physical significance of Uniformity Index?

[Smruti R.]

what does uniformity index refer to? Let's say, if the uniformity index of a variable on a surface will be calculated, it gives one value per time-step. what does that one value per time-step physically signify?

[Omkar Pawar]

The uniformity index of a variable on a surface signifies how uniformly that variable is distributed across the surface. When it gives one value per time-step, it indicates the degree of uniformity at that specific moment. A value of 1 represents the highest uniformity, meaning the variable is evenly distributed across the surface.

[jcooper]

The uniformity index basically compares the variable value in a surface cell to the mean for that surface.  The convention for the area integral used to calculate the value of the uniformity index is setup in such a way that if every cell on the surface has the mean value, a value of 1 is returned for the index.

 

The area-weighted uniformity index definition is shown below.  The area-weighted uniformity index can be used to determine if a variable has a uniform value across a surface.  There is a similar mass-weighted uniformity index that can further determine if the flux of a variable is also uniform across the surface.

These indices are described in the Fluent help documentation here:

https://ansyshelp.ansys.com/Views/Secured/corp/v252/en/flu_th/flu_th_sec_compute_surfint.html#flu_th_surf_int_ui