Numerical Study of Passive and Active Flow Separation Control ...

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Fig. 15. Chord-wise distribution of peak turbulence kinetic energy of baseline case. The three-dimensional isosurfaces of the instantaneous streamwise, spanwise, and wall-normal components of vorticity over the upper surface of the airfoil are shown in Fig. 16. The three-dimensional vortical structures appear after the transition and reattachment as shown in Fig. 16(a), (b) and (c), where the contours of streamwise vorticity ω x , spanwise vorticity ω y , and wall-normal vorticity ω z are displayed. The separated shear layer can be seen from the isosurface of the spanwise vorticity in Fig. 16(b). Near the leading edge of the airfoil, a two-dimensional shear layer is detached from the surface and no three-dimensional streamwise vortical structure can be seen near the separation point. Therefore, the separated shear layer is initially a two-dimensional laminar flow. Then slight distortions become visible on the isosurface of the spanwise vorticity and the three-dimensional fluctuations start to grow rapidly and eventually lead to the shedding of vortices indicating that the separated shear layer undergoes transition, which is followed by reattachment of the separated shear layer, and breakdown of smallscale three-dimensional structures in the immediate downstream region of reattachment. Fig. 16(a) also indicates that the downstream region of the reattachment point between x = 0.25C and x = 0.5C is the most active area that contains more vortical structures. 19
(a) streamwise vorticity (dark color: ω = 100 ; light color: ω = −100 ) x (b) spwanwise vorticity (color: ω = 30 ) y 20 x
Page 1 and 2: Numerical Study of Passive and Acti
Page 3 and 4: Keywords: flow separation, passive
Page 5 and 6: flat plate [34, 35]. Other experime
Page 7 and 8: ⎛ ⎞ ⎜ 0 ⎛ ⎞ ⎟ ⎜ 0 ⎛
Page 9 and 10: Viscous terms are taken into accoun
Page 11 and 12: velocity. The negative value is sho
Page 13 and 14: Fig. 5. Streamline of steady flow p
Page 15 and 16: (Case 2), the motion of two vortex
Page 17 and 18: Angle of attack α 6° 4. Numerical
Page 19: airfoil is shown in Fig. 14. The ne
Page 23 and 24: (a) x = 0.163C 22 (b) x = 0.217C Fi
Page 25 and 26: Fig. 20. Mean pressure coefficient
Page 27 and 28: (a) streamwise vorticity (dark colo
Page 29 and 30: at x = 0.217C shows a wave packet w
Page 31 and 32: of the airfoil at this angle of att
Page 33 and 34: (a) streamwise vorticity (dark colo
Page 35 and 36: I x = 0.312C 5. Concluding Remarks
Page 37 and 38: cylinder using the immersed boundar

Numerical Study of Passive and Active Flow Separation Control ...

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