The mechanism of separation control by sound excitation is investigated on the aft-loaded low-pressure turbine (LPT) blade profile, the L1A, which experiences a large boundary layer separation at low Reynolds numbers. Previous work by the authors has shown that on a laminar separation bubble such as that experienced by the front-loaded L2F profile, sound excitation control has its best performance at the most unstable frequency of the shear layer due to the exploitation of the linear instability mechanism. The different loading distribution on the L1A increases the distance of the separated shear layer from the wall and the exploitation of the same linear mechanism is no longer effective in these conditions. However, significant control authority is found in the range of the first subharmonic of the natural unstable frequency. The amplitude of forced excitation required for significant wake loss reduction is higher than that needed when exploiting linear instability, but unlike the latter case, no threshold amplitude is found. The fluid-dynamics mechanisms under these conditions are investigated by particle image velocimetry (PIV) measurements. Phase-locked PIV data gives insight into the growth and development of structures as they are shed from the shear layer and merge to lock into the excited frequency. Unlike near-wall laminar separation sound control, it is found that when such large separated shear layers occur, sound excitation at subharmonics of the fundamental frequency is still effective with high-Tu levels.

References

References
1.
Hodson
,
H. P.
, and
Howell
,
R. J.
,
2005
, “
The Role of Transition in High-Lift Low-Pressure Turbines for Aeroengines
,”
Prog. Aerosp. Sci.
,
41
(
6
), pp.
419
454
.10.1016/j.paerosci.2005.08.001
2.
Lyall
,
M. E.
,
King
,
P. I.
,
Sondergaard
,
R.
,
Clark
,
J. P.
, and
McQuilling
,
M. W.
,
2012
, “
An Investigation of Reynolds Lapse Rate for Highly Loaded Low Pressure Turbine Airfoils With Forward and Aft Loading
,”
ASME J. Turbomach.
,
134
(
5
), p.
051035
.10.1115/1.4004826
3.
Howell
,
R. J.
,
Ramesh
,
O. N.
,
Hodson
,
H. P.
,
Harvey
,
N. W.
, and
Schulte
, V
.
,
2001
, “
High Lift and Aft-Loaded Profiles for Low-Pressure Turbines
,”
ASME J. Turbomach.
,
123
(
2
), pp.
181
188
.10.1115/1.1350409
4.
Corriveau
,
D.
, and
Sjolander
,
S. A.
,
2004
, “
Influence of Loading Distribution on the Performance of Transonic High Pressure Turbine Blades
,”
ASME J. Turbomach.
,
126
(
2
), pp.
288
296
.10.1115/1.1645534
5.
Coull
,
J. D.
,
Thomas
,
R. L.
, and
Hodson
,
H. P.
,
2010
, “
Velocity Distributions for Low Pressure Turbines
,”
ASME J. Turbomach.
,
132
(
4
), p.
041006
.10.1115/1.3192149
6.
Volino
,
R. J.
,
2010
, “
Separated Flow Measurements on a Highly Loaded Low-Pressure Turbine Airfoil
,”
ASME J. Turbomach.
,
132
(
1
), p.
011007
.10.1115/1.3104608
7.
Volino
,
R. J.
,
Kartuzova
,
O.
, and
Ibrahim
,
M. B.
,
2011
, “
Separation Control on a Very High Lift Low Pressure Turbine Airfoil Using Pulsed Vortex Generator Jets
,”
ASME J. Turbomach.
,
133
(
4
), p.
041021
.10.1115/1.4003024
8.
Bons
,
J. P.
,
Pluim
,
J.
,
Gompertz
,
K.
,
Bloxham
,
M.
, and
Clark
,
J. P.
,
2012
, “
The Application of Flow Control to an Aft-Loaded Low Pressure Turbine Cascade With Unsteady Wakes
,”
ASME J. Turbomach.
,
134
(
3
), p.
031009
.10.1115/1.4000488
9.
Volino
,
R. J.
,
2003
, “
Passive Flow Control on Low-Pressure Turbine Airfoils
,”
ASME J. Turbomach.
,
125
(
4
), pp.
754
764
.10.1115/1.1626685
10.
Bernardini
,
C.
,
Carnevale
,
M.
,
Manna
,
M.
,
Martelli
,
F.
,
Simoni
,
D.
, and
Zunino
,
P.
,
2012
, “
Turbine Blade Boundary Layer Separation Suppression Via Synthetic Jet: An Experimental and Numerical Study
,”
J. Therm. Science
,
21
(
5
), pp.
404
412
.10.1007/s11630-012-0561-2
11.
Huang
,
J.
,
Corke
,
T. C.
, and
Thomas
,
F. O.
,
2006
, “
Plasma Actuators for Separation Control of Low-Pressure Turbine Blades
,”
AIAA J.
,
44
(
1
), pp.
51
57
.10.2514/1.2903
12.
Bons
,
J. P.
,
Sondergaard
,
R.
, and
Rivir
,
R. B.
,
2002
, “
The Fluid Dynamics of LPT Blade Separation Control Using Pulsed Jets
,”
ASME J. Turbomach.
,
124
(
1
), pp.
77
85
.10.1115/1.1425392
13.
Postl
,
D.
,
Balzer
,
W.
, and
Fasel
,
H. F.
,
2011
, “
Control of Laminar Separation Using Pulsed Vortex Generator Jets: Direct Numerical Simulations
,”
J. Fluid Mech.
,
676
, pp.
81
109
.10.1017/jfm.2011.34
14.
McAuliffe
,
B. R.
, and
Yaras
,
M. I.
,
2010
, “
Transition Mechanisms in Separation Bubbles Under Low- and Elevated-Freestream Turbulence
,”
ASME J. Turbomach.
,
132
(
1
), p.
011004
.10.1115/1.2812949
15.
Watmuff
,
J. H.
,
1999
, “
Evolution of a Wave Packet Into Vortex Loops in a Laminar Separation Bubble
,”
J. Fluid Mech.
,
397
, pp.
119
169
.10.1017/S0022112099006138
16.
Baumann
,
J.
,
Rose
,
M.
,
Ries
,
T.
,
Staudacher
,
S.
, and
Rist
,
U.
,
2011
, “
Actuated Transition in an LP Turbine Laminar Separation: An Experimental Approach
,”
ASME
Paper No. GT2011-45852.10.1115/GT2011-45852
17.
Zaman
,
K. B. M. Q.
, 199, “
Effect of Acoustic Excitation on Stalled Flows Over an Airfoil
,”
AIAA J.
,
30
(
6
), pp.
1492
1499
.10.2514/3.11092
18.
Greenblatt
,
D.
, and
Wygnanski
, I
. J.
,
2000
, “
The Control of Flow Separation by Periodic Excitation
,”
Prog. Aerosp. Sci.
,
36
(
7
), pp.
487
545
.10.1016/S0376-0421(00)00008-7
19.
Yarusevych
,
S.
,
Sullivan
,
P. E.
, and
Kawall
,
J. G.
,
2007
, “
Effect of Acoustic Excitation Amplitude on Airfoil Boundary Layer and Wake Development
,”
AIAA J.
,
45
(
4
), pp.
760
771
.10.2514/1.25439
20.
Bernardini
,
C.
,
Benton
,
S. I.
, and
Bons
,
J. P.
,
2013
, “
The Effect of Acoustic Excitation on Boundary Layer Separation of a Highly Loaded LPT Blade
,”
ASME J. Turbomach.
,
135
(
5
), p.
051001
.10.1115/1.4007834
21.
Eldredge
,
R. G.
, and
Bons
,
J. P.
,
2004
, “
Active Control of a Separating Boundary Layer With Steady Vortex Generating Jets—Detailed Flow Measurements
,”
AIAA
Paper No. 2004-0751.10.2514/6.2004-751
22.
Zhou
,
J.
,
Adrian
,
R. J.
,
Balachandar
,
S.
, and
Kendall
,
T. M.
,
1999
, “
Mechanisms for Generating Coherent Packets of Hairpin Vortices in Channel Flow
,”
J. Fluid Mech.
,
387
, pp.
353
396
.10.1017/S002211209900467X
23.
Monkewitz
,
P. A.
, and
Huerre
,
P.
1982
, “
Influence on the Velocity Ratio on the Spatial Instability of Mixing Layers
,”
Phys. Fluids
,
25
(
7
), pp.
1137
1143
.10.1063/1.863880
24.
Ho
,
C. M.
, and
Huang
,
L. S.
,
1982
, “
Subharmonic and Vortex Merging in Mixing Layers
,”
J. Fluid Mech.
,
119
, pp.
443
473
.10.1017/S0022112082001438
25.
Ho
,
C. M.
, and
Huerre
,
M.
,
1984
, “
Perturbed Free Shear Layers
,”
Annu. Rev. Fluid Mech.
,
16
, pp.
365
424
.10.1146/annurev.fl.16.010184.002053
26.
Hultgren
,
L. S.
,
1992
, “
Nonlinear Spatial Equilibration of an Externally Excited Instability Wave in a Free Shear Layer
,”
J. Fluid Mech.
,
236
, pp.
635
664
.10.1017/S0022112092001563
27.
Ho
,
C. M.
, and
Nassier
,
N. S.
,
1981
, “
Dynamics of an Impinging Jet. Part 1. The Feedback Phenomenon
,”
J Fluid Mech.
,
105
, pp.
119
142
.10.1017/S0022112081003133
28.
Halfon
,
E.
,
Nishri
,
B.
,
Seifert
,
A.
, and
Wygnanski
,
I.
,
2004
, “
Effects of Elevated Free-Stream Turbulence on Actively Controlled Separation Bubble
,”
ASME J. Fluids Eng.
,
126
(
6
), pp.
1015
1022
.10.1115/1.1839933
29.
Dovgal
,
A. V.
,
Kozlov
,
V. V.
, and
Michalke
,
A.
,
1994
, “
Laminar Boundary Layer Separation: Instability and Associated Phenomena
,”
Prog. Aerosp. Sci.
,
30
, pp.
61
94
.10.1016/0376-0421(94)90003-5
You do not currently have access to this content.