On the Origin and Evolution of Three Dimensional Effects in the Mixing Layer

Effects of free-stream turbulence intensity on laminar separation bubbles

“…Bradshaw [127] proposed the location of the peak in the turbulence level, which typically occurs around the streamwise location of the first vortex merging event [103]. Jimenez et al [128] suggested the location at which the roll-off exponent of the spectra of velocity fluctuations reached −5/3, indicative of a turbulent flow. This value was shown by Huang and Ho [113] to consistently occur between the second and third merging locations for varying values of R. Finally, transition has been suggested to occur where the level of mixing rapidly grows [119,126], and was shown by Ho and Huerre [103] to agree well with the third merging location.…”

Slat Cove Unsteadiness: Effect of 3D Flow Structures

“…The reasons behind the discrepancy between the two simulations are not clear. They may be caused by the differences in numerical parameters (spanwise grid and temporal discretization parameters), or be an artifact of the somewhat longer duration of averaging enabled by the smaller number of grid points and a larger time step during the grid S1 simulation, or even be related to the facts that mixing layer statistics can vary significantly across individual spanwise locations [44,45] and that the PIV data was acquired at a single location. Nonetheless, the level of agreement between the three sets of profiles is quite encouraging.…”

“…Unfortunately, the higher resolution data does not extend sufficiently farther downstream (as to match with the larger field of view data within a finite region of overlap). It is also known that mixing layer flows tend to exhibit significant spanwise variations in the time averaged flow statistics [38,44,45,47] and, therefore, measurements at multiple spanwise locations are necessary to characterize the streamwise evolution of the flow. In view of the above observations, a more complete validation of the predicted TKE evolution will have to await additional measurements of the slat cove flow field.…”

The plane mixing layer flow visualization results and three dimensional effects

“…If they are an essential part of the structure of a turbulent mixing layer then, it might be argued, their scales should increase as the mixing layer grows downstream. Indeed, there is some evidence for this from spanwise correlation measurements (Jimenez et al, 1979a;Bernal, 1980) and from flow pictures such as the one in Fig. 2.…”