The Nature of Probability Density Functions in Turbulent Channel Flow

The nature of probability density functions of streamwise velocity, wall-normal velocity and Reynolds shear stress fluctuations is analysed for a turbulent channel flow using hotwire anemometry and particle image velocimetry measurements. The hotwire measurements are validated with data from literature. The particle image velocimetry measurements capture the probability density functions well albeit at a smaller acquisition sampling rate when compared to hotwire. The probability density functions of the streamwise and the wall-normal velocity fluctuations exhibit Gaussian behaviour close to the wall at least till the end of the inertial sublayer, while the probability density functions of Reynolds stress fluctuations exhibit non-Gaussian, peaky behaviour throughout the channel, depicting the episodic nature of turbulence production.