Perspectives of LES in Turbomachinery Design

Three-dimensional simulations have become widespread in the analysis of turbomachinery flows over the past decade. Air-intake configurations, blade passages, internal cooling systems, or combustor flows are all investigated using advanced CFD techniques today. However, while the value of CFD for basic research is out of question, its use in the design process of turbomachinery components has remained very limited. Steady 3D computations are often done for final design assessment only, and unsteady methods like uRANS and LES are hardly employed at all. Given the broad design experience already available in the industry today, uRANS and LES are likely to be employed in future design efforts only where flow unsteadiness plays a critical role and where its effects cannot readily be predicted with sufficient accuracy using simplified correlations or steady-state computations. As an example, the present paper discusses a complex swirl-combustor application where LES or uRANS are needed in order to capture large-scale instabilities, which have a substantial impact on the mixing properties of the flow.