On the contemporary definition and identification of flow separation

Kurzfassung

Establishing a connection between flow separation and an observable quantity in the near-wall region requires both a rigorous definition of the phenomenon and a practical framework for measuring the physical variable of interest. This paper aims to bring out the complexity behind the self-evidence of this requirement by examining the historical developments that have shaped the contemporary concept of flow separation, together with the criteria and state-of-the-art of numerical and experimental methodologies now available for its eduction. The unluckily widespread superficial awareness of the limitations implicit in Prandtl [1904]’s seminal definition within the scientific community motivates this proposal. The advent of new measurement techniques, capable of generating data with genuine epistemic value, creates an opportunity to establish a framework in which novel conceptual approaches can be experimentally validated and applied to advance understanding of complex flows. Theoretical insights are supported here by numerical and experimental results, which focus on highlighting the limitations of the original definitions and contextualizing the evolution of concepts.