Cavitation on ship propellers creates pressure fluctuations that are noticeable in vibrations and sound. As the complete avoidance of cavitation limits the efficiency of the propeller in common applications, a better knowledge of the mechanisms behind the dynamics of propeller-excited pressure fluctuations (termed PEPF) due to cavitation is necessary. The pressure fluctuations occur in different frequencies, which are considered in multiples of the blade frequency. The dominant frequencies vary depending on the cause, from the first order due to the displacement effect and sheet cavitation to higher orders due to tip vortex cavitation. It is known from experiments that the sheet and tip vortex cavitation often interact.
In the joint project entitled "Verbesserte Prognose der durch die Wechselwirkung zwischen Schicht- und Spitzenwirbelkavitation bedingten Druckschwankungen höherer Ordnung" (englisch: “Improved prognosis of the higher order pressure fluctuations caused by the interaction between sheet and tip vortex cavitation” (HiOcav for short), new knowledge is gained in an interdisciplinary cooperation between university and industrial project partners, which may be applied in the context of propeller design.
In the project, experimental investigations are carried out and the associated measurement technology is further developed. Together with numerical investigations of flow details, the phenomenological understanding of the interaction of the sheet and tip vortex cavitation should be improved. The findings should guide the development of efficient, numerical prediction methods.
The project is funded in the framework program “Maritime Technologien der nächsten Generation” (englisch “Next Generation Maritime Technologies”) of the Bundesministeriums für Wirtschaft und Energie (englisch Federal Ministry for Economic Affairs and Energy).
In the sub-project "Numerische Simulation der Kavitationsvorgänge an der Propellerblattspitze im Hinblick auf Druckschwankungen höherer Ordnung" (englisch "Numerical simulation of the cavitation processes at the propeller blade tip with regard to higher-order pressure fluctuations") (HiOsim for short), the Institute for Fluid Dynamics and Ship Theory conduct research to reveal tip-flow details and to develop numerical prediction methods. Among other things, further details of the flow are obtained from RANS simulations that cannot be measured in experiments. With a new, numerical model for the dynamics of the tip vortex cavitation and the coupling with an improved sheet cavitation model of the potential solver panMARE, an advanced tool for the prognosis of the occurring cavitation is developed. The further development of the sheet cavitation model and the integration of the new model for tip vortex cavitation including the coupling in panMARE are intended to improve the prognosis of higher-order pressure fluctuations.
Institute for Telecommunications and Chair for Optoelectronics and Photonic Systems at the Institute for General Electrical Engineering at the University of Rostock,
Institute for Fluid Dynamics and Ship Theory at the Hamburg University of Technology,
Shipbuilding Research Institute Potsdam SVA,
FORTecH Software GmbH,
ThyssenKrupp Marine Systems GmbH,
Otto Piening GmbH,
Mecklenburg Metallguss GmbH