Abstract
Wave profile measurements are important for computing wave characteristics and for studying the aqueous boundary layer formed beneath surface waves. The measurement technique presented here made use of digital imagery and a detection algorithm referred to as the variable threshold method. The technique can measure wind generated waves as short as 10 pixels (1.44 mm) in wavelength. The average r.m.s. quantization error was found to be ±0.29 pixels (±0.04 mm) using simulated wave profiles and the average bias error was estimated to be 0.07 pixels (0.01 mm) from real still water profiles. The magnitude of all other types of random errors was estimated to be approximately ±0.64 pixels (±0.09 mm) using real wind wave profiles. A series of morphological operations, used to correct for non-uniform seed densities, improved the accuracy of the detected wave profiles by a factor of five. The variable threshold method detected real wind wave profiles 3.5 times more accurately than the standard constant threshold method and had total r.m.s. errors that ranged from ±0.7 (±0.1 mm) to ±1.1 (±0.16 mm) pixels.
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References
Jähne B (1997) Digital image processing—concepts, algorithms, and scientific applications, 4th edn. Springer, Berlin Heidelberg New York
Law CNS, Khoo BC, Chew TC (1999) Turbulence structures in the immediate vicinity of the shear-free air–water interface induced by a deeply submerged jet. Exp Fluids 27:321–331
Lin HJ, Perlin M (1998) Improved methods for thin, surface boundary layer investigations. Exp Fluids 25:431–444
Melville WK, Veron F, Whitey CJ (2002) The velocity field under breaking waves: coherent structures and turbulence. J Fluid Mech 454:203–233
Mukto MA, Atmane MA, Loewen MR (2005) Accurate detection of wind wave profiles. In: Proceedings of the 2nd coastal, estuary & offshore engineering specialty conference, 33rd CSCE annual conference, Toronto, Canada, 10 p, CD-Rom
Peirson WL (1997) Measurement of surface velocities and shears at a wavy air–water interface using particle image velocimetry. Exp Fluids 23:427–437
Siddiqui MHK, Loewen MR, Richardson C, Asher WE, Jessup AT (2001) Simultaneous particle image velocimetry and infrared imagery of microscale breaking waves. Phys Fluids 13:1891–1903
Stansell P, MacFarlane C (2002) Experimental investigation of wave breaking criteria based on wave phase speeds. J Physical Oceanography 32:1269–1283
Zarruk GA (2005) Measurement of free surface deformation in PIV images. Meas Sci Technol 16:1970–1975
Acknowledgments
We are grateful to the Canadian Foundation for Climate and Atmospheric Sciences (CFCAS) for financial support. The experiments comply with the current laws of the country in which they were performed.
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Mukto, M.A., Atmane, M.A. & Loewen, M.R. A particle-image based wave profile measurement technique. Exp Fluids 42, 131–142 (2007). https://doi.org/10.1007/s00348-006-0226-6
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DOI: https://doi.org/10.1007/s00348-006-0226-6