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Wake-induced ‘slaloming’ response explains exquisite sensitivity of seal whisker-like sensors

  • Heather R. Beem (a1) (a2) and Michael S. Triantafyllou (a1)

Blindfolded harbour seals are able to use their uniquely shaped whiskers to track vortex wakes left by moving animals and identify objects that passed by 30 s earlier, an impressive feat, as the flow features have velocities as low as $1~\text{mm}~\text{s}^{-1}$ . The seals sense while swimming, hence their whiskers are sensitive enough to detect small-scale changes in the flow, while rejecting self-generated flow noise. Here we identify and illustrate a novel flow mechanism, causing a large-amplitude ‘slaloming’ whisker response, which allows artificial whiskers with the identical unique undulatory geometry as those of the harbour seal to detect the features of minute flow fluctuations when placed within wakes. Whereas in open water the whisker responds with very low-amplitude vibration, once within a wake, it oscillates with large amplitude and, importantly, its response frequency coincides with the Strouhal frequency of the upstream cylinder, making the detection of an upstream wake and an estimation of the size and shape of the wake-generating body possible. This mechanism has some similarities with the flow mechanisms observed in actively controlled propulsive foils within upstream wakes and trout swimming behind bluff cylinders in a stream, but there are also differences caused by the unique whisker morphology, which enables it to respond passively and within a much wider parametric range.

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Ahmed, A. & Bays-Muchmore, B. 1992 Transverse flow over a wavy cylinder. Phys. Fluids A 4 (9), 19591967.
Assi, G. R. S. 2014a Wake-induced vibration of tandem and staggered cylinders with two degrees of freedom. J. Fluids Struct. 50, 340357.
Assi, G. R. S. 2014b Wake-induced vibration of tandem cylinders of different diameters. J. Fluids Struct. 50, 329339.
Assi, G. R. S., Bearman, P. W., Carmo, B. S., Meneghini, J. R., Sherwin, S. J. & Willden, R. H. J. 2013 The role of wake stiffness on the wake-induced vibration of the downstream cylinder of a tandem pair. J. Fluid Mech. 718, 210245.
Assi, G. R. S., Bearman, P. W. & Meneghini, J. R. 2010 On the wake-induced vibration of tandem circular cylinders: the vortex interaction excitation mechanism. J. Fluid Mech. 661, 365401.
Assi, G. R. S., Meneghini, J. R., Aranha, J. A. P., Bearman, P. W. & Casaprima, E. 2006 Experimental investigation of flow-induced vibration interference between two circular cylinders. J. Fluids Struct. 22 (6), 819827.
Barth, F. G. 2004 Spider mechanoreceptors. Curr. Opin. Neurobiol. 14 (4), 415422.
Beal, D. N., Hover, F. S., Triantafyllou, M. S., Liao, J. C. & Lauder, G. V. 2006 Passive propulsion in vortex wakes. J. Fluid Mech. 549, 385402.
Dahl, J. M., Hover, F. S., Triantafyllou, M. S. & Oakley, O. H. 2010 Dual resonance in vortex-induced vibrations at subcritical and supercritical Reynolds numbers. J. Fluid Mech. 643 (1), 395424.
Dehnhardt, G., Mauck, B. & Bleckmann, H. 1998 Seal whiskers detect water movements. Nature 394 (6690), 235236.
Dehnhardt, G., Mauck, B., Hanke, W. & Bleckmann, H. 2001 Hydrodynamic trail-following in harbor seals (Phoca vitulina). Science 293 (5527), 102104.
Flemming, F. & Williamson, C. H. K. 2005 Vortex-induced vibrations of a pivoted cylinder. J. Fluid Mech. 522, 215252.
Gao, Y., Sun, Z., Tan, D. S., Yu, D. & Tan, S. K. 2014 Wake flow behaviour behind a smaller cylinder oscillating in the wake of an upstream stationary cylinder. Fluid Dyn. Res. 46 (2), 025505.
Ginter, C. C., DeWitt, T. J., Fish, F. E. & Marshall, C. D. 2012 Fused traditional and geometric morphometrics demonstrate pinniped whisker diversity. PLoS ONE 7 (4), e34481.
Grant, R., Wieskotten, S., Wengst, N., Prescott, T. & Dehnhardt, G. 2013 Vibrissal touch sensing in the harbor seal (Phoca vitulina): How do seals judge size? J. Compar. Physiol. A 199 (6), 521533.
Hanke, W. & Bleckmann, H. 2004 The hydrodynamic trails of Lepomis gibbosus (Centrarchidae), Colomesus psittacus (Tetraodontidae) and Thysochromis ansorgii (Cichlidae) investigated with scanning particle image velocimetry. J. Expl Biol. 207 (9), 15851596.
Hanke, W., Brucker, C. & Bleckmann, H. 2000 The ageing of the low-frequency water disturbances caused by swimming goldfish and its possible relevance to prey detection. J. Expl Biol. 203 (7), 11931200.
Hanke, W., Witte, M., Miersch, L., Brede, M., Oeffner, J., Michael, M., Hanke, F., Leder, A. & Dehnhardt, G. 2010 Harbor seal vibrissa morphology suppresses vortex-induced vibrations. J. Expl Biol. 213 (15), 26652672.
Hans, H., Miao, J. M. & Triantafyllou, M. S. 2014 Mechanical characteristics of harbor seal (Phoca vitulina) vibrissae under different circumstances and their implications on its sensing methodology. Bioinspir. Biomim. 9 (3), 036013.
Hover, F. S. & Triantafyllou, M. S. 2001 Galloping response of a cylinder with upstream wake interference. J. Fluids Struct. 15 (3), 503512.
Kim, J. & Choi, H. 2005 Distributed forcing of flow over a circular cylinder. Phys. Fluids 17 (3), 033103.
Lam, K. & Lin, Y. F. 2009 Effects of wavelength and amplitude of a wavy cylinder in cross-flow at low Reynolds numbers. J. Fluid Mech. 620, 195220.
Lam, K. M. & To, A. P. 2003 Interference effect of an upstream larger cylinder on the lock-in vibration of a flexibly mounted circular cylinder. J. Fluids Struct. 17 (8), 10591078.
Lam, K., Wang, F. H., Li, J. Y. & So, R. M. C. 2004 Experimental investigation of the mean and fluctuating forces of wavy (varicose) cylinders in a cross-flow. J. Fluids Struct. 19 (3), 321334.
Lee, S. J. & Nguyen, A. T. 2007 Experimental investigation on wake behind a wavy cylinder having sinusoidal cross-sectional area variation. Fluid Dyn. Res. 39 (4), 292304.
Liao, J. C., Beal, D. N., Lauder, G. V. & Triantafyllou, M. S. 2003 Fish exploiting vortices decrease muscle activity. Science 302 (5650), 15661569.
Miersch, L., Hanke, W., Wieskotten, S., Hanke, F. D., Oeffner, J., Leder, A., Brede, M., Witte, M. & Dehnhardt, G. 2011 Flow sensing by pinniped whiskers. Phil. Trans. R. Soc. Lond. B 366 (1581), 30773084.
Müller, U. K., Van Den Heuvel, B. L. E., Stamhuis, E. J. & Videler, J. J. 1997 Fish foot prints: morphology and energetics of the wake behind a continuously swimming mullet (Chelon labrosus risso). J. Expl Biol. 200 (22), 28932906.
Murphy, C. T., Eberhardt, W. C., Calhoun, B. H., Mann, K. A. & Mann, D. A. 2013 Effect of angle on flow-induced vibrations of pinniped vibrissae. PLoS ONE 8 (7), e69872.
Owen, J. C., Szewczyk, A. A. & Bearman, P. W. 2000 Suppression of Karman vortex shedding. Phys. Fluids 12 (9), S9.
Papaioannou, G. V., Yue, D. K. P., Triantafyllou, M. S. & Karniadakis, G. E. 2006 Three-dimensionality effects in flow around two tandem cylinders. J. Fluid Mech. 558, 387413.
Sayers, A. T. & Saban, A. 1994 Flow over two cylinders of different diameters: the lock-in effect. J. Wind Engng Ind. Aerodyn. 51 (1), 4354.
Schulte-Pelkum, N., Wieskotten, S., Hanke, W., Dehnhardt, G. & Mauck, B. 2007 Tracking of biogenic hydrodynamic trails in harbour seals (Phoca vitulina). J. Expl Biol. 210 (5), 781787.
Solomon, J. H. & Hartmann, M. J. 2006 Biomechanics: robotic whiskers used to sense features. Nature 443 (7111), 525.
Streitlien, K., Triantafyllou, G. S. & Triantafyllou, M. S. 1996 Efficient foil propulsion through vortex control. AIAA J. 34 (11), 23152319.
Wieskotten, S., Dehnhardt, G., Mauck, B., Miersch, L. & Hanke, W. 2010a Hydrodynamic determination of the moving direction of an artificial fin by a harbour seal (Phoca vitulina). J. Expl Biol. 213 (13), 21942200.
Wieskotten, S., Dehnhardt, G., Mauck, B., Miersch, L. & Hanke, W. 2010b The impact of glide phases on the trackability of hydrodynamic trails in harbour seals (Phoca vitulina). J. Expl Biol. 213 (21), 37343740.
Williamson, C. H. K. 1996 Vortex dynamics in the cylinder wake. Annu. Rev. Fluid Mech. 28 (1), 477539.
Williamson, C. H. K. & Govardhan, R. 2004 Vortex-induced vibrations. Annu. Rev. Fluid Mech. 36 (1), 413455.
Wolfgang, M. J., Anderson, J. M., Grosenbaugh, M. A., Yue, D. K. & Triantafyllou, M. S. 1999 Near-body flow dynamics in swimming fish. J. Expl Biol. 202 (17), 23032327.
Zhang, W. & Lee, S. J. 2005 PIV measurements of the near-wake behind a sinusoidal cylinder. Exp. Fluids 38, 824832.
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