CFD Online Logo CFD Online URL
Home > Forums > General Forums > Main CFD Forum

drag coefficient of cylinder using fluent

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Search this Thread Display Modes
Old   December 20, 2003, 14:11
Default drag coefficient of cylinder using fluent
john lynam
Posts: n/a
please anyone, can you help me to model the drag coeffient of a 2D cylinder using fluent for various Reynolds numbers as I'm unable to obtain accurate results for Reynolds number greater than 100, my aim is to try to compare the experimental results of Re against Cd with those obtained using fluent. I have tried so many options, but to no avail. I would be grateful if anyone has a step by step guide on how i should model this problem, please note I'm not an expert on fluent, as I've only just started using it recently. Thank you john Lynam
  Reply With Quote

Old   December 20, 2003, 14:28
Default Re: drag coefficient of cylinder using fluent
Jim Park
Posts: n/a
Make sure you're running Fluent in transient mode. Above a very low Reynolds number, the shedding behind a cylinder is transient. Re = 100 is above that limit.

Also, try refining your mesh near the surface of the cylinder and in the wake. Errors associated with a coarse mesh can show themselves as 'numerical viscosity', making the computational Reynolds number much less than intended - and thus damping the oscillations.

Look at Schlichting, Boundary Layer Theory, (mine is 4th edition, 1960), p. 17, for some nice pictures of the flow you should compute at Re = 100.
  Reply With Quote

Old   February 15, 2010, 09:16
New Member
Join Date: Nov 2009
Posts: 5
Rep Power: 16
alessios123 is on a distinguished road
Hi guys, i'm tring to calculate the drag force coefficient in a 3-d case and the fluid is behind a cylinder.
the fluid is:
density = 800 kg/m^3
dinamic viscosity = 0.005 kg/ms
velocity = 8 m/s

the cylinder is:
diameter = 13 mm
length = 300 mm
stiffness modulus = 200000 MPa
poisson coefficient = 0.3

to calculate the drag coefficient i push: solve/monitors/force/drag coefficient.....
the direction of the vector of force is in parallel to the flow flowing

i set the reference value:
Area = 0.013*0.3 that is the product for diameter and the length of the cylinder,
Length = 0.013 that is the diameter
then i set other values: viscosity, velocity, density of fluid as i wrote upforward.

i put 90 nodes around the circonference of the cylinder, and 25 along to the length of the cylinder.

the algorytm used is LES, because this is a 3d case
I used PISO
and second order upwind for momentum...

the Cd value is incresing but after 0.02 seconds it is still to 0.7.

How can i do, please help me.
Thank to all

alessios123 is offline   Reply With Quote


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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 Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Calculation of Drag Coefficient manually PRASHANT GHADGE FLUENT 4 December 13, 2012 15:31
Drag and Lift coefficient in Fluent pejmanpark FLUENT 0 July 13, 2011 12:11
Automotive test case vinz OpenFOAM Running, Solving & CFD 98 October 27, 2008 08:43
About drag coefficient of 2D circular cylinder! Haoyin Shan FLUENT 0 May 6, 2007 23:50
drag and lift coefficient No Siemens 5 July 13, 2004 10:21

All times are GMT -4. The time now is 15:13.