g-jitter induced mixed convection flow of newtonian and non - newtonian nanofluid past an inclined stretching sheet

A new class of heat transfer fluid based on nanotechnology known as nanofluid has attracted much attention of many researchers due to its potential to improve the thermal properties of conventional fluids. This new approach which significantly enhance the heat transfer is becoming popular in many industrial applications such as cooling applications, nuclear reactors, transportation industry, electronics and instrumentation and biomedical applications. In this thesis, a mathematical model of mixed convection flow of nanofluid is developed based on Tiwari and Das model to study the influence of solid nanoparticles volume fraction on the Newtonian and non- Newtonian fluid flow with heat transfer. Specifically, the flow of nanofluid past an inclined stretching sheet for viscous, second grade, Jeffrey and Casson fluids with the effect of g-jitter is considered. The velocity and temperature of the sheet are assumed to vary linearly with distance through the sheet. The governing equation which consist of coupled non-linear partial differential equations are solved numerically using an implicit finite-difference scheme known as Keller-box method. The numerical results of surface shear stress in terms of skin friction and heat transfer coefficient in terms of Nusselt number as well as the velocity and temperature profiles for amplitude of modulation, frequency of oscillation, solid nanoparticles volume fraction, inclination angle, second grade parameter, Deborah number, ratio of relaxation to retardation times and Casson parameter for assisting and opposing flows are presented graphically and analyzed in details. Numerical result shows that, the presence of solid nanoparticles in all types of fluid enhance the temperature profiles and consequently increase the heat transfer coefficients. It is also found that, the second grade parameter and Deborah number give rise to the values of the heat transfer coefficient but to a contradiction for the inclination angle, ratio of relaxation to retardation times and Casson parameter. Comparative results amongst all types of fluids also show that, Casson nanofluid has the highest heat transfer coefficient but the lowest for skin friction coefficient

Steady flow of some non-newtonian fluids through a porous medium by using adomian decomposition method

Non-Newtonian fluids are employed in a wide range of industrial applications. Non-Newtonian fluids that shows characteristics of both elastic and viscous fluids as a result of shear stress, are referred to as viscoelastic fluids. Constitutive equations of the viscoelastic fluids, flow patterns and viscous response are important challenges that need to be considered when modelling the flow in a porous medium. The predominant idea of this thesis is to find the analytical solutions of viscoelastic fluid in a porous medium. The primary goal of this research is to create a one-dimensional simulation for three different kinds of viscoelastic fluids, namely, Johnson-Segalman, Powell-Eyring, and Sisko fluids, in a porous medium. Further, Darcy’s law is selected for simulating permeable media saturated by viscoelastic fluid. The effect of external magnetic field is an additional feature to the innovation of the constructed mathematical models. The system of nonlinear coupled partial differential equations supported by related boundary conditions are solved analytically by using the Adomian decomposition method (ADM). In the analysis, the impact of various physical parameters on velocity and temperature are scrutinized and the results are exhibited graphically. The wall shear stress versus governing constraints are also evaluated, and their results are summarised in the form of tables and graphs. The results demonstrated that for both isothermal and non-isothermal circumstances, the inclination angle causes a variation in shear stress. It is also observed that the viscosity and shear stress have a direct connection in the absence of a heating effect. Moreover, the viscosity of the non-isothermal state is sensitive to temperature variations for both lift and drainage problems. The findings validated the efficacy of the suggested technique, and the solutions are successfully approximated to the exact solutions

Non-Newtonian Microfluidics

Microfluidics has seen a remarkable growth over recent decades, with its extensive applications in engineering, medicine, biology, chemistry, etc. Many of these real applications of microfluidics involve the handling of complex fluids, such as whole blood, protein solutions, and polymeric solutions, which exhibit non-Newtonian characteristics—specifically viscoelasticity. The elasticity of the non-Newtonian fluids induces intriguing phenomena, such as elastic instability and turbulence, even at extremely low Reynolds numbers. This is the consequence of the nonlinear nature of the rheological constitutive equations. The nonlinear characteristic of non-Newtonian fluids can dramatically change the flow dynamics, and is useful to enhance mixing at the microscale. Electrokinetics in the context of non-Newtonian fluids are also of significant importance, with their potential applications in micromixing enhancement and bio-particles manipulation and separation. In this Special Issue, we welcomed research papers, and review articles related to the applications, fundamentals, design, and the underlying mechanisms of non-Newtonian microfluidics, including discussions, analytical papers, and numerical and/or experimental analyses

Steady and unsteady mhd mixed convection flow of casson and casson nanofluid over a nonlinear stretching sheet and moving wedge

Casson fluid is a shear thinning fluid which is one of the non-Newtonian fluids that exhibit yield stress. In this fluid, if a shear stress less than the yield stress is applied, it behaves like a solid, whereas if vice-versa the fluid starts to move. The advantage of Casson fluid is that it can be reduced to Newtonian fluid at very high wall shear stress. Due to these reasons, the steady and unsteady two-dimensional, electrically conducting mixed convection flow of Casson fluid was studied in this thesis. Flow that was generated due to nonlinear stretching sheet and moving wedge filled with and without nanoparticles were given attention. Specific problems were studied with various effects include, porous medium, thermal radiation, chemical reaction, slip and convective boundary conditions. Similarity transformations were used to convert nonlinear governing equations into nonlinear ordinary differential equations. The obtained equations were then solved numerically via the implicit finite difference scheme, known as Keller-box method. Moreover, an algorithm was developed in MATLAB software in order to obtain the numerical solutions. The accuracy of the numerical results was validated through comparison with the results available in the published journal. The effects of pertinent parameters on velocity, temperature and concentration profiles as well as wall shear stress, heat and mass transfer rates were displayed graphically and also presented in tabular form. Findings reveals that, when Casson fluid parameter increases the momentum boundary layer thickness reduces in both cases, nonlinear stretching sheet and moving wedge. It is noticed that in the case of moving wedge, the strength of magnetic parameter reduces the wall shear stress. Whereas, opposite trend is observed in the case of nonlinear stretching sheet. In both geometries, the influence of Brownian motion and thermophoresis parameters on the nanoparticles concentration is notably more pronounced

Mathematical and numerical modelling of peristaltic flow and absorption in the small intestine

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Multiphysics CFD modelling of incompressible flows at Low and Moderate Reynolds Numbers

In this Ph.D. thesis, a novel high-resolution Godunov-type numerical procedure has been developed for solving the unsteady, incompressible Navier-Stokes equations for constant and variable density flows. The proposed FSAC-PP approach encompasses both artificial compressibility (AC) and fractional step (FS) pressure-projection (PP) methods of Chorin [3, 4] in a unified solution concept. To take advantage of different computational strategies, the FS and AC methods have been coupled (FSAC formulation), and further a PP step has been employed at each pseudo-time step. To provide time-accurate solutions, the dual-time stepping procedure is utilized. Taking the advantage of the hyperbolic nature of the inviscid part of the AC formulation, high-resolution characteristics-based (CB) Godunov-type scheme is employed to discretize the non-linear advective fluxes. Highorder of accuracy is achieved by using from first- up to ninth-order interpolation schemes. Time integration is obtained from a fourth-order Runge-Kutta scheme. A non-linear fullmultigrid, full-approximation storage (FMG-FAS) acceleration technique has been further extended to the FSAC-PP solution method to increase the efficiency and decrease the computational cost of the developed method and simulations. Cont/d

Mesoscale modelling and simulation of macromolecule transport in microfludic channels

This thesis concerns the numerical simulation of dilute macromolecular solutions. Present work details the development of a novel mesoscale simulation method. The developed modeling approach is capable to describe both the macroscopic flow field of the carrier liquid and the micromechanical behaviour of the transported large molecules. In this modeling method, the concept of micromechanical structures is introduced in order to represent macromolecules. The motion of the considered mechanical structures is governed by forces arising from the motion of the bulk fluid phase and microscopic forces arising from stochastic Brownian motion of the solvent molecules. This document presents the motivation, the objectives and systematic steps of the model development. The work presents detailed discussion, verification and validation of the developed modeling method.EThOS - Electronic Theses Online ServiceGBUnited Kingdo