Mathematical modeling of mixed convection flow in a micropolar fluid filled with hybrid nanoparticles toward a vertical surface

Abstract

Colloidal suspensions of regular fluids and nanoparticles are known as nanofluids. It has a variety of applications in the medical field, including cell separation, drug targeting, destruction of tumor tissue, and so on. On the other hand, the dispersion of two or multiple nanoparticles into a regular or base fluid is referred to as a hybrid nanofluid. It has a variety of innovative applications in the industrial and engineering areas such as water heating in solar, analysis of heat exchanger surfaces, microfluidics, heat dissipation, dynamic sealing, damping, and so on. Because of these numerous applications of hybrid nanofluids, the objective of this study is to examine the characteristics of mixed convection stagnation point flow and heat transfer of micropolar hybrid nanofluids impinging on a permeable stretching/shrinking vertical surface. The following are the five problems considered in this thesis, namely: (i) unsteady micropolar hybrid nanofluid flow past a permeable stretching/shrinking vertical sheet; (ii) magnetohydrodynamic flow of a hybrid nanofluid through a stretchable/shrinkable vertical sheet subject to nonlinear heat source/sink; (iii) stagnation point flow of a micropolar hybrid nanofluid over a non-isothermal stretching/shrinking sheet with characteristics of inertial and microstructure; (iv) stagnation point flow of a micropolar fluid filled with hybrid nanoparticles by considering various base fluids and nanoparticle shape factors; and (v) buoyancy effect on the stagnation point flow of a micropolar hybrid nanofluid toward a vertical plate in a saturated porous medium. The mathematical models of the problems that govern the stagnation point boundary layer flow of a micropolar hybrid nanofluid with some other significant effects are signified by the requisite posited continuity, momentum, angular momentum (microrotation), and energy equations that are formed in terms of the nonlinear partial differential equations (PDEs). In addition, these PDEs are transformed into ordinary differential equations (ODEs) by exercising the pertinent similarity variables. These ODEs are solved numerically via applying the built-in program bvp4c in MATLAB software. The impact of the specific set of distinguished parameters on the velocity profile, the shear stress (or the skin friction coefficient), the angular velocity profile, the couple-stress coefficient (or the gradient of microrotation), the temperature distribution, and the heat transfer (or the local Nusselt number) for the two dissimilar branch solutions are discussed. Outcomes reveal that the fluid motion and microrotation decelerate in the presence of nanoparticle volume fraction, while the temperature augments. However, the temperature distribution escalates with the radiation parameter, while decelerating the velocity and angular velocity. On the other hand, the outcomes divulge that the physical quantities such as skin friction coefficient, couple-stress coefficient, and heat transfer uplift with the higher impact of nanoparticle volume fraction, mass suction parameter, and magnetic parameter. Meanwhile, the rate of heat transfer declines with the internal heat source parameter but escalates with the internal heat sink parameter. Also, the temporal stability analysis is workout to check the stability of the multiple solutions via unraveling the eigenvalue problem. The outcomes display that only one of these outcomes is physically stable while the other is unstable as time evolves.