Stationary Acceleration
The Stationary Acceleration subnode () can be useful to accelerate the solution process for nonlinear problems with a time-periodic stationary solution. You can add it as a subnode to all Time-Dependent Solver and Time Discrete Solver nodes. Instead of time-marching the problem from start to finish, the Stationary Acceleration node solves for a number of periods and then extrapolates the solution forward in time based on the average solution and the average time derivative. This solution process is repeated until the average time derivative has reached steady state.
The Stationary Acceleration node can be used to speed up the solution process for some types of plasma models, but it is not used by default for any physics interfaces.
Stationary Acceleration
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In the Variables list, add the dependent variable for which you want to use stationary acceleration. Click the Add button () to open an Add dialog box that contains all dependent variables in the study. Select the variables that you want to add and then click OK. You can also delete variables from the list using the Delete button ().
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From the Components list, select the dependent variables for which the stationary acceleration performs the averaging and extrapolation. Select All (the default) to perform averaging and extrapolation for all variables, or select Manual to select the variables that you want to apply stationary acceleration from the list that appears.
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In the Frequency field, enter the frequency of the periodic solution. The default value, 13.56 MHz, is a frequency that is commonly used for plasma processes.
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In the Stationary tolerance field, enter the tolerance used to terminate the outer acceleration iterations, when the average time derivatives are small enough (default value: 0.01).
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In the Number of extrapolation cycles field, enter the number of periodic cycles used to extrapolate the solution (default value: 50). The higher this number is, the more the solution process is accelerated, but at the same time the process can lead to an unstable acceleration iteration process.
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In the Number of period averaging cycles field, enter the number of cycles over which the stationary acceleration takes the average (default value: 5).
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In the Number of smoothing cycles field, enter the number of cycles that the stationary acceleration solves for in each iteration of the acceleration scheme (default value: 10). The average is taken over the last cycles.