Computational Modeling of Dynamic Planing Forces
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Waid and Kermeen completed static experiments using cylinders planing on free liquid surfaces. Their data represents the foundation for characterization of forces imparted on a planing cylinder. Several authors have derived simplified or analytic formulations of the impact forces on a cylindrical body interacting with a curved free surface. This article presents a Computational Fluid Dynamics (CFD) based approach to modeling such dynamic forces. A curved free surface is generated in a CFD water tunnel by ventilating a gas filled wake aft of a curved deflector. The computational planing cylinder is then repeatedly plunged into the curved free surface. The CFD force record is used to reveal the dynamically added mass of the cylinder. Results indicate that the modeling approach taken accurately replicates the complex physics of the dynamic motion of the cylinder interacting with the surface. When added mass of the dynamic interaction is significant, a phase difference appears between the cylinder position and force time histories. Phase offsets between cylinder position and force have been observed across different plunging frequencies, suggesting a significant added mass effect. With the success of this approach (obtaining dynamic forces based on CFD), reduced-order models of the added mass can be created.