Control of Flow over a Bluff Body

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1 Annu. Rev. Fluid Mech /97/ Control of Flow over a Bluff Body Haecheon Choi 1,2, Woo-Pyung Jeon 1 and Jinsung Kim 1 1 School of Mechanical and Aerospace Engineering, Seoul National University, Seoul , KOREA; choi@snu.ac.kr, wpjeon@snu.ac.kr, jkim@lscable.com 2 Center for Turbulence and Flow Control Research, Institute of Advanced Machinery and Design, Seoul National University, Seoul , KOREA CONTENTS Supplemental Figures 1

2 2 Choi Jeon Kim List of Supplemental Figures Supplemental Figure 1. Flow past a rectangular cylinder at Re = 100: (a) with flat stagnation surface; (b) with wavy stagnation surface. Shown here are the vortical structures. From Darekar & Sherwin (2001). Supplemental Figure 2. Contours of Δ C pb with respect to λ and l y at Re = u h/ν =40, 000: (a) l z /h =0.1; (b) 0.133; (c) 0.2. Δ C pb =[ C pb (controlled) C pb (uncontrolled)]/ C pb (uncontrolled) 100, and C pb is the mean base-pressure coefficient. Here, denotes the point where the experiment is conducted. From Park et al. (2006). Supplemental Figure 3. Flow over a circular cylinder with tabs of (l y /d, l z /d) = (0.2, 0.2) at Re = 100: (a) variation of the drag coefficient with the spanwise spacing (λ) of tabs; (b) instantaneous vortical structures in the wake at λ = 4d. In (b), vortex shedding completely disappears due to the tab. From Yoon et al. (2007). Supplemental Figure 4. Region of sensor locations for successful feedback control (Re = 65). From Roussopoulos (1993). Supplemental Figure 5. Linear feedback control by Park et al. (1994): (a) schematic of control; (b) variation of the drag coefficient with the sensor location at Re = 60; (c) without (top) and with (bottom) control. From Park et al. (1994). Supplemental Figure 6. Eigenfunctions of the first four POD modes obtained from the streamwise velocity in a cylinder wake at Re = 100. From Siegel et al. (2006). Supplemental Figure 7. Oil flow pattern on the sphere surface at the critical Reynolds number. From Suryanarayana & Prabhu (2000).

3 Control of Flow over a Bluff Body 3 Supplemental Figure 8. Variations of the drag coefficient with respect to the forcing frequency:, φ o /u =0.05;, 0.1;, The vertical bars denote the measurement uncertainty obtained for φ o =0.1u. The drag coefficient at St d = fd/u = 0 decreases by about 5%, indicating that the flow is a little affected by the blowing/suction slot itself. From Jeon et al. (2004). Supplemental Figure 9. Schematic diagram of drag-reduction mechanism by dimples. From Choi, Jeon & Choi (2006). Supplemental Figure 10. Spanwise variation of the separation angle due to the distributed forcing at Re=100 (λ =5d). From Kim & Choi (2005). Supplemental Figure 11. Variation of the base-pressure coefficient with the ratio of body height (h) to the momentum thickness at the separation (θ). From Petrusma & Gai (1994) and Park et al. (2006).

wavy stagnation surface. Shown here are the vortical structures.

4 4 Choi Jeon Kim (a) (b) Figure 1: Flow past a rectangular cylinder at Re = 100: (a) with flat stagnation surface; (b) with wavy stagnation surface. Shown here are the vortical structures. From Darekar & Sherwin (2001). Choi, Jeon & Kim: Supplemental Figure 1

5 Control of Flow over a Bluff Body 5 (a) /h l y /h (b) /h (c) l y /h /h l y /h Figure 2: Contours of Δ C pb with respect to λ and l y at Re = u h/ν = 40, 000: (a) l z /h = 0.1; (b) 0.133; (c) 0.2. Δ C pb = ( Cpb (controlled) C pb (uncontrolled) ) / C pb (uncontrolled) 100, and C pb is the mean base-pressure coefficient. Here, denotes the point where the experiment is conducted. From Park et al. (2006). Choi, Jeon & Kim: Supplemental Figure 2

6 6 Choi Jeon Kim C D 1.34(no control) C D (a) / d (b) Figure 3: Flow over a circular cylinder with tabs of (l y /d, l z /d) =(0.2, 0.2) at Re = 100: (a) variation of the drag coefficient with the spanwise spacing (λ) of tabs; (b) instantaneous vortical structures in the wake at λ = 4d. In(b), vortex shedding completely disappears due to the tab. From Yoon et al. (2007). Choi, Jeon & Kim: Supplemental Figure 3

7 Control of Flow over a Bluff Body 7 3.5d 9d x y Probe alone prevented shedding Control possible Probe detected shedding, but unable to suppress it Figure 4: Region of sensor locations for successful feedback control (Re = 65). From Roussopoulos (1993). Choi, Jeon & Kim: Supplemental Figure 4

(1994): (a) schematic of control; (b) variation of the drag coefficient with the

8 8 Choi Jeon Kim y upper u vx ( x, t) s x s x (a) lower no control C D (b) xs (c) Figure 5: Linear feedback control by Park et al. (1994): (a) schematic of control; (b) variation of the drag coefficient with the sensor location at Re = 60; (c) without (top) and with (bottom) control. From Park et al. (1994). Choi, Jeon & Kim: Supplemental Figure 5

9 Control of Flow over a Bluff Body 9 Figure 6: Eigenfunctions of the first four POD modes obtained from the streamwise velocity in a cylinder wake at Re = 100. From Siegel et al. (2006). Choi, Jeon & Kim: Supplemental Figure 6

10 10 Choi Jeon Kim Figure 7: Oil flow pattern on the sphere surface at the critical Reynolds number. From Suryanarayana & Prabhu (2000). Choi, Jeon & Kim: Supplemental Figure 7

11 Control of Flow over a Bluff Body C D / C D basic St d Figure 8: Variations of the drag coefficient with respect to the forcing frequency:, φ o /u =0.05;, 0.1;, The vertical bars denote the measurement uncertainty obtained for φ o =0.1u. The drag coefficient at St d = fd/u = 0 decreases by about 5%, indicating that the flow is a little affected by the blowing/suction slot itself. From Jeon et al. (2004). Choi, Jeon & Kim: Supplemental Figure 8

12 12 Choi Jeon Kim turbulence generation by the shear layer instability flow separation bubble dimple reattached flow with high momentum near the wall transition point moves further upstream with increasing Reynolds number 60 o 90 o 120 o flow I II III IV V last reattachment occurs at the same dimple irrespective of the Reynolds number fixed main separation angle constant drag coefficient Figure 9: Schematic diagram of drag-reduction mechanism by dimples. From Choi, Jeon & Choi (2006). Choi, Jeon & Kim: Supplemental Figure 9

13 Control of Flow over a Bluff Body 13 sep u o z / d z z / d / d Figure 10: Spanwise variation of the separation angle due to the distributed forcing at Re=100 (λ =5d). From Kim & Choi (2005). Choi, Jeon & Kim: Supplemental Figure 10

14 14 Choi Jeon Kim C pb Petrusma & Gai - laminar (1994) Petrusma & Gai - transition (1994) Petrusma & Gai - turbulent (1994) Petrusma & Gai - tripped b.l. (1994) Pollock (1972) Bearman (1992) Sharma (1986) Maull & Hoole (1967) Maulle & Young (1973) Nash et al. (1963) Park et al. (2006) h/ Figure 11: Variation of the base-pressure coefficient with the ratio of body height (h) to the momentum thickness at the separation (θ). From Petrusma & Gai (1994) and Park et al. (2006). Choi, Jeon & Kim: Supplemental Figure 11

Available online at ScienceDirect. Procedia IUTAM 14 (2015 ) IUTAM ABCM Symposium on Laminar Turbulent Transition

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