Hydraulic characteristics of flow over and under semi-cylindrical structure

الملخص EN

In this study the germane factors influencing the flow over and under semi-cylindrical structure are experimentally investigated.

Four different diameters are tested, each one is operated with four different heights of gate opening to yield sixteen models.

For the purpose of comparison, a vertical rectangular thin-plate model is tested.

Performance of the semi-cylindrical structure proved to be significantly better than the rectangular model.

The laboratory investigations show that at low flow heads that just caused to start operating the weirs, the increase in gate opening from 2 to 5 cm caused an increase in total discharge about 80%, but it decreased to 3 % with an increase in head about 50%.

In addition, the effect of cylinder diameter decreased at relatively high heads for all gate openings when the ratio of head/gate-opening increased to 2.

The contribution of weir flow hinders gate flow causing its submergence and thus the head on the weir relatively increased at an average of 34 %.

The dimensionless parameters that cause increasing or decreasing the total dimensionless discharge are discussed.

The contribution of weir in the total actual discharge is between 7 % - 44 % and that of gate is between 56 % - 93 %, depending on gate opening and cylinder diameter.

Mathematical models are presented to predict the total discharge and the contribution of weir and gate with considerable accuracy.