Coherent structures are key building blocks of complex three-dimensional flows. Such structures provide substantial insight into the dynamics and are correlated to quantities of engineering interest. In complex situations, experimental visualizations of coherent structures are often obtained as projections of the actual 3-D arrangement on a 2-D plane. The relationship between the 2-D projection and the 3-D reality is often non-intuitive and non-unique, leading to difficulties in constructing a model for the overall flowfield. In this paper, we describe the use of high-fidelity CFD to resolve this problem, by collecting results on a wide range of 3-D flowfields including subsonic (flow past an airfoil at angle of attack), low supersonic (jet issuing from a nozzle) and high supersonic (swept shock turbulent boundary layer interactions and base flows). The general procedure is to first demonstrate successful validation with different types of experimental visualization data and to then leverage successful comparison to generate a three-dimensional model of the flow. The analysis highlights many interesting observations that may guide the evolution of automatic data-mining procedures. 3-D separation is seen to yield open flows i.e., no true recirculation or dead air region exists even in the mean sense. Similarly, striking organized patterns obtained experimentally with plasma-based control are synthesized with CFD to describe the effect of control in terms of vortical interactions. For jets, different modes (axisymmetric, helical or mixed) generate a rich variety of structures such as rollers, interacting vortex rings and single or multiple helices. The manner in which this insight can be employed to propose and evaluate control techniques is noted.
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