A comparison between off and on-body control surfaces for the FW-H equation: Application to a non-compact landing gear wheel

This work is a contribution to the ongoing debate about role of quadrupoles in low Mach number flows, studied through use solid and permeable surface Ffowcs-Williams & Hawkings (FW-H) integrals for landing gear numerical noise predictions. It rests upon key idea that dominance sources over volume can only be guaranteed when compact-source condition met. We propose here express this property as on smallness product between Strouhal numbers, or formally MSt < 1. consider canonical isolated wheel, basically consists shallow circular cavity inscribed coin-like cylinder, thus presenting few different length scales, compared full assembly. Zonal Detached Eddy Simulations are performed several gradually refined grids assess grid convergence result. In particular, important computational effort put into accurate resolution acoustic waves up numbers such > Overall, determining real significance was challenging errors misleading effects near-field terms, discretization, source domain truncation biased initial results. Even these bias removed, non-negligible differences found spectra at non-compact St values, while both formulations equivalent lower numbers. The analysis extended determination their impact frequency-domain maps obtained with DAMAS algorithm fed far-field signals computed FW-H approaches. A tentative interpretation wheel finally proposed, highlighting dominant scattering aerodynamic by downstream edge wake dominate higher