Reconstruction of the 3D hydrodynamics in a baffled stirred tank using Proper Orthogonal Decomposition

Abstract

In this work, the unsteady turbulent flow in a four-baffled stirred tank equipped with a Rushton turbine is computed with ANSYS FLUENT® using the sliding mesh technique. The POD algorithm is applied first to each mesh zone (fixed and rotating) and, in a novel and original way, to the full 3D CFD data without distinguishing between the stationary and rotating zones. The resulting modes cannot be regarded as spatial modes revealing the underlying flow structure. The POD results showed that 99.9% of the system variance is recovered with the first three modes. The reconstruction of the velocity field from these modes reveals the trailing vortices plus the mean flow. The accuracy of the POD reconstructed flow fields is quantified. The present work is the first evidence of a POD reconstruction of the unsteady turbulent flow performed over the entire 3D domain in a baffled stirred tank.