OOF2: The Manual
Table of Contents
This appendix contains the “Getting Started with OOF2 2.1” document that served as the surrogate 2.1 manual while the actual manual was being revised. It's being included here because it contains useful hints about migrating from version 2.0.5 to 2.1.0.
You can now solve time dependent problems with OOF2. There is a tutorial in the OOF2 Help menu that walks you through a simple example. This is a summary of the steps involved:
Create Materials using Properties that multiply time derivative terms in the equations. For example, mass density (Mechanical:MassDensity:ConstantMassDensity) couples to the second time derivative of displacement in the force balance equation. Heat capacity (Thermal:HeatCapacity:ConstantHeatCapacity) couples to the first time derivative of temperature in the heat equation.
Create a Skeleton and Mesh, activate Fields and Equations, and create Boundary Conditions as before. Neumann and Dirichlet boundary conditions with continuum profiles can now depend on time,
Use the new Scheduled Output page to define outputs to be produced during the solution process. If you don't define any outputs, the computation will work, but you won't be able to measure anything at intermediate times, because the data won't be stored. Available outputs include:
- Graphics window updates.
- Any quantity that can be computed on the Analysis or Boundary Analysis pages.
- The current state of the Mesh, saved in a file which can be reloaded by OOF2.
For an Output to be usable, it must be given a Schedule and a Destination. The Schedule determines when the Output will be produced. It can be periodic (at fixed time intervals), geometric (at time intervals that increase by a given factor on each step), or at a given time or set of times. The Destination determines what will be done with the Output. It can be a file or the OOF2 message window. Multiple Outputs can be sent to a single file.
Choose a Solver, using the Solver page. A Solver must be chosen for each SubProblem that you want to solve. Solvers come in three classes: Static, Adaptive, and Uniform. Choose Static if you're not solving a time dependent problem. Adaptive Solvers adjust the time step size to maintain a given level of accuracy at the cost of some computational overhead. Uniform Solvers always use the same step size. When selecting a Solver, you can choose either Basic or Advanced mode. Basic Mode gives you fewer options and tries to make reasonable assumptions. Advanced Mode lets you make all the decisions yourself.
Initialize the Fields on the Mesh by creating and applying Field initializers, using the central pane on the Solve page. Initializers can be time-dependent, and can be applied at a given time. If the time is given, then it will be the starting time for subsequent calculations. If it's not given, the starting time will be the end time of the previous calculation, or 0.
Set the end time for the calculation, at the bottom of the Solver page. If the end time is missing or the same as the Mesh's current time (the time of the Field initialization), the problem will be solved statically at the current time. If the end time is later than the current time and non-static Solvers have been chosen, the time evolution will be computed and output produced at each scheduled time up to the end time. If the end time is later than the current time, but static Solvers have been chosen, the solution will be computed quasi-statically at each scheduled output time.
Press the Solve button.
After computing a solution, you can apply the analysis tools on the Analysis and Boundary Analysis pages at any time between the start time and the end time by using the time widget at the top of the page. The buttons on the widget will take you to the times at which output was scheduled, but you type a different time into the widget OOF2 will interpolate to that time.
A Mesh in a graphics window can be displayed at any scheduled output time by using the arrow buttons at the top of the plot. The time can also be adjusted using a slider or by typing a new value into the time display. The data will be interpolated if necessary. It is also possible to animate the graphics display with the Animate option in the graphics window's File menu.
Time dependent solutions can be quite large, since the values of the Fields have to be stored at every Node at every output time. OOF2 allows this data to be cached either in memory or in temporary files on disk. Caching data in memory is faster, unless you don't have enough memory. The initial cache type for new Meshes can be set via the "Settings/Mesh Defaults/Data Cache Type" command in the main OOF2 window. The cache type for an existing Mesh can be changed with the "Set Data Cache Type" option in the "Mesh Operations" pane in the FE Mesh page.