Receptivity to free stream acoustic disturbances due to a roughness element on a flat plate

The boundary-layer receptivity resulting from acoustic forcing over a flat plate with a surface irregularity is investigated. The unsteady free-stream disturbances couple with the steady perturbations resulting from the surface irregularity to form a traveling-wave mode. The resonance condition necessary for receptivity requires a forcing at a wave number equal to that of the Tollmien-Schlichting (TS) eigenmode and a frequency equal to that of the free-stream acoustic disturbance. The basic (mean) flow is calculated using an interacting boundary layer (IBL) scheme that accounts for viscous/inviscid interactions. Then, the method of multiple scales is used to find the total amplitude of the generated wave. Results of this study show how the transition process is significantly stimulated. Also, the dependence of the receptivity on the geometry of the roughness element as well as on the amplitude and frequency of the acoustic disturbance is studied. Application of suction is shown to reduce the receptivity resulting from the roughness element.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Engineering Science and Mechanics

Department dc:contributor.department

Engineering Science and Mechanics

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1993

Author dc:creator

• Ashour, Osama Naim

Chair dc:contributor.committeechair

• Nayfeh, Ali H.

Committee members dc:contributor.committeemember

• Ragab, Saad A.
• Hajj, Muhammad R.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

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

Language dc:language.iso

en

Dc Identifier Other

etd-09052009-040628

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/44581