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Ordered motion in the turbulent boundary layer over wind waves

Published online by Cambridge University Press:  21 April 2006

H. Kawamura  and
Y. Toba
H. Kawamura
Affiliation:
Department of Geophysics, Faculty of Science, Tohoku University, Sendai, 980 Japan
Y. Toba
Affiliation:
Department of Geophysics, Faculty of Science, Tohoku University, Sendai, 980 Japan
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Abstract

The turbulent boundary layer over young wind waves (C/u* ∼ 1, where C is the phase speed of wind waves and u* is the friction velocity) has been investigated in a laboratory tank. Ordered motions have been found, and their structures studied in detail. Visualization of the outer boundary layer (0.4δ–1δ, where δ is the boundary-layer thickness) by paraffin mist has demonstrated the existence of a train of large-scale ordered motions having a horizontal lengthscale that corresponds to the wavelength of the underlying wind waves. Hot-wire measurements combined with the visualization have shown that the passage of the outer boundary-layer bulge is related to the occurrence of a low-speed air mass, usually accompanied by an upward velocity to produce large Reynolds stress. In the vicinity of the wave surface (0–0.15δ), flow separation occurs over these wind waves. Instantaneous velocity shear measurements, using two hot wires 0.15 cm apart vertically, have detected a high-shear layer at the edge of the separation bubbles. This high-shear layer, the potential site for generating much turbulence, reattaches on the windward side of the preceding wind waves. A pressure rise and a shear-stress spike, expected near the reattachment region, could be the mechanisms for supplying energy to the wind waves.

The bursting phenomena over wind waves have been examined in detail in the logarithmic boundary layer (0.15δ–0.3δ). The bursting phenomena are a major mechanism for producing Reynolds stress and have a specific relationship with the phase of the wind wave. To explain the bursting phenomena, two mechanisms (not present in the boundary layer over a flat plate) are proposed, involving air-flow separation and the large-scale ordered motions, respectively. The two mechanisms are a ‘big burst’ related to the discharge of a whole separation bubble, and a ‘small burst’ which is the upward bursting of a low-speed air mass from the unstable separated shear layer into the ordered motions passing over a separation bubble.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 197 , December 1988 , pp. 105 - 138
Copyright
© 1988 Cambridge University Press

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References

Banner, M. L.1986 The influence of wave breaking on the surface pressure distribution in wind-wave interactions. Applied Mathematics. Preprint. AM86/9, The University of New South Wales.
Banner, M. L. & Melville, W. K.1976 On the separation of air flow over water waves. J. Fluid Mech. 77, 825–842.Google Scholar
Banner, M. L. & Phillips, O. M.1974 On the incipient breaking of small scale waves. J. Fluid Mech. 65, 647–656.Google Scholar
Blackwelder, R. F. & Kovasznay, L. S. G.1972 Time scales and correlations in a turbulent boundary layer. Phys. Fluids 15, 1545–1554.Google Scholar
Bradshaw, P. & Wong, F. Y. F.1972 The reattachment and relaxation of a turbulent shear flow. J. Fluid Mech. 52, 113–135.Google Scholar
Brown, G. L. & Thomas, A. S. W.1977 Large structure in a turbulent boundary layer. Phys. Fluids 20, S243–252.Google Scholar
Buckles, J., Hanratty, T. J. & Adrian, R. J.1984 Turbulent flow over large-amplitude wavy surface. J. Fluid Mech. 140, 27–4.Google Scholar
Cantwell, B. J.1981 Organized motion in turbulent flow. Ann. Rev. Fluid Mech. 13, 457–515.Google Scholar
Chambers, A. J. & Antonia, R. A.1981 Wave-induced effect on the Reynolds shear stress and heat flux in the marine surface layer. J. Phys. Oceanogr. 11, 116–121.Google Scholar
Chang, P. C., Plate, E. J. & Hidy, G. M.1971 Turbulent air flow over the dominant component of wind-generated water waves. J. Fluid Mech. 47, 183–208.Google Scholar
Corino, E. R. & Brodkey, R. S.1969 A visual investigation of the wall region in turbulent flow. J. Fluid Mech. 37, 1–30.Google Scholar
Csanady, G. T.1985 Air—sea momentum transfer by means of short-crested wavelets. J. Phys. Oceanogr. 15, 1486–1501.Google Scholar
Falco, R. E.1977 Coherent motions in the outer region of turbulent boundary layers. Phys. Fluids 20, S124–132.Google Scholar
Grass, A. J.1971 Structural features of turbulent flow over smooth and rough boundaries. J. Fluid Mech. 50, 233–255.Google Scholar
Hatori, M.1984 Nonlinear properties of laboratory wind waves at energy containing frequencies. Part 1. Probability density distribution of surface elevation. J. Oceanogr. Soc. Japan 40, 1–11.Google Scholar
Kawai, S.1981 Visualization of airflow separation over wind-wave crests under moderate wind. Boundary-Layer Met. 21, 93–104.Google Scholar
Kawai, S.1982 Structure of air flow separation over wind-wave crests. Boundary-layer Met. 23, 503–521.Google Scholar
Kawamura, H., Okuda, K., Kawai, S. & Toba, Y. 1981 Structure of turbulent boundary layer over wind waves in a wind wave tunnel. Tohoku Geophys. J. (Sci. Rep. Tohoku Univ. Ser. 5) 28, 69–86.Google Scholar
Kim, H. T., Kline, S. J. & Reynolds, W.1971 The production of the wall region in turbulent flow. J. Fluid Mech. 50, 133–160.Google Scholar
Kline, S. J., Reynolds, W. C., Schraub, F. A. & Runstadler, P. W. 1967 The structure of turbulent boundary layers. J. Fluid Mech. 30, 741–773.Google Scholar
Kovasznay, L. S. G., Kibens, V. & Blackwelder, R.1970 Large scale motion in the intermittent region of a turbulent boundary layer. J. Fluid Mech. 41, 283–325.Google Scholar
Laufer, J.1975 New trends in experimental turbulence research. Ann. Rev. Fluid Mech. 7, 307–326.Google Scholar
Lessen, M.1950 On stability of the free laminar boundary layer between parallel streams. NACA Rep. 979.Google Scholar
Okuda, K.1982a Internal flow structure of short wind waves. Part I. On the internal vorticity structure. J. Oceanogr. Soc. Japan 38, 28–42.Google Scholar
Okuda, K.1982b Internal flow structure of short, wind waves. Part II. The streamline pattern. J. Oceanogr. Soc. Japan 38, 313–322.Google Scholar
Okuda, K.1982c Internal flow structure of short wind waves. Part III. Pressure distributions. J. Oceanogr. Soc. Japan 38, 331–338.Google Scholar
Okuda, K.1984 Internal flow structure of short wind waves. Part IV. The generation of flow in excess of the phase speed. J. Oceanogr. Soc. Japan 40, 46–56.Google Scholar
Okuda, K., Kawai, S. & Toba, Y.1977 Measurements of skin friction distribution along the surface of wind waves. J. Oceanogr. Soc. Japan 33, 190–198.Google Scholar
Takeuchi, K., Leavitt, E. & Chao, S. P.1977 Effects of water waves on the structure of turbulent shear flows. J. Fluid Mech. 80, 535–559.Google Scholar
Tani, I., Iuchi, M. & Komoda, H.1961 Experimental investigation of flow separation associated with a step or a groove. Aero. Res. Inst. Univ. Tokyo Rep. 364, pp. 119–137.Google Scholar
Tatsumi, T. & Gotoh, K.1960 The stability of free boundary layers between two uniform streams. J. Fluid Mech. 7, 433–441.Google Scholar
Toba, Y.1972 Local balance in the air—sea boundary processes, I. On the growth process of wind waves. J. Oceanogr. Soc. Japan 28, 109–120.Google Scholar
Toba, Y.1973 Local balance in the air—sea boundary processes, III. On the spectrum of wind waves. J. Oceanogr. Soc. Japan 29, 209–220.Google Scholar
Toba, Y.1978 Stochastic form of the growth of wind waves in a single parameter representation with physical implications. J. Phys. Oceanogr. 8, 494–507.Google Scholar
Toba, Y., Tokuda, M., Okuda, K. & Kawai, S. 1975 Forced convection accompanying wind waves. J. Oceanogr. Soc. Japan 31, 192–198.Google Scholar
Weissman, M. A.1981 Observations and measurements of air flow over water waves. In Wave Dynamics and Radio Probing of the Ocean Surface (ed. O. M. Phillips & K. Hasselmann), pp. 335–352. Plenum.
Zilker, D. P. & Hanratty, T. J.1979 Influence of the amplitude of a solid wavy wall on a turbulent flow. Part 2. Separated flows. J. Fluid Mech. 90, 257–271.Google Scholar