Numerical simulation of a short flexible pipe subject to forced motion and vortex-induced vibration

A series of numerical simulations about a small scale (aspect ratio:63.2) flexible pipe undergoing forced harmonious oscillation and vortex-induced vibration (VIV) have been taken into account. The wake hydrodynamics and pipe deformation were accomplished by ANSYS MFX solution strategy designed for fluid-structure interaction (FSI) problem with well-performed LES model. The configuration of structured mesh, multi-domain design, different mesh stiffness admeasured by User Fortran ensured that the numerical task was competent to deal with large deformation related to this case. The introduction of instantaneous amplitude definition and modeless component decomposition method (Chen and Kim, 2008) was helpful to reveal much more information from modal analysis. Most results from numerical simulation are generally consistent with those from model test (Choi and Hong, 2000) via the comparison between them. As supplementary to model test, visualization of the vortex wake was also provided. It has been proved that the forced oscillation doesn't only excite a complicated dumbbell-like wake pattern around the outer thimble, but also results in inner flow inside the PVC pipe. The velocity of the inner flow increases with the frequency of forced oscillation.