Quadratic radiative Ag − MgO /water hybrid micropolar nanofluid flow along an exponentially contracting permeable Riga surface: Stability and entropy optimization analysis

The present analysis deals with the study of non-Newtonian micropolar Silver-Magnesium Oxide ( Ag − MgO )/ H ⊭ O hybridized nanofluid flow and heat transfer over an exponentially contracting porous Riga surface. We have highlighted the impacts of micropolar characteristic, quadratic thermal radiant energy in the existence of convective conditions and velocity slip at the boundary on the coefficient of shear stress, coefficient of couple-stress , heat transfer factor (Nusselt number), entropy formation, velocity, micro-rotation or angular velocity and temperature profiles under the assumptions of nanomaterial. We have solved the highly non-linear coupled partial differential equations numerically, using the MATLAB programming platform with a fourth-order method to decode the boundary value problem (bvp4c) with all relevant flow parameters. The second law of thermodynamics is used for the calculation of the irreversibility factor. The results point to the presence of dual-nature solutions with a stable upper solution branch and an unstable bottom solution branch in the contracting sheet area for a given value of the mass suction parameter. In the presence of dual solutions, critical values have been found, and a stability analysis is run to find more stable solutions. Two solutions are found for the limited range of contracting parameter λ when λ S < λ and the solutions terminate at λ ↮ λ c in the contracting region. Additionally, the first solution generates a positive minimum eigenvalue ( β ⊮ > ⊬ ) indicating the stability of the solution, whereas the other solution generates a non positive eigenvalue ( β ⊮ < ⊬ ). It was found that the shear stress and couple stress coefficients rise with increasing suction value, however the heat transfer factor (Nusselt number) may fall for a stable solution. With an increase in the solid volume percentage of the hybridized nanofluid and material component, the formation of entropy rises noticeably. Additionally, it is noted that in both solutions, the quadratic thermal radiating parameter, Eckert number, and Biot number all lead to an increase in the temperature with enhancement in thickness of the thermal barrier layer. These findings are important because micropolar hybridized nanofluids are actively used to cool tiny electrical devices like microchips and related equipments.