Near field acoustic radiation from ducts

大多数风扇和螺旋桨都位于风道内，旨在提高其空气动力效率。这包括，例如，涡轮机械管道内的转子、船用螺旋桨或小型带冠无人机螺旋桨。当风扇位于远离管道开口端(多个声波波长)时，来自开口端的辐射以传播管道模式的形式存在。在这种情况下，风管对源辐射有很大的影响，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口端。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)，而是介于这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是很清楚。本项目是对管道在不同距离开口处的声源辐射的基础性研究。该项目的主要目标是评估和了解管道对源辐射的影响，从而协助管道设计以减少噪音。这项研究的结果也将对导管螺旋桨的设计具有重要意义。该项目将是分析、数值和实验方法的结合。成功的博士候选人将加入声学与振动研究所(ISVR)的声学小组。ISVR被公认为世界领先的声音和振动现象研究中心之一。在相关的数学、科学或工程学科，拥有优秀学位(或具有大学认可的其他资格的同等标准)的潜在英国候选人均可申请。优秀的数学能力将是一个优势。学生将得到全额资助，包括已支付的学费(英国/欧盟费率)。幸运的是，我们能够支付比标准金额高得多的免税助学金。

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.