A two-phase flow regime in which the gas phase flows as bubbles dispersed in a flowing liquid. This type of flow tends to occur at low gas superficial velocities and high liquid velocities. The bubbles travel with a complex motion, each with a different velocity. The bubbles may coalesce and are generally of non-uniform size. In horizontal pipes, gravity tends to make bubbles accumulate in the upper part of the pipe except at very high liquid velocities when the intensity of the turbulence is enough to disperse the bubbles about the cross section.