AN EFFICIENT, TWO-DIMENSIONAL IMPLEMENTATION OF THE FFOWCS WILLIAMS AND HAWKINGS EQUATION

This paper describes a two-dimensional formulation of the Ffowcs Williams and Hawkings equation in the frequency domain. By assuming subsonic rectilinear motion of all acoustic sources, an efficient and easily implemented form of the equation is developed. This method is capable of predicting the farfield noise from non-linear nearfield flow quantities. The ability to use non-linear input data is a clear advantage over Kirchhoff methods, that are only valid in regions where the linear wave equation accurately describes the flow. Several example problems are used to demonstrate that the new method performs well for problems with a mean flow, tonal and broadband noise signatures, and non-linear near fields. In most practical acoustic problems, three-dimensionality is important and should not be neglected. For these real-world applications, two-dimensional solutions can be used to guide and augment full three-dimensional calculations, but not replace them.