Author(s): Chen Onn Chin; Wei Li
Linked Author(s): Chen Onn Chin
Keywords: Propeller; Jet; Velocity distribution; Scour
Abstract: Ships with more powerful engines and self-propelled berthing capability are widely engaged recently. Severe propeller jet scour on the bed or bank of navigation channels and port structures may occur. In investigating the mechanics of propeller jet scour, it is crucial to find out the velocity distribution of jet flow. In this study model tests were conducted to examine the axial, tangential and radial velocity of jet flow behind a propeller. From the axial velocity distribution, zone of flow establishment and zone with established flow can be distinguished. At the distance of 3D from propeller jet exit, jet flow was fully set up. Because of air motion above the water surface, velocity distribution is normally slightly asymmetrical about the propeller axis in laboratory condition, especially distant from the hub. Although the axial flow is the main part of propeller jet, it should be noticed that tangential velocity of propeller jet is considerable, which can induce to large scour hole under propeller. Radial velocity is relative small comparing with tangential and axial velocity, and the irregularity of radial velocity distribution is due to the strong influence of tangential and axial velocity. Rotation speed of propeller is the decisive parameter for the formation of jet flow, strength of axial and tangential flow will be increased remarkably with larger rotation speed of propeller.
Year: 2001