Acoustics of Ducted Rotors

Author:

Zentichko, Jacob S

Graduate Program:

Aerospace Engineering

Degree:

Master of Science

Document Type:

Master Thesis

Date of Defense:

November 12, 2010

Committee Members:

Kenneth Steven Brentner, Thesis Advisor/Co-Advisor
Kenneth Steven Brentner, Thesis Advisor/Co-Advisor

Keywords:

Acoustics
Ducted
Rotors
CFD
FLUENT
PSUWOPWOP
FSC
ESM
Fast Scattering Code
Fwocs
Williams
Hawkings

Abstract:

In recent years, ducted rotors have become increasingly important to rotor craft for performance and safety reasons. Although much is understood about the thrust performance of a ducted rotor, the acoustics is less well understood. This dissertation describes the tools and techniques to lay the ground work for an accurate acoustics analysis. Some theoretical work will be presented using the NASA Fast Scattering Code (FSC) for later comparison to noise data obtained from Computational Fluid Dynamics (CFD). The CFD work was be done using the commercial software package Fluent. Both an open rotor and a ducted rotor will be simulated for the purpose of comparison with both momentum theory and acoustics. A converter was written to link Fluent with the rotor noise prediction code PSU-WOPWOP. PSU-WOPWOP uses the Ffowcs Williams-Hawkings approach to calculate the sound field. The duct and the rotor sound fields may be calculated separately, which provides an understanding of the impact of both noise sources. Ultimately, the goal is to compare the ducted rotor acoustics to the open rotor acoustics to analyze the differences and to understand sources of those differences.