Shima kabiri - Msc student , tabriz university
Ali hosein zadeh dalir - lectureship , tabriz university

Water pipes and other fluids which are laid on the bed seas and rivers can simply change the pattern of the flow around themselves. These changes will cause scouring near the pipe and thehole will appear soon. Scouring under the pipe may destroy the pipe and finally impose extracosts and also damages the environmental situations. In this article, experimental results of putting bed sills in decreasing the maximum height of scouring under the pipes which arecompletely under water, have been discussed. Tests are divided into two conditions : 1) scouring under pipe without bed sills 2) scouring under pipe with bed sill. In these tests we used three kinds of pipes with different diameter : 2cm, 3cm and 4 cm. when we are using bed sills, thethickness of the bed sill is 5 mm with the length of 25cm ( the width of the flume ) and the height of 13cm (depth of sandy bed ). These bed sills are located in the distance of D/2 ( pipe diameter ) from the pipe center. The scouring in the front of the pipe will be negligible while thebed sill is located in the downstream of the pipe. In these experiments the mean velocity of the approach flow is almost controlled between 0.8 to 0.9 times of the critical velocity for keeping the condition in a clear-water scour

scour, bed sill, underwater pipelines, unidirectional flow