Investigation of Characteristics of Maneuvering Hydrodynamic Forces and Minimum Required Experimental Conditions for Small Boats at Low Speed

Abstract

　In this study, characteristics of maneuvering hydrodynamic forces acting on a small boat at low speed and minimum required number and range of experimental conditions of captive model tests to obtain adequate maneuvering motion simulation based on a mathematical model are investigated. Range of experimental conditions in drift angle, yaw angular velocity and running attitudes that are heel, trim angle and draught are determined according to measured maneuvering motions of berthing and turning for a real boat. From the measured results by oblique towing tests, it is found that the hydrodynamic forces acting on hull are significantly changed by flow separation from hull caused by large drift angle, on the other hand, the effects of towing speed on the forces are almost disappeared by dividing the forces by the square of towing speed. It is also found that hydrodynamic forces obtained from PMM test with yawing and without towing speed are almost the same magnitude as hydrodynamic forces obtained by PMM test with pure yawing and towing speed due to large longitudinal asymmetry of hull. From the results of PMM tests with pure swaying and pure yawing, it is confirmed that these tests should be conducted in the conditions which include the range of maneuvering motion of real boat. On the other hand, one combination of towing speed and yaw angular velocity is sufficient for PMM test with yawing with constant drift angle since the hydrodynamic forces at same yaw angular velocity and different towing speed divided by towing speeds are almost same.