Author Topic: Integral length scale in DFMethod  (Read 13 times)


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Integral length scale in DFMethod
« on: February 23, 2021, 02:05:30 PM »

I hope that this message finds you very well.
I have a question regarding the integral length scale calculation in Digital filter method.
I run a test case (sort of similar to the homogeneous turbulence available in the tutorial), and plot the mean value, rms of velocity fluctuation on the center-line of the box.
I calculate the cross correlation function for a specified point on the inlet. The value of the correlation is equal to one when Ruu(0) and is equal to zero when Ruu(inf) (Which make sense).
Now my concern is: In the majority of experimental work, the value of the integral length scale is equal to the integration of the correlation function when its value is equal to zero. What I mean is: The correlation function should be integrated from Ruu(0) until Ruu(..) = 0.
In the simulation, I set the value of longitudinal integral length scale to 1 (mm), and by calculating the length scale with the above methodology, I end of getting a value of equal to 2 (mm).
I tested this for a couple of more models and the results are the same!

Please advice me on this issue.