Session: 06-15-01 Unsteady Hydrodynamics, Vibrations, Acoustics and Propulsion

Paper Number: 79699

79699 - Noise Generation and Propagation From Flapping-Foil Thrusters Used for Marine Propulsion 

Biomimetic flapping-foil thrusters are shown to operate efficiently, offering the desirable levels of thrust required for the propulsion of a small vessel or an Autonomous Underwater Vehicle (AUV). Extended review of hydrodynamic scaling laws in aquatic locomotion and fishlike swimming can be found in Triantafyllou et al [1]. Flapping-foil configurations have been investigated both as main propulsion devices and for augmenting ship propulsion in waves; see also the recent review by Wu et al [2].  An important aspect of the advantages offered by the biomimetic propulsion systems is also the reduction of noise generation compared to marine propellers. Many recent studies have shown that underwater-radiated noise from commercial ships may have both short and long-term negative consequences on marine life, especially marine mammals and thus technical guidelines to minimize the introduction of incidental noise were necessary; see IMO [3].

In the present work, biomimetic systems applied to small vessel or AUV propulsion are studied along with their comparative performance to standard marine propellers regarding noise reduction [4]. A combined 3D flow-acoustic analogy method is proposed for the calculation of the foil noise. A three-dimensional model of the lifting flow, based on quadrilateral boundary elements, around the dynamic foil is presented [5]. Subsequently, the Ffowcs-Williams and Hawkings [6] equation (FW-H) analogy is employed for the far-field noise propagation. The pressure field and the forces produced by the wing are assumed to act as dipole and monopole terms in the right-hand side of the FW-H equation, respectively. The proposed time-domain numerical scheme based on Finite Differences incorporates the free-surface as well as additional boundaries acting as scatterers. Finally a PML (perfectly-matched layer) is employed for the approximation of open boundaries.

1.Triantafyllou M.S., Hover F.S., Techet A.H., Yue D.K.P., 2005, Review of hydrodynamic scaling laws in aquatic locomotion and fishlike swimming, Journal of American Society of Mechanical Engineers Vol.58, 226.

2.Wu, X., Zhang, X., Tian, X., Li, X., Lu, W., A review on fluid dynamics of flapping foils. Ocean Engineering Vol.195,  2020, 106712.

3. IMO 2004. Guidelines for the Reduction of Underwater Noise from Commercial Shipping to Address Adverse Impacts on Marine Life – non mandatory technical advices, International Maritime Organization  (2014) MEPC.1/Circ.833.

4. Belibassakis K.A. & Politis G.K.. Hydrodynamic performance of flapping wings for augmenting ship propulsion in waves. Ocean Engineering Vol.72, 2013, pp.227 – 240.

5. Belibassakis K., and Malefaki Iro., Noise generation and propagation by biomimetic dynamic – foil thruster, Euronoise 2021, 25 – 27 October 2021, Madeira, Portugal.

6. Ffowcs Williams, J. E. and Hawkings, D. L., Sound Generated by Turbulence and Surfaces in Arbitrary Motion, Philosophical Transactions of the Royal Society, Vol. 264, No. 1151, 1969, pp. 321–342.

Presenting Author: Iro Malefaki National Technical University of Athens

Authors:

Iro Malefaki National Technical University of Athens
Angeliki Karperaki National Technical University of Athens
Kostas Belibassakis National Technical University of Athens