The 6th FDR prize

Abstract

From the 58 papers published in 2012 in Fluid Dynamics Research, the following paper hasbeen selected for the sixth FDR prize:The finite-difference lattice Boltzmann method and its application in computationalaero-acoustics by Michihisa Tsutahara (Professor Emeritus, Kobe University, Japan),published in volume 44 (August 2012) 045507.This is a review paper of the author's recent work on the finite-difference lattice Boltzmannmethod (FDLBM). In this paper, the author introduces a modified FDLBM and its applicationto aero-acoustics. To solve the discrete Bhatnager, Gross and Krook equation for simulatingfluid flow, the FDLBM applies a stable finite-difference scheme on a curvilinear coordinatesystem, whereas the ordinary lattice Boltzmann method uses regular lattices. It is knownthat for the lattice Boltzmann methods, there is difficulty in simulating high Mach numbercompressible flows in principle. To alleviate this, the author proposed the modified FDLBM,expanding the flexibility of setting time increments. With this FDLBM, the author has shownthat it is possible to simulate compressible flows efficiently around complex bluff bodies andwith complex aero-acoustic behaviour. The author summarizes all those works, includingstudies only available in Japanese up to now, in this review paper.After discussing the details of the FDLBM proposed by the author, example results ofsimulating the Aeolian tone generated from a circular cylinder at the Mach number M = 0.7are shown. Then, the scheme is expanded for moving bodies by combining with the ArbitraryLagrangian Eulerian formulation. Using this moving mesh scheme, the author shows thesimulation results of the very strong sound pressure generated by a high-speed train in atunnel. For issues of sound propagation in compressible two-phase flows whose density ratiois high, the two-particle model is introduced. Also, techniques to reduce noise generationfrom the flow velocity and pressure at gas–liquid interfaces are shown. Finally, the scatteringof sound waves by water droplets is discussed. In thick fog, the sound coming from a distancebecomes faint due to the sound-scattering effects of micro water droplets. The author gives anexample of successfully solving such an issue by the FDLBM.It is highly admirable that the author developed the new FDLBM for aero-acoustic issuesand has summarized it with sub-schemes to overcome several difficulties of engineering aeroacousticsin this review. It will certainly contribute to further development of fluid dynamicsthrough computational aero-acoustics. Consequently, this paper was selected as the winner ofthe sixth FDR prize.