Research Article Computation of Flow Past an In-Line Oscillating Circular Cylinder and a Stationary Cylinder in Tandem Using a CIP-Based Model Yingnan Fu, 1 Xizeng Zhao, 1,2 Xinggang Wang, 2 and Feifeng Cao 3 1 Ocean College, Zhejiang University, Hangzhou 310058, China 2 State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing Hydraulic Research Institute, Nanjing 210029, China 3 Institute of Harbor-Channel and Coastal Engineering, Department of Civil Engineering, Zhejiang University of Technology, Hangzhou 310014, China Correspondence should be addressed to Xizeng Zhao; xizengzhao@gmail.com Received 13 April 2015; Revised 21 May 2015; Accepted 27 May 2015 Academic Editor: Ming Zhao Copyright © 2015 Yingnan Fu et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Viscous fow past an upstream in-line forced oscillating circular cylinder with a stationary cylinder downstream at Reynolds number of 100 is investigated using a CIP model. Te model is established in a Cartesian coordinate system using a high-order diference method to discretise the Navier-Stokes equations. Te fuid-structure interaction is treated as a multiphase fow with fuid and solid phases solved simultaneously. An immersed boundary method is used to deal with the fuid-body coupling. Te CFD model is frstly applied to the computation of fow past a fxed circular cylinder for its validation; then fow over two stationary tandem cylinders is investigated and good agreements are obtained comparing with existing ones. Computations are then performed with fow past two tandem cylinders with an upstream in-line oscillating cylinder with a small spacing =2. Considerable attention is paid to the spectrum characteristics and vortex modes. 1. Introduction Flow over multiple bluf bodies is one of the classical issues in fuid mechanics. It is of great importance in engineering applications, such as heat exchangers, adjacent tall buildings, and piles of ofshore platforms. Te interaction between the multiple bodies and the wake is much more complicated than that of fow past a single body. Te tandem arrangement is one of the simplest confg- urations of the multiple bluf bodies. Extensive experimental and numerical studies have been reported about fow past two stationary tandem circular cylinders. Zdravkovich (1977) [1] revealed a discontinuous “jump” at some critical spacing in his measurements and found the discontinuity is caused by the abrupt change from one stable fow pattern to another at the critical spacing. Li et al. (1991) [2] utilized a fnite element program to simulate fow past two tandem circular cylinders at diferent intervals for  = 100. Discontinuity changes in the fow pattern, the Strouhal number, and the pressure distribution were detected. Mittal et al. (1997) [3] used a fnite element formation to simulate three confgurations at  = 100 and 1000. It was observed that the fow characteristics depend strongly on the arrangements of the cylinders and the Reynolds number. Meneghini et al. (2001) [4] presented the results of fow around tandem circular cylinders for Reynolds number of 200. Vorticity contours and force tine histories were displayed. Jester and Kallinderis (2003) [5] employed a second-order upwind scheme to investigate this problem. Qualitative and quantitative comparisons were made with published experimental data. Te mean and fuctuating lif and drag coefcients were recorded for center-to-center cylinder spacings between 2 and 10 diameters in Sharman et al. (2005) [6]. Results showed that the critical spacing was between 3.75 and 4 diameters. Mussa et al. (2009) [7] applied the LBE (Lattice Boltzmann Equation) method with MRT (multiple relaxation time) to simulate the fow past Hindawi Publishing Corporation Mathematical Problems in Engineering Volume 2015, Article ID 568176, 9 pages http://dx.doi.org/10.1155/2015/568176