City Research Online

Abstract

In this study on behaviour of flow in open channel bends, experimental investigations were carried out in a U-shaped and an S-shaped channel of rectangular cross-section with 180° curvature. The turbulent characteristics were measured by using the Laser Doppler Anemometer (LDA).
Experimental results concerning the distribution of velocity and boundary shear stress together with the distribution of the Reynolds stresses and the instability of secondary flow are presented. The measured velocity distributions in the direction of flow are then compared with those calculated by solving the general equations of motion by the use of finite difference method. The correlation between the velocity and the boundary shear stress distributions is discussed, as well as the distributions of Reynolds stress with the secondary flow.
The growth of the transverse circulation in the U-shaped and S-shaped channels was studied in detail. The striking feature of the instability of flow occurs near the cross-over region of the S-shaped channel, and indicates that the strength of the secondary current produced in the upstream bend is not completely eliminated straight away when the flow enters the downstream bend. The behaviour of the flow patterns in this transition region were studied for three different flow rates and found to be almost identical.
The transverse motion of fluid particles in the cross-section of the bend were observed photographically and compared with the secondary flow pattern revealed by the LDA system.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > T Technology (General) T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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