2021/10/25 by Alex Rogge, Rogge, Alex, Jae Sung Park +1
Chemical Engineering · Engineering · #76F65 #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Fluid Dynamics and Turbulent Flows #Fluid Dynamics and Vibration Analysis #Hydraulic flow and structures #Rheology and Fluid Dynamics Studies
paper · pdf · doi:10.48550/arxiv.2110.13271
openalex publication_date 2021/10/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The underlying mechanisms of three different flow-control strategies on drag\nreduction in a channel flow are investigated by direct numerical simulations at\nfriction Reynolds numbers ranging from 65 to 85. These strategies include the\naddition of long-chain polymers, the incorporation of slip surfaces, and the\napplication of an external body force. While it has been believed that such\nmethods lead to a skin-friction reduction by controlling near-wall flow\nstructures, the underlying mechanisms at play are still not as clear. In this\nstudy, a temporal analysis is employed to elucidate underlying drag-reduction\nmechanisms among these methods. The analysis is based on the lifetime of\nintermittent phases represented by the active and hibernating phases of a\nminimal turbulent channel flow (Xi & Graham, Phy. Rev. Lett. 2010). At a\nsimilar amount of drag reduction, the polymer and slip methods show a similar\nmechanism, while the body force method is different. The polymers and slip\nsurfaces cause hibernating phases to happen more frequently, while the duration\nof active phases is decreased. However, the body forces cause hibernating\nphases to happen less frequently but prolong its duration to achieve a\ncomparable amount of drag reduction. A possible mechanism behind the body force\nmethod is associated with its unique roller-like vortical structures formed\nnear the wall. These structures appear to prevent interactions between inner\nand outer regions by which hibernating phases are prolonged. It should motivate\nadaptive flow-control strategies to exploit the distinct underlying mechanisms\nfor robust control of turbulent drag at low Reynolds numbers.\n