Les Investigation of Coherent Structures in Boundary Layers and Wakes. Volume I: Investigation of Coherent Structure in an Attached Shear Layer

摘要

Purpose of the present investigation was to assess the feasibility of simulating and studying coherent structures in turbulent shear layers, making use of Large Eddy Simulations (LES). The current investigation has been performed across a rather wide range of simulated flows and LES implementations, starting from an established and validated structured LES code based on finite differences and cartesian grids ending to an unstructured LES code under development. The use of the unstructured approach was considered necessary whenever complex geometries have to be analyzed, which cannot be handled by the structured code, regardless its advanced features (like multi-domain approach). The unstructured LES code was developed in the flanie of current GRANT, and it has undergone validation. The structured LES code, which had afready validated over a wide range of flow configurations, was used to analyze the wake behind an obstacle, attempt which was not made before. Extensive studies were needed in the attempt to validate to code for this case. Given the wide scope of present report and the mass of data available from different LES codes, flows and structures, the work has been spit between two work groups, the one devoted to the structured LES and the one devoted to the unstructured LES. In this flame it was found more practical to sub-divide the full report in three volumes: Volume I-- Investigation of Coherent Structures in an Attached Shear Layer; Volume II - -Wake around square Cylinder; Volume III -- Unstructured LES.