Near field acoustic radiation from ducts

大多数风扇和螺旋桨位于管道内，旨在提高其空气动力学效率。这包括，例如，叶轮机的管道内的转子，船用螺旋桨，或小型被笼罩的无人机螺旋桨。当风机位于远离风管开口端（若干声波长）时，从开口端的辐射以传播风管模式的形式存在。在这种情况下，管道对源辐射有显著的影响，这一点从经典理论中可以很好地理解。然而，随着管道变短，螺旋桨变得越来越接近开放端。在这些情况下，它的辐射既不是纯粹以传播管道模式的形式，也不是在开放空间（自由场）中，而是在两个极限之间的某个地方。在这些实际情况下，管道对声辐射的影响还不太清楚。本项目是对管道在不同距离的声源作用下产生的辐射进行基础研究。该项目的主要目的是评估和了解管道对源辐射的影响，从而协助设计降低噪音的管道。研究结果对导管式螺旋桨的设计也具有重要意义。该项目将结合分析、数值和实验方法。成功的博士候选人将加入声音与振动研究所（ISVR）的声学小组。ISVR被认为是世界上声音和振动现象研究的领先中心之一。申请邀请具有相关数学，科学或工程学科优秀学位（或大学认可的其他同等标准资格）的潜在英国候选人。数学能力强者优先。奖学金将全额资助，包括已付学费（英国/欧盟费率）。我们很幸运，我们能够支付免税助学金，大大高于标准税率。

Most fans and propellers are located within ducts aimed at improving their aerodynamic efficiency. This includes, for example, the rotor within a duct of a turbomachine, marine propellers, or small shrouded UAV propellers. When the fan is located far from the open end of the duct (a number of acoustic wavelengths), the radiation from the open end is in the form of propagating duct modes. In this case, the duct has a significant effect on the source radiation, which is reasonably well understood from classical theory. However, as ducts become shorter, the propeller becomes increasingly closer to the open end. In these cases its radiation is neither purely in the form of propagating duct modes, or in open space (free field), but somewhere between the two limits. In these realistic cases, the effect of the duct on the acoustic radiation is much less well understood.This project is a fundamental study into the radiation from ducts due to acoustic sources at varying distances from the open end. The main objective of the project is to assess and understand the effects of the duct on source radiation and hence assist with duct design for reducing noise. The results from this study will also be of significant importance in the design of ducted propellers. The project will be a combination of analytic, numerical and experimental methods. The successful PhD candidate will join the Acoustics group at the Institute of sound and Vibration Research (ISVR). The ISVR is recognised as one of the world's leading centres for the investigation of sound and vibration phenomena. Applications are invited from prospective UK candidates with an excellent degree (or an equivalent standard in other qualifications approved by the University) in a relevant mathematics, science or engineering subject. Strong mathematical skills will be an advantage.The studentship will be fully-funded including paid tuition fees (UK/EU rate). We are fortunate that we are able to pay a tax-free bursary that is significantly greater than the standard rate.