# Calculating shedding frequency of square cylinder

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 November 17, 2005, 08:00 Calculating shedding frequency of square cylinder #1 zonexo Guest   Posts: n/a hello, i've managed to get some answers for my flow past square cylinder simulation. although the velocity plot seems correct, i need to verify against some values. my code gives pressure and velocities at all pts. how am i going to use these data to get the shedding frequency? i've tried reading some papers and search for answers in this forum but to no avail.... hope someone can help... thanks!

 November 17, 2005, 09:38 Re: Calculating shedding frequency of square cylin #2 ramp Guest   Posts: n/a In case of the steady flow, using the velicities and pressure fields you can calculate the drag coefficients, wake length etc. In case of unsteady flow, drag & lift coefficients and Strouhal number. These can be benchmarked with the literature. You can also compare the pressure and vorticity varition over the surface of the cylinder.

 November 17, 2005, 14:52 Re: Calculating shedding frequency of square cylin #3 Mani Guest   Posts: n/a ... the main point being: You have to run a time-accurate unsteady simulation to obtain the vortex shedding frequency. Even for the time-averaged drag, a steady-state solution will not be accurate.

 November 17, 2005, 15:29 Re: Calculating shedding frequency of square cylin #4 ramp Guest   Posts: n/a Under to steady flow regime, the drag will not be dependent of the steady/unsteady simulation. I think the accuarcy will also not be dependent on it. The unsteady computation is required only for the vortex shedding characteristics.

 November 17, 2005, 19:12 Re: Calculating shedding frequency of square cylin #6 CFD Guest   Posts: n/a Zonexo Before all that was told by Ramp and Mani, do not forget to consider the following things before trying to compare your results: - Is your computational model (geometry, Reynolds number, time step, CFL, constraints, etc...) equal or equivalent with the model of your reference? The validation process turns easier when you replicate the problem from the reference. - Is the cylinder fixed or not? - How and where are you applying the no-slip bnd conditions? - For 3D problems: are you solving a problem like a wind tunnel (with no-slip at the bottom, or top, surface) or an idealized problem (without top and bottom walls)? At first, I would not be worried about the accuracy of my solution. I would be engaged to reproduce the solution from some reference, being it high or low accurate (I am just comparing results...). For a first compare, just extract the velocities components from some point in the shedding street and plot against the time. It will give you some idea about your Strouhal number (some papers also have these plots with the velocities). After matching some results you will feel how are you going to try a well elaborated solution and study other parameters (drag, lift, etc...) and the accuracy of your solver. I used to do it: try some relaxed comparison before studying more elaborated parameters. Cheers

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post josik_1982 FLUENT 2 July 17, 2010 10:19 Hari FLUENT 7 April 12, 2006 08:14 zonexo Main CFD Forum 8 March 30, 2006 15:11 liu OpenFOAM Running, Solving & CFD 6 December 30, 2005 18:27 Ruslan FLUENT 1 July 19, 2005 09:49

All times are GMT -4. The time now is 13:41.

 Contact Us - CFD Online - Top