Document Type : Research Paper
Assistant Professor, Civil Engineering Department, Khuzestan Jihad Institute for Higher Education
Professor of Shahid Chamran University, College of Water Science Engineering, Ahwaz-Iran.
Water-hammer is a transient condition which may occur in a network as a result of rapid or slow valve closures, pump failures, etc. It creates high and low pressure waves which travel along the system and decay as a result of wall shear stress. Comparison of experimental and theoretical results revealed the failure of steady or quasi-steady models in correctly predicting the damping process of the pressure waves. The aims of this research are to increase the number of available unsteady velocity profiles and to give a contribution to the understanding of transient flow dynamics and energy dissipation. With this purpose, experimental measurements by Ultrasonic pulsed Doppler Velocimetry of the unsteady velocity field for water hammer transients in a long polyethylene pipe, caused by a downstream sudden valve closure, and are presented. Velocity data are analyzed and compare with results obtained by other authors. Result show the inherent weakness of UDV velocimeter, to measurement of flow rate near the conduit wall, for two reasons: low velocities and reduced dimension of effective sampling volume. By use of corrective method represents the non-symmetric velocity profiles and vortex formation in the conduit wall.