Proper Orthogonal Decomposition of the pressure field in bluff bodies

Proper Orthogonal Decomposition (POD) is used in fluid mechanics to compute optimal basis to span the desired subspace and extract coherent structures in the flow field. POD analysis of the pressure field in bluff body flow can provide insight to the pressure distribution on the surface of the structure. In this paper, we simulate the flow past a square cylinder in confined channel and record the snapshot data of the flow field over one shedding cycle. We compute the POD basis functions from the snapshots and their distribution in the domain. The dominant pressure modes are integrated on the surface to determine their contribution in the lift and drag components. Interestingly, the odd and even pairs of the pressure POD modes contribute to the lift and drag on the cylinder, respectively. Key contribution is that Galerkin expansion of the lift and drag coeffients is independent of the space since pressure POD modes are integrated over the surface of the cylinder.