Abstract
The mathematical and physical model for underwater sealed gun is established to investigate the flow field distribution characteristics for gun muzzle in different mediums. The muzzle flow field for the 12.7 mm gun which is sealed launched underwater is numerically simulated by combining User-Defined Functions (UDF) and dynamic grid technique. The predicted results show that, the muzzle flow field for gun launched underwater is significantly different with that for in air. Unlike that the initial air forming bottle shock wave at the muzzle for gun launched in air, it hits the gas-liquid interface with forming series cylindrical compressed wave in the area before the projectile for gun sealed launched underwater. As the gunpowder gas sprays out, Mach disk appears at 60μs after the projectile shot into water. Meanwhile, the shape of shock waves is fusiform and then turns into a peach heart gradually. However, the bow shock for gun launched in air, which is affected by the projectile base with its structure being bowl-shaped, fails to develop into the Mach disk at even 160μs. Compared with gun launched in air, the muzzle shock wave area for gun launched underwater is obviously smaller.
Highlights
The flight of the projectile is deeply influenced by the muzzle flow field, which will affect or even lower the shooting accuracy when the gun is shot
The gas expansion is less obstructed and the shock wave head is affected by the projectile base too long to form the Mach disk for gun launched in air
(1) Through the analysis of the precursor flow field for underwater sealed launch, it is found that the axial expansion of the initial air is greatly blocked due to the obstruction of water
Summary
The flight of the projectile is deeply influenced by the muzzle flow field, which will affect or even lower the shooting accuracy when the gun is shot. Through the numerically simulation of the horizontal jet of underwater solid rocket motor, it was found that the VOF model can commendably describe the jet structure of the experimental results.[14] A set of experiments were carried out to investigate the behavior of horizontal round noncondensing gas jets that discharge in a stagnant water ambient, considering subsonic and sonic jet exit conditions.[15] It was found that the nozzle diameter and the Froude number had a great influence on the jet shedding and the gas-liquid interface instability. By comparatively analysis of muzzle flow field characteristics for gun launched in air and underwater, the influence of different mediums on muzzle flow field characteristics are discussed
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