Surface instability and primary atomization characteristics of straight liquid jet sprays

► We investigate surface instability on straight liquid jet for high-speed injection. ► The liquid jet core behaves like a solid wall. ► The gas-phase boundary layer plays a dominant role, leading to TS mode. ► Interaction with jet head makes core instability and head atomization synchronized. ► TS-type transition is also confirmed by gas vortical structures near surface.