029MI - Carene veloci

A.A. 2019/20

Aliscafi

Docente: Mitja MorgutUniversita degli Studi di TriesteDipartimento di Ingegneria e ArchitetturaVia A. Valerio 10, 34127 TriesteEdificio C5 - Stanza C5 2.44mail: mmorgut@units.it

Military hydrofoils Passenger Ferry Craft cavitation

Military hydrofoils

Carene veloci, A.A. 2019/20

I In the 1960 the desire was for an ocean-going patrol craft that could outrun ahigh-speed submarine.

Large patrol submarines in both Soviet and NATO Navies were able to reachspeeds in excess of 40 knots

I The possible solution was the fully submerged hydrofoil, with a proper stabilizationsystem capable to control surfaces at the foils in a similar way to an aircraft.

I Boeing Marine Systems started its hydrofoil developments in June 1960 when itwon a contract to build a 120-t hydrofoil to test antisubmarine warfare from the USNavy.

Military hydrofoils Passenger Ferry Craft cavitation

PCH-1 High Point

Carene veloci, A.A. 2019/20

I Boeing delivered PCH-1 to US Navy in 1963I Service speed: more than 40 knotsI Foil configuration: Canard

- single forward T foil and- twin aft T foils in the stern quarter, either sideof the hull, supporting 70% of the craft weight

I Propulsion system:- two Rolls Royce Proteus marine gas turbines- contra-rotating subcavitating propellers- Z-drive trasmission

I Observed problems:- protective coatings applied to the foils cameaway leading to hydrodynamic problems- both the propellers and foils suffered fromcavitation- the stabilization system was not properlydesigned

Military hydrofoils Passenger Ferry Craft cavitation

Military hydrofoils and Boeing

Carene veloci, A.A. 2019/20

After the experience with PCH-1 Boeing invested in a small research craft to providetest data for:I foil design

I control design

I water jet system

Testing with High Point continued in the US Navy until 1965 when it was passed over tothe Hydrofoil Development office of the David Taylor Model Basin.High Point was used as a test platform investigating foil hydrodynamics, motionresponse, and performance correlation over the period to December 1984 when thevessel was deactivated.

Boeings experience with its water-jet test craft gave it the confidence to employ waterjets for its competitor in the Patrol Hydrofoil field, PGH-2 Tucumcari.

Military hydrofoils Passenger Ferry Craft cavitation

Tucumcari

Carene veloci, A.A. 2019/20

I Delivered to US Navy in 1968I More than 50 knots in calm waterI Foil arrangement:Canard, following the

general arrangement of High PointI Propulsion system:

two-hull-mounted water jets taking waterfrom a forward-facing intake at the root ofthe strutswater was delivered up the struts to thewater-jet pump which ejected the waterfrom exhausts

I Improved control system for the flaps andbow strut regulations.

Military hydrofoils Passenger Ferry Craft cavitation

Italy

Carene veloci, A.A. 2019/20

I In Europe, Italy went ahead to build a single craft, the Sparviero (swordfish), in1974 which was a direct development of Tucumcari, with similar dimensions, foilarrangement, etc. while being fitted with twin missile launchers at the stern and alarge gun on the foredeck.

I The craft was successful enough for a further six of the type to be procured by theItalian Navy up to 1983, and in 1991 the Japanese Maritime Defense forcefollowed up with an order for three craft to the design to be built by SumitomoHeavy Industries. The design can, therefore, be considered a success.

Military hydrofoils Passenger Ferry Craft cavitation

Boeing - Jetfoil 929

Carene veloci, A.A. 2019/20

I The prototype Jetfoil 929-100 was built in1974

I service speed: 42 knotsmaximum speed: 50 knots

I foil configuration: canard- forward single inverted T foil- three struts, full-span foil aft- all foils with trailing-edge flaps

Foils and struts retract hydraulically abovewaterlineThe forward foil assemby can rotate, 7 degin either direction.

I Propulsion system:- two gas turbines- water-jet propulsion with axial pumps

Military hydrofoils Passenger Ferry Craft cavitation

Jetfoil

Carene veloci, A.A. 2019/20

Key features:I Fully submerged bow and stern foils, set at depth to reduce the wave

disturbance forces in flight.I Automated control system for controlling the lift generated by both bow

and stern foils, in order to give a smooth ride. Small displacementmotions and accelerations for vertical, transverse and longitudinalmotions.

I Water jet with a forward-facing water inlet at the stern foil strut and thepump impellor at the hull elevation, resulting in no complicated powertransmission system on the craft caused by the deep-submerged foilsystem.

I Retractable foils.

Military hydrofoils Passenger Ferry Craft cavitation

In Italy

Carene veloci, A.A. 2019/20

Rodriquez Cantieri Navali in Messina now Intermarine SPA (gruppo IMMSI)

I Intermarine, under the Rodriquez brand, has been a pioneer of this kind of vessel,being since 1956 at the forefront of the construction of hydrofoils with surfacepiercing foils.

I The most recent achievement is the innovative Fully Submerged Hydrofoil (FSH).In comparison with the traditional hydrofoil, the full immersion of the foils reducesthe drag coefficient and the effects of the waves, allowing to keep high speedseven in rough sea, very high level of comfort for passengers and lower fuelconsumption.

Military hydrofoils Passenger Ferry Craft cavitation

Cavitation

Carene veloci, A.A. 2019/20

I Cavitation appears when the pressure in the water is equal to the vaporpressure

I The negative consequence of cavitation is that:

- the material of the foil can be quickly destroyed and the lift capabilitiesof the foils may be significantly reduced.

- the drag on the foils increases

- noise is generated

Military hydrofoils Passenger Ferry Craft cavitation

Cavitation-free buckets

Carene veloci, A.A. 2019/20

I Cavitation-free buckets for a given foil are used to identify the possibility ofcavitation.