ABSTRAKT

In this numerical work, we compare the acoustic properties of a fractal square grid with those of a regular grid by means of a hybrid approach based on Lighthill's analogy and Direct Numerical Simulation (DNS). It has been shown that the turbulence generated by fractal objects can have different properties than those generated by a regular object: whereas a regular object effectively introduces a single length-scale into the flow, a fractal object can introduce a wide range of length-scales into the flow. These distinct turbulent states depending on the grid are found to lead to different acoustic radiations both in terms of sound pressure levels and frequencies.