How can I access time and spatial derivatives of variables with CFX?
The following applies to CFX 11.0 SP1. Additional capabilities may be available in future releases. Time derivatives are partially supported in CEL; Velocity time derviatives can be accessed with the .Time Derivative operator by setting up an additional variable as follows: LIBRARY: ADDITIONAL VARIABLE: utderiv Option = Definition Tensor Type = VECTOR Units = [m s^2 ] Variable Type = Unspecified END END ... ... ADDITIONAL VARIABLE: utderiv Option = Vector Algebraic Equation Vector xValue = u.Time Derivative Vector yValue = v.Time Derivative Vector zValue = w.Time Derivative END ... ... Time deriviatives of other variables have not yet been added and must be accessed through USER FORTRAN. The spatial derivatives of most scalar variables can be accessed with the .Gradient X , .Gradient Y and .Gradient Z operators. An example for epsilon is shown below: LIBRARY: ADDITIONAL VARIABLE: epsgrad Option = Definition Tensor Type = VECTOR Units = [m s^3 ] Variable Type = Specific END END ... ... ADDITIONAL VARIABLE: epsgrad Option = Vector Algebraic Equation Vector xValue = Turbulence Eddy Dissipation.Gradient X Vector yValue = Turbulence Eddy Dissipation.Gradient Y Vector zValue = Turbulence Eddy Dissipation.Gradient Z END ... ... 

