Within the Research Training Group "Ports for Container Ships of Future Generations funded by the German Research Foundation (DFG) the program panMARE is enhanced for the calculation and analysis of propeller induced loads on quay walls and harbor ground.

During the ship maneuvering process the propeller induces a slipstream. This slipstream affects the river bed and quay walls in the harbor. For a better understanding of these complex interactions between ship and port facilities and for the prediction of operational loads induced by propeller flows there is a need in computational simulation tools. For this purpose panMARE is extended related to the propeller-quay wall-interaction and cavitation modeling. Cavitation has a significant influence on the pressure distribution in the flow and occurs in many forms. A very common form is the sheet cavitation defined as a closed vapor region attached at the propeller blades. Sheet cavitation operates pressure fluctuations which in turn cause vibrations on the ship hull. In addition, cavitation can lead to noise and erosions, as well as, variations in the developed thrust and torque.

The main goal of the project is the implementation of a reliable and stable numerical model for the calculation of the cavitation extension on propeller blades as well as the computation of pressure pulses on the quay walls and harbor ground induced by the cavitation behaviour.

There are two main sheet cavitation types: partial cavitation and supercavitation. Partial cavitation describes a cavity which closes on the propeller blade. Supercavitation describes a cavity which closes downstream of the blade trailing edge. Both the partial cavitation and the supercavitation can be modeled in potential theory by two types of boundary conditions: the dynamic and the kinematic boundary condition. The dynamic boundary condition states that the pressure on the cavity surface must be equal to the vapour pressure: $$ p = p_{vapour} \quad \text{on the cavity surface} . $$ The kinematic boundary condition states that there is no flow throw the cavity surface: $$ \frac{D F(\eta, s_{1}, s_{2}, s_{3})}{Dt} =0 $$ where \( \eta \) is the cavity thickness, \(F\) the cavity shape and \(s_{1}, s_{2}, s_{3} \) the local coordinate vectors.

The discretized boundary conditions on the cavity surface together with the discretized boundary conditions on the non-cavitating part of the body (s. Code->Numerics) result in a linear system of equations which can be solved with usual solvers like Gauss or Gauss-Seidel algorithm.

Personnel

Dipl.-Math Maria Bauer
Prof. Dr.-Ing. Moustafa Abdel-Maksoud

Funding

German Research Foundation (Deutsche Forschungsgemeinschaft, DFG)