Author(s): P.F.A. Manso; E.F.R. Bollaert; A.J. Schleiss
Keywords: Dynamic pressures; plunging jets; pressure distribution; spillways; turbulence intensity
Abstract: This paper presents experimental work on the characteristics of jets issuing from water-releasing structures. Systematic experimental tests have been performed at near-prototype velocities of up to 30 m using a cylindrical jet nozzle. Dynamic pressures were measured along the diameter at the nozzle outlet with an acquisition rate of up to 2 kHz, for different upstream supply conditions. These measurements allowed assessing the mean and the fluctuating characteristics of the jet. The influence of supply circuit secondary currents, aeration and geometrical contraction on jet turbulence intensity and velocity profiles is discussed. The initial turbulence intensity varies from 2 to 8%, whereas the kinetic energy correction factor ranges from 1.0 to 1.1. Statistical analysis of pressure measurements shows that jet core pressures follow a Gaussian distribution fairly well for non-exceedence probabilities between 0.1 and 0.999. The experimental results and an extensive literature survey are used to define issuance parameters relevant for engineering practice.