For study purpose, a simplified model of a hydrofoil craft is constructed with the assumption that it has: heave only motion; no surface proximity effect on the foil; no foil broaching. It is then shown that a fully submerged hydrofoil, mounted at the bottom of rigid struts, can transmit large vertical force fluctuations to the hull, even in an idealized sinusoidal seaway because of the orbital velocity in the water. But if the foil support struts are hinged, inclined aft and resiliently supported, so that hydrofoil can swing about the struts pivot in response to the changes in local water velocity, then the vertical accelerations to the hull are reduced. The more the strut is inclined to the vertical, the smaller are the accelerations transmitted to the hull. A hinged strut whose equilibrium angle (for 1 g) is 60 deg to the vertical can reduce the vertical accelerations by an order of magnitude. It also has two other practical advantages. The strut(s) and foil will ride up towards horizontal during the rare but inevitable impacts with large marine objects (such as whales or flotsam) and during groundings. And when they encounter a region of water moving rapidly (which can cause a conventional fully submerged hydrofoil to experience a violent hull impact on the water) they move in such a way as to maintain a roughly constant lift force on the hull, so that there is negligible hull motion in heave.
The response of a hydrofoil to wave orbital velocity fields
Die Reaktion eines Tragflügels auf Orbitalgeschwindigkeitsfelder von Wellen
Ocean Engineering ; 24 , 3 ; 235-263
1997
29 Seiten, 22 Bilder, 2 Tabellen, 27 Quellen
Aufsatz (Zeitschrift)
Englisch