# Velocity profiles

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

 LinkBack Thread Tools Display Modes
 July 17, 2002, 03:35 Velocity profiles #1 Rex Guest   Posts: n/a Hi all, I've been simulating turbulent flow through an annulus with Fluent and have been looking at the velocity profiles, some of which look dubious (some look asymmetric, some show a steep sides with a small flat profile in the middle). I want to compare these with 'hand calculated' velocity profiles, so does anyone know of the equation to calculate annular velocity profiles?

 July 17, 2002, 09:20 Re: Velocity profiles #2 Laika Guest   Posts: n/a Watch out with flow in an annulus. Flow instabilities can occur!! Laika, still orbiting

 July 18, 2002, 15:16 Re: Velocity profiles #3 Lanre Guest   Posts: n/a Since the flow is turbulent, the velocity profile would be a correlation. I don't know of any in the literature...haven't looked yet. What is the gap to diameter ratio? If large, i.e., 1/100, use the turbulent velocity profile between flat plates as a close approximation.

 July 20, 2002, 19:15 Re: Velocity profiles #4 Peter Guest   Posts: n/a There is a equation for a flat plate relating velocity, BL thickness, free stream velocity and perpendicular distance to the wall: (u/u_fs)=(y/delta)^(1/n) Usually for turbulent flows you take n=7 although some other values (8,9) are also valid. Cheers

 July 23, 2002, 19:35 Re: Velocity profiles #5 Matt Guest   Posts: n/a I have had a number of issues with correct velocity profiles for simple geometries. With turbulent flows, you need to be very careful with your y+ value and placement of the 1st grid point from the wall. Use the right wall function. Good luck with things. FLUENT 6.02 has developed new wall functions to ease the restrictions on the strict adhearance to the y+, but you still need to be careful or you will get bad results. I have actually found the most luck with the k-omega turbulence model for a RANS solver of internal flow. Matt

 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 ashtonJ CFX 2 April 24, 2012 04:30 saurus FLUENT 0 January 26, 2011 16:35 Sal FLUENT 3 August 2, 2007 09:06 Antech Main CFD Forum 0 April 25, 2006 02:15 shaheeb FLUENT 0 February 7, 2006 19:00

All times are GMT -4. The time now is 12:21.

 Contact Us - CFD Online - Top