Experimentally visualizing the mechanism of acoustic liners in flow

What is it about?

Acoustic liners are commonly used devices to reduce aircraft noise. These devices are mounted in the nacelles and serve to reduce engine noise before being emitted. When used, liners are subjected to complex flow field due to the airflow inside the running engine. It is difficult to fully understand the noise reduction mechanisms of the liners under these complex conditions. Therefore, the authors have realized an experimental method to visualize the phenomena inside of the liner using the Schlieren method.

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Photo by Felix Berger on Unsplash

Photo by Felix Berger on Unsplash

Why is it important?

Due to the complex flow and sound fields, it is highly challenging to accurately simulate the phenomena inside and around the liners using numerical methods. Therefore, experimental visualization methods are of great value, but there have been only a few precedents to date. This study is one of the few, if not the first, successful attempts to visualize the interior of a liner using experimental methods.