I see much use of the peak coherent turbulent kinetic energy in tech report about TurbSim. But I really want to know how the peak Ecoh is defined. Is it the peak value in every 10 minutes or so?

Ecoh is defined as 0.5*sqrt( (u’w’)^2 + (u’v’)^2 + (v’w’)^2 ), where u’, v’, and w’ are the fluctuating parts of the streamwise, transverse, and vertical wind speeds. By fluctuating, I mean that the average wind speed–typically over a 10-minute period–has been removed. (By definition, the u component is aligned with the average wind direction over a given time period–again, typically 10 minutes. Thus, the average transverse wind speed and average vertical wind speed are both zero over that time period.) The peak value in Neil’s report is the maximum value of Ecoh over that 10 minute period.