Pseudospectral Matrix Element Modeling for Flow Past a Long Flexible Cylinder

Ming-Jyh Chern*, Jhe-Ming Lin

Department of Mechanical Engineering, National Taiwan University of Science and Technology

The present study simulates the complex oscillation of a long flexible cylinder. An in-house numerical model was developed using pseudopsectral methods coupled with the direct-forcing immersed boundary (DFIB) method to investigate this phenomenon. The domain decomposition method and coordinate transformation were also applied to optimize the proposed numerical model. The model was validated first by simulations of flow through a fixed cylinder in a free stream. The preciseness and convergence analysis are presented in the validation section. The domain decomposition method was used to divide the computational domain into smaller domains. A solid body can be identified more precisely using the adopted PSME-DFIB model. This model was used to simulate the flow-induced vibration of an elastically mounted rigid cylinder. The variation of vibration frequency and maximum amplitude with respect to Reynolds number and reduced velocity was investigated in the lock-in region and compared against published results. When solids move through grids, the coordinate transformation can eliminate noise in the resultant force, as determined by the numerical integral. In addition, the in-house model was used to investigate the flow-induced vibration of an infinitely long flexible cylinder at various wavelengths, cylinder tensions and lower Reynolds numbers. A short-wavelength cylinder was considered due to the feasibility of simulations. Periodic boundary conditions were utilized. The effects of cylinder vibration on the flow patterns were also explored in detail.

Keywords:Pseudospectral matrix element method (PSME), direct-forcing immersed boundary method (DFIB), domain decomposition, coordinate transformation, flow-induced vibration

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