  In finite-volume-based flow simulations, absorbing layers are widely used to
reduce pressure wave reflections at boundaries of the computational domain. A
disadvantage of absorbing layers is that they contain case-dependent
parameters; thus the question is how to optimally tune these parameters, so
that a desired reduction of reflections can be obtained? As a step towards the
answer of these questions, this article presents a theory which predicts
reflection coefficients for absorbing layers. The theory is given for 1D-wave
propagation and is then extended to 2D and 3D to cover waves of oblique
incidence. The theory is validated via flow simulations of regular and
irregular pressure waves in air and water, based on Navier-Stokes-type
equations and the finite-volume method. Theory predictions and simulation
results show good agreement. It is demonstrated how the theory can be used to
optimally tune the absorbing layer parameters to minimize undesired wave
reflection. Thus the theory has benefits for a wide range of applications of
finite-volume-based flow simulations in industrial practice.
