When solar irradiation or high-energy optical beams strike the surface of photothermal aerogel composites, nanoparticles convert photon energy into localized heat, establishing temperature gradients across internal micro-pores. Under standard gravity, such thermal gradients drive natural gas convection within pore cavities. However, when pore dimensions shrink to the nanometer-to-micrometer scale, viscous shear resistance exceeds buoyancy forces, suppressing macroscopic convection. Analyzing temperature-gradient-driven microgravity gas flows and vortex dissipation within constrained micro-channels clarifies heat and mass transport in porous media.

Within open aerogel pore networks, localized heating induces density reductions, generating buoyancy forces within micro-cavities. Although overall gas flow faces viscous wall resistance across narrow pathways, regions with steep thermal gradients exhibit localized thermal creep flow. This thermal creep drives directed molecular migration along temperature gradients, establishing mesoscopic micro-vortex loops.

This photothermal convection and buoyancy-driven gas flow dictates the apparent thermal conductivity of aerogels. In photothermal conversion and solar evaporation applications, excessive internal gas convection enhances heat dissipation, lowering energy conversion efficiencies. Restricting gas convection through pore-size optimization represents a physical strategy for thermal management efficiency. Numerical fluid dynamics simulations and thermal imaging map the dynamic evolution of gas flow within photothermal porous media.