Which display method demonstrates turbulence by showing variance among velocities?

• A. Variance
• B. Autocorrelation
• C. Zero-crossing detection
• D. Phase quadrature detection

Answer: (A)

Turbulence shows up as velocity values that fluctuate around a mean, so the display that best captures this behavior is one that highlights how widely those velocities vary from the average. A variance display does exactly that by measuring the spread of velocity samples—their deviations from the mean squared—providing a direct sense of turbulence intensity.

Autocorrelation looks at how the velocity values relate to themselves at different times, revealing whether fluctuations persist or repeat, but it doesn’t directly show how spread out the velocities are at any given moment. Zero-crossing detection counts when the velocity signal crosses zero, which tells you about the frequency of fluctuations rather than their magnitude distribution. Phase quadrature detection uses phase information to resolve velocity from two signals, focusing on phase relationships rather than the overall dispersion of velocities.