Example of the result of an optimisation exercise with a PreSwirl Stator for a twin screw ship

Example of a PROCAL-TRIDENT analysis of a flexible composite propeller blade: deformed blade with bent tip (in foreground with blue grid) versus rigid blade (in background)

inside ducts. After three more years, thanks to MARIN’s close cooperation with IST, it became clear how ducted propellers should be modelled in a boundary element method. It appeared to be very important to iteratively align the wake of the propeller blades with the flow. The reduced velocity in the boundary layer on the duct had to be taken into account when aligning the tip vortex. PROCAL was then extensively validated for ducted propellers. A very interesting validation study was using full- scale observations of cavitation on the propeller of a VLCC with the largest ducted propeller ever built. These observations were made by CRS way back in the seventies.

Optimising propellers CRS propeller tools were put to good use from 2016 onwards within the PROPAGATE group from 2016 onwards, in which an automated propeller design workflow was created. This consisted of a geometry generator, an optimisation routine, a workflow manager and goal & constraint functions. These functions quantified blade stress, radiated noise, propeller-induced hull-pressure fluctuations and cavitation erosion risks - all

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quantities that are in direct competition with fuel efficiency. Towards the end of the project, workflows emerged that can go toe-to-toe with classical design methods.

Flexible propulsors Monique had been using composite materials in her Pre-Swirl Stator design for some time and used to work in close cooperation with a propeller manufacturer on composite propeller designs. Tools to enable them to do this had been developed a decade before within COMPROP. First, a tool for the analysis of flexible propellers in open water was made. PROCAL and the FEM package TRIDENT, developed by LR-MARTEC, were coupled in an iterative way, including geometrically nonlinear effects. COMPROP-2 then extended this tool by enabling the analysis for in-behind ship conditions, applying the methodology developed at TU Delft using several FEA packages.

Where are we heading? In 2019, Monique was still taking classes at university, unaware of the propeller toolbox and guidelines that were being developed in CRS for hull-propeller-ESD integration. Tools and guidelines that lead to the design of a ship that is ideally suited for its mission. Whilst the vision is there, and early demonstrations of propeller and ESD optimisation have been proven, the tuning of tools, optimisation strategies and skills for using it, is expected to remain a challenge for CRS for another 50 years!

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