MATLAB: Rules of Reynolds Averaging

derivativederivative of vectorMATLABMATLAB and Simulink Student Suitereynolds averagevector

According to the rules of Reynold's Averaging, Which can be found here under 11.1,
. Is there anyway to show this and the other rules in Matlab either numerically or symbolically?
I tried to create an array, u:
u = [1,3,6,8,24];
uprime = diff(u)
which output a vector of differences (not sure if this is what I wanted).
Then I tried to take an average of uprime using the following code below:
mean(uprime)
According to the rule, I should have gotten 0, but I got an average of the numbers in the vector which was nonzero. Am I misinterpreting the rule or is the diff function not actually taking a derivative?

Best Answer

  • uprime doesn't mean du/dt here. It means u - umean.
    u = [1,3,6,8,24];
    umean = mean(u);
    uprime = u-umean;
    mean(uprime)
    ans =
    -3.5527e-16