engleski

Harmonic balance method for incompressible turbomachinery applications

Harmonic Balance method for non–linear, temporally–periodic turbulent incompressible flows is presented in this work. Assumption of time periodic flow allows us to formulate 2n+1 coupled steady state problems using Fourier series expansion. Solving 2n+1 equations yields quasi–steady state flow fields with transient features which depend on the number of harmonics, n. The main advantage of the Harmonic Balance is CPU time decrease compared to transient simulation, which shall be presented in detail. Higher number of harmonics used will increase accuracy, but also prolong the simulation time. The implementation is carried out in a second–order accurate, polyhedral Finite Volume framework developed within foam–extend, a community driven fork of the OpenFOAM toolkit. The Harmonic Balance method is validated on canonical test cases and will be applied on turbomachinery test cases. 2D and 3D pumps and turbines will be simulated and compared with available experimental data. The comparison will also include CFD results obtained with Multiple Reference Frame (MRF) steady state approach, conventional transient simulation and Harmonic Balance. To investigate the potential of the Harmonic Balance method, global pump parameters shall be compared. Furthermore, local flow features such as pressure distribution on blades, flow instability and detailed flow features will also be examined.

harmonic balance method; periodic flows; openFoam; fourier expansion; turbomachinery

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