Helicopter Noise Modeling With Varying Fidelity Prediction Systems
Open Access
- Author:
- Weist, Lauren
- Graduate Program:
- Aerospace Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 24, 2022
- Committee Members:
- Amy Pritchett, Program Head/Chair
Kenneth Steven Brentner, Thesis Advisor/Co-Advisor
Eric Greenwood, Committee Member
Joseph Francis Horn, Committee Member - Keywords:
- Acoustics
rotorcraft
noise prediction systems
helicopter noise - Abstract:
- Rotorcraft are a versatile and important class of vehicles within the aerospace industry, but they experience a highly varied aerodynamic environment that causes unique acoustic conditions. These acoustics are highly tonal, and are often found to cause community annoyance. Due to this, providing acoustic considerations for rotorcraft is a necessary area of research within the industry. To aid in these considerations, this thesis addresses noise via modeling through two noise prediction systems (NPS). To account for rotorcraft acoustics in the design stage, a low fidelity NPS, the NDARC NPS, was used. For acoustic considerations of existing helicopters, the high fidelity Penn State NPS is used. The low fidelity system, the NDARC NPS, is described first. As acoustic consideration in the design stage is not often conducted, development of a rapid tool to give to a designer is paramount. The NDARC NPS was created to fill this desire, and has been further developed as a part of this thesis. The NDARC NPS was fully exercised to identify issues and improve the system. Improvements to the blade-vortex interaction model, comprised of the Beddoes wake model and Vatistas implementation of the Biot-Savart law were completed. Improvements were made to the user interface, the complete suite of example cases was improved and expanded, and the User's Manual was completed. The mid-fidelity system, known as the Penn State NPS, is used to aid in providing guidance on noise abatement procedures for existing vehicles to aid in the reduction of community annoyance.In this work, the Penn State NPS was used to conduct several studies on the effects of real flight variations on noise. First, a study of longitudinal and vertical accelerations through the lens of flight path angle were conducted for the Sikorsky S-76D helicopter to understand how flight path angle and flight path angle rate changes can effect noise. Then, a study of helicopter configuration and the impact of weight and number of blades on noise was conducted. Four vehicles, the Sikorsky S-76D, the Bell 205, the Bell 407, and the Bell 206 were all analyzed in descent to understand how vehicle configuration influences noise.