Burst Frequency effect of DBD Plasma actuator on the control of separated flow over an airfoil

Transcription

1 24 Burst Frequency effect of DBD Plasma actuator on the control of separated flow over an airfoil,, , ISAS/JAXA, , Kengo Asada, The University of Tokyo, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, , Japan Kozo Fujii, Institute of Space and Astronautical Science, JAXA, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, , Japan The flow-fields controlled by DBD plasma actuator on burst mode around the NACA0015 airfoil are simulated with implicit large eddy simulation (ILES) using compact difference scheme, and the burst frequency effect of DBD plasma actuator on the control of separated flow over the airfoil is discussed. The Reynolds number based on chord length is set to 6,3000 and the angle of attack is set to 14 [deg]. The DBD plasma actuator is installed at the 0 % and 5 % chord length from the leading edge, and actuated in burst mode. For the burst mode, the nondimensional burst frequency is set to 1 and 6. Through the present analysis, the two mechanisms of separation control are discussed. The first mechanism enhance the vortex shedding from the separation shear layer and avoid the massive separation from the leading edge on burst mode with nondimensional burst frequency of 1. The second mechanism improves the airfoil performance by suppressing the separation region on the burst mode with nondimensional burst frequency of 6. In addition, it is clarified that the first mechanism is more sensitive to the location of DBD plasma actuator than the second mechanism and it is associated with large fluctuation of lift. (1)(2) (3)(4) Dielectric Barrier Discharge (DBD) (5)(6) Figure 1 2 m/sec (7) (8) (9) (10) (11)(12)(13) Induced flow Exposed electrode Plasma region Dielectric Insulated electrode A.C. voltage source T base T Figure 1 Configuration of plasma actuator. T=1/f + Figure 2 Burst wave image. 1

2 Figure 2 on off f + U c F + F + Corke F + =1 (11)(12) F + =10 (13)(14) Greenblatt (15) F + F + Visbal 3 (16) 3 (17)(18) Burst mode khz MHz 10Hz LES (11) F + =1 (14) F + =6 (11)(14) 5% Navier-Stokes (1) (2) (3) 3 u i, q i,, p, e, ij, ij t (2), (3) (D c q c E i ) (D c q c u k E k ) 3 Re, M, Pr Re = u c μ, M = u a, Pr = μ c p k (4) μ, c, a, c p k D c q c E i, D c q c u k E k q c E k D c D c = q c,ref E ref c u 2 = q c,ref ref u 2 (5) ref D c D c D c D c D c q c,ref ref ref

3 q c,ref q c,ref D c q c E i Suzen (19) Suzen D c (10) Figure 3 Suzen force magnitude Figure 3Force image of Suzen model. Figure , (11)(14) 0 % 5 % 0 50 force magnitude 24 3 Navier-Stokes LES ISAS/JAXA LANS3D c 6 (20) (21) f = (22) ADI-SGS (23) (24) Implicit LES (25) 2 (5 ) Figure 5, Figure 6 Figure 5 C c 20c 0.2c Zone1 () Zone2 () 2 (26) Zone2 () 2 Zone1: Zone2: : (121)LES Zone1, Zone2 1,000 Zone1, Zone ,, ( +, +, + min) = (15, 20, 1) 7 x, y, z M =0.2 Re c =6,3000 =14 Figure 4Force distribution of Suzen model (D C =8). 3

4 24 S(x, y,z,t) = S Suzen (x, y,z)sin 2 (2f base t) z x y Figure 5 Computational grids Whole image. Figure 6 Computational grids near the leading edge: Zone1 (blue), Zone2 (red) and model grid (green). (11) f + sine f base BR BR = T base T BR=100% n f + = f BR base = 1 n T f + F + = f + c U S(x,y,z,t) Suzen S Suzen (x,y,z) 4 sin 2 (2f base t) S ave (x,y,z) D c S ave T on ( x,y,z)= Sx, ( y,z,t) dt 0 = 1 2 D S x,y,z c Suzen( ) D c 8 Table 1 f base, BR, f + F + F + F + =1 F + =6 BR 10 % (11) 5 % Table 1. Plasma actuator parameters. DBD location f base [Hz] BR [%] f + [Hz] DBD-OFF N/A N/A N/A N/A N/A BM_5p_F6 5 % 6, BM_5p_F1 5 % 6, BM_0p_F6 0 % 6, BM_0p_F1 0 % 6, Figure 7 =4 =14 F +

5 LES alp4 LES alp14 Exp. alp4 Exp. alp14 24 Cp -10 x-vorticity 10 x Figure 7C p distributions of the computations and experiments at = 4, 14 deg u/a Figure 8 Time averaged chord direction velocity distributions and stream lines at = 14 deg. 5 0 u/a 0.3 Figure 9 Iso-surfaces of 2nd invariant of the velocity gradient tensors and chord direction velocity distributions (iso-surface is colored by x-vorticity). Figure 8 Figure 10 x Figure 9 x BM_0p_F1, BM_5p_F6, BM_0p_F6 2 2 BM_5p_F1 Figure 11 DBD-OFF F + =6 F + =1 0.6 ~ 5 % 0.8 DBD-OFF 5 % C p C p Burst mode BM_5p_F1 F + =6 0 %, 5 % BM_5p_F1 C P BM_5p_F1 Figure 12 y n (a)(f) 0 % 40 % 5 % 0 % C p

6 BM_5p_F6, BM_0p_F6 (b) 5 % (c)(e) BM_0p_F6, BM_5p_F6, BM_0p_F1, BM_5p_F1 F + =6 0 %, 5 % F + =1 (14) F + =1 Figure 13 -u w -u w F + =6 10 % 20 % F + =6 BM_5p_F6 (17)(18) 3 Cp 24 DBD-OFF BM 5p F6 BM 5p F1 BM 0p F6 BM 0p F1 Figure 11 C p distributions of the No-control case, Normal mode case and Burst mode case at = 14 deg. y n x (a) BM_0p_F1 (b) BM_5p_F1 u/u (a) 0 % (b) 5 % (c) 10 % (c) BM_0p_F6 (d) BM_5p_F6 y n u/a Figure 10 Time averaged chord direction velocity distributions and stream lines at = 14 deg. u/u (d) 15 % (e) 20 % (f) 40 % Figure 12 Velocity profiles at the upper airfoil surface. 6

7 (a) BM_0p_F1 (c) BM_0p_F6 (b) BM_5p_F1 (d) BM_5p_F6 24 (b) BM_5p_F1 Figure 14 (b) Figure 15 BM_5p_F1 C L Figure 14 (b) step F + =1, u w Figure 13Reynolds stress distributions of No-control case, Normal mode case and Burst mode case at =14 deg. (a) BM_0p_F1 (b) BM_5p_F1 Figure 15C L history of BM_0p_F1. (c) BM_0p_F6 (d) BM_5p_F6-10 x-vorticity 10 0 u/a 0.3 Figure 14 Iso-surfaces of 2nd invariant of the velocity gradient tensors and chord direction velocity distributions (iso-surface is colored with x-vorticity). Figure 14 x 2 (a) BM_0p_F1, (c) BM_0p_F6, (d) BM_5p_F6 10 % 20 % 7 BM_0p_F1, BM_0p_F6 2 Figure 16 BM_0p_F1, BM_0p_F6 C L sin 2 (2f base t) Force fluctuation (a) BM_0p_F1 (b) BM_0p_F6 2 (a) C L (b) BM_0p_F6 C L Figure 17 Figure 18 time step C L u C L C L C p C L, C p u Figure 17 BM_0p_F1 (a) step Figure 16 (b) 10 % 20 % 2

8 (d) 70 % BM_0p_F1 F + =1 Figure 18 BM_0p_F6 BM_0p_F1 BM_0p_F1 BM_0p_F6 (a) 10 %(d) 3 F + =6 5 %(18) BM_0p_F6 3 BM_5p_F1 5 % F + =1 F + =6 3 F + =1 BM_5p_F1 (27) NACA0015 Implicit LES 0 % 5 % F % 5 %F + =6 F + =1 F + =1 F + =6 F + =1 F + =6 F + = F + =1 DBD 2 ( (A) No ) (a) BM_0p_F1 (b) BM_0p_F6 Figure 16 C L and force magnitude histories on BM_0p_F1 and BM_0p_F6.

9 24 (a) step (a) (b) step (b) (c) step (c) (d) step (d) (e) step (e) Figure 17 Local C L distributions and C p distributions of BM_0p_F1 9 Figure 18 Local C L distributions and C p distributions of BM_0p_F6

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