Investigation on Aerodynamic Noise Generated by Porous Coated, Staggered Tandem Cylinders

Kurzfassung

The aerodynamic noise generated by the landing gear of an aircraft or the protective guard grille of a fan is often studied by a tandem cylinder configuration, modeling the interaction between main strut and hydraulic lines and the rods of the mesh, respectively. Previous investigations have shown that the angle between the upstream and downstream cylinder has a great effect on the peak sound pressure level. The present study describes both acoustic and hot-wire measurements of a tandem cylinder configuration to investigate the flow field around the staggered cylinders and to evaluate the effects of porous coatings of the cylinders. A cylinder spacing of S = 4.7D was used, where D represents the diameter of the cylinders. Spacing and diameter of the cylinders are known to affect the flow behavior. The results show that increasing the angle up to a certain limit of 30° to 35° leads to complex interactions of the wake flows. For large angles, the interference between the two cylinders decreases. It can also be observed that porous materials with high permeability reduce the tonal noise better than materials with low permeability, effectively shifting the peak towards lower frequencies.