The velocities and the associated pressure gradients of infinitely long liquid-borne cylinders flowing freely in pipes are related analytically to their radial positions. These velocities and pressure gradients are compared with those of liquids in cylinder-free pipes and expressed as ratios. A digital computer was used to evaluate the resultant equations for values of the cylinder/pipe diameter ratio between 0·25 and 0·97, with radial positions varying from the fully eccentric to the fully concentric position. As the clearance between the pipe and the bottom of the cylinder increases, the pressure ratio (RP) decreases and the velocity ratio (RV) increases. The relationship between RP and RV is independent of liquid viscosity and density, capsule density and pipe diameter, and is shown to be nearly linear for the larger diameter ratios. The R, R relationships are compared with data from three experimental capsule pipelines with pipe diameters from ½ to 4 in., involving a variety of diameter ratios, cylinder lengths and densities, and oil viscosities. The experimental results for single capsules of finite length are shown to be in close agreement with the predictions for infinitely long cylinders.
The relevance of the analysis to capsule pipelining is indicated by relating experimental values of capsule velocity over a wide range of densities to the theoretical clearance of the capsules. A general relationship of this type would permit the optimization of the power requirements of any particular throughput of a given commodity.