A theory for the analysis of partially submerged (PS) propellers applied to fast displacement ships is presented. For this purpose the UPCA91 unsteady vortex lattice model has been extended to allow for the presence of a free surface. The concept of submersion factors is introduced to calculate the influence coefficients in a co-ordinate system rotating with the propeller. Some experimental effects observed in testing PS propellers are explained with the help of this theory. A simple three-dimensional water entry-and-exit model with little ventilation has been developed for these applications in which ventilated flows are to be avoided to the maximum extent. Kerwin's vortex-lattice lifting-line theory for propeller design has also been extended to illustrate the relative influence of some components of the vortex system on the induced velocities and efficiency. The time-dependent behaviour of a sample propeller is finally simulated by the analysis theory. Transcavitating blade sections of the Newton-Rader type are used in this calculation. The results include forces and moments as a function of the blade angular position, and mean values of thrust and torque, for 50 per cent and full submergence.
|Title of host publication||4th International Conference on Fast Sea Transportation FAST97, Sydney (Australia) July 1997|
|Publisher||Baird Publications Pty Ltd|
|Number of pages||8|
|Publication status||Published - 1997|
|MoE publication type||A4 Article in a conference publication|