By default, Ansys Polyflow automatically calculates an initial solution by evaluating at all parameters for which an dependency has been declared. If (the default value in Ansys Polydata), and you are using the evolution function , Ansys Polydata will automatically change to 0.001 and issue a warning message.

In free surface problems, an initial solution is calculated on the initial mesh; the kinematic condition is dropped but the force boundary condition is maintained. See Theory and Equations for details.

If a previously-saved results file (called res, by default) is available, then Ansys Polyflow can read the initial solution from it. See Starting an Evolution or Time-Dependent Calculation from Existing Results and Restart Files for details. With a corresponding restart file (which is automatically saved during an evolution calculation and called rst by default), Ansys Polyflow can also read the derivative of the solution. Without an rst file, Ansys Polyflow will not be able to perform a first-order or second-order continuation, and will not find the old value of . Should you want to continue the calculation starting from the res file anyway, you need to first modify the initial values of and in the Numerical parameters menu. Specifying the values that correspond to the res file is almost equivalent to using an res file and an rst file. The only difference is that the derivative of the solution is not available and the convergence of the continuation may be different.

With an rst file, Ansys Polyflow will find the last value of and be able to restart exactly at the level where the program was interrupted. Typically, when the second-order Adams-Bashforth scheme is used, the derivatives at two previous evolution steps are used to extrapolate the solution. When the first-order explicit Euler scheme is used, the derivative at the previous evolution step is used for the extrapolation.

When the zero-order scheme is used, in order to avoid a small evolution step, the initial evolution step (dsini) is the maximum between the value you specified and the one read in the rst file. You should never modify problem data such as model parameters or boundary conditions when starting from an rst file. Any deviation will result in an ill-posed problem.