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A New View on Origin, Role and Manipulation of Large Scales in Turbulent Boundary Layers.

N8315588

Publication Date	1982
Personal Author	Corke, T. C.; Nagib, H. M.; Guezennec, Y. G.
Page Count	378
Abstract	The potential of passive 'manipulators' for altering the large scale turbulent structures in boundary layers was investigated. Utilizing smoke wire visualization and multisensor probes, the experiment verified that the outer scales could be suppressed by simple arrangements of parallel plates. As a result of suppressing the outer scales in turbulent layers, a decrease in the streamwise growth of the boundary layer thickness was achieved and was coupled with a 30 percent decrease in the local wall friction coefficient. After accounting for the drag on the manipulator plates, the net drag reduction reached a value of 20 percent within 55 boundary layer thicknesses downstream of the device. No evidence for the reoccurrence of the outer scales was present at this streamwise distance thereby suggesting that further reductions in the net drag are attainable. The frequency of occurrence of the wall events is simultaneously dependent on the two parameters, Re2 delta sub 2 and Re sub x. As a result of being able to independently control the inner and outer boundary layer characteristics with these manipulators, a different view of these layers emerged.
Keywords	Turbulent boundary layer Two dimensional flow Velocity distribution Wall flow Flow visualization Image processing Parallel plates Pattern recognition
Source Agency	National Aeronautics and Space Administration
NTIS Subject Category	46B - Fluid Mechanics 51A - Aerodynamics
Corporate Authors	Illinois Inst. of Tech., Chicago.; National Aeronautics and Space Administration, Washington, DC.
Document Type	Technical Report
Title Note	Interim Report.
NTIS Issue Number	198311

A New View on Origin, Role and Manipulation of Large Scales in Turbulent Boundary Layers.

A New View on Origin, Role and Manipulation of Large Scales in Turbulent Boundary Layers.
N8315588

Publication Date	1982
Personal Author	Corke, T. C.; Nagib, H. M.; Guezennec, Y. G.
Page Count	378
Abstract	The potential of passive 'manipulators' for altering the large scale turbulent structures in boundary layers was investigated. Utilizing smoke wire visualization and multisensor probes, the experiment verified that the outer scales could be suppressed by simple arrangements of parallel plates. As a result of suppressing the outer scales in turbulent layers, a decrease in the streamwise growth of the boundary layer thickness was achieved and was coupled with a 30 percent decrease in the local wall friction coefficient. After accounting for the drag on the manipulator plates, the net drag reduction reached a value of 20 percent within 55 boundary layer thicknesses downstream of the device. No evidence for the reoccurrence of the outer scales was present at this streamwise distance thereby suggesting that further reductions in the net drag are attainable. The frequency of occurrence of the wall events is simultaneously dependent on the two parameters, Re2 delta sub 2 and Re sub x. As a result of being able to independently control the inner and outer boundary layer characteristics with these manipulators, a different view of these layers emerged.
Keywords	Turbulent boundary layer Two dimensional flow Velocity distribution Wall flow Flow visualization Image processing Parallel plates Pattern recognition
Source Agency	National Aeronautics and Space Administration
NTIS Subject Category	46B - Fluid Mechanics 51A - Aerodynamics
Corporate Authors	Illinois Inst. of Tech., Chicago.; National Aeronautics and Space Administration, Washington, DC.
Document Type	Technical Report
Title Note	Interim Report.
NTIS Issue Number	198311