Insights into Ventilation Demand Estimation for High-Speed Supercavitating Underwater Vehicles

Abstract

The difference between the typical peak speeds of an aerial and an underwater vehicle is enormous. Evidently, the reason behind this huge disparity lies in the tremendous skin friction drag experienced by an underwater vehicle. However, this difference can be bridged if the underwater vehicles were somehow engulfed by elongated gas/vapor bubbles or cavities as these vehicles travel underwater. Such huge cavities or ‘supercavities’ can be generated via two different approaches—cavitation or ventilation. Among the two, the generation of a supercavity through ventilation is more interesting, since it can be accomplished at much lower speeds. For the operation of such underwater vehicles in the ventilation mode, it is imperative to determine the ventilation demand, or the amount of gas to be carried on board. The present study reports some interesting insights into the factors that determine the estimation of this ventilation demand. Two most important factors governing the estimation of ventilation demand are the ventilation requirement for the formation and sustenance of a supercavity. These two factors, in turn, are dependent upon the operational conditions of a vehicle, as well as unsteady state conditions prevailing under the ocean. The current work explores the dependence of the formation and sustenance air entrainment rates of a supercavity at different operational conditions of the supercavitating vehicle.