Title page for ETD etd-09052009-040628
|Type of Document
||Ashour, Osama Naim
||Receptivity to free stream acoustic disturbances due to a roughness element on a flat plate
||Master of Science
||Engineering Science and Mechanics
|Nayfeh, Ali H.
|Hajj, Muhammad R.
|Ragab, Saad A.
|Date of Defense
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
|| Approximate Download Time
| 28.8 Modem
|| 56K Modem
|| ISDN (64 Kb)
|| ISDN (128 Kb)
|| Higher-speed Access
next to an author's name indicates that all
files or directories associated with their ETD
are accessible from the Virginia Tech campus network only.
If you have questions or technical
problems, please Contact DLA.