fundamental CFD development for ducts, the design of biomechanical propulsion, to groundbreaking model tests to provide benchmark cases for CFD.


Ventilation of pods For pods, an in-depth study is being carried out regarding the pos- sibilities of placing the pod unit at a position optimised for total vessel efficiency. Risk of ventilation, especially in open sea conditions, is at this moment the limiting factor. Only cavitation behaviour in calm water conditions is assessed during the propulsion system design under current practice, although it is known that shaft and bearing loads in operational conditions impose important constraints on the design. Ventilation can sometimes occur on pods, a phenomenon which affects blade forces and moments, and consequently the shaft loading as well. MARIN carried out a unique series of tests


in the DWB where these phenomena are simulated to fully understand the ventilation effects, therefore allowing more freedom in the positioning of the pod. For this purpose a cruise liner model was selected and fitted with podded propulsors. The forces and moments of the propeller were measured on both pods in all directions. The portside pod was instrumented to measure the entire propeller, while the star- board pod had only one of the four blades instrumented in order to measure the blade root loading in detail. The test setup and instrumentation were similar to the setup used for the CRS ProPolar project (see Report No. 104). Seven different cameras were used to record the tests, including two high-speed video cameras.


The light loading condition of the vessel was used in combination with a series of wave periods with the highest chance


of ventilation. Using high-speed video recordings with 2000 fps, both cavitation and ventilation events were captured in great detail together with synchronised force and moment measurements on the instrumented blade. The fluctuations of the blade root loading showed significant fluctuations during a cavitation or ventila- tion event.


These first results show that already from the first project on, the DWB is making an important contribution to knowledge development and it is certain to play a vital role in improving the safety and efficiency of propulsion systems in operational conditions.


The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n°233896.


report 11


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