  Acoustic models of resonant duct systems with turbulent flow depend on fitted
constants based on expensive experimental test series. We introduce a new model
of a resonant cavity, flush mounted in a duct or flat plate, under grazing
turbulent flow. Based on previous work by Goody, Howe and Golliard, we present
a more universal model where the constants are replaced by physically
significant parameters. This enables the user to understand and to trace back
how a modification of design parameters (geometry, fluid condition) will affect
acoustic properties. The derivation of the model is supported by a detailed
three-dimensional direct numerical simulation as well as an experimental test
series. We show that the model is valid for low Mach number flows (M =
0.01-0.14) and for low frequencies (below higher transverse cavity modes).
Hence, within this range, no expensive simulation or experiment is needed any
longer to predict the sound spectrum. In principle, the model is applicable to
arbitrary geometries: Just the provided definitions need to be applied to
update the significant parameters. Utilizing the lumped-element method, the
model consists of exchangeable elements and guarantees a flexible use. Even
though the model is linear, resonance conditions between acoustic cavity modes
and fluid dynamic unstable modes are correctly predicted.
