مطالعه آزمايشگاهي ميدان جريان اطراف صفحات مستغرق مقابل دهانه آبگير جانبي در كانال uشكل

Experimental Study on turbulent flow field around submerged vanes at a lateral diversion in a U shape rectangular channel bend

In design of intakes, it is important that we choose conditions that maximum water and minimum sediment is diverted. Locating intakes in outer bank of bends and using submerged vanes are some of methods for reducing sediment entry into the lateral intake. Submerged vanes are small flow training structures, designed to modify the near bed flow pattern and redistribution of flow and sediment transport within the channel cross section. The vanes are generating secondary circulation in the flow. The flow field around lateral intakes located in the outer bank of channel bends and the interaction between this flow field and secondary flow due to submerged vanes is completely three dimensional and complex. The study of this flow field is useful for the engineers engaged in designing such structures. In this paper, measurement of three-dimensional turbulent flow field around a two array submerged vanes at a lateral intake in a U shape channel bend, was taken using an Acoustic Doppler Velocimeter (ADV). The results show that the submerged vanes generate a secondary flow that is unidirectional with secondary flow in the bend. Also with the installation of submerged vanes at lateral intakes, the width of dividing stream line in lower layers of flow is reduces. The strength of secondary flow in various sections of the bend was also calculated using vortex strength criteria. It was found that the maximum strength of secondary flow occurs at section 45 degree of the bend. However there is another local peak value around section 135 degree. The installation of vanes, causes increasing of strength of secondary flow around the intakes. The bed shear stresses in the vicinity of the intake are determined by Reynolds shear stresses. The results presented in this paper would be useful for the development and validation of numerical models, for studying the flow field around the submerged vanes at lateral intake in U shape bends.