International Shipbuilding Progress

Observations of cavitation on a ducted propeller of a VLCC showed abnormal discrepancies with the cavitation pattern, observed on model scale in comparable conditions. To establish the cause of these discrepancies variations of propeller loading, model wake, nuclei content of the fluid and propeller boundary layer were applied. The condition of the propeller boundary layer was found to have a major effect in this case and application of roughness at the leading edge could remove the differences between model and prototype.

The paper describes a new method using finite elements for ship hull surface design. A constrained variational principle is proposed in which the fairness criterion is included in the actual functional and the given design coefficients are as constraints. Constraints can be treated by using Lagrangian multipliers or penalty functions. The finite element method is used to solve the variational problem. The final resulting equations in both the cases are derived. Some examples employing rectangular and triangular elements are presented.