Does anyone have any experience of using CFD results to assess the mixing efficiency in a system using a coefficient of variation (CoV) calculation?

I am trying to simulate some physical lab tests which have measured dye concentrations using LIF (laser induced fluorescence) to calculate the CoV. Although hydraulic losses in the model match the physical results well, the CoV values are significantly different.

I have used the point parameters function to extract detailed concentrations across the test section to carry out the CoV calculation from the CFD model. The LIF measurement uses the dye concentration of each pixel (200,000) to calculate the CoV. The CoV from the CFD model using the point parameters function to extract the data does not really vary once the number of points increases over 500-1000, although I have been using 7000 points, still significantly less than the pixel count.

My thoughts are that possibly:

- the model isn't representing the turbulence or secondary flows adequately

- the CFD results aren't suitable for a comparative CoV calculation

Any thoughts?