Abstract: The velocity and locate formula of a rising small bubble in the water are derived from the second law of Newton. The variation rate of radius of the rising bubbles in the water is obtained by using the state equation of ideal gas and the pressure difference formulas of the spherical liquid surface. Taking into account the varying regularity of the radius and locate of bubbles with time in the rising process, we simulate the rising process of small bubble under difierent incipient conditions by using computer.

Key words: bubble, velocity, varying-rate of radius, the state equation of ideal gas, pressure