Experimental Investigation of Noise Generation by Porous Coated Tandem Cylinder Configurations

The aerodynamic noise generated by aircraft landing gear components is often studied using a so-called tandem cylinder configuration, consisting of two circular cylinders arranged in a streamwise row and separated by a certain distance. Based on previous studies that show the effectiveness of porous coatings to reduce the flow noise generated by single cylinders, the subject of the present study is the experimental investigation of the effect of porous coatings on the noise generated by such a tandemcylinder configuration. This was done by performing acoustic and flow measurements in a small aeroacoustic wind tunnel at Reynolds numbers(based on cylinder diameter) between 15,000 and 130,000. In agreement with a previous numerical study it is found that the porous coatings have an impact on both the peak Strouhal number and the peak level of the resulting tonal noise. Thereby, the influence is notably stronger when the upstream cylinder is modified compared to the application of porous material to the downstream cylinder. A modification of both cylinders further strengthens these effects.