Mechanisms of Sound Absorption in Nanofibrous Materials

在这个项目中，我们将与我们的工业伙伴合作，研究声波如何在各种形状和形式的管道中传播。我们将特别研究两个具体方面：-背景流对声传播的影响-表面衬里对声传播的影响。目的是将声音传播简化为一个简单的方程，在管道表面上有一些边界条件（阻抗类型），同时保留问题的重要物理方面。在过去的20年中，在这一领域进行了大量的工作，包括-考虑考虑流动边界层的边界条件，并确保所获得的方程在数值上是稳定的-考虑不同类型的背景流动-考虑粘度的影响-具有不同截面和/或缓慢变化的几何形状的管道。最终目的是考虑声在环形管道内的传播，其外半径在下游方向缓慢增加。管道内的流动将是旋涡型的，我们将假设管道的壁是内衬的。我们的目标是获得一个简单的方程和相关的阻抗型边界条件，以有效地模拟这些管道内的声音传播，我们的工业合作伙伴可以将其用作预测建模工具。该学生将混合使用分析和数值技术。其中，复特征值跟踪算法将起到至关重要的作用。

In this project, in collaboration with our industrial partner, we will investigate how acoustic waves propagate in ducts of various shapes and forms. We will in particular study two specific aspects:- the influence of a background flow on the acoustic propagation- the influence of surface lining on the acoustic propagationThe aim being to reduce the sound propagation to one simple equation with some boundary conditions (of impedance type) on the surface of the duct while retaining the important physical aspects of the problem.Over the past 20 years, a lot of work has been carried out in this area including- considering boundary conditions that take the boundary layer of the flow into consideration and ensure that the obtained equations are numerically stable- considering different types of background flows- considering the effect of viscosity- ducts with different cross-sections and/or with slowly varying geometryThe project will start by reviewing and reproducing these results. The ultimate aim being to consider acoustic propagation within an annulus duct whose outer radius increases slowly in the downstream direction. The flow within the duct will be of swirling type, and we will assume that the walls of the duct are lined. The objective is to obtain a simple equation and associated impedance type boundary condition that will effectively model the acoustic propagation within such ducts that our industrial partner could use as a predictive modelling tool.The student will use a mix of analytical and numerical techniques. In particular, a complex eigenvalue tracking algorithm will play a crucial role in the project.