Acoustics in variable area duct - Finite element and finite difference comparisons to experiment

Abstract

Plane wave sound propagation without flow in a rectangular duct with a converging-diverging area variation is studied experimentally and theoretically. The area variation was of sufficient magnitude to produce large reflections and induce modal scattering. The rms pressure and phase angle on both the flat and curved surface were measured and tabulated. The "steady"-state finite element theory of Astley and Eversman and the transient finite difference theory of White are in good agreement with the data. It is concluded that numerical finite difference and finite element theories appear ideally suited for handling duct propagation problems which encounter large area variations.

Nonisentropic propagation of sound in uniform ducts using Euler equations

“…17, a distinct advantage of this method is that the storage requirements and the computer time required are low. The only quantities that need to be stored are the #/_i, 7 and Qt-2j> m order to compute the Qij.…”

Theoretical prediction of sound propagation in an annular duct

“…Recently, the attenuation of sound propagation in a circular duct with shear mean flow was treated by the authors [3]. Investigations [1,2,4,9] using various schemes to solve similar problems with different geometric shape were also found to have good results.…”

Sound transmission across duct constrictions with and without tapered sections

“…3 The prediction of sound transmission characteristics across these ducted elements is very important and thus, the topic has attracted the attention of many researchers in the past few decades. For instance, Miles 4,5 and Baumeister et al 6 investigated the plane wave propagation across a variable area duct. Silcox and Lester 7 examined sound wave transmission across a conical constriction with a wall slope of 3.6°.…”