抄録
A model test method, a partly captured PMM test, to measure unstable motions of a planing craft induced by periodic maneuvering motion is developed. The experimental results of a planing craft at Fn=2.0 by the method demonstrates that a violent motion which is large rolling, heaving and pitching coupling motion occurs when the frequency of motion given by PMM coincides with the rolling natural frequency, and with the half of the heaving and pitching natural frequency of the craft. It should be noted that the rolling motion has the same frequency as the forced motion given by PMM, but that the heaving and pitching motions have the twice of the frequency of the forced motion.
In order to clarify the cause of the violent motion, the hydrodynamic forces acting on the hull in periodic maneuvering motions are measured by PMM tests for a captured model and obliquely towing tests. The experimental results show that the rolling displacement of the craft generates hydrodynamic heaving force and pitching moment at high speed. A non-linear time-domain simulation of the motions using the measured hydrodynamic forces is carried out. The simulated motions are in fairly good agreement with the experimental ones.
