Study on a new method for generating a gas curtain in the gas-curtain launching

To decrease the launching resistance of underwater guns, a new gas-curtain formation method is proposed based on the gas-curtain launching principle, which is setting up several rectangular grooves on the internal wall of the barrel to guide the gas flow to the front of the projectile and form a gas curtain. A three-dimensional unsteady two-phase flow model of the drainage is established. The formation and drainage characteristics of the gas curtain are studied under the different number of grooves with a constant injection area and 10 MPa injection pressure. The results indicate that the circumferential and radial converging effects of multi-gas jets are enhanced, but the axial expansion is enhanced first and then weakened when the number of grooves increases from 4 to 12. The vortex scale in the Taylor cavity increases with the increase in the number of grooves, but the distance moving downstream is shortened. The gas volume fraction in the tube increases with the increase in the number of grooves. However, the drainage efficiency of the gas curtain on the warhead increases first and then decreases with the increase in the number of grooves, while the change of the gas efficiency–cost ratio is just the opposite.