The creation of a new type of high-speed ships, the Air Cavity Ships (ACS), is based on the successful usage of the air-ventilation aimed at reducing
frictional resistance. The air is supplied under a specially profiled bottom, so that a steady air layer is formed, separating a part of the bottom from contact with the water (see pictures above). Such a flow is named artificial cavitation; it has much in common with the natural cavitation, but it is able to generate large stable cavities in wide range of speeds including low speeds. The one of advantages of an ACS is the low gas consumption required to maintain the cavity (ten times less than that for SES/hovercraft).
The concept of reducing a ship hydrodynamic resistance by supplying air to the wetted surface of the hull has a long history. Since the 19th century there
were a lot of unsuccessful attempts to implement the air cavity. The reason for failures is the deceptive simplicity of this concept. It appears that the parameters of the cavity are very sensitive to the bottom configuration and operational conditions, and without deep physical understanding of this phenomenon it is impossible to create a good ACS. Systematic research on ACS started in Russia in the 1960's. My father, Matveev I.I., built the first high-speed air cavity boat in 1972. The results of the theoretical and experimental study were reflected in the mass production of mid-size
passenger and military ACS (some photos are available here). At the present time large ACS, such as ferries and transatlantic cargo ships, are also being designed.
Experimental trials show that spending less than 3% of
the power of the propulsion system for air injection results in 25% drag reduction on a well-designed ACS. The wide application of the air cavity concept may result in the revolution in shipbuilding, comparable with the change from sailing ships to powerboats.
You can find some further information about ACS concept in my papers. The paper written in the most popular form is here(PDF file, 5 MB).
At the present time I am working together with DK Group. We are developing
large cargo ships and fast Ro-Pax ships with artificial cavitation on the bottom. Below are the photos of our tests in MARIN.
Below is one of my analytical results in this area. I showed that propulsors (imitated by sinks and dipoles) reduce the length of the air cavity, while trim tabs and interceptors (sources) increase the length. This is in agreement with experimental observations. This also has important implication on the development process of ASC (models or intermediate-scale prototypes must tested with propulsors) and shows that the air cavity can be controlled by hydrodynamic devices, which is critical in waves and in the transitional regimes.
Simplistic animations showing air flow through the air-cavity system:
