Implementacija i validacija modela propagiranja zvučnih valova

master's thesis

• Title (english): Implementation and validation of acoustic wave propagation model
• Author: Adam Azenić
• Mentor: Hrvoje Jasak (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2016-03-25, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Zagađenje bukom negativno utječe na živote ljudi te su posljedice utjecaja buke na njihovo zdravlje često značajne. Zbog toga je predviđanje izvora zvuka te propagacije zvučnih valova sve aktualnija tema inženjera i znanstvenika. U ovome je radu provedena implementacija, verifikacija i validacija lineariziranih Eulerovih jednadžbi (eng. Linearised Euler Equations, skraćeno LEE), koje matematički opisuju propagaciju zvučnih valova. LEE su implementirane u jedinstveni rješavač (eng. solver), koristeći programski paket OpenFOAM-extend. Jednadžbe su riješene koristeći metodu kontrolnih volumena (eng. Finite Volume Method, skraćeno FVM). Verifikacija i validacija rješavača provedene su putem tri validacijska slučaja, uspoređujući s analitičkim rješenjima. Provedena je i studija kovergencija mreža kontrolnih volumena. Implementirana je pojednostavljena metoda za određivanje izvora zvuka koristeći podatke turbulencije iz RANS simulacije te je testirana na simulaciji dvodimenzionalnog vrtložnog sloja. Rezultati su pokazali da rješenja dobivena LEE rješavačem konvergiraju prema analitičkim rješenjima. Simulacija odbijanja zvučnog vala od zida pokazala je da numerički proračuni reflektiranog i nereflektiranog vala daju rješenja praktički jednake točnosti. Rezultati kasnijih vremenskih trenutaka sadrže kontaminirajuće valove koji su reflektirani od otvorenih granica domene proračuna zbog neadekvatih rubnih uvjeta korištenih u simulacijama. Može se zaključiti da je implementacija metode za propagaciju zvučnih valova uspješno provedena, što dokazuju rezultati tri validacijska slučaja. Pokazano je da se propagacija akustičnih valova u homegenom srednjem strujanju može s dovoljnom točnošću predvidjeti koristeći implementirani rješavač. Metodu za generiranje izvora zvuka treba poboljšati, što zajedno s implementacijom nereflektirajućih rubnih uvjeta ostaje zadatak za buduća istraživanja.

Abstract (english)

Noise pollution negatively influences the quality of people’s lives and the consequences on the health are often significant. Therefore, the problem of predicting the sound sources and propagation of acoustic waves is an everyday growing issue that the engineers and scientists encounter. In this thesis the implementation, verification and validation of the Linearised Euler Equa- tions (LEE), which govern the acoustic wave propagation, have been conducted. The LEEs have been implemented as a stand-alone solver, using OpenFOAM-extend C++ libraries. The system of LEEs has been discretised by using the conservative Finite Volume Method (FVM). Verification and validation of the solver have been carried out with three test cases, comparing the results with analytical solutions. The grid convergence study for the validation test cases has been carried out. The simplified method for the sound source prediction using RANS pre- dicted turbulence data has been implemented and tested on the simulation of noise generated by 2D mixing layer. Results have shown that the solutions obtained with the LEE solver converge towards the analytical solutions. Simulation of acoustic wave reflection off a wall has shown that the nu- merical predictions of the reflected and non-reflected wave give solutions of practically the same accuracy. Results for later time instants contain spurious waves, reflected off the open boundaries, due to inadequate boundary condition used in simulations. It can be concluded that the implementation of sound propagation method has been success- fully conducted, as evidenced by the results of three test cases. It is shown that the propagation of acoustic waves in an uniform mean flow can accurately be computed with the implemented solver. The method for the sound source generation needs improvements, what together with the implementation of a non-reflecting boundary condition remains a task for future research.

• Keywords: Računalna aeroakustika; linearizirane Eulerove jednadžbe; propagacija zvučnih valova; OpenFOAM-extend; metoda kontrolnih volumena
• Keywords (english): Computational Aeroacoustics; Linearised Euler Equations; Finite Volume Method; OpenFOAM-extend; acoustic wave propagation
• Language: croatian
• URN:NBN: urn:nbn:hr:235:925035
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-05-22 16:31:59