Mixed convective flow of CNTs nanofluid subject to varying viscosity and reactions

The addressed work explains SWCNTs (Single walled carbon nanotubnes) and MWCNTs (Multi walled carbon nanotubnes) nanofluid flow under the influences of temperature dependent viscosity and mixed convection. Comparative study of SWCNTs and MWCNTs suspended in base liquid is presented. Further heat and mass transfer are addressed for nanofluid effected by radiation, heat generation/absorption and diffusion species. Mathematical development of problem is taken in cylindrical coordinates. System of highly nonlinear differential equations are constructed via appropriate transformations. The system of equations are tackled numerically by bvp4c MATLAB solver. The findings of the study show that larger volume fraction $$\left( \phi \right)$$ ϕ contributes to enhance the nanoliquid flow. The velocity by submerging MWCNTs is noted higher than SWCNTs. Furthermore, the relationship between the viscosity variable $$\left( \theta _{r}\right)$$ θ r and the temperature is such that the temperature near the surface decreases with increase in $$\left( \theta _{r}\right)$$ θ r , while at the same time the temperature away from the surface increases. Subsequently, higher temperature is observed in SWCNTs-liquid compared to the MWCNTs-liquid to the similar values of $$\left( \theta _{r}\right)$$ θ r . Further, heat transfer is an increasing function of varying viscosity variable $$\left( \theta _{r}\right)$$ θ r .

Effects of Variable Fluid Properties on Double Diffusive Mixed Convection with Chemical Reaction Over an Accelerating Surface

In this study, we investigate the effect of variable fluid properties such as variable viscosity, porosity, permeability, thermal conductivity, and solutal diffusivity on double-diffusive mixed convective flow over an accelerating surface under the influence of a higher-order chemical reaction. The governing equations of the physical problem involve a coupled nonlinear partial differential equations and which are transformed into a coupled nonlinear ordinary differential equations using a suitable similarity transformation. Numerical computation using shooting technique is adopted to study the physical characteristics of velocity, temperature and concentration for various values of non-dimensional parameters like Prandtl number, Eckert number, buoyancy parameters, viscosity parameter, porous parameter, a ratio of thermal conductivities, a ratio of solutal diffusivities and chemical reaction parameter etc are involved in the problem. The computed numerical results are presented in the graphs to illustrate the details of the flow characteristics and their dependence on physical parameters. Our computed results are compared with earlier works of Seddeek in the absence of a magnetic field and found in good agreement.

Dual similarity solutions because of mixed convective flow of a double-nanoparticles hybrid nanofluid: critical points and stability analysis

Purpose The purpose of this article is to study the steady laminar magnetohydrodynamics mixed convection stagnation-point flow of an alumina-graphene/water hybrid nanofluid with spherical nanoparticles over a vertical permeable plate with focus on dual similarity solutions. Design/methodology/approach The single-phase hybrid nanofluid modeling is based on nanoparticles and base fluid masses instead of volume fraction of first and second nanoparticles as inputs. After substituting pertinent similarity variables into the basic partial differential equations governing on the problem, the authors obtain a complicated system of nondimensional ordinary differential equations, which has non-unique solution in a certain range of the buoyancy parameter. It is worth mentioning that, the stability analysis of the solutions is also presented and it is shown that always the first solutions are stable and physically realizable. Findings It is proved that the magnetic parameter and the wall permeability parameter widen the range of the buoyancy parameter for which the solution exists; however, the opposite trend is valid for second nanoparticle mass. Besides, mass suction at the surface of the plate as well as magnetic parameter leads to reduce both hydrodynamic and thermal boundary layer thicknesses. Moreover, the assisting flow regime always has higher values of similarity skin friction and Nusselt number relative to opposing flow regime. Originality/value A novel mass-based model of the hybridity in nanofluids has been used to study the foregoing problem with focus on dual similarity solutions. The results of this paper are completely original and, to the best of the authors’ knowledge, the numerical results of the present paper were never published by any researcher.