Radiation and Exciting Forces of Axisymmetric Structures with a Moonpool in Waves
- 57 Downloads
A highly efficient “hybrid integral-equation method” for computing hydrodynamic added-mass, wave-damping, and wave-exciting force of general body geometries with a vertical axis of symmetry is presented. The hybrid method utilizes a numerical inner domain and a semi-infinite analytical outer domain separated by a vertical cylindrical matching boundary. Eigenfunction representation of velocity potential is used in the outer domain; the three-dimensional potential in the inner domain is solved using a “two-dimensional” boundary element method with ring sources and ring dipoles to exploit the body symmetry for efficiency. With proper solution matching at the common boundary, both radiation and diffraction potentials can be solved efficiently while satisfying the far-field radiation condition exactly. This method is applied to compute the hydrodynamic properties of two different body geometries: a vertical-walled moonpool with a bottom plate that restricts the opening and a spar-like structure with a diverging bottom opening inspired by designs of floating Oscillating Water Columns. The effects of the size of the bottom opening on the hydrodynamic properties of the body are investigated for both geometries. The heave motion of the floater as well as the motion of the internal free surface under incident wave excitation are computed and studied for the spar-like structure.
KeywordsMoonpool Spar Oscillating water column Potential flow Hybrid method Axisymmetric body
Partial support for this work was provided by the American Bureau of Shipping Endowed Chair in Ocean Engineering held by the first author.
- Chau FP, Yeung RW (2012) Inertia, damping, and wave excitation of heaving coaxial cylinders. In: Proceedings of the ASME 31st international conference on ocean, offshore and arctic engineering. Rio de Janeiro, Brazil, pp 803–813. https://doi.org/10.1115/OMAE2012-83987
- Haskind MD (1957) The exciting forces and wetting of ships in waves. Izv Akad Nauk SSSR, Otd Tekh Nauk 7:65–79Google Scholar
- Kristiansen T, Sauder T, Firoozkoohi R (2013) Validation of a hybrid code combining potential and viscous flow with application to 3D moonpool. In: Proceedings of the ASME 2013 32nd international conference on ocean, offshore and arctic engineering. Nantes, France, V009T12A029. https://doi.org/10.1115/OMAE2013-10748
- Lee M-Y (1985) Unsteady fluid-structure interaction in water of finite depth. PhD thesis, University of California, BerkeleyGoogle Scholar
- Matsui T, Kato K (1991) The analysis of waveinduced dynamics of ocean platforms by hybrid integral equation method. Int J Offshore Polar Eng 1(2):146–153Google Scholar
- Wehausen JV (1971) The motion of floating bodies. Ann Rev Fluid Mech 3(1):237–268. https://doi.org/10.1146/annurev.fl.03.010171.001321 CrossRefzbMATHGoogle Scholar
- Wehausen JV, Webster WC, Yeung RW (2016) Hydrodynamics of ships and ocean systems, lecture notes for course ME241. University of California, Berkeley. RevisedGoogle Scholar
- Yeung RW (1975) A hybrid integral-equation method for time-harmonic free-surface flow. In: Proceedings of the first international conference on numerical ship hydrodynamics. Gaithersburg, Maryland, USA, pp 581–607Google Scholar
- Yeung RW (1985) A comparative evaluation of numerical methods in free-surface flows. In: Hydrodynamics of ocean-wave utilization, IUTAM symposium, Lisbon, Portugal. Springer-Verlag, Berlin, pp 325–356Google Scholar