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The next seminar is on September 19, 2025!
Remote Colloquium on Vortex Dominated Flows (ReCoVor) is an online seminar series that emerged out of the need to facilitate scientific engagement in the face of the COVID-19 pandemic. Widespread social-distancing measures had handicapped what had historically been a fundamental tenet of scientific inquiry - the exchange of new ideas, critical feedback, and engagement with the broader scientific community. In view of this challenge, ReCoVor was created to serve as a forum for encouraging scientific discussion with a focus on graduate students and early stage researchers. ReCoVor was also meant to provide a platform for these researchers to regain some of the opportunities lost for presenting their work to a larger scientific community and for networking, which had resulted from cancelled conferences, collaborative visits, on-campus seminars, etc. Despite the fact that the pandemic is now in our rear-view mirror, there has been overwhelming support for continuing this online series, and in fact, the membership and participation in the series has continued to grow.
As suggested by the name, this colloquial series is focused on the flow-physics of unsteady, vortex dominated flows, particularly as it applies to fluid-structure interaction, bioflight/swimming, physiological flows, massively separated flows, and other such shear flows. If the flow is unsteady and it involves multiple interacting vortices that induce important effects on the flow, then this research probably belongs in this colloquium. Experimental, computational and/or analytical contributions are all welcome.
Rajat Mittal (JHU), Jeff Eldredge (UCLA), Anya Jones (UCLA), Karen Mulleners (EPFL), Karthik Menon (Georgia Tech)
Diederik Beckers (Caltech) & Hanieh Mousavi (UCLA)
Upcoming seminar: September 19, 2025
Upcoming seminar: September 19, 2025
95A: Control of deep dynamic stall by duty-cycle actuation informed by stability analysis
95A: Control of deep dynamic stall by duty-cycle actuation informed by stability analysis
Lucas Feitosa de Souza, University of Campinas
PI: William Roberto Wolf and Chi-An Yeh
Abstract: A flow control framework based on linear stability analysis is proposed focusing on reducing the aerodynamic drag due to dynamic stall through a finite-window temporal actuation. The methodology is applied on a periodically plunging SD7003 airfoil. Finite-time Lyapunov exponent (FTLE) fields reveal a saddle point near the airfoil leading edge, where a shear layer forms and feeds a dynamic stall vortex (DSV). A local stability analysis conducted at this saddle point identifies a Kelvin-Helmholtz instability, and the most unstable eigenvalue frequencies remain constant when the variation in the effective angle of attack is minimal. The findings from the FTLE fields and the stability analysis are used to inform the position and finite duty cycle of a periodic blowing and suction actuation applied in a wall-resolved large eddy simulation (LES). The present framework reduces the actuation duty cycle by 77.5\% during the airfoil plunging motion, while maintaining the same performance as a continuous actuation throughout the entire cycle. The LES results demonstrate that disturbances from the stability-analysis-informed actuation modify the leading-edge dynamics, preventing the formation of the coherent DSV and significantly reducing the drag.
95B: Surface Roughness Influences Vortex Interactions and Jet Stability in Pitching Foils in Quiescent Flow
95B: Surface Roughness Influences Vortex Interactions and Jet Stability in Pitching Foils in Quiescent Flow
Lokesh Silwal, University of Michigan
PI: Anchal Sareen
Abstract:This study investigates the impact of surface indentations, shaped as dimples, on the flow dynamics of a pitching foil under zero-freestream conditions. A series of systematic experiments were conducted employing flow field measurements using Particle Image Velocimetry. The dimple depth ratio (d/D, where d is the dimple depth and D is the dimple diameter) was varied from 0.022 to 0.088 across Reynolds numbers (defined based on the maximum trailing edge velocity and foil chord) of 3700, 10000 and 20000. The impact of dimples on the wake characteristics was evaluated by analyzing the time-averaged jet behavior and vortex dynamics. The results reveal that the deepest dimpled case modified the far wake of the pitching foil, particularly at higher Reynolds numbers. Under these conditions, the vortices shed from the trailing edge persisted longer, and the jet exhibited greater coherence. The dimples appear to influence dipole interactions in the wake, reducing the jet deflection. These findings suggest that surface roughness can be strategically employed to modulate wake dynamics and improve the stability of the jet, potentially enhancing the propulsion efficiency of bio-inspired flapping foil systems.
Details
Details
Format
Format
Two 15-minute talks, each followed by 10 minutes of Q&A
Two 15-minute talks, each followed by 10 minutes of Q&A
When?
When?
Friday, every two weeks, at 11am Eastern Time / 8am Pacific Time.
Friday, every two weeks, at 11am Eastern Time / 8am Pacific Time.
Where?
Where?
Zoom, of course! A Zoom link with password will be provided to registered members.
Zoom, of course! A Zoom link with password will be provided to registered members.
Video Recordings
Video Recordings
The link to the recordings will be shared only with the members of the Recovor community (i.e. you will need to log in to Google Drive with the email address you provided when you registered for ReCoVor). Please keep the link to yourself, and let us know if you don't want your talk to be recorded.
The link to the recordings will be shared only with the members of the Recovor community (i.e. you will need to log in to Google Drive with the email address you provided when you registered for ReCoVor). Please keep the link to yourself, and let us know if you don't want your talk to be recorded.
Contact
Contact
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