Generalised implementation of Low-Mach preconditioning for arbitrary three-dimensional geometries

Kurzfassung

Turbomachinery flows involves a wide range of compressible and incompressible flow regimes. In the design process the application of various solvers for different flow speeds is cost- and time-intensive and mostly unattractive. Therefore, low Mach preconditioning methods have become a powerful tool to improve the accuracy of the solution of the Navier-Stokes equations obtained by compressible solvers at low speeds, whilst accelerating convergence. Particulary in three-dimensional problems, such as in turbomachinery design practice preconditioning is an extremely difficult task, which has not been extensively treated in the literature. In this work an enhanced preconditioning method is presented in its full three-dimensional formulation and its implementation in the DLR-code TRACE discussed. Computations of classic academic testcases (e.g. GAMM bump series, flow in a cavity) are presented. The flow in a labyrinth seal of a LP gas turbine has also been investigated with excellent results, which will be also briefly illustrated.