Naslov
Harmonic Balance Method for Turbomachinery Applications

Autori
Cvijetić, Gregor ; Jasak, Hrvoje

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Second Annual PhD Workshop, Book of Abstracts / - Zagreb : Fakultet strojarstva i brodogradnje Sveučilišta u Zagrebu, 2016, 18-18

ISBN
978-953-7738-41-9

Skup
Second Annual Phd Workshop

Mjesto i datum
Zagreb, Hrvatska, 01.07.2016

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

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

Sažetak
Harmonic Balance method for non--linear, temporally--periodic incompressible flows is presented in this work. Assumption of a time periodic flow allows us to formulate 2n+1 coupled steady state problems using Fourier series expansion. By solving 2n+1 steady state problems, we obtain a flow field with transient effects. Fourier series expansion is the core of the Harmonic Balance method, therefore the accuracy of the method depends on the number of specified harmonics, n. Moreover, the accuracy of the method also depends on the periodic nature of the problem. The Harmonic Balance method will be presented on turbomachinery test cases and compared to conventional steady-state and transient solvers. The method was previously successfully validated and verified on pitching airfoil and pitching wing test cases. Its applications will now be further extended to include moving mesh and multiple frequencies, and presented on turbomachinery cases. Harmonic Balance results will first be compared against conventional steady state solver using Multiple Reference Frame (MRF) approach. Head, efficiency and power will be compared, as well as the flow field details at specific locations of interest. Additionally, Harmonic Balance method will be compared against conventional transient solver, discussing the accuracy and simulation speed—up. The accuracy and simulation speed-up of the Harmonic Balance method will be presented for the well established 2D ERCOFTAC centrifugal pump geometry. Steady-state solution with MRF and transient solution will be compared against several Harmonic Balance solutions with different number of harmonics used. Higher number of harmonics used provide more accurate solution but yield longer 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 should provide an efficient compromise between accuracy and efficiency as it is capable of capturing transient flow features, while still providing a significant CPU time decrease. Steady state methods lack transient effects, but provide reasonable CPU time savings. On the other hand, transient simulations usually require unacceptably large computational resources in order to achieve periodic steady—state solution.

Izvorni jezik
Engleski

Znanstvena područja
Strojarstvo

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