cleaning. In the dairy industry, the associated operating cost and environmental impact are substantial. Antifouling coatings are one mitigation option. In this work, the fouling behaviour of fluoropolymer, polypropylene and stainless steel heat transfer surfaces in processing raw milk and whey protein solution are studied. Methodologies to assess the economics of antifouling coatings are developed and applied. Two experimental apparatuses were designed and constructed to study fouling at surface temperatures around 90 °C. A microfluidic system with a 650 x 2000 µm flow channel enables fouling studies to be carried out by recirculating 2 l of raw milk. The apparatus operates in the laminar flow regime and the capability to probe the local composition of delicate fouling deposit $\textit{in-situ}$ with histological techniques employing confocal laser scanning microscopy. A larger bench-scale apparatus with a 10 x 42 mm flow channel was built to recirculate 17 l of solution in the turbulent flow regime which is more representative of conditions in an industrial plate HEX. Experimental results demonstrate that fluoropolymer coatings can reduce fouling masses from raw milk and whey protein solution by up to 50 %. Surface properties affect the structure and composition of the deposit. At the interface with apolar surfaces raw milk fouling layers are high in protein, whereas a strongly attached mineral-rich layer is present at the interface with steel. Whey protein deposits generated on apolar surfaces are more spongy and have a lower thermal conductivity and/or density than deposits on steel. The attraction of denatured protein towards apolar surfaces and the formation of a calcium phosphate layer on steel at later stages of fouling are explained with arguments based on the interfacial free energy of these materials in water. The financial attractiveness of coatings is considered for HEX subject to linearly and asymptotically increasing fouling resistance and using a spatially resolved fouling model. An explicit solution to the cleaning-scheduling problem is presented for the case of equal heat capacity flow rates in a counter-current HEX. Scenarios where the use of coatings may be attractive or where there is no financial benefit in cleaning a fouled exchanger are identified. Finally, experimental data are used to estimate the economic potential of fluoropolymer coated HEXs in the ultra-high-temperature treatment of milk. In the considered case, the value of a fluoropolymer coating inferred from the reduction in fouling is estimated to be around 2000 US$/m².The sponsorship of this work by Chemours is appreciated

Нелінійна динаміка — 2013

The book of Proceedings includes extended abstracts of presentations on the Fourth International conference on nonlinear dynamics

HAM and DQM solutions for slip flow over a flat plate in the presence of constant heat flux

In this paper, an analytical solution for boundary layer flow over a flat plate with slip flow and constant heat flux surface condition has been presented for the first time. The Navier-Stokes and energy equations are reduced by a similarity transform in order for a set of nonlinear ordinary differential equations to be formed. Then, governing equations will be solved analytically by using a kind of analytic technique for nonlinear problems which has been named the homotopy analysis method (HAM). The obtained results of this study have been compared with the results of differential quadrature method (DQM) as a promising numerical method. Very good agreement has been shown between analytical results and those obtained by DQ. Finally, effects of the Prandtl number and rarefaction parameter K on velocity and temperature profiles are investigated.</p