Wing-Wake Interaction and its Proper Orthogonal Decomposition Zongxian Liang 1 , Haibo Dong 2 and Hui Wan 3 Department of Mechanical & Materials Engineering, Wright State University, Dayton, OH 45435 Philip Beran 4 Air Force Research Laboratory AFRL/RBSD, BLDG 146, 2210 EIGHTH ST WPAFB, OH 45433 Mingjun Wei 5 Department of Mechanical and Aerospace Engineering, New Mexico State University, Las Cruces, NM 88003 Direct numerical simulation (DNS) of tandem wings in pitching and plunging motion is conducted. The POD-Galerkin projection for a fixed, high angle of attack flat plate is performed using two algorithms which differ in the method of pressure processing. It has shown the importance of pressure correction in terms of the reduced prediction error. POD on pitching and plunging wings has shown that most of energy (95%) is contained by the first six modes. However, the first two modes only account for 60% of energy in tandem wings, in contrast to 80% in the case of single wing. It also shows the effectiveness of POD method in a system of two-dimensional flapping tandem wings. Nomenclature   POD base element of velocity   POD base element of pressure   Prediction error   Velocity snapshot   Mean velocity over snapshots  Exact velocity field   Fluctuating velocity field   Mean velocity field   Velocity field predicted by Galerkin projection  Mean pressure over snapshots 1 Ph.D Student, AIAA student member liang.5@wright.edu. 2 Assistant Professor, AIAA senior member, haibo.dong@wright.edu. 3 Research Scientist, AIAA member, hui.wan@wright.edu 4 Principle Aerospace Research Engineer, AIAA associate fellow, Philip.Beran@wpafb.af.mil. 5 Assistant Professor, AIAA senior member, mjwei@nmsu.edu. 28th AIAA Applied Aerodynamics Conference 28 June - 1 July 2010, Chicago, Illinois AIAA 2010-5084 Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.