# Additional Variable - Diffusive Transport Equation

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 September 21, 2007, 01:17 Additional Variable - Diffusive Transport Equation #1 RadheShyam Das Guest   Posts: n/a Hi, I want to solve a transport equation for an additional variable that contains just the transient term and the source term. i.e. no need of diffusion and advection terms. Using the Diffusive transport equation and trying to set Kinematic Diffusivity to zero does not seem to work. Doing so, the solver throws an error and terminates after a few iterations. This is the error during the run. Fatal bounds error detected --------------------------- Variable: AggV.Dynamic Diffusivity where AggV is the additional variable. Should I set the kinematic diffusivity of the additional variable in the Pre to a sufficiently lower value instead of setting it to zero. Looks like setting it to zero is causing numerical problem I am solving for a multicomponent gas phase problem where the diffusivity of all components are in the order of 10^-5 m^2/s. Can anyone suggest a safe value for diffusivity? Or is there any other way to "trick" CFX into solving just the transient and the source terms? Thanks, RadheShyam Das.

 September 21, 2007, 11:54 Re: Additional Variable - Diffusive Transport Equa #2 CycLone Guest   Posts: n/a Hi RadheShyam, Based on your description it sounds like you still need the advection term. If that is the case, you can specify it is a "Transport Equation" and set your kinematic diffusivity directly as 1e-5 [m^2/s]. -CycLone

 October 18, 2007, 11:24 Syntax of "GRANTEMP " variable #3 Nut Guest   Posts: n/a How we insert the "GRANTEMP" variable in the expression? We found the error; ERROR # 001100279 has occured in subroutine ErrAction. Message: Name_MOD: Error finding variable "GRANTEMP_FL2"

 October 18, 2007, 12:35 Re: Syntax of "GRANTEMP " variable #4 opaque Guest   Posts: n/a Dear Nut, It seems you tried to access the granular temperature variable, and the variable has not been defined for your setup. This variable is internal to the ANSYS CFX solver, and it is only defined based on the physical models you have selected. Without additional information, it is not easy to help. Opaque