# Turbulent Schmidt Number

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

 August 2, 2002, 06:46 Turbulent Schmidt Number #1 John Guest   Posts: n/a Hi. For the past few months I have been modelling the movement of neutrally buoyant dye through a pipe with the species model in Fluent 5.5. I have found that altering the turbulent Schmidt number from 0.5 to 1.5 makes a 300% difference to the results. I know Fluent claims that a value of 0.7 is generally OK, but does anybody know if there is more detailed information for pipe flow. Thanks John villager and IET like this.

 August 13, 2002, 07:06 Re: Turbulent Schmidt Number #2 Michael Malin Guest   Posts: n/a I don't know about your precise configuration or modelling practices, but for classical developed pipe flow with passive heat or species transport, the turbulent Prandtl/Schmidt number varies from around 0.9 at the wall to 0.6 at the flow axis. Experimental data exists which permits determination of the Prandtl number variation across the pipe. It can be deduced from measurements of the mean velocity profile, mean concentration profiles and the radial profiles of the Reynolds shearing stress and radial turbulent concentration/heat flux.

 August 13, 2002, 13:08 Re: Turbulent Schmidt Number #3 John Guest   Posts: n/a Thanks for your reply. Can you give me the reference for variation in the turbulent Schmidt number for a pipe? Also is the Prandtl and Schmidt number the same thing? Thanks once again. John

 August 14, 2002, 06:50 Re: Turbulent Schmidt Number #4 Michael Malin Guest   Posts: n/a I will dig out the reference. The Prandtl and Schmidt number will be the same when dealing with passive contaminents.

 August 15, 2002, 02:31 Re: Turbulent Schmidt Number #5 Michael Malin Guest   Posts: n/a The references are: Launder, "Heat and Mass Transport" in Turbulence, Chapter 6, Ed. Bradshaw, Springer, Berlin, (1978). Reynolds, "The prediction of turbulent Prandtl and Schmidt numbers", Int.J.Heat Mass Transfer, Vol.18, p1055, (1975). Hinze, "Transport of a scalar quantity in wall turbulence" in Turbulence, 2nd Edition, Chapter 7, McGraw Hill, (1975). villager and amir.a.aliabadi like this.

 August 27, 2002, 09:23 Re: Turbulent Schmidt Number #6 John Guest   Posts: n/a Sorry for the delay, but I now have the references. I will have a look and let you know how I get on. Thanks once again for your time. John

 August 29, 2002, 11:04 Re: Turbulent Schmidt Number #7 John Guest   Posts: n/a I have now looked through the references - I had now idea the issue was so complicated! I have found a further reference you may be interested in: The height dependence of the turbulent Schmidt number within the boundary layer, Koeltzsh 2000, from the journal of atmospheric environment (I think). Thanks once again for your time. John

 May 31, 2015, 22:36 #8 New Member   yunhaifeiyang Join Date: May 2015 Posts: 4 Rep Power: 4 In Fluent, the default schmidt number is 0.85 for conventional fluid (air and water et al.), but for heavy metal (lead bismuth eutectic et al.), its schmidt number is larger than 1.0. So I want to set it 4.22 instead of 0.85. But I don't know how to do it? Use UDF? Please help me!

 June 1, 2015, 05:04 #9 Senior Member   Cees Haringa Join Date: May 2013 Location: Delft Posts: 545 Rep Power: 10 Hi, If you go to viscous to set the turbulence model, there is a column on the right with a number of constants. if you have species enabled, this will include the turbulent schmidt number as well. Best, Cees villager likes this.

 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 Sohail FLUENT 14 December 21, 2015 19:05 vinz OpenFOAM Pre-Processing 18 January 26, 2011 03:17 chelvistero OpenFOAM 11 January 15, 2010 20:43 ap Main CFD Forum 0 March 26, 2008 19:58 Chetan Kadakia FLUENT 3 October 10, 2002 03:31

All times are GMT -4. The time now is 00:34.