RELATIVE BUBBLE DENSITY AND FLUX DISCHARGED FROM AN UNDERWATER GEYSER VARYING WITH TIDE

Abstract

We estimated relative bubble density and flux based on the ultrasonic echo intensity and the upward velocity. We derived a relational expression between the relative bubble density and the ultrasonic echo intensity, after assuming that the (a)bubbles can be replaced by simple rigid spheres with a constant radius, (b)the radius is enough larger than the wavelength of the incident wave of the acoustic current meter, and (c)the sound absorption by the sea water can be regarded as the constant. At high tide, at erupting state the relative bubble density had large value, while at halting state it had quite small value. At low tide, however, the relative bubble density had almost always positive value, thus the bubbles always were present in the sea water. And the similarity between the relative bubble density and the upward velocity confirmed that the bubbles in the sea water were transported by the fluid discharged from the underwater geyser.