Direct Simulation of Evolution and Control of Nonlinear Instabilities in Attachment{line Boundary Layers
نویسنده
چکیده
The unsteady, incompressible Navier-Stokes equations are used for the direct numerical simulation (DNS) of spatially evolving disturbances in a threedimensional (3-D) attachment-line boundary layer. Two-dimensional (2-D) disturbances are introduced either by forcing at the in ow or by harmonic-source generators at the wall; 3-D disturbances are introduced by harmonic-source generators at the wall. The DNS results are in good agreement with both 2-D nonparallel theory (for small-amplitude disturbances) and weakly nonlinear theory (for nite-amplitude disturbances), which validates the two theories. The 2-D DNS results indicate that nonlinear disturbance growth occurs near branch II of the neutral stability curve; however, steady suction can be used to stabilize this disturbance growth. For 3-D instabilities that are generated o the attachment line, spreading both toward and away from the attachment line causes energy transfer to the attachment-line and downstream instabilities; suction stabilizes these instabilities. Furthermore, 3-D instabilities are more stable than 2-D or quasi-2-D instabilities.
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تاریخ انتشار 1998