Turbulent intensity and scales of turbulence after hydraulic jump in rectangular channel

Abstract

Turbulent intensity and scales of turbulence after hydraulic jump in rectangular channel. Experimental research was undertaken to investigate the changes in spatial turbulence intensity and scales of turbulent eddies (macroeddies) in a rectangular channel and the influence of the hydraulic jump on vertical, lateral and streamwise distributions of relative turbulence intensity and scales of turbulent eddies. The results of three tests for different discharges are presented. An intensive turbulent mixing that arises as a result of a hydraulic jump has a significant effect on instantaneous velocity, turbulent intensities and sizes of eddies, as well as their vertical and longitudinal distributions. In the analysed case the most noticeable changes appeared up to 0.5 m downstream the hydraulic jump. In the vertical dimension such an effect was especially seen near the surface. The smallest streamwise sizes of macroeddies were present near the surface, maximum at the depth of z/h = 0.6 and from that point sizes were decreasing towards the bottom. The intensive turbulent mixing within the hydraulic jump generates macroeddies of small sizes.

Local scour modelling on the basis of flume experiments

“…Available methods to predict scouring are still very inaccurate because of velocity diversification and turbulences in water stream. In the case of the civil engineering, the modelling of the local scouring is one of the most important issues, due to its effect on the bed shape nearby bridges, piers or bank revetments, what is especially important in the case of flooding but also a durability of hydraulic infrastructure itself (Graf, 1998;Gaudio & Marion, 2003;Ettema, Kirkil & Muste, 2006;Kozioł, Urbański, Kiczko, Krukowski & Siwicki, 2016).…”

Turbulence intensity and spatial scales of turbulence after hydraulic jump over scour hole in rectangular channel

“…Nezu and Nakagawa (1993) proposed the equations describing relative turbulence intensity distributions in single channels for a steady and uniform 2D flow. However, the conditions of water flow after a water plant or in a compound channel are significantly different and very complex (Ali et al, 2014;Czernuszenko et al, 2007;Dargahi, 2003;Kozioł, 2013Kozioł, , 2015Kozioł and Kubrak, 2015;Kozioł et al 2016;Mazurczyk, 2007;Nezu and Nakagawa, 1993;Nikora et al, 1994;Oliveto and Comuniello, 2009;Oliveto et al, 2011;Pagliara and Palermo, 2013;Rowiński et al, 1998;Rowiński et al, 2002;Shiono and Knight, 1991;Siniscalchi et al, 2012). The turbulence generation produces fluctuations of the flow velocity associated with big vortices, and the turbulent energy is converted into an energy cascade to smaller scale eddies until it is dissipated into heat by the molecular viscosity (Nezu and Nakagawa, 1993).…”

“…Urbański, 2006Urbański, , 2012. Preliminary results for three different discharges in the channel with a flat and horizontal bed were provided by Kozioł et al (2016).…”