5.8.2. Saving Data at a Specified Point

There may be cases where you want to keep track of the value of one or more solution fields at a specific point in the domain (or at several points). You can do this by defining a data probe in Ansys Polydata. The data probe definition will be used by Ansys Polyflow to save the probe data at specified intervals during the calculation. The procedure for defining a data probe is as follows:

  1. In the top-level Ansys Polydata menu, select the Outputs menu item.

      Outputs

  2. Select Manage Probe(s) output near the bottom of the menu.

      Manage Probe(s) output

    You can specify a probe file name, a location, and a mode of probing (Moving node or Fixed geometry location). Ansys Polyflow creates a set of .prb files that contains the evolution of a field as a function of time (or S, if evolution task). The mode of probing are as follows:

    •   Moving node: The closest node to the given location is determined in the initial configuration. You can get the evolution of fields for the closest node as a function of S or time.

    •   Fixed geometry location: You should determine value of the fields at the given location at every time/evolution step. As the mesh can deform, value of the fields will not be fixed at a given node.

  3. Select Creation of a new probe to define a new data probe.

      Creation of a new probe

  4. Specify the naming convention for the probe files, using the Change prefix of probe files menu item.

      Change prefix of probe files

    The probe file prefix will be used at the beginning of each probe file name. If, for example, the prefix is myrun1 and the simulation contains velocity, pressure, and temperature fields, Ansys Polyflow will write the following files:

    • myrun1_XYZ.prb for the coordinates field

    • myrun1_UV.prb for the velocity field

    • myrun1_P.prb for the pressure field

    • myrun1_PSI.prb for the stream function field (2D only)

    • myrun1_T.prb for the temperature field

  5. Specify the location of the probe, using the Change probe position menu item.

      Change probe position

    When prompted for each, specify the value of the , , and (for 3D) coordinates of the probe position.

  6. Select Upper level menu to return to the Manage probe(s) output menu. You will see a new menu item for the probe you created (for example, 1-st probe).

    If you need to modify the probe’s definition, select this item and repeat the appropriate step. If you want to create additional probes, repeat all steps starting with the selection of Creation of a new probe.

During a steady-state calculation, Ansys Polyflow will save the probe files once at the end of the calculation. For a time-dependent or evolution calculation, the probe files will be saved according to your specification of the output triggers, described in Output for Time-Dependent, and Evolution Calculations. The files are written in ASCII format, so you can examine them yourself using a text editor, or manipulate the contents for use in an external plotting program or spreadsheet.

Here is an example probe file with time in the left column and flow rate in the right column:

Field FLOW_RATE on (Subdomain 1*Boundary 1).
 
 
 
 5.0000000e-02  7.6653222e-02
 1.0000000e-01  5.1644472e-02
 1.5000000e-01 -2.8483866e-02
 2.0000000e-01 -7.4048509e-02
 2.7500000e-01 -1.6863891e-01
 3.8750000e-01 -3.2648889e-01

Note:  Probe files are automatically generated for any solution field listed in the listing viewer that has a single value on a boundary or sub-domain (for example, torque on a moving part, dissipated power—when postprocessing is enabled, and convective heat flux—when postprocessing is enabled).

Probe files are also automatically created for:

  • parameters defined with an evolution scheme

  • extracted values (those generated by internal optimization)

  • extracted values (those used as stopping criteria for transient or evolution simulations)