Frequencies associated to vortex-induced vibration of a single cylinder
 

Hello everyone!



I am conducting numerical simulations of the flow around an oscillating single cylinder using a moving mesh in ANSYS Fluent 19.0. I found no problems in setting up the simulation. I determine through a UDF the oscillating mass of the system, a natural frequency, and other parameters. The cylinder motion response is in agreement with literature data, however, when I analyze the amplitude data through Fast Fourier Transform, there is only one frequency peak, which corresponds to the Strouhal frequency of vortex shedding. The peak associated with the natural vibration frequency is absent. Does anybody know the reason this is happening and how to overcome it?



Thanks in advance.