High-frequency microgravity modulation effects on free convection.

This article investigates the effects of microgravity modulation on free convection heat transfer within a closed cavity, focusing on oscillation frequencies higher than the system's natural frequency. Using the Lattice Boltzmann method (LBM) and fast Fourier transformation (FFT), the study reveals that at lower normalized frequencies (frequency ratio ω* < 4), inertia-driven convection dominates, producing fewer but larger vortices that enhance heat transfer. As frequency increases (4 ≤ ω* < 7), viscous effects become more significant, leading to numerous smaller vortices and chaotic flow patterns; however, heat transfer shifts from convection to conduction due to reduced fluid velocity magnitudes. At even higher frequencies (ω* ≥ 8), longitudinal flow patterns emerge, viscosity remains the primary driver of vorticity transport, and heat transfer continues to be governed by conduction despite complex flow structures. The number and size of vortices correlate directly with the normalized frequency, highlighting the evolving interplay between inertia, viscosity, and gravity modulation in microgravity environments relevant to spacecraft and satellite applications.