City Research Online

Abstract

Circular holes with a mean bias flow passing through them can amplify or damp acoustic energy and this property is relevant for many industrial applications. In this work, we propose a methodology to design the edges of such holes so that the acoustic damping is maximised. The approach relies on a Bayesian optimisation framework and is illustrated in a short circular hole with a mean laminar bias flow. The acoustic response of the perforation is characterised numerically using a two-step approach where, first, a steady mean flow is computed as the solution of the incompressible Navier–Stokes equations. Second, small-amplitude acoustic perturbations are superimposed on this mean flow and their dynamics are obtained as the solution of the linearised compressible Navier–Stokes equations. Both the upstream and downstream edges of the hole are modified with 45°chamfers. The sizes of these two chamfers are the control parameters optimised to maximise the acoustic absorption coefficient. The results of this letter show that the careful design of the edges can dramatically increase the acoustic energy that holes can damp: the hole investigated here goes from one generating 55% more acoustic energy than incident upon it at a given frequency to one that damps 46% of this acoustic energy.

Publication Type:	Article
Additional Information:	© 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Publisher Keywords:	Acoustic damping, Perforations, Holes, Optimisation
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Engineering
SWORD Depositor:	Symplectic Administrator

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