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Brizzolara Stefano

CFD Calculation of the Hydrodynamic Characteristics of Planing Hulls


Dipartimento di Ingegneria navale e Tecnologie marine, Università degli Studi di Genova


Dipartimento di Ingegneria navale e Tecnologie marine, Università degli Studi di Genova


Dipartimento di Ingegneria navale e Tecnologie marine, Università degli Studi di Genova


Dipartimento di Ingegneria navale e Tecnologie marine, Università degli Studi di Genova

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     Last modified: November 26, 2007

Abstract
Paper presents the main results achieved by the hydrodynamic CFD group of the University of Genova for the CFD modeling of the hydrodynamic characteristics of planing hulls. The commercial software Starccm+ has been used for the presented studies which are currently ongoing and under continuous evolution. The hydrodynamic problem of the external flow on the hull is of course complicated by the quite rapid evolution of the free
surface along the hull, with the formation of forward jet spray and a highly curved free surface shape at bow, the large pressure gradients in the stagnation area on the bottom, the sharp flow separation along the chines downstream, and the formation of the wavy free surface at stern. The ability of the code to accurately define all these physical phenomena has been tested and validated in the studies. Numerical results are presented and discussed in the paper in terms of distributed hydrodynamic parameters, such as wave heights, pressure and wall strain rates distribution along the hull and where possible compared with available experimental results on standard hull shapes taken from systematic model series of experiments in
towing tanks. Global hydrodynamic parameters such as the lift, drag and moment coefficients numerically predicted by the RANSE solver for the hull at given speed and fixed dynamic attitude are compared with the available measurements done for scaled models tested in towing tank.
Particular attention is also given to the solution of the steady dynamic attitude (trim and sink) prediction through the numerical simulations. In fact, in case the hull is left free to move in the longitudinal plane, with respect to the initial static attitude (at rest), it will experience a different dynamic attitude at high speeds, very much depending on the running speed. The lift trim moment and finally induced resistance experienced by the hull
are largely dependent from the dynamic attitude which in turn are influenced by the hull shape, so the accurate prediction of the global forces and moments at high speed is essential for the design of the hull. The validation of the results show a very good correlation with available experimental results, at least for engineering purposes, in a field (that of planing hulls) where at present the design practice relies mainly in expensive and time consuming model tests or very approximate prediction methods based on simplified semi-empirical theories.

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