Prediction of Tonal Underwater Noise Pattern from Cavitating Propellers with Special Attention to Ice Cover Effects

• Autorzy: Streckwall H. , Bretschneider H.
• Języki publikacji: EN

Abstrakty

EN

To predict underwater noise spectra associated to regular occurrence of propeller cavitation we have extended an existing method [1] (used for the prediction of fluctuating hull pressures) to become applicable for effects that are linked to a finite speed of sound. In [2] an intermediate approach was realized where (besides the hull) far field boundaries were introduced but the incompressible flow assumption was kept. However compressibility effects become noticeable in the far field, which may be judged to start at some 2-3 propeller-diameters distance from the centre of the cavitation events, if we confine to emissions at 1st- 4th blade frequency. It was a logical continuation of our former efforts to realize a compressible flow model and integrate the propeller as a noise source. Having increased the functionality of our approach by referencing the speed of sound, the precision of the method was also somehow reduced. In our former approach, like in comparable approaches (see for instance [3] and [4]), the singularity system generating the near field propeller induced pressures involved various sources and vortices distributed on the propeller blades. With our current compressible approach this complexity was dropped, as a single point source substitutes the cavitating propeller. Such a simplification correlates with the assumption, that the monopole character of a noise source is decisive for the far field noise levels. In this contribution we outline the steps characterizing the procedure for predicting tonal underwater noise from cavitating propellers. In the first step a Vortex Lattice Method (VLM) is used to access the cavitation pattern on the propeller with special focus on the cavity volume attached to one blade. The second step accumulates the distributed cavities to establish a fluctuating point source of equivalent far field noise characteristic. As relevant limits the hull, the free surface, the sea bottom and an ice cover are introduced. Using finally a Boundary Element Method (BEM) approach the relevant noise characteristics are derived, accounting for external boundaries and for the finite speed of sound. The results provided here are focused on a comparative treatment of different scenarios, mainly addressing ice cover effects at finite the water depth.

Słowa kluczowe

EN

cavitation; underwater noise; ice-covered areas

• Wydawca: Gdańsk University of Technology, Faculty of Ocean Engineering & Ship Technology
• Czasopismo: Polish Maritime Research
• Rocznik: 2014
• Tom: nr 4
• Strony: 35--40
• Opis fizyczny: Bibliogr. 5 poz., rys.

Twórcy

autor

Streckwall H.

• Hamburg Ship Model Basin, Bramfelder Strase 164, Hamburg, Germany

autor

Bretschneider H.

• Hamburg Ship Model Basin, Bramfelder Strase 164, Hamburg, Germany

Bibliografia

• 1. Streckwall, H.: Numerical Models for Cavitationand Propeller Pressure Fluctuations. Jahrbuch der Schiffbautechnischen Gesellschaft, 97th Edition; pp 44-49, Springer-Verlag Berlin and Heidelberg GmbH V, 2003
• 2. Streckwall, H., Bretschneider, H.: A Study on propeller noise emission with special attention to the influence of an ice coverage and finite water depth, 2nd Intern. Symp. on Marine Propulsors, SMP’11, Hamburg, Germany, 2011
• 3. Breslin, J.P., Van Houten, R.J., Kervin, J.E., Johnson, C.- A.: Theoretical and experimental propeller-induced hull pressures arising from intermittent blade cavitation, loading and thickness, Soc. Nav. Archit. Mar. Eng. Trans. 90; 111-151, 1982
• 4. Kanemaru, T., Ando, J.: Numerical analysis of cavitating propeller and pressure fluctuation on ship stern using a simple surface panel method ’SQCM’, SMP’11, Hamburg, Germany, 2011
• 5. Shin, H.-J., Lee, J.-S. ,Lee, K.-H., Han, M.-R.,Hur, E.-B.. Shin, S.-C: Numerical and experimental Investigation of conventional and un-conventional preswirl duct for VLCC’, Int. Journ. of Naval Archit. and Ocean Engin., volume 5, issue 3, 2013, Pages 414-430.