Naslov
Implementacija i validacija spektralne valne metode viših redova za numeričke simulacije površinskih valova
(Analysis and Implementation of the Harmonic Balance Method in Computational Fluid Dynamics)

Autori
Gatin, Inno

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, diplomski rad, diplomski

Fakultet
Fakultet strojarstva i brodogradnje

Mjesto
Zagreb

Datum
15.07

Godina
2015

Stranica
62

Mentor
Jasak, Hrvoje

Ključne riječi
spektralna metoda viših redova ; nelinearni površinski valovi ; računalna dinamika fluida
(higher order spectral method ; nonlinear surface wave propagation ; computational fluid dynamics)

Sažetak
In this work Higher Order Spectral (HOS) method for three–dimensional nonlinear water wave propagation is implemented and validated. Implementation is conducted in a specialised Computational Fluid Dynamics (CFD) open–source software OpenFOAM. HOS is a pseudo–spectral method for solving nonlinear differential equations, which describe free surface wave phenomena. The pseudo–spectral approach enables fast calculation of surface wave problem with arbitrary number of wave components. The order of nonlinearity of the HOS calculation is arbitrary, making this method highly flexible. Multiple wave components, or harmonics, can reproduce a realistic sea state. The problem is divided into a spectral and a physical part, where the projection between the spectral and physical space is performed via Fourier transforms. Large number of wave components may be used due to high efficiency of the FFT algorithm. Mathematical model of the HOS method is outlined and its numerical model is shown in detail. The reason for implementation of HOS method is its coupling with high–fidelity CFD simulations regarding wave–structure interaction. The capability of low–cost, long time evolution of input spectra can be used to obtain realistic freak waves. Validity of the implemented algorithm is verified on three test cases. The first test case consists of nonlinear propagation of a monochromatic wave using HOS compared with the analytical solution. The second test case demonstrates the ability of accurate wave spectrum propagation by comparing the result with viscous two–phase simulation. In the third test case emergence of Benjamin–Feir instabilities in monochromatic wave train is observed. Finally, CFD simulations of extreme wave are presented. Extreme wave is initialized using HOS solution.

Izvorni jezik
Hrvatski

Znanstvena područja
Brodogradnja

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