Session: 08-01-01 Waves and Loads

Paper Number: 79446

79446 - Investigation of Springing Responses to High Harmonics of Wave Loads by Direct Coupling Between CFD and FEM 

Springing of hull girder to very high harmonics of wave loads is investigated thoroughly using one-way and two-way direct coupling between Computational Fluid Dynamics (CFD) and Finite Element Method (FEM). A segmented barge is chosen as a subject model, in which each segment is connected to a backbone. The springing response of the ship model to very high harmonics was reported in the tank tests by the present authors. For CFD a commercial software STAR-CCM+ and for FEM modeling LS-DYNA is used. Semi-Implicit Pressure Linked Equations (SIMPLE) are used to achieve an implicit coupling between pressure and velocity. Overset mesh approach is chosen to model the dynamic motion of the hull in STAR-CCM+. The structural domain has been modeled using the three-dimensional Highues-Liu type shell elements with hull segments and a backbone. Newmark-beta explicit solver has been used to solve the FE domain in the time domain. The coupling platform for exchanging related information to capture hydro-elastic behavior is developed separately by the authors. The Inverse Distance Weighting (IDW) method has been chosen to exchange the information between two separate domains. As the direct coupling is expensive but advantageous, the coupling is developed focusing on the number of inner iterations at each timestep required for a particular simulation. First, the numerical methods are compared for rigid body motions, then flexible behavior is studied. In the one-way coupling, the effect of added mass associated with the springing is considered manually by adjusting the total mass of the body. However, in the case of two-way coupling, such manual adjustment is not necessary as the added mass effect is directly considered in the simulation. In the present paper, the comparison between one-way and two-way coupling with benefits, drawbacks of individual methods are discussed in detail. Most of the existing literature is mainly focused on the lower order harmonics for the springing phenomenon, however, in this paper possible case of 14th order harmonics is discussed.

Presenting Author: Sumit Kumar Pal Osaka University

Authors:

Sumit Kumar Pal Osaka University
Kazuhiro Iijima Osaka University