gen-bl: secondary instability of saturated cf-vortices*
DESCRIPTION
low-frequency type-III (z)-mode. u s -amplitude in crosscut. high-frequency type-I (z)-mode. w s. u s. GEN-BL: Secondary Instability of Saturated CF-Vortices*. * from a steady mode packet. t-modal amplitude development. „steady“ 2-D. „steady“ 3-D. - PowerPoint PPT PresentationTRANSCRIPT
1Animations of crossflow transition scenarios Animations of crossflow transition scenarios (to J. Fluid Mech. vols. 456, 483, 530. (to J. Fluid Mech. vols. 456, 483, 530. © © Kloker & Wassermann)Kloker & Wassermann)
GEN-BL: Secondary Instability of Saturated CF-Vortices*
t-modal amplitude development
ws
us
low-frequency type-III (z)-mode
high-frequency type-I (z)-mode
us-amplitudein crosscut
*from a steady mode packet
2Animations of crossflow transition scenarios Animations of crossflow transition scenarios (to J. Fluid Mech. vols. 456, 483, 530. (to J. Fluid Mech. vols. 456, 483, 530. © © Kloker & Wassermann)Kloker & Wassermann)
„steady“ 3-D „steady“ 2-D
moving coordinate system
GEN-BL: Secondary Instability of Traveling CF-Vortices
medium-frequency 'z-y'-mode
high-frequency 'y'-mode
3Animations of crossflow transition scenarios Animations of crossflow transition scenarios (to J. Fluid Mech. vols. 456, 483, 530. (to J. Fluid Mech. vols. 456, 483, 530. © © Kloker & Wassermann)Kloker & Wassermann)
“natural”
GEN-BL: Transition-Delay by Upstream Flow Deformation
„Natural“ scenario
With excitation ofcloser-spacedvortices upstream (UFD)
vortices+
pulsing+
UFD
Wassermann & Kloker (UFD)Saric & al. (DRE)
4Animations of crossflow transition scenarios Animations of crossflow transition scenarios (to J. Fluid Mech. vols. 456, 483, 530. (to J. Fluid Mech. vols. 456, 483, 530. © © Kloker & Wassermann)Kloker & Wassermann)
GEN-BL-APG: small-amplitude vortices + T-S-wave: part III
t-modal amplitude development
t-z-modal amplitude development
T-S wave
vortex modeIncreased initialT-S amplitude breakdown
but:
- T-S just generates secondary crossflow modes
- secondary growth independent of T-S (unlike K-type!)
- active control on T-S useless!
(see JFM 530, 2005)
5Animations of crossflow transition scenarios Animations of crossflow transition scenarios (to J. Fluid Mech. vols. 456, 483, 530. (to J. Fluid Mech. vols. 456, 483, 530. © © Kloker & Wassermann)Kloker & Wassermann)
GEN-BL: Convective nature of Secondary Instability - DNS
t = t0
t = t0+3T
t = t0+6T
Switching-offthe backgroundpulses relaxationto steadysaturated state
Isofläche 2