Comparison between triangular cylinder and screen far wakes

Triangular cylinder and screen (50%, solidity) far wakes have been examined and compared with a view to understand the effect of initial conditions on the self-preserving turbulence structures of various scales. Velocity data were obtained in the (x.y)-plane, i.e. the plane of mean shear, using an array of 8 X-wires. Measurements were made at x/h (x is the streamwise distance downstream of the cylinder and h is the height of the wake generator) = 330 for the triangular cylinder and 220 for the screen. The wake has been previously verified to be approximately self-preserving at these downstream stations. A two-dimensional orthogonal wavelet transform is used to analyse the measured velocity data. This technique enables the turbulence structures of different scales to be separated and characterized. Sectional streamlines and vorticity contours are examined and compared between the two wake generators. Discernible differences are observed in the turbulence structures of large-down to intermediate-scales. The differences are further quantified in terms of the contributions from the turbulence structures of different scales to the Reynolds stresses and vorticity variance. (C) 2003 Elsevier Science Inc. All rights reserved.