Welcome to another look into our free, online library of inspiring and informative design and engineering presentations. This time we’re looking at the perennial issue of noise and vibrations in the aerospace sector. The following videos highlight just a small sample of all the great content available. See the full list, follow the link at the end of this blog.
Noise is a constant issue in the aerospace sector. When you consider the amount of energy needed to lift an aircraft off the ground and keep it in the air, it’s hardly surprising. Take-off and landing are only part of the story. Noise and vibration has a big impact on customer satisfaction in passenger aircraft. Excessive vibration can also damage vital components. With supersonic vehicles there is the well-known phenomenon of the sonic boom – discussed in our first presentation:
1. Supersonic engine fan inlet noise
Mention commercial supersonic aircraft in conversation and there’s only one that comes to mind, Concord. Today we are 20 years on from the last supersonic passenger flight, but research and development has not stopped. Nasa continues working on supersonic aircraft and there have been many studies in recent years. One of the problems is noise, a sonic boom sounds like a loud thunderclap. Even before that point the engines are very loud, especially during take-off and landing.
In this presentation Dr. David Stephens, NASA Glen Research Centre, Cleveland, Ohio, talks about acoustic simulation in commercial supersonic flight. He explains about NASA’s research including how and why they use acoustic simulations. Finally, he talks about his own experiences with computational methods.
Watch the presentation here: https://events.hexagon.com/hxgnlive-designandengineering/agenda/session/592604
2. Study of noise and vibration due to gas discharge in hermetic compressors
Purdue University has taught some of the biggest names in aerospace. Famous alumni include Neil Armstrong and Eugene Cernan (the first and last astronauts to walk on the moon). Dazhuang He, post-doctoral research assistant, talks about part of a study using Actran to prevent vibration from hermetic compressors. This is an important factor to ensure customer satisfaction and compliance.
With vibro-acoustic analysis in Actran we can identify exterior acoustic responses at different frequencies. This information can then be used to reduce noise radiation. Manufacturers can adjust the structure of their compressors in response to the models and so reduce noise.
See the full video here: https://events.hexagon.com/hxgnlive-designandengineering/agenda/session/619510
3. Vibro-acoustic numerical simulations of spacecraft instrument subjected to diffuse sound field using MSC Nastran and Actran
In the search for supermassive black holes, the Advanced Telescope for High Energy Astrophysics (ATHENA) is likely to become our greatest tool. It’s an X-ray observatory planned for launch in the early 2030s and operated by the ESA (European Space Agency). One of the challenges faced by researchers on the project is how to transport the delicate equipment without damaging it during take-off. The vibrations of a rocket launch induce dynamic loads which can easily damage components and scientific instruments.
In this presentation, Dr. Zbigniew Rarata, Managing Director at Uniflow Dynamics, explains the set up and software used to investigate the vibro-acoustic behaviour of complex mechanical systems in a rocket launch. This will form part of the wider research assisting the ESA to transport sensitive and delicate equipment into space.
4. Core noise reduction for UHBR engines and CIRRUS Cleansky 2 project overview and objectives
Sustainability means reducing fuel consumption, to achieve this, aircraft manufacturers have turned to UHBR (Ultra High Bypass Ratio) engines. These new types of engine have large fans rotating at low speeds. This uses less fuel, but it also creates a completely new acoustic signature. Jet and fan noise is reduced, but core noise is increased.
This presentation gives an overview of project CIRRUS (core noise reduction for UHBR engines). CIRRUS aims to predict, design and test low noise solutions for UHBR engines. The first half of this presentation is an introduction to CIRRUS by Romain Leneveu, Aeronautics Director at Vibratec. Yves Detandt, Technical Director (Research and Development) at Hexagon leads part two covering a study with three objectives:
- To identify combustion noise source mechanisms
- To assess new technology for acoustic liners in high temperature engine parts
- To develop numerical processes and confirm these with consolidated experimental data
5. Computation of adjoint Green’s functions by flow reversal: Application to jet noise
The final presentation details a research study by Étienne Spieser, a post-doctoral researcher at LMFA (Fluid Mechanics and Acoustic Laboratory) in Lyon, France. He worked in conjunction with Professor Christophe Bailly at LMFA and César Legendre of Hexagon. The acoustic radiation of a turbo fan installed on an aircraft in service differs from that of an isolated engine. The purpose of the study was to predict the noise spectra of a jet by computing adjoint Green’s function tailored to the flow geometry.
Étienne explains how the adjoint formulation (Tam and Auriault 1998) helps identify acoustic propagation when modelling jet noise from the turbulent flow. We can use this technique in Actran TM by means of flow reversal and applied to solve Pierce’s wave equation. Watch the presentation for a deep dive into this fascinating topic.
Remember that these are just a sample of the 256 talks we’ve made freely available to all. Click here to see the full list of inspiring and informative presentations from industry leaders.