Objective: This paper introduces a methodology for the non-intrusive detection of von Kármán vortex street cavitation. It is based on the cyclostationary analysis of the airborne noise radiated by the collapsing bubbles.Materials and methods: A hydrodynamic profile is mounted in the test section of a high-speed cavitation tunnel and the phenomenon is reproduced under controlled conditions of flow and pressure. The angle of incidence is kept constant. Flow velocity is varied to regulate the vortex generation frequency and pressure is adjusted to control the cavitation onset. High-speed photography is used to confirm the occurrence of cavitation in the core of the vortices. A laser vibrometer pointing to the upper surface of the profile validates the fluid-structure interaction due to the vortex shedding. A microphone is used to sense the sound produced by the phenomenon and transmitted to the environment.Results and discussion: The cyclic coherence showed out uncoupled evidence of the periodic detachment of vortices and the presence or absence of cavitation in their cores, reaching values close to 0.7 for specific frequencies.Conclusion: A non-intrusive monitoring approach along with a statistical indicator were implemented to allow the diagnosis of such phenomena.
non-intrusive monitoring, vortex street cavitation, von Kármán vortex shedding, cyclostationary analysismonitoreo no invasivo, cavitación en calles de vórtices, vórtices de von Kármán, análisis cicloestacionario
 A. Zobeiri, “Effect of hydrofoil trailing edge geometry on the wake dynamics,” Ph.D. dissertation, EPFL, Lausanne, 2012. [Online]. Available: https://infoscience.epfl.ch/record/168992/files/EPFL_TH5218.pdf
 K. P. Chopra, “Atmospheric and oceanic flow problems introduced by islands,” Adv.Geophys., vol. 16, pp. 297–421, 1973.
 NASA, “NASA Earth Observatory: A swirl of clouds over the Pacific,” 22-May-2013. [Online]. Available: http://earthobservatory.nasa.gov/IOTD/view.php?id=81883, Accessed on: Jun 19, 2015.
 A. Roshko, “On the development of turbulent wakes from vortex streets,” CA Inst. Tech, 1954. [Online]. Available: http://authors.library.caltech.edu/428/1/ROSnacarpt1191.pdf
 J. H. Gerrard, “The mechanics of the formation region of vortices behind bluff bodies,” J. Fluid Mech., vol. 25, no. 2, p. 401, Jun. 1966.
 P. W. Bearman, “Vortex shedding from oscillating bluff bodies,” Annu. Rev. Fluid Mech., vol. 16, no. 1, pp. 195–222, Jan. 1984.
 O. M. Griffin and O. M., “A note on bluff body vortex formation,” J. Fluid Mech., vol. 284, no. 1, p. 217, Feb. 1995.
 C. H. K. Williamson and A. Roshko, “Vortex formation in the wake of an oscillating cylinder,” J. Fluids Struct., vol. 2, no. 4, pp. 355–381, 1988.
 C. Trivedi, “A review on fluid structure interaction in hydraulic turbines: A focus on hydrodynamic damping,” Eng. Fail. Anal., vol. 77, pp. 1–22, 2017.
 D. Ni, M. Yang, N. Zhang, B. Gao, and Z. Li, “Unsteady flow structures and pressure pulsations in a nuclear reactor coolant pump with spherical casing,” J. Fluids Eng., vol. 139, no. 5, p. 51103, Mar. 2017.
 J. Tian, Z. Zhang, Z. Ni, and H. Hua, “Flow-induced vibration analysis of elastic propellers in a cyclic inflow: An experimental and numerical study,” Phys. Procedia, vol. 65, pp. 47–59, 2017.
 A. Müller, A. Favrel, C. Landry, and F. Avellan, “Fluid–structure interaction mechanisms leading to dangerous power swings in Francis turbines at full load,” J. Fluids Struct., vol. 69, pp. 56–71, 2017.
 H. Kou, J. Lin, J. Zhang, and X. Fu, “Dynamic and fatigue compressor blade characteristics during fluid- structure interaction: Part I—Blade modelling and vibration analysis,” Eng. Fail. Anal., vol. 76, pp. 80–98, 2017.
 J. Cisonni, A. D. Lucey, N. S. J. Elliott, and M. Heil, “The stability of a flexible cantiléver in viscous channel flow,” J. Sound Vib., vol. 396, pp. 186–202, 2017.
 W. K. Bonness, J. B. Fahnline, P. D. Lysak, and M. R. Shepherd, “Modal forcing functions for structural vibration from turbulent boundary layer flow,” J. Sound Vib., vol. 395, pp. 224–239, 2017.
 A. Bauknecht, B. Ewers, O. Schneider, and M. Raffel, “Blade tip vortex measurements on actively twisted rotor blades,” Exp. Fluids, vol. 58, no. 5, p. 49, May 2017.
 Y. Zhao, G. Wang, and B. Huang, “Vortex structure analysis of unsteady cloud cavitating flows around a hydrofoil,” Mod. Phys. Lett. B, vol. 30, no. 2, p. 1550275, Jan. 2016.
 M. J. Thorsen, S. Sævik, and C. M. Larsen, “Fatigue damage from time domain simulation of combined in-line and cross-flow vortex-induced vibrations,” Mar. Struct., vol. 41, pp. 200–222, Apr. 2015.
 Z. Yao, F. Wang, M. Dreyer, and M. Farhat, “Effect of trailing edge shape on hydrodynamic damping for a hydrofoil,” J. Fluids Struct., vol. 51, pp. 189–198, Nov. 2014.
 P. Ausoni, M. Farhat, X. Escaler, E. Egusquiza, and F. Avellan, “Cavitation Influence on von Kármán Vortex Shedding and Induced Hydrofoil Vibrations,” J. Fluids Eng., vol. 129, no. 8, p. 966, Aug. 2007.
 R. N. Govardhan and O. N. Ramesh, “A stroll down Kármán street,” Resonance, vol. 10, no. 8, pp. 25–37, Aug. 2005.
 J. Wang, S. Fu, R. Baarholm, J. Wu, and C. M. Larsen, “Fatigue damage induced by vortex-induced vibrations in oscillatory flow,” Mar. Struct., vol. 40, pp. 73–91, Jan. 2015.
 E. Egusquiza, C. Valero, X. Huang, E. Jou, A. Guardo, and C. Rodriguez, “Failure investigation of a large pump-turbine runner,” Eng. Fail. Anal., vol. 23, pp. 27–34, 2012.
 K. J. Lockey, M. Keller, M. Sick, M. H. Staehle, and A. Gehrer. “Flow-induced vibrations at stay vanes: experience on site and CFD simulations of von Kármán vortex shedding,” Int. J. Hydropow. Dams, no. 5, pp. 102–106, 2006. [Online]. Available: http://fsh.g.andritz. com/c/com2011/00/01/94/19494/1/1/0/738757959/hy-2006-hydro-flow-inducedvibrations-experience-cfd-karman.pdf
 Q. Shi, “Abnormal noise and runner cracks caused by von Karman vortex shedding: A case study in Dachaoshan hydroelectric project,” in Proceedings of the 22nd IAHR Symposium on Hydraulic Machinery and Systems, 2004, paper no. A13-2:1–12.
 M. Čudina and J. Prezelj, “Detection of cavitation in operation of kinetic pumps. Use of discrete frequency tone in audible spectra,” Appl. Acoust., vol. 70, no. 4, pp. 540–546, 2009.
 G. Sridhar and J. Katz, “Effect of entrained bubbles on the structure of vortex rings,” J. Fluid Mech., vol. 397, pp. 171–202, Oct. 1999.
 J. O. Young and J. W. Holl, “Effects of cavitation on periodic wakes behind symmetric wedges,” J. Basic Eng., vol. 88, no. 1, p. 163, 1966.
 W. Yang, “Multiobjective optimization design of a pump–turbine impeller based on an inverse design using a combination optimization strategy,” J. Fluids Eng., vol. 136, no. 1, p. 14501, Oct. 2013.
 V. Hasmatuchi, M. Farhat, S. Roth, F. Botero, and F. Avellan, “Experimental evidence of rotating stall in a pump-turbine at off-design conditions in generating mode,” J. Fluids Eng., vol. 133, no. 5, p. 51104, 2011.
 C. Widmer, T. Staubli, and N. Ledergerber, “Unstable characteristics and rotating stall in turbine brake operation of pump-turbines,” J. Fluids Eng., vol. 133, no. 4, p. 41101, Apr. 2011.
 F. Avellan, P. Henry, and I. L. Ryhming, “A new high speed cavitation tunnel,” ASME Winter Annu. Meet., vol. 57, pp. 49–60, 1987.
 J. Antoni, “Cyclic spectral analysis in practice,” Mech. Syst. Signal Process., vol. 21, no. 2, pp. 597–630, 2007.
 R. B. Randall, Vibration-based condition monitoring: Industrial, aerospace and automotive applications. New York: Wiley, 2011.
 H. Nyquist, “Certain topics in telegraph transmission theory,” Proc. IEEE, vol. 90, no. 2, pp. 280–305, 2002.
 C. E. Shannon, “Communication in the presence of noise,” Proc. IEEE, vol. 86, no. 2, pp. 447–457, Feb. 1998.
 J. Antoni, “Cyclic spectral analysis of rolling-element bearing signals: Facts and fictions,” J. Sound Vib., vol. 304, no. 3, pp. 497–529, 2007.
 J. H. Lienhard, Synopsis of lift, drag, and vortex frequency data for rigid circular cylinders. Pullman, Wash.: Technical Extension Service, Washington State University, 1966.
 P. D. Welch, “The use of fast Fourier transform for the estimation of power spectra: A method based on time averaging over short, modified periodograms,” IEEE Trans. Audio Electroacoust., vol. 15, no. 2, pp. 70–73, Jun. 1967.
 M. Farhat, F. Avellan, and F. Pereira, “Pressions instationnaires générées par une poche de cavitation partielle,” Houille blanche, vol. 47, no. 7–8, pp. 579–585.
 X. Escaler, E. Egusquiza, M. Farhat, F. Avellan, and M. Coussirat, “Detection of cavitation in hydraulic turbines,” Mech. Syst. Signal Process., vol. 20, no. 4, pp. 983–1007, 2006.
 F. Botero, V. Hasmatuchi, S. Roth, and M. Farhat, “Non-intrusive detection of rotating stall in pump-turbines,” Mech. Syst. Signal Process., Apr. 2014.
 F. Botero, S. Guzman, V. Hasmatuchi, S. Roth, and M. Farhat, “Flow visualization approach for periodically reversed flows,” J. Flow Vis. Image Process., vol. 19, no. 4, pp. 309–321, 2012.