Flow past a single stationary sphere, 1. Experimental and numerical techniques

Flow separation across bluff bodies has been a fascinating area of fluid mechanics since 1851. A large number of computational and experimental studies have been performed in the last several decades which have enabled the understanding and hence helped in distinguishing the flow regimes based on the characteristics exhibited by different flow parameters. These signify some physical phenomena resulting due to flow separation under different flow conditions. A lot of research from the 70's to 90's was conducted using hot wire techniques for investigating the flow features. These techniques provided three-dimensional insights into the flow and helped in quantitative, reliable and robust corroboration of earlier qualitative findings which were based on inadequate visualization techniques. Moreover, the rapid growth in computing resources in the last couple of decades, have made it possible to use highly efficient numerical techniques to investigate separated flows with much higher accuracy and control. Also, the introduction of sophisticated measurement techniques such as PIV/PLIF has aided in gaining deeper insights into the physics of sphere wakes. This work aims to present the developments and findings in the study of flow past a stationary sphere with respect to experimental and computational investigations. The statistical and signal processing techniques which form the chief medium to characterize the turbulence in such adverse pressure gradient wake flows, have also been discussed briefly. All the previous studies have been critically analysed presented as a coherent theme. This paper also brings out the knowledge gaps and accordingly recommendations have been made for the future research. (C) 2019 Elsevier B.V. All rights reserved.