Transient analysis of third-grade viscoelastic nanofluid flow external to a heated cylinder with buoyancy effects

Nanotechnology is rapidly embracing numerous areas of manufacturing and process engineering. New types of nanomaterials are being exploited to improve, for example, coating integrity, anti-corrosion characteristics and other features of fabricated components. Motivated by these developments, in the current study a mathematical model is developed for unsteady free-convective laminar flow of third-grade viscoelastic fluid (doped with nano-particles) from a semi-infinite vertical isothermal cylinder, as a model of thermal coating flow of a pipe geometry. Non-Newtonian behavior is simulated with the thermodynamically robust third grade Reiner-Rivlin model which accurately represents polymer fluids. Nanoscale effects are analyzed with the Buongiorno two-component nanofluid model. The governing equations comprise a set of highly coupled, nonlinear, multi-degree partial differential equations featuring viscoelastic and nanofluid parameters. An implicit Crank-Nicolson numerical scheme is implemented to solve the emerging nonlinear problem with appropriate initial and boundary conditions. Detailed graphical plots for velocity, temperature and nano-particle volume fraction are presented for a range of different parameters (i.e., third-grade fluid parameter, Brownian motion parameter, thermophoretic parameter, buoyancy ratio parameter, Lewis number). Additionally, distributions of the heat transfer coefficient, skin friction and Sherwood number at the cylinder surface are visualized. Furthermore, streamlines, isotherms and nano-particle volume fraction contour plots are included for variation of the third-grade parameter. Contour plots for the third-grade nanofluid flow are found to deviate significantly from those corresponding to Newtonian nanofluids. Validation of the numerical solutions with earlier studies is also included. KEYWORDS: Third-grade viscoelastic nanofluid, Thermal convection, Cylinder, Thermophoresis, Brownian motion, Implicit numerical method, Contour plots, Industrial coating

Recent Trends in Coatings and Thin Film–Modeling and Application

Over the past four decades, there has been increased attention given to the research of fluid mechanics due to its wide application in industry and phycology. Major advances in the modeling of key topics such Newtonian and non-Newtonian fluids and thin film flows have been made and finally published in the Special Issue of coatings. This is an attempt to edit the Special Issue into a book. Although this book is not a formal textbook, it will definitely be useful for university teachers, research students, industrial researchers and in overcoming the difficulties occurring in the said topic, while dealing with the nonlinear governing equations. For such types of equations, it is often more difficult to find an analytical solution or even a numerical one. This book has successfully handled this challenging job with the latest techniques. In addition, the findings of the simulation are logically realistic and meet the standard of sufficient scientific value

Radiative and magnetohydrodynamics flow of third grade viscoelastic fluid past an isothermal inverted cone in the presence of heat generation/absorption

A mathematical analysis is presented to investigate the nonlinear, isothermal, steady-state, free convection boundary layer flow of an incompressible third grade viscoelastic fluid past an isothermal inverted cone in the presence of magnetohydrodynamic, thermal radiation and heat generation/absorption. The transformed conservation equations for linear momentum, heat and mass are solved numerically subject to the realistic boundary conditions using the second-order accurate implicit finite-difference Keller Box Method. The numerical code is validated with previous studies. Detailed interpretation of the computations is included. The present simulations are of interest in chemical engineering systems and solvent and low-density polymer materials processing

Chebyshev collocation computation of magneto-bioconvection nanofluid flow over a wedge with multiple slips and magnetic induction

In this paper the steady two dimensional stagnation point flow of a viscous incompressible electrically conducting bio-nanofluid over a stretching/shrinking wedge in the presence of passively control boundary condition, Stefan blowing and multiple slips is numerically investigated. Magnetic induction is also taken into account. The governing conservation equations are rendered into a system of ordinary differential equations via appropriate similarity transformations. The reduced system is solved using a fast, convergent Chebyshev collocation method. The influence of selected parameters on the dimensionless velocity, induced magnetic field, temperature, nanoparticle volume fraction and density of motile microorganisms as well as on the local skin friction, local Nusselt number, local Sherwood number and density of motile microorganism numbers are discussed and presented graphically. Validation with previously published results is performed and an excellent agreement is found. The study is relevant to electromagnetic manufacturing processes involving bionano-fluids

Similarity solutions of boundary layer flows in a channel filled by non-newtonian fluids

Similarity solutions of non-Newtonian fluids are getting much attention to researchers because of their practical importance in the field of science and engineering. Currently, most of researchers focus their work on non-Newtonian fluids over a sheet. However, only a few of them pay their attention towards the geometry of channel due to the complexity of governing equations. Therefore, this study attempts to investigate the numerical solutions of new problems of laminar incompressible Nanofluids, Casson fluids and Micropolar fluids under various fluid flow conditions. Each considered fluid involves porous channel walls, stretching or shrinking walls, and expanding or contracting walls with the influence of various physical parameters. Mathematical formulations such as the law of conservation, momentum or angular momentum, heat and mass transfer are performed on the new problems. After the mathematical formulation is developed, the governing fluid flow equations of partial differential equations are then transformed into boundary value problems (BVPs) of nonlinear ordinary differential equations (ODEs) by using the suitable similarity transformations. After converting high order BVPs into the equivalent first order system of BVPs, shootlib function in Maple 18 software is employed to obtain the similarity solutions of nonlinear ODEs. The numerical results in this study are compared with the existing solutions in literature for the purpose of validation. The results are found to be in good agreement with the existing solutions. Multiple solutions of some of the problems particularly in porous channel with expanding or contracting walls also exist for the case of strong suction. This study has successfully find the numerical solutions of the new problems for various fluid flow conditions. The results obtained from this study can serve as a theoretical reference in related fields

Unsteady flow of a nanofluid over a sphere with nonlinear Boussinesq approximation

A theoretical study is presented of transient mixed convection boundary layer flow of a nanofluid in the forward stagnation region of a heated sphere which is rotating with time dependent angular velocity. The effect of the non-linear Boussinesq approximation is taken into account. The nanofluid is treated as a two-component mixture i.e. nano-particles distributed homogenously in a base fluid (water or gas). The effects of the Brownian motion and thermophoresis are included for the nanofluid and constant wall temperature is imposed at the sphere surface. The first and second laws of thermodynamics are employed in order to study thermophysics as well as heat and mass transfer phenomena. By introducing appropriate similarity variables the governing equations are transformed into a system of dimensionless, nonlinear, coupled, ordinary differential equations which are solved numerically by applying the second-order accurate implicit finite difference Keller box method. The reliability and efficiency of the obtained numerical results are validated via comparison with the previously published results for special cases. The effects of various parameters on primary and secondary velocities, temperature, nanofluid volume fraction (concentration), primary and secondary shear stress functions, Nusselt number function (wall heat transfer rate) and Sherwood number function (wall nanoparticle mass transfer rate) are visualized. Furthermore the influence of non-linear temperature parameter, Brinkman parameter (ratio of Brinkman number to dimensionless temperature ratio), local Reynolds number and unsteadiness parameter on entropy generation number is computed. A strong elevation in entropy generation number is computed with both increasing Brinkman parameter and unsteadiness parameter. Primary and secondary surface shear stresses, Nusselt number and Sherwood number also increase with unsteadiness and rotation parameters. Primary shear stress is boosted with increasing mixed convection parameter and Brownian motion effect whereas secondary shear stress is depressed. Temperatures are suppressed with increasing nonlinear temperature parameter whereas nano-particle concentrations are elevated. Increasing thermophoresis parameter enhances both temperatures and nano-particle concentration values. The simulations find applications in rotating chemical engineering mixing systems and nano-coating transport phenomena

Exact solutions on unsteady convective flow of viscous, casson, second grade and maxwell nanofluids

The heat and mass transfer flow of Newtonian and non-Newtonian nanofluids caused by convection has much practical significance, such as in industries, chemicals, cosmetics, pharmaceuticals and engineering. In this thesis, the unsteady convection flows of Newtonian, non-Newtonian and non-Newtonian hybrid nanofluids such as Casson hybrid, second grade and Maxwell nanofluids in a vertical channel or past a vertical plate will be studied. Carbon nanotubes (CNTs), graphene, cobalt, copper and alumina nanoparticles are used for the enhancement of heat transfer rate of fluids in this research work. Nanofluids have a range of applications in automobiles as coolants, microelectronics, microchips in computer, fuel cells and biomedicine. The problem of free and mixed convection flow of nanofluids is studied in a porous as well as non-porous media, with or without magnetohydrodynamics (MHD) influence. Other conditions like oscillating vertical plate, radiation effect and heat generation have been considered. The idea of Caputo time fractional derivative is used in some problems which is a novel topic nowadays. The advantage of fractional derivative is that the range of derivative increases in this case and the derivative of variable are used for a range of numbers. Appropriate non-dimensional variables are used to reduce the dimensional governing equations along with imposed initial and boundary conditions into dimensionless forms. The exact solutions for velocity, temperature and concentration are acquired via Laplace Transform technique and, in some places, regular perturbation technique along with inverse Laplace transform i.e. Zakian technique. The corresponding expressions for skin friction, Nusselt number and Sherwood’s number have been calculated. The outcomes acquired are plotted via computational software MathCAD-15 using the specific thermophysical properties of nanoparticles and base fluids. The graphical outcomes have been discussed to delineate the impact of various embedded parameters such as radiation parameter, Peclet number, Grashof number, fractional parameter and volume fraction of nanoparticles. Throughout the objectives, velocity of the nanofluid is found to be increasing with increasing thermal/solutal Grashof number, radiation parameter while decreasing with volume fraction of nanoparticles. Temperature profile increases with radiation parameter, heat generation and volume fraction. Thermal conductivity and Nusselt number of the nanofluids exhibit significant increment with increasing volume fraction

Challenges and progress on the modelling of entropy generation in porous media: a review

Depending upon the ultimate design, the use of porous media in thermal and chemical systems can provide significant operational advantages, including helping to maintain a uniform temperature distribution, increasing the heat transfer rate, controlling reaction rates, and improving heat flux absorption. For this reason, numerous experimental and numerical investigations have been performed on thermal and chemical systems that utilize various types of porous materials. Recently, previous thermal analyses of porous materials embedded in channels or cavities have been re-evaluated using a local thermal non-equilibrium (LTNE) modelling technique. Consequently, the second law analyses of these systems using the LTNE method have been a point of focus in a number of more recent investigations. This has resulted in a series of investigations in various porous systems, and comparisons of the results obtained from traditional local thermal equilibrium (LTE) and the more recent LTNE modelling approach. Moreover, the rapid development and deployment of micro-manufacturing techniques have resulted in an increase in manufacturing flexibility that has made the use of these materials much easier for many micro-thermal and chemical system applications, including emerging energy-related fields such as micro-reactors, micro-combustors, solar thermal collectors and many others. The result is a renewed interest in the thermal performance and the exergetic analysis of these porous thermochemical systems. This current investigation reviews the recent developments of the second law investigations and analyses in thermal and chemical problems in porous media. The effects of various parameters on the entropy generation in these systems are discussed, with particular attention given to the influence of local thermodynamic equilibrium and non-equilibrium upon the second law performance of these systems. This discussion is then followed by a review of the mathematical methods that have been used for simulations. Finally, conclusions and recommendations regarding the unexplored systems and the areas in the greatest need of further investigations are summarized

Anisotropic slip magneto-bioconvection flow from a rotating cone to a nanofluid with Stefan Blowing effects

A mathematical model for two dimensional steady laminar natural convective anisotropic slip boundary layer flows from a rotating vertical cone embedded in ethylene glycol bionanofluid is presented. The influence of Stefan blowing is also taken into account. Four different nonparticles namely Copper (Cu), Alumina (Al2O3), Copper Oxide (Cuo), Titanium Oxide (TiO2) are explored. Suitable similarity transformations are used to convert the governing equations into non-linear ordinary differential equations. These are then solved numerically, with appropriate boundary conditions, utilizing an implicit finite difference method (the BVP5C code in MATLAB). During computation Sc, Lb, Le and Lb are presented as unity, whilst Pr is taken as 151.The effects of the governing parameters on the dimensionless velocities, temperature, nanoparticle volume fraction, density of motile microorganisms as well as on the local skin friction, local Nusselt, Sherwood number and motile micro-organism number density are thoroughly examined via tables and graphs. It is found that the skin friction factor increases with tangential slip, magnetic field and Schmidt number whilst it decreases with blowing parameter and spin parameters. It is further observed that both the friction and heat transfer rates are highest for copper nanoparticles and lowest for TiO2 nanoparticles. Validation of the BVP5C numerical solutions with published results for several special cases of the general model is included. The study is relevant to electro-conductive bio-nano-materials processing

Computational Treatment of Transient MHD Slip Flow of an Arrhenius Chemical Reaction in a Convectively Heated Vertical Channel

A numerical computational treatment of transient electrically conducting fluid with an Arrhenius chemical reaction in the presence of Navier slip and Newtonian heating is obtained by using implicit finite difference scheme. A transverse magnetic field is applied to the flow direction due to the exothermic nature of the fluid. Numerical computation shows that, higher values of Frank-Kamenetskii parameter (λ) and Biot number (Br) significantly influence the transport phenomenon. Irrespective of smaller or larger time, Magnetic parameter (M) reduces velocity of the fluid as well as wall shear stress