Abstract

The boundary layer developing over the suction side of a low-pressure turbine cascade operating under unsteady inflow conditions has been experimentally investigated. Time-resolved particle image velocimetry (PIV) measurements have been performed in two orthogonal planes, the blade-to-blade and a wall-parallel plane embedded within the boundary layer, for two different wake-reduced frequencies. Proper orthogonal decomposition (POD) has been used to analyze the data and to provide an interpretation of the most significant flow structures for each phase of the wake passing cycle. Detailed information on the most energetic turbulent structures at a particular phase is obtained with a newly developed procedure that overcomes the limit of classical phase average. The synchronization of the measurements in the two planes allows the computation of the characteristic dimension of boundary layer streaky structures that are responsible for transition. The largest and most energetic structures are observed when the wake centerline passes over the rear part of the suction side, and they appear practically the same for both reduced frequencies. The passing wake forces transition leading to the breakdown of the boundary layer streaks. Otherwise, the largest differences between the low and high reduced frequency are observed in the calmed region. The postprocessing of these two planes allowed computing the spacing of the streaky structures and making it nondimensional by the boundary layer displacement thickness observed for each phase. The nondimensional value of the streaks spacing is about constant, irrespective of the reduced frequency.

References

References
1.
Hodson
,
H. P.
, and
Howell
,
R. J.
,
2005
, “
The Role of Transition in High Lift Low Pressure Turbines for Aero Engines
,”
Prog. Aerosp. Sci.
,
41
(
6
), pp.
419
454
. 10.1016/j.paerosci.2005.08.001
2.
Stieger
,
R. D.
, and
Hodson
,
H. P.
,
2005
, “
The Unsteady Development of a Turbulent Wake Through a Downstream Low-Pressure Turbine Blade Passage
,”
ASME J. Turbomach.
,
127
(
2
), pp.
388
394
. 10.1115/1.1811094
3.
Cattanei
,
A.
,
Zunino
,
P.
,
Schröder
,
T.
,
Stoffel
,
B.
, and
Matyschok
,
B.
,
2006
, “
Detailed Analysis of Experimental Investigations on Boundary Layer Transition in Wake Disturbed Flow
,”
ASME Turbo Expo 2006: Power for Land, Sea, and Air
,
Barcelona, Spain
,
May 8–11
, Paper No. GT2006-90128.
4.
Simoni
,
D.
,
Ubaldi
,
M.
,
Zunino
,
P.
, and
Bertini
,
F.
,
2012
, “
Transition Mechanisms in Laminar Separation Bubbles With and Without Incoming Wakes and Synthetic Jet Effects
,”
Exp. Fluids
,
53
(
1
), pp.
173
186
. 10.1007/s00348-012-1281-9
5.
Gompertz
,
K. A.
, and
Bons
,
J. P.
,
2011
, “
Combined Unsteady Wakes and Active Flow Control on a Low-Pressure Turbine Airfoil
,”
AIAA J. Propul. Power
,
27
(
5
), pp.
990
1000
. 10.2514/1.B34032
6.
Kubacki
,
S.
,
Lodefier
,
K.
,
Zarzycki
,
R.
,
Elsner
,
W.
, and
Dick
,
E.
,
2009
, “
Further Development of a Dynamic Intermittency Model for Wake-Induced Transition
,”
Flow Turbul. Combust.
,
83
(
4
), pp.
539
568
. 10.1007/s10494-009-9206-2
7.
Lengani
,
D.
,
Simoni
,
D.
,
Ubaldi
,
M.
,
Zunino
,
P.
, and
Bertini
,
F.
,
2017
, “
Coherent Structures Formation During Wake-Boundary Layer Interaction on a LP Turbine Blade
,”
Flow Turbul. Combust.
,
98
(
1
), pp.
57
81
. 10.1007/s10494-016-9741-6
8.
Michelassi
,
V.
,
Chen
,
L.
,
Pichler
,
R.
,
Sandberg
,
R.
, and
Bhaskaran
,
R.
,
2016
, “
High-Fidelity Simulations of Low-Pressure Turbines: Effect of Flow Coefficient and Reduced Frequency on Losses
,”
ASME J. Turbomach.
,
138
(
11
), p.
111006
. 10.1115/1.4033266
9.
Lengani
,
D.
,
Simoni
,
D.
,
Ubaldi
,
M.
,
Zunino
,
P.
, and
Bertini
,
F.
,
2017
, “
A POD-Based Procedure for the Split of Unsteady Losses of an LPT Cascade
,”
Int. J. Turbomach., Propul. Power
,
2
(
4
), p.
17
. 10.3390/ijtpp2040017
10.
Coull
,
J. D.
, and
Hodson
,
H. P.
,
2011
, “
Unsteady Boundary-Layer Transition in Low-Pressure Turbines
,”
J. Fluid Mech.
,
681
, pp.
370
410
. 10.1017/jfm.2011.204
11.
Sarkar
,
S.
,
2008
, “
Identification of Flow Structures on a LP Turbine Blade Due to Periodic Passing Wakes
,”
ASME J. Fluid Eng.
,
130
(
6
), p.
061103
. 10.1115/1.2911682
12.
Lengani
,
D.
,
Simoni
,
D.
,
Nilberto
,
A.
,
Ubaldi
,
M.
,
Zunino
,
P.
, and
Bertini
,
F.
,
2018
, “
Synchronization of Multi-Plane Measurement Data by Means of POD: Application to Unsteady Boundary Layer Transition
,”
Exp. Fluids
,
59
(
12
), p.
184
. 10.1007/s00348-018-2642-9
13.
Simoni
,
D.
,
Berrino
,
M.
,
Ubaldi
,
M.
,
Zunino
,
P.
, and
Bertini
,
F.
,
2015
, “
Off-Design Performance of a Highly Loaded Low Pressure Turbine Cascade Under Steady and Unsteady Incoming Flow Conditions
,”
ASME J. Turbomach.
,
137
(
7
), p.
071009
. 10.1115/1.4029200
14.
Lengani
,
D.
,
Simoni
,
D.
,
Pichler
,
R.
,
Sandberg
,
R.
,
Michelassi
,
V.
, and
Bertini
,
F.
,
2019
, “
On the Identification and Decomposition of the Unsteady Losses in a Turbine Cascade
,”
ASME J. Turbomach.
,
141
(
3
), p.
031005
. 10.1115/1.4042164
15.
Lengani
,
D.
, and
Simoni
,
D.
,
2015
, “
Recognition of Coherent Structures in the Boundary Layer of a Low-Pressure-Turbine Blade for Different Free-Stream Turbulence Intensity Levels
,”
Int. J. Heat Fluid Flow
,
54
, pp.
1
13
. 10.1016/j.ijheatfluidflow.2015.04.003
16.
Istvan
,
M. S.
, and
Yarusevych
,
S.
,
2018
, “
Effects of Free-Stream Turbulence Intensity on Transition in a Laminar Separation Bubble Formed Over an Airfoil
,”
Exp. Fluids
,
59
(
3
), p.
52
. 10.1007/s00348-018-2511-6
17.
Sciacchitano
,
A.
,
Neal
,
D. R.
,
Smith
,
B. L.
,
Warner
,
S. O.
,
Vlachos
,
P. P.
,
Wieneke
,
B.
, and
Scarano
,
F.
,
2015
, “
Collaborative Framework for PIV Uncertainty Quantification: Comparative Assessment of Methods
,”
Meas. Sci. Technol.
,
26
(
7
), p.
074004
. 10.1088/0957-0233/26/7/074004
18.
Sirovich
,
L.
,
1987
, “
Turbulence and the Dynamics of Coherent Structures. Part I–III
,”
Quat. Appl. Math.
,
45
, pp.
561
590
. 10.1090/qam/910462
19.
Lengani
,
D.
,
Simoni
,
D.
,
Ubaldi
,
M.
,
Zunino
,
P.
, and
Bertini
,
F.
,
2017
, “
Experimental Investigation on the Time–Space Evolution of a Laminar Separation Bubble by Proper Orthogonal Decomposition and Dynamic Mode Decomposition
,”
ASME J. Turbomach.
,
139
(
3
), p.
031006
. 10.1115/1.4034917
20.
Legrand
,
M.
,
Nogueira
,
J.
, and
Lecuona
,
A.
,
2011
, “
Flow Temporal Reconstruction From Non-Time-Resolved Data Part I: Mathematic Fundamentals
,”
Exp. Fluids
,
51
(
4
), pp.
1047
1055
. 10.1007/s00348-011-1111-5
21.
Lengani
,
D.
,
Kindermann
,
S.
,
Selic
,
T.
,
Marn
,
A.
, and
Heitmeir
,
F.
,
2014
, “
Measurement and Decomposition of Periodic Flow Structures Downstream of a Test Turbine
,”
Exp. Fluids
,
55
(
1
), p.
1632
. 10.1007/s00348-013-1632-1
22.
Lengani
,
D.
,
Simoni
,
D.
,
Ubaldi
,
M.
, and
Zunino
,
P.
,
2014
, “
POD Analysis of the Unsteady Behavior of a Laminar Separation Bubble
,”
Exp. Therm. Fluid Sci.
,
58
, pp.
70
79
. 10.1016/j.expthermflusci.2014.06.012
23.
Gomez-Ramirez
,
D.
,
Ekkad
,
S. V.
,
Moon
,
H.-K.
,
Kim
,
Y.
, and
Srinivasan
,
R.
,
2017
, “
Isothermal Coherent Structures and Turbulent Flow Produced by a Gas Turbine Combustor Lean Pre-Mixed Swirl Fuel Nozzle
,”
Exp. Therm. Fluid Sci.
,
81
, pp.
187
201
. 10.1016/j.expthermflusci.2016.10.010
24.
Hussain
,
A. K. M. F.
, and
Reynolds
,
W. C.
,
1970
, “
The Mechanics of an Organized Wave in Turbulent Shear Flow
,”
J. Fluid Mech.
,
41
(
2
), pp.
241
258
. 10.1017/S0022112070000605
25.
Canepa
,
E.
,
Cattanei
,
A.
,
Zecchin
,
F. M.
, and
Parodi
,
D.
,
2019
, “
Large-Scale Unsteady Flow Structures in the Leakage Flow of a Low-Speed Axial Fan With Rotating Shroud
,”
Exp. Therm. Fluid Sci.
,
102
, pp.
1
19
. 10.1016/j.expthermflusci.2018.10.020
26.
Schröder
,
A.
, and
Kompenhans
,
J.
,
2004
, “
Investigation of a Turbulent Spot Using Multi-Plane Stereo Particle Image Velocimetry
,”
Exp. Fluids
,
36
(
1
), pp.
82
90
. 10.1007/s00348-003-0644-7
27.
Matsubara
,
M.
, and
Alfredsson
,
P. H.
,
2001
, “
Disturbance Growth in Boundary Layers Subjected to Free-Stream Turbulence
,”
J. Fluid Mech.
,
430
, pp.
149
168
. 10.1017/S0022112000002810
You do not currently have access to this content.