Research Papers

Exploitation of Subharmonics for Separated Shear Layer Control on a High-Lift Low-Pressure Turbine Using Acoustic Forcing

[+] Author and Article Information
Chiara Bernardini

Visiting Researcher
Department of Energy Engineering,
University of Florence,
Via di S. Marta,
Florence 3, Italy
e-mail: bernardini.3@osu.edu

Stuart I. Benton

e-mail: benton.53@osu.edu

Jen-Ping Chen

Associate Professor
e-mail: chen.1210@osu.edu

Jeffrey P. Bons

e-mail: bons.2@osu.edu
Department of Mechanical and
Aerospace Engineering,
The Ohio State University,
2300 West Case Rd.,
Columbus, OH 43235

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 9, 2013; final manuscript received August 8, 2013; published online October 24, 2013. Editor: Ronald Bunker.

J. Turbomach 136(5), 051018 (Oct 24, 2013) (9 pages) Paper No: TURBO-13-1144; doi: 10.1115/1.4025586 History: Received July 09, 2013; Revised August 08, 2013

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.

Copyright © 2014 by ASME
Your Session has timed out. Please sign back in to continue.


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. [CrossRef]
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. [CrossRef]
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. [CrossRef]
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. [CrossRef]
Coull, J. D., Thomas, R. L., and Hodson, H. P., 2010, “Velocity Distributions for Low Pressure Turbines,” ASME J. Turbomach., 132(4), p. 041006. [CrossRef]
Volino, R. J., 2010, “Separated Flow Measurements on a Highly Loaded Low-Pressure Turbine Airfoil,” ASME J. Turbomach., 132(1), p. 011007. [CrossRef]
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. [CrossRef]
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. [CrossRef]
Volino, R. J., 2003, “Passive Flow Control on Low-Pressure Turbine Airfoils,” ASME J. Turbomach., 125(4), pp. 754–764. [CrossRef]
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. [CrossRef]
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. [CrossRef]
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. [CrossRef]
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. [CrossRef]
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. [CrossRef]
Watmuff, J. H., 1999, “Evolution of a Wave Packet Into Vortex Loops in a Laminar Separation Bubble,” J. Fluid Mech., 397, pp. 119–169. [CrossRef]
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. [CrossRef]
Zaman, K. B. M. Q., 199, “Effect of Acoustic Excitation on Stalled Flows Over an Airfoil,” AIAA J., 30(6), pp. 1492–1499. [CrossRef]
Greenblatt, D., and Wygnanski, I. J., 2000, “The Control of Flow Separation by Periodic Excitation,” Prog. Aerosp. Sci., 36(7), pp. 487–545. [CrossRef]
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. [CrossRef]
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. [CrossRef]
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. [CrossRef]
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. [CrossRef]
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. [CrossRef]
Ho, C. M., and Huang, L. S., 1982, “Subharmonic and Vortex Merging in Mixing Layers,” J. Fluid Mech., 119, pp. 443–473. [CrossRef]
Ho, C. M., and Huerre, M., 1984, “Perturbed Free Shear Layers,” Annu. Rev. Fluid Mech., 16, pp. 365–424. [CrossRef]
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. [CrossRef]
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. [CrossRef]
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. [CrossRef]
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. [CrossRef]


Grahic Jump Location
Fig. 1

Schematic of test section

Grahic Jump Location
Fig. 2

Suction surface acceleration parameter K from inviscid calculations for L1A and L2F blade profiles

Grahic Jump Location
Fig. 3

Uncontrolled PIV time-averaged normalized velocity magnitude contours superposed on normalized Reynolds stress isocontours (four levels from 0.01 to 0.04). Top to bottom: low-, med-, high-Tu. Left column: L1A. Right column: L2F.

Grahic Jump Location
Fig. 4

PSD in the uncontrolled separating shear layer; left: L1A; right: L2F

Grahic Jump Location
Fig. 12

Left: time-averaged normalized velocity magnitude superposed on normalized Reynolds stress isocontours (four levels from 0.01 to 0.04). Right: ensemble averaged normalized spanwise vorticity at phase t/T = 0.0. Control at ff = 50 Hz, med-Tu, at four forcing amplitudes. L1A.

Grahic Jump Location
Fig. 11

Integrated wake loss coefficient normalized by the uncontrolled case versus forcing amplitude; top: L1A; control at ff = 50 Hz; bottom: L2F; control at ff = 110 Hz

Grahic Jump Location
Fig. 10

PSD in the controlled separating shear layer (75% < Cx < 80%) for three ff at med-Tu. L1A.

Grahic Jump Location
Fig. 9

Evolution of spectral components at ff and 2ff for ff = fn/2 and momentum thickness versus downstream distance (adaptation from Ref. [24])

Grahic Jump Location
Fig. 8

Instantaneous streamlines superposed on normalized spanwise vorticity contours from phase-locked PIV data; left: t/T = 0.0; right: t/T = 0.2; control at ff = 50 Hz. L1A.

Grahic Jump Location
Fig. 7

Ensemble-averaged swirl strength contours from phase-locked PIV data; left: control at ff = 50 Hz; right: control at ff = 120 Hz. L1A.

Grahic Jump Location
Fig. 6

PIV time-averaged normalized velocity magnitude contours superposed on normalized Reynolds stress isocontours (four levels from 0.01 to 0.04); left: control at ff = 50 Hz; right: control at ff = 120 Hz. Med-Tu. L1A.

Grahic Jump Location
Fig. 5

Integrated wake loss coefficient normalized by the uncontrolled case versus forcing frequency; top: L1A; bottom: L2F. Amplitude held constant at Δu/Uin = 2.7% for L1A and Δu/Uin = 0.5% for L2F.

Grahic Jump Location
Fig. 13

PSD in the cascade passage at three Tu levels

Grahic Jump Location
Fig. 14

Time-averaged normalized velocity magnitude superposed on normalized Reynolds stress isocontours (four levels from 0.01 to 0.04); left: control at ff = 50 Hz; right: control at ff = 120 Hz at three Tu levels. L1A.

Grahic Jump Location
Fig. 15

Ensemble averaged isolevels of Sw = 200, phase t/T = 0.0; top: control at ff = 50 Hz; bottom: control at ff = 120 Hz. L1A.



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In