Drag reducing rubber casing for snorkel for swimmer is bonded to circular-section vertical pipe and has regular pattern of longitudinal ridges and grooves

摘要

The drag reducing rubber casing for a swimmer's snorkel is bonded to circular-section vertical pipe. It has regular pattern of longitudinal ridges and grooves. The grooves may be 1 mm deep and spaced 3 mm apart. The inside diameter of the casing is 19 mm and its outside diameter is 21 mm. There are 24 longitudinal grooves which modify the behavior of the boundary layer.