After you have determined the parameter on which you will apply evolution, follow the steps below to set up the problem:
In the Create a new task menu, specify an evolution problem, and define the geometry type, etc., in the usual way.
Evolution problem(s)
To set an evolutive parameter, use the following steps to define the parameter’s value as
: For nonisothermal problems, you can easily apply appropriate evolution schemes related to three typical sources of nonlinearities (that is, viscous and wall friction heating, thermal convection, and the temperature dependence of the viscosity) in order to improve convergence by performing the following steps. See Using Evolution in Heat Conduction and Nonisothermal Flow Calculations for details.
Click Numerical parameters in the task menu.
Click Enable evolution for non-isothermal flows.
The current task will then be converted into an evolution task if it was previously defined as a steady task, and predefined evolution functions will be automatically defined on the following parameters: viscous and wall friction heating, thermal conduction, and the temperature dependence of the viscosity. Note that if you manually define evolution functions on these parameters (using the button), such manual definitions will be ignored during the calculation and the automatic definitions will prevail.
As stated in Using Evolution in Heat Conduction and Nonisothermal Flow Calculations, it is important to note that the evolution for nonisothermal flows takes care of the nonisothermal component of the flow case only. In other words, it is always a good idea to make sure that the corresponding isothermal calculation converges.
For viscoelastic problems, you can apply appropriate evolution scheme s to the viscoelastic model in order to improve convergence by performing the following steps. See Convergence Strategy for Viscoelasticity for further details.
Click in the task menu.
Click Enable convergence strategy for viscoelasticity.
The current task will then be converted into an evolution task if it was previously defined as a steady task, and predefined evolution functions will be automatically defined on parameters of the viscoelastic modes. Note that if you manually define evolution functions on these parameters (using the EVOL button), such manual definitions will be ignored during the calculation and the automatic definitions will prevail.
As stated in Convergence Strategy for Viscoelasticity, it is important to note that the convergence strategy for viscoelasticity takes care of the viscoelastic component of the simulation case only. In other words, it can be a good idea to make sure that the corresponding Newtonian calculation converges.
For an evolutive material parameter, follow these steps:
Go to the menu appropriate for setting the value of this parameter. For instance, if the parameter is density, select the Density menu item in the Material data menu.
Density
Click the button at the top of the Ansys Polydata menu to enable the evolution inputs.
The button will change to EVOL [on] to indicate that the evolution inputs are enabled.
Select the menu item appropriate for the evolutive parameter. For density, this would be Modification of density.
Modification of density
Enter
when Ansys Polydata prompts for the
New value. Click to accept this new value.
A menu will appear from which you will select the function
. The available functions are described in
Available Evolution Functions. If several parameters are evolutive, a different function
can be chosen for each one. Select Upper level menu to complete the specification.
Click the button again to disable the evolution inputs.
The button will change to EVOL [off] to indicate that the evolution inputs are disabled.
For an evolutive boundary condition, follow these steps:
Select Flow boundary conditions or Thermal boundary conditions from the sub-task menu, or Fluid Fraction boundary conditions from the Material Data menu of the fluid fraction transport sub-task.
Select the boundary condition you want to set, and click Modify.
Click the button at the top of the Ansys Polydata menu to enable the evolution inputs.
The button will change to EVOL [on] to indicate that the evolution inputs are enabled.
Select the type of boundary condition you want to impose. For instance, for a flow boundary condition, you might choose Normal and tangential velocities imposed (vn, vs).
After you enter the value of each numerical parameter (such as
) associated with this boundary condition,
clicking Upper level menu will cause a
menu to appear, from which you can select the function
. The available functions are described in
Available Evolution Functions. Boundary conditions can be position dependent (such as a linear function of coordinates) and evolutive (
dependent). That is, 
may be a constant, or a function of
coordinates. If several parameters are evolutive, a
different function 
can be chosen for each one. Select Upper level menu to complete the specification.
Click the button again to disable the evolution inputs.
The button will change to EVOL [off] to indicate that the evolution inputs are disabled.
Repeat this step for each evolutive parameter.
Continue setting up your problem in the usual way.
After all sub-tasks have been defined, select Numerical parameters from the F.E.M. Task menu.
Numerical parameters
In the Numerical parameters menu, select Modify the evolution parameters.
This will bring up the Evolution parameters menu, where you can modify the following parameters of the evolution:
initial value of S
This is the value of
used to calculate the parameter value(s) for the
first computation. Important: If
is being used for any parameter, the initial
value and upper limit of 
should be chosen to prevent 
being set to 
.upper limit of S
This value of
should be chosen to give parameter value(s) that
correspond to the value(s) in the problem you want to solve. initial value of delta-S
This is the starting value for the
increment 
. min value of delta-S
If
is too large, the problem obtained will not
converge. When this happens, 
will be decreased, and a new problem tried. To
prevent an infinite loop, you should select a lower bound for
here. If this lower bound is reached, the
evolution process is terminated. max value of delta-S
This sets an upper bound for
. max number of successful steps
Here you can set the upper bound on the number of steps used to reach the original problem.
You can also choose the integration method for the evolution calculation. These methods are equivalent to those used in time-dependent flows, and are described in Theory :
0-order method (explicit Euler)
implicit Euler method (the default scheme)
Galerkin method
Crank-Nicolson method
When you have enabled evolution on moving boundaries and/or evolution for nonisothermal flows, you still have the ability to modify the evolution parameters, including the initial value of
and the upper limit of 
. If you change the evolution parameters (for example, the
initial / final values of 
), the parameters of the evolution functions will be
adapted / scaled in order to preserve the evolution path.