Gamma Uniformity Index

The Gamma Uniformity Index is a measure of flow uniformity on a clip plane.

It is the normalized RMS of the difference between the local velocity and the spatial mean of the velocity integrated over the area of the clip plane.  See the attached equation.

Gamma Uniformity Equation

Equation for Gamma Uniformity

Attached is a demonstration of EnSight Python for calculating the Gamma Uniformity Index. This is only intended as a prototype demonstration script for calculating this variable.

Directions for use: make a clip plane in your flow. Select the clip plane part.  If your velocity variable is different than ‘VELOCITY’ then you will have to edit this .py file to the correct variable name. Now run this script. You will have several intermediate variables calculated, but the gamma uniformity index is a constant named gam_uniform.


Transient STL File Conversion

Do you have a series of STL files which represent moving geometry? If this geometric motion is simple (constant rotation, or translation), you can utilize the “Rigid Body Motion” capability already in EnSight. However, what if the motion is complex, or if the STL surfaces change from timestep to timestep? The native STL file reader in EnSight expects steady state STL file information (either a single STL file, or multiple STL files via .xct; but still only for a single timestep).

A short Python routine can be used here to actually help out. This python routine takes a series of STL files, and assumes that they are part of a transient sequence, with one STL file per timestep. The Python routine converts the STL information into EnSight Case Gold format files, with multiple .geo files, allowing you to view your STL information in a transient nature. This routine can be further modified and customized to suit your needs, file conventions, or time information (since no time information is explicitly available within the .stl file).

Please feel free to contact CEI, or the author of the routine ( for further customization or questions.

To download this example Python utility, please click on the link below, and place into your User Defined Tools area.

Click here to download Multiple Transient STL Conversion Tool

Current Version : 1.0 (11-January-2013)

Current Limitations/Assumptions:

a. A series of ASCII stl files all with ‘.stl’ extension
b. Will convert and assume ALL “*.stl” files in the directory are to be converted.
c. All STL files have the same number of parts (but can change triangles from timestep to timestep)
d. Since there is no Time information with STL, will force Time 0 = 0.0 seconds, Time 1 = 1.0 seconds, etc
If user needs other time information, just change the time values in the .case file
e. STL files are all triangles (no quads)

Help Documentation can be found here :