Direct Simulation of Acoustic Waves Emitted from Moving Bodies by the Finite Difference Lattice Boltzmann Method

Direct simulation of acoustic waves emitted from rotating elliptic cylinder has been performed by the finite difference lattice Boltzmann method (FDLBM) formulated by the arbitrary Lagrangian Eulerian (ALE) scheme. The flow field is almost periodic after the calculation fully develops. The large vortexes appear outside of the elliptic cylinder, and move slowly to the same direction as the cylinder’s rotation. The positive and negative vorticity is alternately generated at the edge by those large vortexes. The acoustic waves propagate synchronizing with the rotation. The acoustic waves consist of those whose frequency is two and four times that of the rotation. One of the sound sources is the potential like doublet due to the motion of the edge and the other is the doublet that is formed by the interaction between the above-mentioned vortexes and the surface of the edge. The bladevortex interaction is also directly simulated. The wave patterns of the acoustic waves by the simulation are compared with those by the experimental result, and both agree well qualitatively.