Mixing and boundary interactions of 30° and 45° inclined dense jets

Abstract

60 • inclined dense jets had been recommended for brine discharges from desalination plants to achieve a maximum mixing efficiency. However, the terminal rise associated with 60 • is relatively high and thus the angle may be too large for disposal in shallow coastal wasters. In this study, we investigate the mixing behavior of dense jets discharging at smaller angles of 30 • and 45 • in a stationary ambient. Combined Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) were used as the measurement approaches that captured the velocity and concentration fields, respectively. Based on the experimental results, the characteristic geometrical features of the inclined dense jets, including the location of the centerline peak and the return point where the dense jet returns to the source level, etc., are quantified. The mixing and diluting behaviors are also revealed through the analysis of the axial and cross-sectional velocity and concentration profiles. In addition to the free inclined discharges, the present study also examines the effect of the proximity to the bed. Through the comparison of the results between two experimental series with distinct z 0 /D but overlapping z 0 /L M , the latter is identified as the deciding factor for the boundary influence.

k-ε Predictions of the initial mixing of desalination discharges

“…Here we will continue to focus on the location of, and conditions at, the maximum height, because accurate predictions of these is essential if conditions at the return point are to be estimated with reasonable accuracy. Figure 6 Roberts et al [11] Roberts & Toms [10] Shao & Law [12] Calibrated k-ε Standard k-ε shows the dimensionless coefficients for determining the horizontal (k xm ) and vertical (k zm ) coordinates of the centreline maximum height, relative to the source. These coordinates are linearly dependent on the source densimetric Froude number and the associated relationships are given in the figure caption.…”

“…An important physical process (previously noted by Lane-Serff et al [6]), associated with the presence of buoyancy induced instabilities on the inner side of the flow, was also observed. More recently Shao and Law [12] employed planar optical measuring systems (LIF, Laser Induced Fluorescence and PIV, Particle Image Velocimetry) to investigate the behaviour of negatively buoyant discharges released at 30 and 45 • . Their results largely confirm those obtained by Kikkert et al Previously, Cipollina et al [2] had examined in detail the trajectory of discharges at 30, 45 and 60 • , focusing on the 45 • case.…”

A modified integral model for negatively buoyant jets in a stationary ambient

“…This means that as F o decreases, θ o affects more the variability of the detrained smf. [4,11,12,15,19,24], Present study X i /DF o 2.42 ± 0.11 3.11 ± 0.14 3.17 ± 0.17 2.75 ± 0.31 [4,7,11,12,14,15,20,22,24] Table 3. Also, in these figures the predictions of RBF, EMA, CorJet and the analytical solutions of Kikkert et al [11] are depicted.…”

“…Ferrari and Querzoli [7], also, used the LIF technique to study the geometrical characteristics of the axis of NBJ discharged at angles greater than 45 • . Shao and Law [24] used a combination of LIF and PIV experimentation techniques measuring geometrical characteristics, concentration and velocity fields of 30 • and 45 • NBJ. Papakonstantis et al [19,20] conducted visual and micro-conductivity probe measurements determining the characteristics of 45 • to 90 • discharged jets.…”

Experimental Studies for the characterization of the mixing processes in negative buoyant jets

“…These works, were generally, performed by means of optical techniques, such as Light Attenuation (LA) or Light Induced Fluorescence (LIF), so the only measured quantities were the concentration fields investigations were conducted using Particles Image Velocimetry (PIV) techniques to study the velocity fields Cenedese et al 2005 [30] used both Tracking Velocimetry (PTV) techniques, velocity and concentration profiles at different Froude numbers for horizontal jets. A paper based on PIV measures for inclined NBJs, released at the end of a pipe is the one by Lai and Lee (2012) [31]: the were between 15° and 60° and, the authors compared their results with two previous work of (2010 [32], 2011 [33]), with inclination of 30° and 45°T he main target of this work is to investigate the influence of the Reynolds number on some turbulent quantities that govern the mixing processes, Feature Tracking Velocimetry (FTV) technique.…”