Dynamic modeling of sail mounted hydroplanes system-part II: Hydroelastic behavior and the impact of structural parameters and free-play on flutter

Flutter of sail mounted hydroplanes system is a self-excited dynamic hydroelastic phenomenon due to an undesirable coupling occurring between the elastic structure and hydrodynamic flows. The flutter behavior depends on both structure parameters and free-play nonlinearities in the hydroplanes system. The free-play nonlinearity introduces persistent limit cycle oscillations (LCO) which can cause water noise, and it will have an undesirable effect on the concealment capability of marine vehicles. The impact of structure parameters and free-play of the hydroplanes systems on the hydroelastic stability is not fully understood and is an active area of research. In order to explore the fundamental nature of the hydroplanes system, the present paper, Part II of this work, focus on two aspects: (i) the analysis of the full-scale hydroplanes system hydroelastic response based on Computational Fluid Dynamics/Computational Structure Dynamics (CFD/CSD) two-way coupling method which verified by the AGARD 445.6 wing standard flutter model. Results show that the hydroplanes system hydroelastic response is completely symmetrical, and it proves Part I work, that is the full-scale system can be simplified as one hydroplane with a torsional spring. Additionally, (ii) the 2-DOF structural model and the Theodorsen's theory of hydroplanes system are used to get a better understanding of the structure parameters and free-play effect on linear/nonlinear flutter of the hydroplanes system. To validate the accuracy of the modeling predictions, the linear/nonlinear simulation in-home codes are compared with those theoretical and experimental reported in the existing literature, and good results within engineering error margins are obtained. Results show that structural parameters might effect on the classical flutter speed and LCO only occurred in low flow speed due to free-play.