MEASUREMENTS OF VORTEX GENERATION AND MOTION AT WIND WAVE SURFACES

Yasuhide Takano, Goji T. Etoh, Gozo Tsujimoto

Abstract


Vortices generated at water surface under wind wave condition are most important phenomena for mass exchange between atmosphere and ocean. To extract vortices from randomly distributed velocity vectors obtained by a PTV, a new method to accurately estimate vorticity is proposed. The proposed method uses the Moving Least Square method which has been developed for grid-less numerical simulation. The optimal size of fitting area is derived theoretically and is confirmed by Monte Carlo simulation. Comparison of the accuracy between the proposed method and the commonly used method shows the advantage of the proposed method. The developed method is applied to the measurements of vorticity near the wind wave interfaces. The results show the generation and movements of the vortices at water surfaces.

Keywords


wind waves; Vortex Motion; Particle Tracking Velocimetry; Moving Least Square Method

References


Adrian, R.J. (1990): Particle-imaging technique for experimental fluid mechanics, Annual Review of Fluid Mechanics, 23, 261.http://dx.doi.org/10.1146/annurev.fl.23.010191.001401

Banner, M. L., W.L. Peirson (1998): Tangential stress beneath wind-driven air-water interfaces, J. Fluid Mech., Vol. 364, pp.115-145.http://dx.doi.org/10.1017/S0022112098001128

Dean, M. A., W.M. Drennan, E.S. Saltzman, R. Wanninkhof, eds (2002): Gas transfer at water surfaces, AGU, 383p.

Devasenathipathy, S., J. G. Santiago, S.T. Wereley, C.D. Meihart, K. Takehara(2003), Particle imaging techniques for microfabricated fluidic systems, Experiments in Fluids, Vol.34, pp. 504-514.

Etoh, T.G., K. Takehara (1995): Development of a new algorithm and supporting technologies for PTV, Proc. of the International Workshop on PIV-Fukui'95, pp.91-106.

Etoh, T., K. Goda, K. Takehara (1999) Evaluation of errors in quadratic approximation and derivation of the optimum size of fitting subdomain in MLS to combine PTV and CFD, Proc. of the 3 rd International Workshop PIV '99, Santa Barbara, pp.231-236.

Komori, S., R. Nagaosa and Y. Murakami (1993): Turbulence structure and mass transfer across a sheared air-water interface in wind-driven turbulence, Journal of Fluid Mechanics, Vol. 249, pp.161-183.http://dx.doi.org/10.1017/S0022112093001120

Ootsuka, N., K. Takehara, N. Mizutani, G. Tsujimoto, T.G. Etoh and Y. Takano (2003): PTV Measurements of Micro Scale Breaking of Wind Waves, Proceedings of Coastal Engineering, JSCE, Vol.50, pp.86-90 (In Japanese) .http://dx.doi.org/10.2208/proce1989.50.86

Siddiqui M.H.K., M.R. Loewen, C. Richardson, W.E. Asher and A.T. Jessup (2001): Simultaneous particle image velocimetry and infrared imagery of microscale breaking waves, Physics of Fluids, Vol.13, No. 7, pp.1891-1903.http://dx.doi.org/10.1063/1.1375144

Takehara, K., R. J. Adrian, G. T. Etoh, and K. T. Christensen (2000): A Kalman tracker for superresolution PIV, Experiments in Fluids, Vol. 29, pp. S34 -S41.http://dx.doi.org/10.1007/s003480070005

Takehara, K., M. Maki, G. Tsujimoto, T.G. Etoh, Y. Takano(2002): Simultaneous PTV Measurement of Air and Water Flow Close to Water Surfaces under Wind-Wave Conditions, Proceedings of Coastal Engineering, JSCE, Vol.49, pp.66-70 (In Japanese).http://dx.doi.org/10.2208/proce1989.49.66

Takehara, K., T.G. Etoh, Y. Takano, T. Shigematsu, K. Tanaka (2003): PTV measurements of flow in porous media by using refractivity matching, Proc. of the 7 TH Asian Symposium on Visualization, pp.2B2-1-6 .

Takehara, K., Ohtsuka, N., Etoh, T.G., Takano, Y., Tsujimoto, G., Mizutani, N. (2004): Development of Simultaneous plane measurement techniques of air and water flows close to wind wave interfaces, Proc. of the 29 th International Conference on Coastal Engineering, pp.1060-1071.

PMid:15380896

Toba, Y., M. Tokuda, K. Okuda and S. Kawai (1975): Forced convection accompanying wind waves, Journal of Oceanographical Society of Japan, Vol.31, pp192-198.http://dx.doi.org/10.1007/BF02150958

Yagawa, M. and Y. Sakai (1997): Meshless scheme, Research of Mechanics, Vol. 49, No.1, pp.103-110 (In Japanes).


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