Simulation investigation of the oscillatory motion of two elliptic obstacles located within a quarter-circle cavity filled with Cu-Al2O3/water hybrid nanofluid

Abstract

This study investigates the consequences of introducing a pair of oscillating elliptical obstacles on the natural convection and entropy generation within a quarter-circle cavity that is filled with a water-based hybrid nanofluid. The Galerkin Finite Element Method was utilized to perform numerical simulations on a 2-dimensional cavity, where the outer wall was set to a low temperature and the inner wall was kept at a high temperature, while the other walls were adiabatic. The hybrid nanofluid containing Cu-Al2O3 nanoparticles was used. The impact of changes in the values of dimensionless parameters, such as the Rayleigh number, heated wall length, oscillation frequency, oscillation amplitude, and oscillation period, on the flow and heat transfer within the cavity was examined. Results showed that an increase in the length of the hot source resulted in a decrease in heat transfer rate and that increasing the Rayleigh number led to a significant increase in total entropy generation and heat transfer irreversibility. A drop in the average Bejan number was noted as the Rayleigh number increased, demonstrating the prevalence of entropy caused by fluid friction. The effect of changing the amplitude had a higher impact on the average Nusselt number compared to the frequency value. At low Rayleigh numbers, the average Nusselt number was higher when the elliptical obstacles oscillated in the same direction, while the opposite trend was observed at higher Rayleigh numbers.