Numerical Analysis of Rocket Launch Acoustics
Open Access
- Author:
- Yenigelen, Evren
- Graduate Program:
- Aerospace Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 28, 2021
- Committee Members:
- Daniel Haworth, Outside Field Member
Kenneth Brentner, Major & Minor Field Member
Philip Morris, Chair & Dissertation Advisor
Victor Sparrow, Outside Unit Member
Amy Pritchett, Program Head/Chair - Keywords:
- jet noise
rocket launch
aeroacoustics
computational fluid dynamics
ffowcs williams and hawkings analogy
noise reduction - Abstract:
- Rocket launch acoustics are an important part of the launch vehicle design process. Using numerical simulations to estimate the flow and acoustic properties have become increasingly viable with the improvements in computational capabilities. In this study, a hybrid methodology combining computational fluid dynamics (CFD) and computational aeroacoustics (CAA) is used for rocket launch acoustic calculations. The objective of this thesis is to estimate the noise levels at desired locations and ultimately develop a method to decrease these noise levels. A CFD code called "CHOPA" (Compressible High Order Parallel Acoustics) is used for flow simulations. Unsteady Reynolds-averaged Navier-Stokes (URANS) equations are solved using a modified version of the Detached Eddy Simulation (DES) approach to predict the noise sources in the source region. The noise at far-field and near-field observers is calculated by a Ffowcs Williams and Hawkings analogy based code called PSJFWH (Permeable Surface Jet noise prediction with the Ffowcs Williams and Hawkings theory). Baseline calculations include a free-jet simulation, a simulation of a jet impinging on a flat plate, and a jet impinging on an angled plate. Noise levels are predicted close to the nozzle and in the far-field. Using the results gathered from these simulations, a wall with a circular cut-out is placed between the nozzle exit and the impingement plates as a noise reduction method. The aim of this technique is to block the upstream traveling acoustic waves while not disturbing the jet flow significantly. The mesh for the new configurations are produced by removing the grid points that correspond to the wall with a cut-out, while keeping the mesh structure and grid sizes the same. Different acoustic data extraction surfaces are used for different configurations to make sure that all the acoustic sources are included in the computations. The results show that the noise reduction method used in this thesis attenuates the noise levels significantly at both near-field and far-field observers. However, placing a wall with a cut-out between the nozzle exit and the impingement plates creates new acoustic sources that result in high amplitude peaks in the acoustic spectra. The investigations show that these peaks are related to feedback loops that are speculated to be closed by the acoustic waves that are produced by the interaction of the jet flow with the cut-out edges and acoustic waves being reflected by the wall with a cut-out.