I am using ansys for a vortex induced vibration case, I am trying to find the correct shedding frequency on ansys but I am limited to number of elements due to the limit on the student version of Ansys. My geometry is just a simple rectagular domain with a cylinder with in the domain. It has been set up like this to mimick an experiement where vortex induced vibrations were achieved.
The model I am running is K-omega SST and my method is PISO. I calculated the the shedding frequency as 40Hz however the best I can achieve on fluent is 30Hz. I used equation F=st*(v/d) to calculate the shedding frequency.
I would suggest a new strategy given in:
Multiple hopf bifurcations and flow dynamics inside a 2D singular lid driven cavity - Lucas Lestandi, Swagata Bhaumik, G.R.K.C. Avatar, Mejdi Azaiez, T. K. Sengupta, Computers and Fluids, vol. 166, pp 86-103 (2018)
You excite the dynamical system at any frequency (may be closer to your anticipated value, if you know before hand- as you do here!) and once the limit cycle oscillation is achieved, switch off the excitation. You will note that the dynamical system will settle down to its natural frequency. The details are given in the above reference -available in RG.
This exercise was done using our own code and you may encounter difficulty with canned software due to high built-in diffusion. Still it is worth a try. Best wishes!
Are you using FFT analysis of ANSYS for determining the vortex shedding frequency. ? Or is it that you are determining it from non-periodic some time-variant plots ?
YOU CAN CREATE DIFFERENT MONITOR POINTS NEAR CYLINDER FOR VELOCITY. THEN AFTER SIMULATION YOU CAN DO FFT ANALYSIS OF THESE TIME AND VELOCITY SIGNALS BY USING CHART IN CFD POST TO REVEAL THE SHEDDING FREQUENCY. STROUHAL NUMBER CAN BE EVALUATED FROM THIS FREQUENCY.
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