Three-Dimensional Investigations for Axial Turbines by an Implicit Unstructured Multi-Block Flow Solver

Abstract

An unstructured 3D implicit approach (HybFlow) is briefly described for gas turbine applications. The numerical approach is based in an upwind finite volume scheme with an implicit time marching algorithm. The linear solver is GMRES with right preconditioning obtained by the ILU(0) incomplete factorization. A two k-w turbulence model is considered for viscous flows. The new multiblock extension of the code is here considered for improving the computational efficiency of the basic procedure in view of the application to complex 3D geometries. Particular concern has been placed in the new approach for memory saving while keeping at the same time a great geometrical flexibility and grid transparency. The strategy developed is therefore described considering the whole process and all phases required in the solution of internal flows. Both memory and CPU time costs are addressed to verify the performances of the multiblock scheme as also computational accuracy for 2D tests. The flow conditions investigated range from the low speed regime up to the transonic one to prove the accuracy of the approach using hybrid unstructured configurations. Finally the application to the transonic cooled annular IGV blade row is considered to assess the multiblock strategy for a 3D case.