Experimental investigation of the bursting characteristics under sheared air-water interface
剪切水-气界面下湍流猝发特征的实验研究

The bursting phenomenon under a sheared air-water interface is quantitatively examined using combined-time-streak markers of hydrogen bubbles. Based upon samples of instantaneous velocity profiles derived from flow visualization pictures, the signal characteristics of bursting event are analyzed, and particular emphasis is placed on the relation between bursting processes and the production of turbulence near air-water interface. During a bursting, the instantaneous velocities and Reynolds shear stress near air-water interface fluctuate in relatively large amplitude, which appear to be associated with the ejection phenomena of low-speed streak. Their high degree of coherence in time and in the vertical direction is the most notable characteristic of bursting event. In bursting times, the values of Reynolds shear stress and turbulence intensity rise considerably in the region where bursting phenomenon is observed, and become much higher than the mean value and that in non-bursting period. The present data establish, for the case studied, that bursting processes is the main contributor of turbulent kinetic energy near sheared air-water interface.