Numerical and Experimental Investigation of Supercavitating Flow Development Over Different Nose Shape Projectiles

Recently, the interest for new technologies to speed up underwater vehicles has increased. In this work, one of these technologies is investigated by creating a gaseous cavity, in which the high-speed underwater vehicles flow, to reduce the drag forces acting on these vehicles. A supercavitating flow over different nose projectile shapes is studied numerically and experimentally to understand the effect of the projectile nose shape on the supercavitating flow behavior. The numerical simulations are accomplished by using a commercial code named ESI-CFD through an unstructured mesh. Also, supercavity flow characteristics are investigated experimentally over the projectile body by using a high-speed camera. The numerical results are validated with other experimental results, where the stages of growth of the cavity over the different shapes projectiles are distinguished briefly and the existence of wake vortex is observed. The cavitator shape controls the time of cavity appearance and the drag coefficient value. The hemispherical nose projectile has the lowest drag coefficient value among all the tested projectiles. So, the cavitating flow behavior is investigated for the hemispherical nose projectile at different cavitation numbers ranging from 0.065 to 1.0. A new correlation is deduced to investigate the drag coefficient for the hemispherical projectile. Good agreement is obtained from the result of this correlation and previous data. Also, a new cavitator shape (a modified conical cavitator projectile) is examined, which is a modification of previously used one. The supercavity has not been formed using the modified conical cavitator projectile but it moves faster than any other examined projectile because it takes longer time before the cavity begins to decay.