Flow separation control with rotating cylinders

The hydrodynamic forces on ocean vehicles increase dramatically during sharp maneuvers as compared to forward motion due to large areas of separated flow. These large forces severely limit maneuverability and reduce efficiency. Applying active flow separation control to ocean vehicles would reduce resistance during maneuvers and thereby improve maneuvering performance. In this thesis I discuss experiments in active separation control in a simpler, but still relevant, two-dimensional flow past a circular cylinder at moderate sub-critical Reynolds numbers (37,000 and 52,000 in experiment and 100 and 10,000 in simulation). The active control injects momentum into the boundary layer via the moving surfaces of two small control cylinders located near boundary layer separation and rotated by servo motors. The relationship between drag and rotation rate is found to be Reynolds number regime dependent; at Re = 100 the drag decreases linearly with rotation rate and at Re = 10,000, the relationship is non-linear. This nonlinearity appears to be due to the interaction between vortex shedding from the small control cylinders (which does not occur at Re = 100) and the main cylinder wake. Computational two-dimensional viscous simulations are consistent with the physical experiment and help to illustrate the phenomenon. Finally, the power consumed by the active control mechanism is considered and estimated to be significantly smaller than the power savings in reduced drag.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2012

Author dc:creator

• Schulmeister, James Crandall

Advisor dc:contributor.advisor

• Michael S Triantafyllou.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/78196

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/78196