At the initial stage of liquid injection into a gas, the injection liquid has not yet been broken up, and at a low surrounding pressure of less than about 0.1 MPa, the tip of the injection liquid forms the shape of a thin string. This phenomenon and the reason for the shape have not been well studied. At a higher pressure of about 3.0 MPa, the tip of the flow forms a mushroom shape. In this paper, the MARS method for simulating free surfaces is applied to analyze the initial shape of the injection liquid. The above phenomena are reproduced and the reason for them is clarified. Another focus in this paper is the throttling effect due to the nozzle, which causes the formation of small air bubbles near the nozzle wall. These bubbles induce large eddies at the surface of the liquid column and promote the disintegration of the liquid film.
