Flow of High Expansion Foam in Pipes

The results of tests of the flow of high expansion foam in smooth and rough pipes are presented. It is concluded that foam is non-Newtonian with pressure loss a function of average velocity to a power less than unity. In addition, it is found that at a given velocity, pressure loss is an inverse function of bubble size with expansion factor of little significance in the range of velocities studied. The effect of bubble size on pressure loss decreases with increasing velocity in both rough and smooth pipes. The presence of apparent wall slip or the sliding of the foam on a thin liquid film on the wall of the smooth pipes was observed. The flow mechanism is described qualitatively using photographs taken from motion pictures of the flow.