Development of aeroacoustic control devices for a square cylinder using adjoint lattice Boltzmann method

The control of aerodynamic noise is essential in various fields, including mechanical and aerospace engineering applications such as pantographs of high-speed trains and aircraft landing gears. Traditional devices, such as splitter plates, have long been employed to suppress wake flows and the resulting noise; however, the development of novel devices that outperform these classical designs has yet to be achieved. The present study seeked to develop innovative control devices using an aeroacoustic optimization framework that integrates the lattice Boltzmann method (LBM) with the adjoint method to modify the rear surface of a square cylinder. The Reynolds number was set to 150 for a two-dimensional laminar flow, and the Mach number was set to 0.2. The optimization created a ridge shape near the rear edge. Flow and acoustic analyses using the LBM showed that this shape successfully suppressed wake flow oscillations and mitigated the generation of aeolian tones. Additionally, a new passive control technique, namely, the installation of tapered splitter plates near the rear edge of the square cylinder, was proposed by simplifying the optimized shape. The LBM simulations demonstrated that the tapered splitter plates outperformed the conventional straight splitter plates in controlling the wake flow and flow-induced sound of the square cylinder.