Role of ambient pressure on bouncing and coalescence of colliding jets

In this Letter, the merging vs bouncing response of obliquely oriented colliding jets under elevated and reduced gaseous environment pressures was experimentally examined. Experiments with water and n-tetradecane confirmed that the collision outcome transitions from merging to bouncing and then to merging again, when the impact velocity was increased. This behavior which was previously reported for atmospheric pressure has now also been observed at elevated and reduced pressures. New results also show that there exists a critical pressure (0.9 bar for n-tetradecane and 5 bar for water) below which increasing pressure promotes bouncing (expands the bouncing regime), while beyond this, merging is promoted (reduces the bouncing regime) instead. This leads to a non-monotonic influence of pressure on the non-coalescence outcomes of collisional jets, which was not previously reported. The study provides evidence of new behaviors in colliding jets at reduced and elevated pressures, which differs from well-studied droplet-droplet collisions.