Bubbly flow structure in hydraulic jump

2016

Environ Fluid Mech

The flow structure in the aerated region of the roller generated by breaking waves remains a great challenge to study, with large quantities of entrained air and turbulence interactions making it very difficult to investigate in details. A number of analogies were proposed between breaking waves in deep or shallow water, tidal bores and hydraulic jumps. Many numerical models used to simulate waves in the surf zone do not implicitly simulate the breaking process of the waves, but are required to parameterise the wave-breaking effects, thus relying on experimental data. Analogies are also assumed to quantify the roller dynamics and the energy dissipation. The scope of this paper is to review the different analogies proposed in the literature and to discuss current practices. A thorough survey is offered and a discussion is developed an aimed at improving the use of possible breaking proxies. The most recent data are revisited and scrutinised for the use of most advanced numerical models to educe the surf zone hydrodynamics. In particular, the roller dynamics and geometrical characteristics are discussed. An open discussion is proposed to explore the actual practices and propose perspectives based on the most appropriate analogy, namely the tidal bore.

Section: Hydraulic Jumpsmentioning

confidence: 99%

Are breaking waves, bores, surges and jumps the same flow?

Lubin

2016

Environ Fluid Mech

“…At the given measurement location, one-dimensional (i.e. longitudinal) clusters were identified based upon a defined clustering criterion, and clustering properties such as the formation rate and average size of clusters were analysed (Chanson 2007, Gualtieri & Chanson 2010, Chachereau & Chanson 2011. Similar studies of clustering events were not only restricted to hydraulic jumps, but also conducted for dropshaft jets and stepped spillway flows (Chanson & Toombes 2002, Gualtieri & Chanson 2007, Felder 2013.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional bubble clustering in hydraulic jumps

Wang

Experimental Thermal and Fluid Science

2015

Hydraulic jumps are characterised by turbulent flow structures and air entrainment. As a result of the turbulence-bubble interaction, non-random bubble distributions are observed in the bubble transport processes, forming bubble clusters. This paper presents a physical investigation of bubble/droplet clustering events in hydraulic jumps based upon a two-dimensional near-wake clustering criterion. Clusters were identified with consideration of bubble-bubble interplay in both longitudinal and transverse directions. In the highly-aerated flow region of the roller, more than 50% of bubbles were advected in two-dimensional clusters. Though the largest percentage of clusters was formed by two bubbles, over 10% of clusters were large two-dimensional cluster structures consisting of six bubbles or more. Clustering properties such as cluster production rate, average cluster size and clustered particle size distributions were analysed and their spatial distributions were presented for an inflow Froude number 7.5 with various Reynolds numbers from 3.4×10 4 to 1.4×10 5 . All clustering properties decreased in the longitudinal direction as the turbulence dissipated and flow de-aerated.Comparison between the one-dimensional and two-dimensional clustering criteria was discussed along with their limitations. The quantification of the clustering properties provided a valuable measure of the correlation between air entrainment and turbulence development in such complex airwater flows. Dimensionless coefficient for side-by-side particle clustering characterisation Superscript (l) Property of leading particle (t) Keywords

“…Resch and Leutheusser (1972) performed hot-film probe measurements in the bubbly flow region and showed some effects of the upstream flow conditions. Recent developments included Chanson (1995), Mossa and Tolve (1998), Chanson and Brattberg (2000), Murzyn et al (2005) and Chanson (2007). In this study, detailed air-water flow measurements were performed in hydraulic jump flows for two inflow Froude numbers (Fr 1 = 5 & 8.5, Re= 38,000 & 62,000).…”

Section: Introductionmentioning

confidence: 99%

“…The channel width was 0.50 m. The sidewall height and flume length were respectively 0.45 m and 3.2 m. The sidewalls were made of glass and the channel bed was PVC. This channel was previously used by Chanson (2006Chanson ( ,2007. The water discharge was measured with a Venturi meter located in the supply line and which was calibrated on-site with a large V-notch weir.…”

mentioning

confidence: 99%

Froude Similitude and Scale Effects Affecting Air Entrainment in Hydraulic Jumps

World Environmental and Water Resources Congress 2008

Murzyn²

2008

A hydraulic jump is the rapid transition from a high-velocity to a low-velocity open channel flow. It is characterized by strong turbulence and air bubble entrainment. Detailed air-water flow properties were measured in hydraulic jumps with partially-developed inflow conditions. The present data set together with the earlier data of Chanson (2006) yielded similar experiments conducted with identical inflow Froude numbers but Reynolds numbers between 24,000 and 98,000. The comparative results showed some drastic scale effects in the smaller hydraulic jumps in terms of void fraction and bubble count rate distributions. The present comparative analysis demonstrated quantitatively that dynamic similarity of twophase flows in hydraulic jumps cannot be achieved with a Froude similitude. In experimental facilities with Reynolds numbers up to 10 5 , some viscous scale effects were observed in terms of the rate of entrained air and air-water interfacial area.