Air-water flow measurements are of importance for the coastal and ocean engineering fields. Although kinematic investigations of the multi-phase flows have been conducted for long time, velocity measurements still are concerned with many researchers and engineers in coastal and ocean areas. In the present study, an imaging technique using shadowgraphy and fiber optic probe for velocity measurements of air bubbles is introduced. The shadow graphy image technique is modified from the typical image velocimetry methods, and optical fibers are used for the well-known intrusive coupled phase-detection probe system. Since the imaging technique is a non-intrusive optical method from the air, it is usually applied for 2D flows. On the other hand, the double fiber optic probes touch flows regardless of flow patterns. The results of the flow measurements by both methods are compared and discussed. The methods are also applied to the measurements of overtopping flows by a breaking wave over the structure fixed on the free surface.
Experimental Study on Behavior of Green Water for Rectangular Structure, Journal of Ocean Engineering and Technology, 2016, 30, 1, 44
Application of Image Technique and Optical Fiber Sensor for Air-water Mixture Flow, Journal of the Korean Water Resources Association, 2015, 48, 7, 535
Chang, K.A. and Liu, P.L.F. (1999). "Experimental Investigation of Turbulence Generated by Breaking Waves in Water of Intermediate Depth," Physics of Fluids, Vol11, pp 3390-3400.
Chang, K.A. and Liu, P.L.F. (2000). "Pseudo Turbulence in PIV Breaking-wave Measurements," Experiments of Fluids, Vol 29, pp 331-338.
Govender, K., Mocke, G.P. and Alport, M.J. (2002). "Videoimaged Surf Zone Wave and Roller Structures and Flow Fields," J. of Geophysics Research, Vol 107. pp 3072-3092.
Chanson, H. (1997). Air Bubble Entrainment in Free-surface Turbulent Shear Flows, Academic Press, London, UK
Jansen, P.C.M. (1986). "Laboratory Observations of The Kinematics in The Aerated Region of Breaking Waves," Coastal Engineering, Vol 9, pp 453-477.
Melville, W.K., Veron, F. and White, C.J. (2002). "The Velocity Field under Breaking Waves: Coherent Structures And Turbulence," J. of Fluid Mechanics, Vol 454, pp 203-233.
Nishino, K., Kato, H. and Torii, K. (2000). "Stereo Imaging for Simultaneous Measurement of Size and Velocity of Particles in Dispersed Two-phase Flow," Measurement Science and Technology, Vol 11, pp 633-645.
Ryu, Y., Chang, K.A. and Lim, H.J. (2005). "Use of Bubble Image Velocimetry for Measurement of Plunging Wave Impinging on Structure and Associated Greenwater," Measurement Science and Technology, Vol 16, pp 1945-1953.