Foam coarsening in a two-phase natural circulation loop with seawater

Experiments are conducted to elucidate how foams coarsen periodically in a periodic density wave oscillation in a two-phase natural circulation loop with seawater. This paper reports detailed data by image analysis on visualized foam coarsening dynamics and quantitative distributions of foamability, bubble size, aspect ratio, orientations, and coarsening rates for three stages of density wave oscillation. We have demonstrated a lamella-like foam regime after significant coarsening process characterized by a sharp decline in foamability. Such a unique lamella-like foam regime is with a mean thickness of 1.48 mm and the mean angle at which three foam-like lamellae intersect is 121 o . The distinct characteristic normalized coarsening rate is captured. We confirm the dominant role by periodic mass flux inducing strong shear forces to foam coarsening. These findings offer critical guidance for modelling interfacial transport and optimizing heat transfer in energy-water systems. • First study of foam coarsening under density wave oscillation. • Lamella-like foam skeletons formed with mean thickness 1.48 mm. • Quantitative foamability decline and coarsening dynamics. • Bubble size peaks at normalized diameter 0.96–1.12, aspect ratio shifts to 0.8–0.9. • Normalized coarsening rate and periodic behavior driven by shear.