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Accession Number:
ADA172812
Title:
Vortex Loop Dynamics - A Phenomenological Model for Turbulent Boundary Layer Structure.
Descriptive Note:
Annual rept. 1 Jan-31 Dec 83,
Corporate Author:
NOTRE DAME UNIV IN DEPT OF AEROSPACE AND MECHANICAL ENGINEERING
Report Date:
1984-04-01
Pagination or Media Count:
28.0
Abstract:
Unsteady development of three-dimensional vortex loops in the vicinity of solid surfaces and under the influence of a crossflow is detailed. These results are important if the dynamics of the coherent structures present within the turbulent boundary layer are to be understood--it has long been recognized that the 3-D convecting stretching vortex loop is a major component of these flows. A new piston-orifice vortex generator and test section was designed to provide reliable and repeatable vortex rings in air, which are allowed to propagate across the test section and interact with a large plexiglass plate. The rings are marked with smoke tracers. The subsequent interaction is recorded using high-speed motion picture photography. Results are given for normal and oblique impacts in still air and for oblique impacts in uniform flow. The analytic effort was devoted to improving the efficiency of the 3-D inviscid vortex trajectory program. This program uses a modified Biot-Savart integration technique to consider the unsteady inviscid development of vortex structures in vicinity of solid surfaces. Studies of normal and oblique impacts with solid surfaces under conditions of no imposed flow are detailed, as well as oblique impacts in uniform and linear shear flows. The experimental and analytic results were compared and excellent correspondence between the two techniques was found. These studies indicate that substantial loop growth occurs due to the presence of an imposed shear, and it is this interaction between the loop and the imposed crossflow that plays a dominant role in the loop deformation process.
Distribution Statement:
APPROVED FOR PUBLIC RELEASE
