The nacelle of aircraft engines is coated with acoustic liners to reduce engine noise. An undesirable effect of these liners is that they increase aerodynamic drag. We study this drag penalty by performing Direct Numerical Simulations of a turbulent boundary layer over an acoustic liner array at friction Reynolds number, Re τ ≈ 850–2500. We use this simulation to confirm several findings that we recently brought forward using a simpler channel flow setup. We show that acoustic liners lead to high wall-normal velocity fluctuations that can be directly correlated with a modulation of the classical near-wall cycle and to an increase in drag. We also confirm that the acoustic liners act as permeable surface roughness and the non-linear Forchheimer coefficient is the relevant permeability parameter for scaling the drag increase.
|Title of host publication||AIAA AVIATION 2023 Forum|
|Publisher||American Institute of Aeronautics and Astronautics Inc. (AIAA)|
|Number of pages||8|
|Publication status||Published - 2023|
|Event||AIAA AVIATION 2023 Forum - San Diego, United States|
Duration: 12 Jun 2023 → 16 Jun 2023
|Conference||AIAA AVIATION 2023 Forum|
|Period||12/06/23 → 16/06/23|
Bibliographical noteGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care
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