Weld Pool Convection Cross-Section: Marangoni vs Buoyancy (2D)

Weld a metal plate with an electron beam and watch what actually stirs the molten pool, sliced open in cross-section. On Earth, gravity-driven buoyancy convection and surface-tension-driven Marangoni convection compete inside the melt, and the winner decides whether the weld comes out shallow and wide or narrow and deep. Toggle from Earth's 1g to orbital microgravity to strip away buoyancy entirely and isolate the pure Marangoni flow — the physics behind real electron-beam welding experiments flown on Salyut, Mir and the ISS — and drag the sulfur/surfactant slider through the point where the surface-tension gradient flips sign, reversing the pool's internal circulation. A live regime map and velocity-comparison panel show exactly where your settings sit on the buoyancy-vs-Marangoni landscape.