One-and two-dimensional density probability distributions for turbulent velocities and for gradients of turbulent velocities were measured using high-speed computing methods. Measurements made downstream of a grid and in the turbulent boundary layer are compared. The higher-order correllations where h is a time interval and f is either the fluctuating turbulent velocity u(t) or its gradient ∂u∂t , are determined. The probability density distribution is represented as a Graan Charlier distribution of the type where The coefficients Aj,k in the above expressions are determined as functions of the measured correllations Tm,n and the resulting probability distribution derived from the Gram-Charlier distribution is compared to the measured distribution.
In comparing the statistical characteristics of the turbulent field downstream of a grid to those in the turbulent boundary layer their interrelation with the theoretical ideas involving the intermittency of the small-scale structure is discussed.
This work was performed with partial support of the Division of Biology and Medicine of the Atomic Energy Commission.
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