Abstract
The formation of air bubbles ejected through a single hole in a flat plate was observed in uniform flow of 2–10 m/s It was confirmed that the size of the air bubbles was governed by main flow velocity and air flow rate. According to previous experiments, the size of the bubbles is an important factor in frictional drag reduction by microbubble ejection. Usually bubbles larger than a certain diameter (for example 1 mm) have no effect on frictional drag reduction. Three different methods were proposed and tested to generate smaller bubbles. Among them, a 2D convex (half body of an NACA 64-021 section) with ejection holes at the top was the best and most promising. The diameter of the bubbles became about one-third the size of the reference ejection on a flat plate. Moreover, the bubble size did not increase with increasing flow rate. This is a favorable characteristic for practical purposes. The skin friction force was measured directly with a miniature floating element transducer, and decreased drastically by microbubble ejection from the top of the 2D convex shape.
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References
McCormick ME, Bhattacharyya R (1973) Drag reduction of a submersible hull by electrolysis. Nav Eng J 85:11–16
Madavan NK, Deutsch S, Merkle CL (1984) Drag reduction of turbulent skin friction by microbubbles. Phys Fluids 27:356–363
Madavan NK, Deutsch S, Merkle CL (1985) Measurements of local skin friction in a microbubble-modified turbulent boundary layer. J Fluid Mech 156:237–256
Madavan NK, Deutsch S, Merkle CL (1985) Numerical investigation into the mechanisms of microbubble drag reduction. J Fluid Eng 107:370–377
Merkle CL, Deutsch S, Pal S et al (1986) Microbubble drag reduction. Proceedings of the 16th Symposium on Naval Hydrodynamics, Berkeley, pp 199–215
Pal S, Merkle CL, Deutsch S (1988) Bubble characteristics and trajectories in a microbubble boundary layer. Phys Fluids 31:744–751
Pal S, Deutsch S, Merkle CL (1989) A comparison of shear stress fluctuation statistics between microbubble modified and polymer modified turbulent boundary layers. Phys Fluids A 1:1360–1362
Kato H, Miyanaga M, Haramoto, Y et al (1994) Frictional drag reduction by injecting bubbly water into a turbulent boundary layer. Cavitation and gas-liquid flow in fluid machinery and devices. FED vol 190, ASME, pp 185–194
Kato H, Miyanaga M, Yamaguchi H et al (1994) Frictional drag reduction by injecting bubbly water into a turbulent boundary layer and the effect of plate orientation. In: Serizawa A, Fukano T, Bataille J (eds) Advances in multiphase flow. Elsevier, Amsterdam, Kyoto, pp 85–96
Guin MM, Kato H, Yamaguchi H, et al (1996) Reduction of skin friction by microbubbles and its relation with nearwall bubble concentration in a channel. J Mar Sci Technol 1:241–254
Bogdevich VG, Evseev AR, Malyaga AG et al (1977) Gassaturation effect of near-wall turbulence characteristics. 2nd International Conference on Drag Reduction, Cambridge, UK, BHRA, pp 25–37
Zurber N, Tribas M, Westwater JW (1961) International development heat transfer ASME, p 230
Meng JCS, Uhlman JS Jr (1989) Microbubble formulation and splitting in a turbulent boundary layer for Turbulence reduction. Symposium in Honor of Maurice Holton on his 70th Birthday
Yoshida Y, Takahashi Y, Kato H et al (1998) Study on the mechanism of resistance reduction by means of micro-bubble sheet and on applicability of the method to full-scale ship. 22nd Symposium on Naval Hydrodynamics, Washington
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Kato, H., Miura, K., Yamaguchi, H. et al. Experimental study on microbubble ejection method for frictional drag reduction. J Mar Sci Technol 3, 122–129 (1998). https://doi.org/10.1007/BF02492919
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DOI: https://doi.org/10.1007/BF02492919