Congratulations to Yorgos Stergiou for his successful PhD defense

On 02 June 2025, Dipl.-Ing. Yorgos Stergiou successfully defended his dissertation entitled "Chemohydrodynamic instabilities in flow-driven reaction fronts: influence of buoyancy".

This thesis investigates Reaction-Diffusion-Advection (RDA) fronts under varying gravitational conditions to understand buoyancy-driven chemo-hydrodynamic instabilities. Experiments with bimolecular reactions (A + B → C) were conducted in radial and rectilinear configurations using miscible and multiphase fluids. Techniques such as image processing, shadowgraphy, and laser diffraction were used to analyze front dynamics and product formation. Microgravity experiments onboard parabolic flights and sounding rockets revealed that buoyancy significantly alters front behavior, increasing product yield and front width. In contrast, under microgravity, mixing is reduced, leading to thinner fronts and unique features like double peaks. Numerical simulations show that 2D models better capture dynamics in thicker systems where Taylor–Aris dispersion is significant. Additional ground-based experiments explored multiphase systems, including CaCO₃ precipitation and coacervation, revealing viscous fingering, gelation, and buoyancy-driven instabilities. The results help isolate buoyancy effects from dispersion, validate theoretical models, and enhance understanding of RDA front behavior in both engineering and natural contexts.