Numerical simulation of a slit resonator in a grazing flow under acoustic excitation
Numerical simulation of a slit resonator in a grazing flow under acoustic excitation
复制标题
DOI：
10.1016/j.jsv.2007.12.018
复制
发表时间：
2008-06-17
影响因子：
4.7
通讯作者：
Walker, Bruce E.
中科院分区：
文献类型：
--
作者：
Tam, Christopher K. W.;Ju, Hongbin;Walker, Bruce E.
实验表明，掠流对谐振声衬垫的性能有显著影响。到目前为止，还无法从流体动力学或声学角度详细了解这种效应。造成这种情况的一个主要原因是当今喷气发动机声学衬垫的谐振器开口很小。孔的小尺寸使得在掠流存在的情况下，对谐振腔开口周围的流体流场进行深入的实验观察和绘制极为困难。因此，数据的缺乏直接导致了理解的缺乏。声学衬垫的表面完全覆盖着孔（下面的谐振器的开口）。因此，相邻谐振器之间存在流体力学相互作用的可能性。然而，目前还没有这种相互作用的证据。目前工作的目标之一是揭示轻油是否可能以及可能的相互作用机制是什么。本文对狭缝腔在声强迫作用下存在掠流的流场进行了数值模拟。观察到，在高声压级时，谐振腔开口的四角会产生涡流。其中一些漩涡合并在一起。另一些则被壁面边界层吸收或被黏性消散。模拟结果表明，强合并涡被掠流向下游对流，并持续较长时间。这表明，由于该对流涡对下游谐振腔流场的干扰，所有声学衬里相邻谐振腔之间可能存在流体力学相互作用。这种相互作用，就目前所知，还没有包括在任何理论或半经验模型的声学衬垫。给出了计算模型的详细表述和计算算法。通过将计算结果与精确线性解进行比较，并与伴随实验的测量结果进行比较，验证了计算代码的正确性。(C) 2007 Elsevier Ltd.版权所有。
It is known experimentally that a grazing flow has significant influence on the performance of a resonant acoustic liner. As yet, detailed understanding of the effect in fluid dynamics or acoustics terms is not available. One principal reason for this is the small size of the openings of the resonators of present day jet engine acoustic liners. The small size of the holes makes in-depth experimental observation and mapping of the fluid flow field around the opening of a resonator in the presence of a grazing flow extremely difficult. As a result, there is a genuine lack of data leading directly to a lack of understanding. The face sheet of an acoustic liner is entirely covered with holes (the openings of resonators underneath). There is, therefore, a possibility of fluid mechanical interaction between neighboring resonators. However, evidence for such interaction is not available at this time. One of the objectives of the present work is to shed light oil whether this is possible and what is a possible interaction mechanism. In this study, numerical simulations of the flow field around a slit resonator in the presence of a grazing flow under acoustic forcing are carried out. It is observed that at high sound pressure level, vortices are shed from the corners of the resonator opening. Some of these vortices merge together. Others are absorbed by the wall boundary layer or dissipated by viscosity. The simulated results indicate that a strong merged vortex is convected downstream by the grazing flow and persists for a long distance. This suggests that possible fluid mechanical interaction between neighboring resonators of ail acoustic liner could, indeed, be possible because of the interference of this convected vortex with the flow field of the downstream resonator. This interaction, as far as is known, has not been included in any theoretical or semi-empirical model of acoustic liners. Detailed formulation of the computational model, as well as computational algorithm, is provided. The computation code is verified by comparing computed results with an exact linear solution and also validated by comparing with measurements of a companion experiment. (C) 2007 Elsevier Ltd. All rights reserved.