Heat Flux As a Key to Predicting Optical Turbulence: Experimental Validation of a Scaling Constant in Rayleigh-Bénard Turbulence

Optical turbulence caused by refractive index fluctuations poses a major challenge for imaging, free-space communication, and directed-energy systems. Rayleigh-B & eacute;nard (RB) convection offers a controlled laboratory analog for studying buoyancy-driven turbulence and its optical effects. Building on theoretical predictions that link turbulence strength to heat flux, we experimentally determine the scaling constant gamma by simultaneously measuring the refractive index structure constant (Cn2) and heat flux in an RB environment. Using a variable turbulence generator (VTG), we validate RB conditions through Nusselt-Rayleigh scaling and direct numerical simulations (DNS). Three independent optical diagnostics were employed to estimate Cn2 (scintillation, beam wander, and long-term beam spot size), while embedded sensors captured heat flux. This scaling constant validation is confined to the experimental conditions described. Results confirm the predicted Cn2 proportional to Q4/3 relationship, with gamma = 8.79 +/- 0.61 closely matching simulations (8.65). This strong agreement demonstrates the robustness of the heat-flux-based scaling relationship and establishes RB systems as effective testbeds for turbulence characterization. These findings provide a practical framework for predicting optical performance in complex environments and advancing turbulence mitigation strategies. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement