EXPERIMENTAL INVESTIGATION OF VELOCITY AUTOCORRELATION FUNCTIONS IN TURBULENT PLANAR MIXING LAYER

The velocity autocorrelation coefficient correlates the velocity in the time domain but at the same spatial position. Turbulent planar mixing layer consists of two types of turbulence, that is, shear turbulence in the central shear layer and nearly homogeneous turbulence in both the high-and low-speed free stream sides. It is interesting to know what kind of function forms can be used to represent faithfully the experimental observations of the velocity autocorrelation coefficients in the mixing layer. Various velocity autocorrelation functions are tested with the measured data. It is found that the Frenkiel function family is the most proper form to represent the measured velocity autocorrelation coefficients in both the shear layer and free stream regimes.