Vortex Shedding

Nikhil Kumar · July 22, 2010, 12:32

Hi,

I've beent rying to model flow over bluff object to observe vortex shedding but havn't been able to achieve it. I only get one vortex at the beginning and then the system goes into steady state. I used 'Implicit unsteady', 'k-epsilon', 'RANS' and default settings for the time steps. The other parameters are as follows,

Velocity - 10m/s
PipeDiameter - 0.5m
Cylinderdiameter - 0.2m

Can anyone tell me where the problem might be?

nomad · July 23, 2010, 13:01

The default time step is too large. Your mesh might be too coarse.

coolio · July 26, 2010, 05:07

Hi!

Fisrt : check if under implicit unsteady you are using the second order scheme discretization!

Second: Check if the lateral boundaries are periodicities!

Third: Estimate the frequency of vortex sheding based on the Strouhal number (0.21) and set the time step to be at the most 1/10 of the computed period!

Regards!

Vinicius · July 28, 2010, 13:25

Also use LES or DES. RANS methods are not very suitable since your time step is to small...

Nikhil Kumar · December 7, 2010, 11:17

Thank you all for the reply.. I got it...

July 22, 2010, 12:32	Vortex Shedding	#1
Nikhil Kumar New Member Nikhil Shastry Yelleswarapu Join Date: Jul 2010 Posts: 5 Rep Power: 15	Hi, I've beent rying to model flow over bluff object to observe vortex shedding but havn't been able to achieve it. I only get one vortex at the beginning and then the system goes into steady state. I used 'Implicit unsteady', 'k-epsilon', 'RANS' and default settings for the time steps. The other parameters are as follows, Velocity - 10m/s PipeDiameter - 0.5m Cylinderdiameter - 0.2m Can anyone tell me where the problem might be? Last edited by Nikhil Kumar; July 22, 2010 at 12:39. Reason: insufficient information

July 26, 2010, 05:07		#3
coolio New Member NVilius Join Date: Jul 2010 Posts: 3 Rep Power: 15	Hi! Fisrt : check if under implicit unsteady you are using the second order scheme discretization! Second: Check if the lateral boundaries are periodicities! Third: Estimate the frequency of vortex sheding based on the Strouhal number (0.21) and set the time step to be at the most 1/10 of the computed period! Regards! Last edited by coolio; July 28, 2010 at 15:56.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
K-Epsilon for Vortex Shedding	Sham	FLUENT	33	March 29, 2017 05:48
Transiet Animation - vortex shedding	derz	CFX	5	May 10, 2010 09:21
instantaneous frames of vortex shedding	jamal	FLUENT	1	January 24, 2008 09:57
Vortex shedding behind cylider in cross flow	Muthu	FLUENT	0	March 6, 2006 10:29
basic vortex shedding	john	Main CFD Forum	4	November 6, 2000 13:23

July 23, 2010, 13:01		#2
nomad Member John Join Date: Aug 2009 Posts: 92 Rep Power: 16	The default time step is too large. Your mesh might be too coarse.

July 28, 2010, 13:25		#4
Vinicius Member Vinicius Girardi Join Date: Mar 2009 Location: Sao Paulo, Brazil Posts: 80 Rep Power: 17	Also use LES or DES. RANS methods are not very suitable since your time step is to small...

December 7, 2010, 11:17		#5
Nikhil Kumar New Member Nikhil Shastry Yelleswarapu Join Date: Jul 2010 Posts: 5 Rep Power: 15	Thank you all for the reply.. I got it...