Time scales eddy turnover

This time scale is usually referred to as the eddy turnover time. 

Equation (3.82) illustrates the importance of the scalar spectral energy transfer rate in determining the scalar dissipation rate in high-Reynolds-number turbulent flows. Indeed, near spectral equilibrium, 7 (/cd, 0 (like Tu(kDi, 0) will vary on time scales of the order of the eddy turnover time re, while the characteristic time scale of (3.82) is xn <[Pg.99]

The scalar spectral energy transfer rate XA m)- t) will vary on time scales proportional to the eddy turnover time re. At high Reynolds numbers, (3.131) and (3.132) quickly attain a quasi-steady state wherein... 

The flame lift-off height, which is related to the ignition distance, was inversely affected by the excitation frequency. Since the flow time scale decreased with increasing frequency, the data were plotted as a function of the Damkohler number in Fig. 29.14, where the characteristic flow time scale was estimated by large-eddy turnover time as 1/17 and the characteristic chemical reaction time was computed using an ignition delay model [21] for ethylene jet. While the results did not show any evidence of critical Damkohler number, the range... 

Unfortunately, the simplified engineering method doesn t provide much information about the structure of turbulence and the dynamics of the interactions between the turbulent vortexes. The only structural information extracted from the second moments in relation to the structure of turbulence is the length scale. A, and the only information in relation to the dynamics of turbulence is the time constant representing the eddy turnover time, A A A ... 

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