Heat Transfer Enhancement in Oscillatory Cavities Filled With Graphene‐Carbon Nanotube Hybrid Nanofluids: A Lattice Boltzmann Study

ABSTRACT The thermal performance of hybrid nanofluids is subject to complex molecular and colloidal interactions that are not yet fully understood. This study uses the Lattice Boltzmann Method model to reveal the microscopic processes that enhance heat transfer in aqueous nanofluids containing a hybrid mixture of graphene nanosheets and multi‐walled carbon nanotubes (MWCNTs). Through thermal engineering simulations, we analyze the synergistic effect of nanoparticle size, mixing ratios, and flow dynamics characterized by Strouhal and Richardson numbers on thermal conductivity. Our results show that graphene‐rich hybrid fluids form filter‐like network structures that significantly alter local thermal conduction pathways. Increases in the Strouhal number enhance boundary layer turbulence and nanoparticle motion; this behavior is directly related to modifications in the microscopic structure of the fluid and a reduction in thermal resistance between surfaces. This study provides new insights into the interaction between structural organization, dynamic behavior and thermal performance in carbon‐based colloidal dispersions. Specifically, it demonstrates how molecular‐level ordering and flow‐induced structure under buoyancy‐driven conditions lead to microscopic improvements in thermal conductivity. These results advance our fundamental understanding of the behavior of multicomponent nanofluids and provide valuable guidance for the design of effective thermal management systems.