The Fluid Mechanics of Capsule Pipelines : 2nd Report, Analysis of the Pressure Loss in Concentric Capsules, Pipelines and Annular Pipes

This paper presents the theoretical and experimental results obtained by a study of cylindrical capsules traveled concentrically in pipeline. Considering the total pressure loss of a capsule flow to be established by friction drag and pressure drag, the authors make them clear respectively from both a theoretical and an experimental study. In particular, the flow in the annular section of a capsule is approximated by the flow through annular pipes when the inner pipe moves. Then a general formula, concerned with the pressure loss due to friction drag in a turbulent flow regime for the moving concentric annuli, is derived by taking account of the one-seventh power law for an axial velocity profile and the boundary-layer characteristics on pipe walls. In conclusion, it is confirmed that the capsule velocity as well as the total pressure loss can be estimated with reasonable accuracy.