Abstract
Three-dimensional deformation and merging of instability waves in a radial liquid sheet was clarified. A radial liquid sheet forms when a radially flowing liquid film on a disk emerges from the disk and destabilizes just outside the disk. Such instability is caused by the inflection point in the flow velocity profile, and is therefore referred to as "inflectional instability." The instability initially generates two-dimensional waves that grow and deform to cause turbulent transition. The three-dimensional deformation of instability waves is similar to that of of vortices formed by inflectional instability in a single-phase free shear flow. This suggests that the deformation of the waves is caused by the enhancement of perturbed vortex filaments. However, the waves scarcely merge, whereas vortices in the free shear flow merge frequently. This implies that merging of instability waves in liquid sheets is prevented by surface tension.
