Effects of Helical Ribs of Capsule Surface on a Flow in a Horizontal Hydraulic Pipeline
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It is well-known that in a hydraulic capsule pipeline capsules are smoothly transported without wheels due to lubricated water flow in the clearance between the capsule and the pipe wall. When wheels are attached to keep the capsule in concentric with the pipe, the mean velocity of capsule becomes higher than that of water, and this suggests that the core flow is favorable. To increase the capsule velocity and to reduce the pressure gradient due to capsules, Ellis et al.  argued that the clearance between the capsule and the pipe bottom should be increased and that the capsule should be supported in a slightly nose-up position. In order to raise the capsule from the pipe bottom they found that a simple collar around the leading half of the cylinder is the most effective. As for helical runners, they predicted in discussion  that helical runners would not increase the lift more than a collar, which raises the nose. They  also investigated several methods to reduce the pressure gradient by modification of the capsule surface which brings about the reduction of coefficient of friction.
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