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

非反射边界条件通常用于声传播的数值预测，以防止来自域边缘的伪数值反射污染感兴趣的结果。应用于空气动力学计算流体动力学，特别是工业标准RANS计算流体动力学代码，一直是不完整的，重点是管道内的声学预测。最近与Rolls-Royce合作的工作表明，将非反射边界条件应用于空气动力学和声学应用的外流CFD计算可能具有显著的优势。设想的研究将包括以下内容：1.调查计算流体力学和声学代码中使用的无反射边界条件的范围。2.考虑到与复杂几何形状和网格、非均匀平均流和涡流扰动的存在（在区域出口处）相关的问题，列出并测试最有希望的气动CFD应用候选方案。3.在工业CFD代码中提出、开发、实施和验证新的无反射边界条件。主要应用目标是计算喷气发动机进气道和排气的空气动力学和航空声学性能，尽管在该计划的后期可能有机会考虑其他应用（如海洋CFD）。该项目得到了罗尔斯·罗伊斯公司的支持，罗尔斯·罗伊斯公司将提供有关工业要求的指导，并提供实施方面的支持和建议。关键词：非反射边界条件，本征模，波分裂，完全匹配层，海绵层，无限元，Calderon投影

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