A pressure jump method for modeling waterjet/hull interaction

• The pressure jump method (PJM) is developed for modeling waterjet–hull interaction.
• PJM along with a panel method code provides a fast and robust approach.
• PJM is validated against experimental data provided by the ITTC.
• The sign and magnitude of the thrust deduction can be studied employing PJM.
• The waterjet system increases the hull sinkage, resulting in increased resistance.

A fast and robust method for the simulation of waterjet hull interaction is presented. Balancing the thrust force of the waterjet unit with the hull resistance, a method is developed for the prediction of the flow rate through the unit. The method is called the Pressure Jump Method and may be used in combination with both potential flow/boundary layer methods and more advanced viscous flow methods, for instance of the RANS type. In the present work the potential flow/boundary layer approach has been used. Validation of the method is accomplished through comparison of predicted results with measured data. The inlet velocity ratio, nozzle velocity ratio, gross thrust and thrust deduction are all within the experimental scatter. For the case studied the force and moment created by the waterjet unit cause the hull to sink deeper and attain a bow down trim compared to the bare hull case. The thrust deduction fraction is positive both in the computations and the measurements.