Hi,

My final year project is based on simulating the radiated sound field of a low Reynolds number mach 0.75 single stream jet. The current method I'm debating to use is a LES, transient analysis to determine the near field spectrum and then using Kirchoffs surface integration to determine the far field characteristics. What I'm not sure about is the number of time steps I need to employ to catch all the emitted frequencies from both large and small scale structures. I have read that the cell size is paramount to this process. Is there a way I can calculate this with out knowing what frequencies are emitted. The program I will be using for the analysis is Ansys Workbench and CFX5.

Thanks for any advise on this matter

Indy

Yeah, if you know the frequesncies then you'll need a few timesteps for each period. Timestep = 1/10 period should do the trick.