Operation of the propeller in a non-uniform wake field leads to unsteady hydrodynamic loads which induce vibrations. Depending on the magnitude of these vibrations, reactions of the surrounding water will occur. These reactions are effects of added masses and added moments of inertia and of damping, either parallel or normal to the vibrational motion. For a number of propellers from the Wageningen B-screw series these reactions have been calculated, using the unsteady lifting surface theory. It is shown that no fixed percentage of the propeller mass can be used to estimate the magnitude of the added mass. Based on basic considerations for airfoils, an attempt is made to derive simple expressions to characterize the hydrodynamic reactions, using overall geometrical propeller data. The effect of the reactions on the forced propeller vibrations is shown in some detail. For the transverse vibrations the hydrodynamic damping is found to be most important: about 9 % of the critical damping. For torsional vibrations a value of about 6 % is found, for the longitudinal vibrations the hydrodynamic damping is about 3 % of the critical damping. (Wassmann)
Hydrodynamic reactions to propeller vibrations
Hydrodynamische Reaktionen auf Propellerschwingungen
1979
14 Seiten, 10 Bilder, 10 Tabellen, 7 Quellen
Aufsatz (Konferenz)
Englisch
Hydrodynamic reactions to propeller vibrations
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