The use of integral solutions to the acoustic-analogy-based Ffowcs Williams-Hawkings (FW-H) formulation is the de facto industrial and academic approach for assessing far-field acoustic behavior from airframe noise simulations. The methodology utilizes time-accurate flow variables obtained at arbitrary data surfaces to determine far-field spectra. The solid surface approach, where the time history of pressure is recorded on the surface of the aircraft, is generally preferred. Permeable surfaces, where pressure and velocity are recorded on a user-defined surface enclosing the aircraft, are also used. This paper seeks to share some of the valuable lessons we learned over the past several years on the limitations of the FW-H formulation and best practices for its successful application. We show results for various configurations comprising isolated landing gears, a business jet, a large commercial transport, and a generic low boom supersonic prototype, all at landing conditions. We demonstrate that the solid FW-H approach has significant accuracy limitations for most realistic cases and that the permeable FW-H approach may also fail in specific scenarios, requiring additional costly steps to extract the correct far-field noise spectra. Suggested guidelines for proper FW-H calculations are also given.

使用基于声学类比的 Ffowcs Williams-Hawkings (FW-H) 公式的积分解决方案是从机身噪声模拟评估远场声学行为的事实上的工业和学术方法。该方法利用在任意数据表面获得的时间精确的流量变量来确定远场光谱。通常首选固体表面方法，其中记录飞机表面压力的时间历程。还使用可渗透表面，其中压力和速度记录在用户定义的包围飞机的表面上。本文旨在分享我们在过去几年中就 FW-H 配方的局限性和成功应用的最佳实践所吸取的一些宝贵经验。我们展示了各种配置的结果，包括独立起落架、公务机、大型商用运输机和通用低臂超音速原型机，均处于着陆条件。我们证明固体 FW-H 方法在大多数实际情况下具有显着的准确性限制，并且可渗透的 FW-H 方法在特定情况下也可能失败，需要额外的昂贵步骤来提取正确的远场噪声频谱。还给出了正确计算 FW-H 的建议指南。需要额外的昂贵步骤来提取正确的远场噪声频谱。还给出了正确计算 FW-H 的建议指南。需要额外的昂贵步骤来提取正确的远场噪声频谱。还给出了正确计算 FW-H 的建议指南。