Sensitivity of Double‐Diffusive Mixed Convection in an Enclosure With a Zigzag Bottom Wall and a Torsionally Oscillating Lid Using Hybrid Nanofluid

ABSTRACT

This study investigates the nature of sensitivity in an unsteady double‐diffusive mixed convective analysis in a trapezoidal enclosure featuring a zigzag bottom wall and a torsionally oscillating lid. This cavity is filled by a hybrid nanofluid ( Ag ‐ MgO ‐ H ₂ O ). The cavity also contains internal heat generation. The finite element method (FEM) is applied to solve the governing equations, while sensitivity analysis is conducted using RSM. The impacts of several dimensionless factors, including Reynolds number (10 ≤  Re  ≤ 40), volume fraction (0.02 ≤  φ  ≤ 0.1), and oscillation frequency (0.8 ≤  ω  ≤ 5), were studied while keeping the other parameters constant. These variables are examined in connection with the streamlines, isotherm lines, iso‐concentration lines, average Nusselt number ( Nu _avg ), and average Sherwood number ( Sh _avg ). The observations suggest the nanofluid's thermal performance is strengthened by the increasing values of Re and φ , whereas higher dimensionless time decreases it. Dynamic instabilities from the oscillating lid reduce heat and mass transport. Higher solid volume fractions increase heat transport but decrease mass transport. Additionally, the Re is positively sensitive to both Nu _avg and Sh _avg . Ultimately, the outcome indicates that cavity shape, lid oscillation, and hybrid nanofluid characteristics are significant factors in regulating convective transport, with potential uses in energy systems, microfluidic devices, and effective cooling.