Effects of initial conditions on a wavelet-decomposed turbulent near-wake

The effect of initial conditions on the turbulent structures of various scales in a near-wake has been investigated for two wake generators, i.e., a circular cylinder and screen of 50% solidity, of the same characteristic dimension. Velocity data were obtained at x/h (x and h are the stream-wise distance downstream and the height of the wake generators, respectively) =20 using 16 X wires, eight aligned in the plane of mean shear and eight in the plane parallel to both the cylinder axis and the flow direction. A wavelet multi-resolution technique was used to decompose the velocity data into a number of wavelet components based on the central frequencies, which correspond to the scales of turbulent structures. It was found that the behaviors of intermediate- as well as large-scale structures depend on the initial conditions. In the circular cylinder wake, the large- and intermediate-scale structures make the largest (and comparable) contribution to Reynolds stresses, but in the screen wake there is a significant difference in the contribution between the two types of structures. The two-dimensionality of the wavelet component is also examined.