Motion of a single capsule in a hydraulic pipeline

The method of characteristics is used to numerically analyse the motion of a single solid capsule in a hydraulic horizontal straight pipe. The capsule is assumed to be a point mass and the coaxial-annular-flow model around the capsule is used to derive the boundary conditions for water flow at the capsule discontinuity. The results are compared with experimental measurements which were taken in a pipeline 28 m in length and with an inside diameter of 40 mm. The capsule had wheels to keep its position coaxial with the pipe axis and always had a higher velocity than the water flow. The measurements are explained quite well by the analysis.