Aeroacoustic time-reversal in the presence of a reflecting surface

The influence of a rigid-wall reflecting surface on aeroacoustic Time-Reversal (TR) is investigated in this work. To this end, a forward simulation of a Gaussian pulse propagation in 2-D computational domain with a uniform mean flow was implemented by numerically solving the Linearised Euler Equations subject to a rigid-wall condition (by setting the normal velocity to zero) at the bottom boundary modelling the reflecting condition. The anechoic conditions were implemented at the remaining three boundaries, thereby modelling a semi-infinite 2-D free-space. The acoustic pressure time-history was stored at all boundaries during the forward simulation. A set of TR simulations were carried out wherein rigid-wall condition was implemented at bottom boundary in each of the test-cases and time-reversed acoustic pressure was enforced at (1) all four boundaries, (2) three boundaries excluding the bottom boundary, (3) the top and bottom boundaries and (4) only the top boundary in the first, second, third and fourth test-case, respectively. It was observed that the initial emission point of the pulse was accurately predicted in all four test-cases, thereby demonstrating that acoustic pressure need not be measured at the rigid-wall. Rather, taking advantage of wave-reflection, only one microphone Line Array located outside flow can be used during aeroacoustic TR for source localisation.