Advanced

Reverse Pathlines

From time to time, we have users that wish to trace pathlines backward in time. This can be accomplished fairly easily using the EnSight casefile format.

Note:  If your data is in a different format, you can use File → Export → Geometric Entities to convert it into casefile format).

  1. Example 6: Reverse the Order for the Timeset Files, by Using a Negative Filename Increment.

    TIME

    time set: 1

    filename start number: 1

    filename increment: 1

    time values: 0.0 2.0 4.0 6.0 8.0

    Change to:

    TIME

    time set: 1

    filename start number: 5

    filename increment: -1

    time values: 0.0 2.0 4.0 6.0 8.0


  2. Create a vector variable that is the negative of the normal vector field. Simply use the variable calculator to create a new vector variable (neg_vector = - vector).

  3. Create pathlines using the neg_vector variable.

Limiting Pathlines

If your geometry is much larger than your region of interest, you can try setting the total time limit value in the particle trace dialog (with the Advanced toggle turned on). This will stop traces after a given time and avoid wasted computational time outside your region of interest. You can estimate the total time as follows. Determine the total distance of your region of interest, and divide it by an average velocity to get a time (making sure all units are consistent in this calculation and within EnSight. Then try the run with a few pathlines. If you have significant recirculation within sections of your flow, this method will stop particles long before they exit your region of interest. In this case, you may want to consider using spatial limits on your flowfield.

If your geometry is much larger than your region of interest and temporal limits stop some of the traces too soon, then you can set spatial limits for your particle trace. There are two ways to limit the volume in which your pathline is traced. The first is to create a new part of limited volume and use this part as the trace parent; you can do this by using the box tool to define the region of interest and do an interior cut of your model volume (and then select the cut part as your parent part for your pathline trace). The trace will stop when it reaches the box tool volume limits. The second is to set six environmental variables before you start up EnSight to limit the x, y, or z max and/or min:

  • ENSIGHT10_MIN_TRACE_X

  • ENSIGHT10_MAX_TRACE_X

  • ENSIGHT10_MIN_TRACE_Y

  • ENSIGHT10_MAX_TRACE_Y

  • ENSIGHT10_MIN_TRACE_Z

  • ENSIGHT10_MAX_TRACE_Z

The trace will stop when it falls outside the bounds set by the environmental variables. The downside of using the box tool is that it costs memory to create a new part (which can be substantial on a large dataset). The downside of setting environmental variables is that you must do this before you start EnSight.