FEATool
v1.9 Finite Element Analysis Toolbox |

Postprocessing

The last step in the simulation process is postprocessing and visualization. FEATool automatically switches to postprocessing mode after a solution has been computed. Alternatively, one can press the mode button to manually switch to postprocessing mode.

The toolbar button and corresponding menu option opens the **Postprocessing Settings** dialog box which controls various postprocessing options explained in the section below.

Images or snapshots of the current plot can be saved in jpeg or png formats by using the toolbar button. In the corresponding dialog box exporting and sharing results to Facebook, LinkedIn, Twitter and, Plotly is also supported.

Alternatively, the **Plotly** button renders the current visualization with the Plotly javascript library and opens a corresponding html web page in the default web browser. The Plotly plot can be actively inspected, manipulated, exported, and shared via the plotly cloud.

The **Post** menu allows for switching to **Postprocessing Mode**, opening the **Postprocessing Settings...** dialog box, and advanced postprocessing options such as subdomain and boundary integration, and export and interfacing with external tools as explained in the section below.

The visualization options in **Postprocessing Settings** dialog box shown in the following figure include choosing pre-defined or entering user defined custom expressions for surface, height, contour, and arrow plots. Moreover, there are options for choosing the solution to display (for time dependent solutions), selecting or excluding which cells to display, setting the min and max plot scale limits, and switching the colorbar on and off. The options are explained in more detail below.

Note that as is usual in FEATool postprocessing expressions accept general expressions involving dependent variables, space dimensions, constants, and mathematical operators. Expressions such as *v+ux+sin(2*pi*y)* where *u* and *v* are dependent variables (so that *ux* is the derivative in the x-direction), are perfectly valid.

Surface plots allows visualization of both predefined postprocessing expressions and user defined ones on the domain surface. To use the surface plot option check the corresponding check box and enter the expression to visualize.

For convenience, clicking on a 2D surface plot will evaluate the surface expression at the corresponding point and print the evaluated value.

In two dimensions the height expression option is available which scales a surface plot in the z-direction with the computed value of the height expression. To use the height expression option check the corresponding check box.

Two dimensional problems also allow for contour or isoline plots. To use the contour plot option check the corresponding check box and select or enter an expression for the contour values. The contour values can be specified in the *Contour levels* edit field, either as an integer for the number of contours, or a space separated vector to specify fixed values for the contour levels.

Similarly to contour plots, three dimensional problems allow for isosurface plots. To use the isosurface plot option check the corresponding check box and select or enter an expression for the isosurface values. The iso plot values can be specified in the *Iso levels* edit field, either as an integer for the number of isosurfaces, or a space separated vector to specify fixed values for the iso levels.

Three dimensional problems also allow for slice plots which are surface plots perpendicular to the coordinate axes. To use the slice plot option check the corresponding check box and select or enter a slice expression. The *Slice positions* can be prescribed as a single integer signifying the number of equally spaced slices, or a space separated list indicating the exact position of each slice for the chosen axis.

Arrow plots are available in two and three dimensions. To use arrow plots check the corresponding check box and select or enter expressions for the vector field defining the direction of the arrows.

General settings allow for selecting **Solution time** if several solutions are available as with time-dependent problems. Moreover, with **Cell selection** one can limit the postprocessing to a certain subset of cells by entering a logical expression. For example, the cell selection expression *x>0* would only plot cells on the positive x-axis. The **Colorbar** check box toggles the colorbar on and off, and the **Limits** vector indicates and prescribes the minimum and maximum values of the colorbar range.

The **Post** menu allows for the following advanced postprocessing options.

Evaluates the minimum and maximum values for expressions on subdomains or boundaries. The **Evaluation Expression** can either be selected from a list of predefined postprocessing expressions, or entered as a user defined custom expression in the corresponding edit field. The **Solution Number/Time** can also be selected if more than one is present. In the **Selection** edit field a space separated list of **Subdomains** or **Boundaries** is specified for which the minima and maximia should be evaluated. The numerical **Integration Rule** prescribes how many evaluation points should be used for each grid cell in the evaluation process. The result will be printed in the **Evaluation Result** field as well as the command log in the main Gui.

Allows both pre and user-defined expressions to be evaluated on single points or lines. Coordinates for the evaluation points can be entered as space separated vectors for each space dimension in the corresponding edit fields. The **Solution Number/Time** to evaluate can be selected in the drop-down listbox. The result will be printed in the **Evaluation Result** field as well as the command log in the main Gui.

Integration of postprocessing expressions over subdomains **Subdomain Integration...** (calling intsubd) and boundaries **Boundary Integration...** (calling intbdr) can be performed by selecting the corresponding menu options. The integration dialog box allows for selecting predefined postprocessing or entering user defined expressions in the **Integration Expression** edit field. Numerical **Integration Rule**, **Solution Number/Time**, and **Subdomain/Boundary:** to integrate over can also be set. The result will be printed in the **Integration Result** field as well as the command log in the main Gui.

The default postplot postprocessing function call command can be edited and changed with the **Postprocessing Command...** menu option.

The solution and postprocessing data can be exported to be used with the General Mesh Viewer (GMV) through the **Export Results... > GMV Format...** menu option.