This paper is concerned with theoretical analysis and experiments to obtain air-lift artificial upwelling flow characteristics induced by airbubble screen. An artificial upwelling by using the technique of airbubble screen was developed theoretically. According to results of experiments in a laboratory, the air-lift artificial upwelling induced by air-bubble screen is promising. Because the water depth for artificial upwelling is much deeper than those of the usual air-bubble screen technique, field studies are necessary.
The deep seawater is an important resource for the mankind. Almost all natural upwelling areas are significant fishing grounds. This is due to the nutritious deep seawater, which is rich in inorganic nutrient salts, such as nitrate, phosphate and silicate. These nutrient salts are essential for the growth of plants. The concept of artificial upwelling in this paper is to upwell the deep seawater directly in the surface of an open ocean by air-bubble screen. Using horizontal contraction & expansion tube (Venturi-type tube), an artificial upwelling induced by ocean currents was studied by Liang et al. (1978). Instead of contraction & expansion (C & E) tube, a tube-pair, which consists of two C & E tubes was proposed by Liang et al. (1979). After some laboratory and field experiments, it was concluded that the flow rate of the C & E tube-pair with a long pipe is rather small. A wave-driven artificial upwelling device is designed by using Isaacs wave pump (Isaacs et al., 1976; Chen et al., 1994). The Isaacs wave pump consists of a buoy and a vertical long pipe with a one-way valve. An estimated flow rate is about 0.45 to 0.95 m3/s for a 1.90m wave height and 12sec wave period (Liu and Jin, 1995). But the stiff long pipe may not survive in a storm wave.