Development of a Generic Surface Mapping Algorithm for Fluid-Structure-Interaction Simulations in Turbomachinery

Abstract

The practice of three dimensional time accurate computational fluid dynamics (CFD) methods and the use of computational structural mechanics solver (CSM) are essential for the turbomachinery design process. New technologies like the blisk design for aeroengines or the increased requirements on flexible loading of stationary gas or steam turbines for power generation makes a tight integration and coupling of both CFD and CSM tools indispensable. Especially the effects of fluid-structure-interaction (FSI) are an important field for investigations even in early stages of the modern design and optimization process. The DLR in-house CFD code TRACE is a time accurate Reynolds-averaged Navier-Stokes-solver including a time linearized module developed for the efficient investigation of FSI phenomena. The linear solver allows to reduce response times for flutter calculations by up to two orders of magnitude compared to nonlinear time accurate calculations. Combined with the CSM solver CalculiX a process chain for aeroelastic design optimization for turbomachinery is established. An essential ingredient of this process is the mapping of surface displacements computed by the CSM solver onto the mesh of the CFD solver. A mapping algorithm has been implemented which does not rely on topology information, e.g. the position of the leading and trailing edge of a blade, but uses geometric data, i.e. vertex coordinates and surface elements, only. The focus of this article will be on the algorithms for a topology independent mapping including the approximation of the structural model and the handling of complex mode shapes. The application of this algorithm to a turbine vane and high pressure turbine blade cluster is presented. The process for flutter investigations is shown for a high pressure ratio single stage fan.