How to modify the Schmidt number in CFX for additional variables model?
In order to simulate the thermal tracing,I apply additional variables (as temperture T)in the caculation.Then,how to change the turbulence Schmidt number in CFX?

You can just enter whatever Schmidt number you like. But I seem to remember it must be constant in space and time.

where can i do this in CFX ?

In the turbulence model details, I cannot remember the details of exactly where as I am not at the computer right now.

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For an additional variable it's under Fluid Models/Additional Variable Models/Turbulent Flux Closure/Turb. Schmidt Num. 
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"For an additional variable it's under Fluid Models/Additional Variable Models/Turbulent Flux Closure/Turb. Schmidt Num" is found in CFX GUI? The version i used is 12.1. In "Fluid Models/Additional Variable Models" option,there is no "Turbulent Flux Closure" option. 
Is your additional variable a convection and diffusion AV? This is the only type of AV where you get these options I suspect.

I am not clear about that.
how can i define the AV as convection adn diffusion? I add a AV in "Expression,Functions and VariablesAdditional Variables",and define the AV option as Transport Equation. Is it right? 
Transport equation is convection only. Turbulence adds diffusion so is not available for that AV option. You want a transport & diffusion AV.

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The transport equation for AVs include both convection and diffusion, so there should be an option for Turbulent Flux Closure. The settings available in the gui are the Eddy Diffusivity model and the Turbulent Schmidt number. 
Firstly I must admit I did not check this answer before I posted it so if I goofed then thanks Lance for picking it up.
I seem to remember that AVs could be either algebraic equation, transport equation only, diffusion equation only or transport and diffusion equation. The transport equation equation option has no diffusion component. But if my memory is incorrect then oops :) 
Thank you for all your replay.
I find the reason for the Schmidt seeting problem. Befor version 12.1 of CFX ,threre is no Turbulent Flux Closure option in GUI. We have to use CCL for changing the Schmidt Nb.I find the related CCL as follows: HEAT TRANSFER MODEL: Option = Thermal Energy TURBULENT FLUX CLOSURE: Option = Eddy Diffusivity Turbulent Prandtl Number = XX END END After i import the CCL,how to see the changed Schmidt value? 
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