The importance of controlling the upstream body wake in tandem cylinders system for noise reduction

This work numerically investigates the importance of controlling the wake of upstream body in the tandem cylinders aiming at aerodynamics noise reduction. The two-dimensional unsteady Reynolds-averaged Navier–Stokes approach with the k–ω turbulence model and Ffowcs Williams–Hawkings method are employed to simulate the flow field and the aerodynamics noise, respectively. The flow in the porous media is calculated by a volume-averaged model. Analogy to the mass-spring-damper system, one preliminary model is proposed to reveal the key role of stabilizing the upstream body wake. The simulations of different porous materials coating designs are implemented to corroborate the model and provide more details of flow modification by porous materials coating. Results indicate that the porous materials coating designed on the upstream cylinder can decrease the wake impingement on the downstream cylinder via suppressing the vortex shedding. Subsequently, not only the tonal noise but also the broadband noise level of tandem system can be reduced. It is also clarified that the effects of downstream cylinder absorption and downstream cylinder wake control by porous materials coating is not comparable with the upstream cylinder wake control. The present study gives a new idea to flow control and noise reduction of the multibody systems considering efficiency and economy.