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Confined plunging jets are investigated as potential outfalls for the discharge of desalination brine. Compared to offshore submerged outfalls that rely on momentum to induce mixing, plunging jets released above the water surface utilize both momentum and negative buoyancy. Plunging jets also introduce air into the water column, which can reduce the possibility of hypoxic zones. In contrast to unconfined plunging jets, confined plunging jets include a confining tube, or downcomer, around the jet, which increases the penetration depth of the bubbles and can provide better aeration. However, the presence of this downcomer can hinder mixing with surrounding water. Therefore, laboratory measurements of dilution are reported here and compared to the dilution of unconfined plunging jets. In addition, qualitative observations of bubble penetration depth are also used to discuss aeration potential. For designs that increase the bubble penetration depth as compared to unconfined plunging jets, results show that dilution decreases as the depth of the downcomer is increased. However, it is shown that confined plunging jets can be designed with a short downcomer to provide higher dilution than unconfined jets. The effect of the diameter of downcomer on dilution is also investigated and a non-monotonic effect is observed.
Ishita Shrivastava; Edward Adams; Bader Al-Anzi; Aaron Chow; Jongyoon Han. Confined Plunging Liquid Jets for Dilution of Brine from Desalination Plants. Processes 2021, 9, 856 .
AMA StyleIshita Shrivastava, Edward Adams, Bader Al-Anzi, Aaron Chow, Jongyoon Han. Confined Plunging Liquid Jets for Dilution of Brine from Desalination Plants. Processes. 2021; 9 (5):856.
Chicago/Turabian StyleIshita Shrivastava; Edward Adams; Bader Al-Anzi; Aaron Chow; Jongyoon Han. 2021. "Confined Plunging Liquid Jets for Dilution of Brine from Desalination Plants." Processes 9, no. 5: 856.
Laboratory experiments were conducted to measure entrained air bubble penetration depth and dilution of a dense vertical unconfined plunging jet to evaluate its performance as an outfall to dilute brine from desalination plants as well as a means to aerate water column. Experiments involved neutrally buoyant or dense plunging jets discharging in quiescent receiving water. The density difference between effluent and receiving water, the plunging jet length (height above water surface), and the receiving water salinity were varied in the experiments. Observed penetration depth for neutrally buoyant jets was somewhat greater than previously reported, and increased modestly with jet density. Increasing density also resulted in an increasing number of fine bubbles descending together with the dense plume. These observations can help guide the design of plunging jets to mitigate anoxic conditions in the water column when brine is introduced to a receiving water body, as with seawater desalination.
Aaron C. Chow; Ishita Shrivastava; E. Eric Adams; Fahed Al-Rabaie; Bader Al-Anzi. Unconfined Dense Plunging Jets Used for Brine Disposal from Desalination Plants. Processes 2020, 8, 1 .
AMA StyleAaron C. Chow, Ishita Shrivastava, E. Eric Adams, Fahed Al-Rabaie, Bader Al-Anzi. Unconfined Dense Plunging Jets Used for Brine Disposal from Desalination Plants. Processes. 2020; 8 (6):1.
Chicago/Turabian StyleAaron C. Chow; Ishita Shrivastava; E. Eric Adams; Fahed Al-Rabaie; Bader Al-Anzi. 2020. "Unconfined Dense Plunging Jets Used for Brine Disposal from Desalination Plants." Processes 8, no. 6: 1.
The effect of receiving water depth on the dilution of a unidirectional diffuser discharging dense effluent in quiescent conditions is analyzed. Dilution measurements from previous studies are reviewed to determine the effect of shallowness on the mixing of submerged single port outfalls. For a unidirectional multiport diffuser, the width of the effluent plume is observed to contract in shallow water. A model is proposed relating the dilution of a unidirectional diffuser to the dilution of a single jet using the contracted width. Measurements of the contracted width in shallow water are made to support the proposed model, which is verified by additional measurements of dilution. Three flow regimes, namely, deep, shallow, and vertically mixed, are identified based on the value of D0F0/H. Here, D0 is the diameter of the jet, F0 is the densimetric Froude number of the jet, and H is the depth of receiving water. It is shown that shallow water depth affects the dilution in two ways—the dilution of individual jets is reduced, and the contraction in plume width leads to further reduction in dilution.
Ishita Shrivastava; E. Eric Adams. Effect of Shallowness on Dilution of Unidirectional Diffusers. Journal of Hydraulic Engineering 2019, 145, 06019013 .
AMA StyleIshita Shrivastava, E. Eric Adams. Effect of Shallowness on Dilution of Unidirectional Diffusers. Journal of Hydraulic Engineering. 2019; 145 (12):06019013.
Chicago/Turabian StyleIshita Shrivastava; E. Eric Adams. 2019. "Effect of Shallowness on Dilution of Unidirectional Diffusers." Journal of Hydraulic Engineering 145, no. 12: 06019013.
Ishita Shrivastava; E. Eric Adams. Mixing of Tee Diffusers in Shallow Water with Crossflow: A New Look. Journal of Hydraulic Engineering 2019, 145, 04019006 .
AMA StyleIshita Shrivastava, E. Eric Adams. Mixing of Tee Diffusers in Shallow Water with Crossflow: A New Look. Journal of Hydraulic Engineering. 2019; 145 (4):04019006.
Chicago/Turabian StyleIshita Shrivastava; E. Eric Adams. 2019. "Mixing of Tee Diffusers in Shallow Water with Crossflow: A New Look." Journal of Hydraulic Engineering 145, no. 4: 04019006.
High discharge salinity of reject brine from desalination plants necessitates the use of submerged jets which induce mixing with ambient water and lead to reduction in concentrations of salt and other contaminants. Pre-dilution, in which brine is blended with a lighter effluent prior to discharge, can also cause reduction in contaminant concentrations. Condenser cooling water from a co-located power plant, treated wastewater effluent from a treatment plant and seawater can be used for pre-dilution. The effect of pre-dilution on shallowness and contaminant concentrations in the diluted effluent is examined for discharge using single port and multiport outfalls. The density difference between the effluent and ambient seawater is lower for the discharge of pre-diluted brine, which leads to shallow conditions. Pre-dilution also results in lower concentrations of contaminants in the diluted effluent by reducing the discharge concentrations as well as increasing outfall dilution in deep water by increasing the densimetric Froude number. This helps in satisfying regulatory requirements on contaminant concentrations with small discharge velocity or using outfalls with small number of ports. While discharge of pre-diluted brine using an existing outfall helps save on the capital cost, it can cause a significant increase in pumping cost. For a new outfall, design parameters can be adjusted such that pumping cost stays constant.
Ishita Shrivastava; E. Eric Adams. Pre-dilution of desalination reject brine: Impact on outfall dilution in different water depths. Journal of Hydro-environment Research 2018, 24, 28 -35.
AMA StyleIshita Shrivastava, E. Eric Adams. Pre-dilution of desalination reject brine: Impact on outfall dilution in different water depths. Journal of Hydro-environment Research. 2018; 24 ():28-35.
Chicago/Turabian StyleIshita Shrivastava; E. Eric Adams. 2018. "Pre-dilution of desalination reject brine: Impact on outfall dilution in different water depths." Journal of Hydro-environment Research 24, no. : 28-35.
We report upon laboratory experiments and numerical simulations examining the evolution of an interfacial internal solitary wave incident upon a triangular ridge whose peak lies below the interface. If the ridge is moderately large, the wave is observed to shoal and break similar to solitary waves shoaling upon a constant slope, but interfacial waves are also observed to transmit over and reflect from the ridge. In laboratory experiments, by measuring the interface displacement as it evolves in time, we measure the relative transmission and reflection of available potential energy after the incident wave has interacted with the ridge. The numerical simulations of laboratory- and ocean-scale waves measure both the available potential and kinetic energy to determine the partition of incident energy into that which is transmitted and reflected. From shallow-water theory, we define a critical amplitude,$A_{c}$, above which interfacial waves are unstable. The transmission is found to decrease from one to zero as the ratio of the incident wave amplitude to$A_{c}$increases from less than to greater than one. Empirical fits are made to analytic curves through measurements of the transmission and reflection coefficients.
B. R. Sutherland; S. Keating; I. Shrivastava. Transmission and reflection of internal solitary waves incident upon a triangular barrier. Journal of Fluid Mechanics 2015, 775, 304 -327.
AMA StyleB. R. Sutherland, S. Keating, I. Shrivastava. Transmission and reflection of internal solitary waves incident upon a triangular barrier. Journal of Fluid Mechanics. 2015; 775 ():304-327.
Chicago/Turabian StyleB. R. Sutherland; S. Keating; I. Shrivastava. 2015. "Transmission and reflection of internal solitary waves incident upon a triangular barrier." Journal of Fluid Mechanics 775, no. : 304-327.