Prediction of Rod-Airfoil Interaction Noise Using the Ffowcs-Williams-Hawkings Analogy

Abstract

Sound generated at low Mach number by an airfoil in the wake of a rod is investigated numerically. The Gaussian spanwise loss of coherence of the vortex shedding is shown to have a signi cant in uence on the broadband noise. Spanwise effects are successfully introduced into a time-domain formulation of the Ffowcs-Williams-Hawkings analogy, which is applied to aerodynamic data computed on various contours around the source region. It is shown that a careful choice of these contours is required. The ow eld is obtained from a two-dimensional Reynolds averaged Navier-Stokes calculation. Computed far-eld spectra compare very well to measurements obtained in an accompanying experiment.

Characterization of the Noise Sources in a Rod-Airfoil Configuration by Means of Time-Resolved Tomographic PIV

“…The spectra feature a strong tonal peak at about 90 Hz which is slightly lower than the nominal vortex shedding frequency of the rod alone case. The same phenomenon was observed by Casalino et al 19 and Lorenzoni et al 6 and was attributed to an hydrodynamic feedback of the airfoil onto the rod shedding mechanism. The comparison of the spectra reveals minimal changes between the 2D and the 3D case similarly to what concluded by Violato 12 for the pressure time signal at a point in front of the airfoil.…”

A parametric study of the noise radiated by the flow around multiple bodies: direct noise computation of the influence of the separating distance in rod-airfoil flow configurations

“…Several attempts have already been made to predict sound spectra radiated by the flow around a rod-airfoil. Casalino et al 9 applied the Ffowcs Williams-Hawkings (FW-H) formulation 14 to flow data provided by an unsteady RANS (Reynolds-Average Navier-Stokes) simulation. In a similar manner, Boudet et al 8 coupled a LES calculation with a FW-H acoustic analogy.…”

Two techniques for PIV-based aeroacoustic prediction and their application to a rod-airfoil experiment

“…The techniques developed are applied to a time-resolved rod-airfoil PIV experiment, which is a useful benchmark for turbulence structure interaction noise Jacob et al 2005) and has received quite some treatment including Jacob et al (2008), Siller et al (2005), and Casalino et al (2003). This benchmark is particularly tractable for aeroacoustic analysis, as the dominant acoustic source is the impingement of large 2-D vortex rolls on the airfoil leading edge, which are readily resolvable by the PIV measurement.…”