Non-Reflective Boundary Conditions for Computational Fluid Dynamics of External Flows

非反射边界条件通常用于声音传播的数值预测，以防止来自域边缘的伪数值反射污染感兴趣的结果。气动CFD的应用，特别是工业标准的RANS CFD代码，一直是不完整的，重点是在管道内的声学预测。最近与Rolls-Royce的合作表明，将非反射边界条件应用于气动和声学应用的外部流动CFD计算可能具有显着的优势。设想的研究将包括以下内容：调查CFD和声学规范中使用的非反射边界条件的范围。2. 考虑到复杂的几何形状和网格、非均匀平均流动和存在（在区域出口）旋涡扰动等问题，对气动CFD应用中最有前途的候选者进行候选名单和测试。3. 在工业CFD代码中提出，开发，实施和验证一个新的非反射边界条件。主要的应用目标是计算喷气发动机进排气空气动力学和气动声学性能，尽管在项目的后期可能会考虑其他应用（如船舶CFD）。该项目由罗尔斯·罗伊斯公司提供支持，罗尔斯·罗伊斯公司将为工业需求提供指导，并为实施提供支持和建议。关键词：非反射边界条件，特征模，波分裂，完美匹配层，海绵层，无限元，卡尔德隆投影仪

Non-reflective boundary conditions are regularly used in numerical predictions of sound propagation to prevent spurious numerical reflections from the edges of the domain contaminating the results of interest. Application to aerodynamic CFD, and to industrial standard RANS CFD codes in particular, has been patchy, with an emphasis on in-duct acoustic prediction. Recent work in conjunction with Rolls-Royce suggests there may be a significant advantage in applying non-reflecting boundary conditions to external flow CFD calculations for both aerodynamic and acoustic applications. The research envisaged will include the following: 1. Survey the range of non-reflecting boundary conditions used in CFD and acoustics codes. 2. Shortlist and test most promising candidates for aerodynamic CFD application, taking into account issues related to complex geometry and mesh, non-uniform mean flow and the presence (at domain exit) of vortical disturbances. 3. Propose, develop, implement and validate a new non-reflecting boundary condition in an industrial CFD code. The primary application objective is the calculation of jet engine inlet and exhaust aerodynamic and aeroacoustic performance, though there may be opportunity later in the programme to consider other applications (such as Marine CFD). The project is supported by Rolls-Royce, who will provide guidance as to the industrial requirements and also provide support and advice on implementation. KeyWords: Non-Reflective Boundary Conditions, Eigenmodes, Wave-Splitting, Perfectly Matched Layers, Sponge Layers, Infinite Elements, Calderon Projectors