Some unsteady features of turbulent boundary layers

For steady free-stream, zero and favorable pressure gradient turbulent boundary layers, the unsteadiness in the form of turbulent fluctuations was investigated. Phase ensemble-averaged flow characteristics of a large amplitude periodic unsteady turbulent boundary layer was also investigated at a reduced frequency k = 0.61 based on the length of the converging and diverging test section with amplitude to mean velocity ratio of 0.8. In steady flow cases, both zero and favorable pressure gradient flows show good two-dimensional flow characteristics and mean flow characteristics are compared with other researchers’ data. Measured power spectral data show good agreement with those of Klebanoff, Ueda and Hinze, Perry, Lim and Henbest for the zero pressure gradient flows and Jones and Launder for the favorable pressure gradient flow. The power spectral data measured in the turbulent wall region of the zero pressure gradient flow closely follow the model equation proposed by Perry, Lim and Henbest. Convective wave speed also show good agreement with those of Favre, Gaviglio and Dumas and Sternberg within the experimental uncertainties. In the inner region of the boundary layer where y+ < 40, convective wave speed is higher than local mean velocity at all eddy scales as observed by Kline, Reynolds, Schraub and Runstadler. In the unsteady flow case, in the absence of flow reversal, the flow behaves in a quasi-steady manner and can be described by the steady flow structure as in the case of moderate amplitude flows. The Ludwieg·Tillmann skin friction equation and the Perry-Schofield universal velocity defect law hold at these phases. Except the laminariscent velocity profile observed during the acceleration phases, the large amplitude unsteady flow shows basically the same flow characteristics as the moderate amplitude flows.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Aerospace Engineering

Department dc:contributor.department

Aerospace Engineering

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1986

Author dc:creator

• Ahn, Seungki

Chair dc:contributor.committeechair

• Simpson, Roger L.

Committee members dc:contributor.committeemember

• Marchman, James F. III
• Neu, Wayne L.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/53090

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/53090