碎波帶運動特性

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1 28 立 26 年 Proceedings of the 28th Ocean Engineering Conference in Taiwan ational Sun Yat-Sen University, ovember 26 (/3) (PIV) /2 The Characteristics of two Phase Flow of Boundary Layer in Surf and Swash Zone(/3) Hwung-Hweng Hwung Zhi-Cheng Huang Wen-Yang Hsu Kao-Shu Hwang ABSTRACT This paper describes the experimental results of 2D temporal and spatial flow structures of spilling breakers in the surf zone. The Particle Image Velocimetry (PIV) was employed to measure the internal velocity field on a :2 slope. To synchronize the measuring systems and solve the problem of phase identification, the triggering signals were precisely controlled. Surface profiles were obtained from an image processing method automatically. Entire spatial distributions of ensemble-averaged velocities in the surf zone were integrated properly by using a mosaic method. The spatial resoltution of velocity is less than the turbulence length scale. The generation and dissipation process of horizontal eddies are investigated. Other temporal and spatial evolutions of coherent structures in the surf zone are also discussed. Peregrine (983) Battjes (988) Duncan (2) Christensen et al. (22) Lin & Hwung (992) odaoka(989) (horizontal eddies) (oblique eddies) (Laser Doppler Velocimetry, LDV)( adaoka & Kondoh,982 Ting & Kirby, 996)Stansby and Feng (25) LDV /2-23-

2 PIV Chang & Liu (999) PIV Melville (22) PIV LDV PIV (ensemble average method) (mosaic method; Melville, 22) PIV 4.63cm 2.5cm (Cox et al., 994) i b ( tan β / Hb / L =.327; Battjes,974) (spilling breaker) T i(s) H i(cm) L i(cm) d i(cm) H i/l i H b(cm) d b(cm) Hz (mosaic method) (FOV~FOV7) 74 PIV Hz (DAQ) PIV.% 5 µ s % mm 2 (~.4-.8h; Cox et al., 994) (white and pepper noise) (median filter)

3 25m ref. trig. z y x 2.5cm.7m.359m 4.63cm :2 mirror.3m Wavemaker PC synchronizer Power 3-D movable table CCD pulse laser PC 2 δ k k k2 = ; =,2,, 2 (5) k 4 8 4% 4 % 5 6 8% relative error FOV FOV2 FOV3.8 FOV4 FOV5 FOV6.6 FOV7.4 3 U ( x, t ) u ( x, t ) u ( x = =, t ) i () i= u i i u ( x, t) = u( x, t) U ( x, t) (2) relative error FOV FOV2 FOV3 FOV4 FOV5 FOV6 FOV7.33 k = ( uu + w w ) (3) 2.33 (Svendsen, 987) (Melville et al., 22) 2 δ U 2 U U 2 = ; =,2,, 2 2 U 2 (4) ( gh ) ( Ting & Kirby, 996) g h (Lin and Liu, 998)Cheng and Liu (999) C

4 Stansby & Feng (25) Stive (98).8 2 7(cm/s) Stansby & Feng (25) present study 2-2 C/(gh) / h/h b x 5 z 3 t/t= Svendsen et al (978) x ~3mm (x ~5mm) (x 5~3mm) (bore establishment region).2c(stansby & Feng, 25) 85cm/sec.2C (Qiao and Duncan, 2) x 3~74mm Stive(98) (inflow region) x(mm) 7 (t/t=~.9) flow reverse wake region stagnation point interaction region with graviry interaction region with bottom mixing region stagnation point x(mm).5c=.3m/sec inflow region 8 (bore) (mixing region) (interaction Mag m/s region with gravity)(interaction with bottom)(wake or decay region) 8.5C Stive(98) -26-

(989) Chang and Liu (999) x=23.64 (t/t=.2) -C/h t/t=.3 t/t=.4 -.

5 (staganation poin) 7 (undertow) 4.2 Ω=.5( v / x u / y) 9 ( ) (toe) (Qiao and Duncan, 2) (x 2cm, t/t=.2) adaoka et al.(989) (horizontal eddy) (x 2~7cm, t/t=.3~.9) (adaoka et al., 989 Standby and Feng, 25) -2~3(s - ) -C/h adaoka et al. (989) Chang and Liu (999) x=23.64 (t/t=.2) -C/h t/t=.3 t/t= C/h PIV z/h 9 (t/t=~.9).5 t/t= t/t=. t/t=.2 t/t=.3 t/t=.4 t/t=.5 t/t=.6 t/t=.7 t/t=.8 t/t=.9.5 length scale= Ωh/C (x=23.64) (mosaic method) (stretching).5~.3 gh Stive(98) -27-

6 .5C (toe) -C/h ( SC E-6-4). Battjes, J. A. (974) Surf similarity, Proc. 4 th Int. Con. Coastal Eng. ASCE pp Battjes, J. A. (988) Surf-zone dynamics, Annu. Rev. Fluid Mech Chang, K. A. and Liu, P. L. F. (999) Experimental investigation of turbulence generated by breaking waves in water of intermediate depth, Phys. Fluids. Vol. o. 3 pp Christensen, E. D., Walstra, D. J. and Emerat,. (22) Vertical variation of the flow across the surf zone, Coastal Eng. Vol. 45 pp Cox, D. T., Kobayashi,. and Okayasu, A. (994) Vertical variations of fluid velocities and shear stress in surf zones, Proc. 24 th Int. Con. Coastal Eng. ASCE pp Duncan, J. H. (2) Spilling breakers, Annu. Rev. Fluid Mech. Vol. 33 pp Lin, C. and Hwung, H. H. (992) External and internal flow fields of plunging breakers, Exp. Fluids. Vol. 2 pp Lin, P. and Liu, P. L. F. (998) A numerical study of breaking waves in the surf zone, J. Fluid Mech. Vol. 359, pp Melville, W. K., Veron. F. and White, C. J. (22) The velocity field under breaking waves: coherent structures and turbulence, J. Fluid Mech., Vol. 454, adaoka, K. and Kondoh, T. (982) Laboratory measurement of velocity field structure in the surf zone by LDV, Coastal Eng. in Japan, Vol. 25 pp adaoka, K., Hino, M. and Koyano, Y. (989) Structure of the turbulent flow field under breaking waves in the surf zone, J. Fluid Mech., Vol. 24, pp Peregrine, D. H. (983) Breaking waves on beaches, Annu. Rev. Fluid Mech., Vol. 5, pp Qiao, H. and Duncan, J. H. (2) Gentle spilling breakers: crest flow-field evolution, J. Fluid Mech., Vol. 439, pp Stansby, P. K. and Feng, T. (25) Kinematics and depth-integrated terms in surf zone waves from laboratory measurement, J. Fluid Mech., Vol. 529, pp Stive, M. J. F. (98) Velocity and pressure field in spilling breakers, Proc. of the 7 h Int. Conf. on Coast Eng., Vol., pp Svendsen, I. A. (987) Analysis of surf zone turbulence, J. Geophys. Res., Vol. 92, C5 pp Ting, F. C. K. and Kirby, J. T. (996) Dynamics of surf zone turbulence in a strong spilling breaker, Coastal Eng., Vol. 27, pp

[1] Nielsen [2]. Richardson [3] Baldock [4] 0.22 mm 0.32 mm Richardson Zaki. [5-6] mm [7] 1 mm. [8] [9] 5 mm 50 mm [10] [11] [12] -- 40% 50%

[1] Nielsen [2]. Richardson [3] Baldock [4] 0.22 mm 0.32 mm Richardson Zaki. [5-6] mm [7] 1 mm. [8] [9] 5 mm 50 mm [10] [11] [12] -- 40% 50% 38 2 2016 4 -- 1,2, 100190, 100083 065007 -- 0.25 mm 2.0 mm d 10 = 0.044 mm 640 3 300. Richardson--Zaki,,, O359 A doi 10.6052/1000-0879-15-230 EXPERIMENTAL STUDY OF FLUID-SOLID TWO-PHASE FLOW IN A VERTICAL