Engineering Analysis of Unsteady Micropolar Hybrid Nanofluid Flow over a Riga Plate for Improved Heat and Mass Transfer

• This paper is an investigation of the unsteady flow of UMHNF through a Riga plate. • The Riga plate is a magnetised surface that influences fluid motion and boundary layer properties. Heat transmission, industrial operations, and aerodynamics are all affected by it. • The base fluid SA, has been used in the preparation of a HNF consisting of CeO 2 and Al 2 O 3 NPs. • The influence of numerous parameters on velocity, microrotation, energy, and fluid concentration profiles are demonstrated and explained. This research offers a comprehensive engineering investigation of an unsteady, incompressible flow of a micropolar hybrid nanofluid over a Riga plate embedded in a Darcy-Forchheimer porous medium. A novel hybrid nanofluid (HNF), consisting of alumina (Al 2 O 3 ) and titanium carbide MXene (Ti 3 C 2 ) is dispersed in vacuum pump oil (VPO) to improve heat transfer and lubricating properties. The proposed mathematical model includes a spatially exponential heat source/sink and multiple slip conditions (velocity, and thermal) to mimic industrial applications. The nonlinear partial differential equations (PDEs) are reduced to ordinary differential equations (ODEs) through suitable similarity transformations. The PCM is employed to numerically solve these equations. A detailed parametric study is performed to investigate the effect of the Riga parameter, porosity, and micropolar material constants on the velocity, microrotation, temperature and concentration fields. It is found that the hybrid nanofluid (Al 2 O 3 -Ti 3 C 2 /VPO) enhances the heat and mass transfer rates of conventional nanofluids. Additionally, variation in velocity slip factor (0.3 to 0.9) drops the couple stress and Nusselt number up to 8.48682% and 33.9688%. The effect of heat sink factor (-1.0 to -3.0) and thermal slip factor (0.1 to 0.9) accelerates the energy transfer rate by up to 71.3862% and 84.2107% respectively. The combined effects of the electromagnetic force from the Riga plate and the Darcy-Forchheimer resistance offer an effective means of boundary layer control. The numerical findings are verified with published results, showing the effectiveness of the PCM for high-viscosity lubricants in nanotechnology and advanced manufacturing.