Boundary Layer Effects on Experimental Impedance Eduction

The noise emission of a simplified two-wheel nose landing gear configuration featuring a detachable porous fairing is investigated by a hybrid CFD/CAA approach. The noise mitigation properties of the porous fairing are discussed and compared against two reference configurations, i.e., baseline configurations with and without a solid fairing. The time resolved flow and acoustic near field is computed by a lattice Boltzmann (LB) method with a collision step based on countable cumulants, and the noise radiation into the far field is predicted by solving a permeable surface Ffowcs Williams and Hawkings formulation. The porous material is represented by an equivalent forcing term in the LB equation based on a Forchheimer-extended Darcy model. The porous material has a deterministic geometric structure such that the modeling parameters describing the porous material properties are determined by results from a flow simulation through the resolved micro-structures in a periodic pressure drop setup. The effect of the different fairings on the flow field and the resulting acoustic far field pressure are discussed.