The theory of a vertical gas-liquid jet formed by discharge of a gas (usually air) into liquid (usually water), producing a horizontal flow of liquid along the surface, is proposed. The case of a relatively deep (several meters) liquid layer, in which a quasisteady-state bubble column is established is discussed. This column can be used to protect water bodies from the spread of oil slicks, ice formation, penetration of salt water into fresh water, and damping of sea and shock waves. The theory is compared with experimental results. Several existing devices are described.
