Vertical dense jet in flowing current

Abstract

The discharge of brackish water, as a dense jet in a natural water body, by the osmotic power plants, undergoes complex mixing processes and has significant environmental impacts. This paper focuses on the mixing processes that develop when a dense round jet outfall perpendicularly enters a shallow flowing current. Extensive experimental measurements of both the salinity and the velocity flow fields were conducted to investigate the hydrodynamic jet behavior within the ambient current. Experiments were carried out in a closed circuit flume at the Coastal Engineering Laboratory (LIC) of the Technical University of Bari (Italy). The salinity concentration and velocity fields were analyzed, providing a more thorough knowledge about the main features of the jet behavior within the ambient flow, such as the jet penetration, spreading, dilution, terminal rise height and its impact point with the flume lower boundary. In this study, special attention is given to understand and confirm the conjecture, not yet experimentally demonstrated, of the development and orientation of the jet vortex structures. Results show that the dense jet is almost characterized by two distinct phases: a rapid ascent phase and a gradually descent phase. The measured flow velocity fields definitely confirm the formation of the counter-rotating vortices pair, within the jet cross-section, during both the ascent and descent phases. Nevertheless, the experimental results show that the counter-rotating vortices pair of both phases (ascent and descent) are of opposite rotational direction.

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Abbreviations

A 0 :

Jet source area (m2)

B :

Mean channel width (m)

B 0 :

Initial buoyancy flux (m4 s−3)

c :

Local fluid conductivity (S m−1)

c a :

Ambient fluid conductivity (S m−1)

c 0 :

Initial jet fluid conductivity (S m−1)

C :

Dimensionless jet excess salinity (conductivity) (−)

D :

Jet source diameter (m)

F :

Jet densimetric Froude number (−)

g :

Gravity acceleration (m s−2)

g′ :

Initial reduced gravity (m s−2)

H :

Flow depth (m)

l M :

Jet-to-plume length scale (m)

l m :

Jet-to-crossflow length scale (m)

l Q :

Discharge length scale (m)

l B :

Plume-to-crossflow length scale (m)

M 0 :

Initial momentum flux (m4 s−2)

Q 0 :

Initial discharge volume flux (m3 s−1)

Re 0 :

Initial jet Reynolds number (−)

Ri d :

Richardson number (−)

S,s :

Dilution (−)

S i ,s i :

Minimum dilution at the impact point (−)

S t ,s t :

Minimum dilution at the position of the terminal rise height (−)

U,V,W :

Streamwise, spanwise and vertical time-averaged velocity (ms−1)

U a :

Mean ambient channel velocity (m s−1)

U c :

Velocity scale (m s−1)

U 0 :

Initial jet velocity (m s−1)

u r :

Ratio of ambient to jet velocity (−)

x, y, z :

Longitudinal, lateral and vertical coordinates, respectively (m)

x i :

x-Position of the jet impact point (m)

x t :

x-Position at which the jet attains its maximum rising height (m)

z L :

Thickness of the bottom layer of the spreading density current (m)

z mt :

Jet terminal rise height (m)

z t :

Jet centerline rising height (m)

z 0 :

Jet port height (m)

Φ, Φ′ :

Functions

ν 0 :

Initial jet kinematic viscosity (m2 s−1)

θ :

Angle relative to the horizontal (°)

ρ :

Local fluid density (kg m−3)

ρ a :

Ambient fluid density (kg m−3)

ρ 0 :

Initial jet fluid density (kg m−3)

References

  1. 1.

    Fischer HB, List EJ, Koh RCY, Imberger J, Brooks NH (1979) Mixing in inland and coastal waters. Academic, San Diego

    Google Scholar 

  2. 2.

    Mossa M, De Serio F (2016) Rethinking the process of detrainment: jets in obstructed natural flows. Sci Rep 6:39103. doi:10.1038/srep39103

    Article  Google Scholar 

  3. 3.

    Andreopoulos J, Rodi W (1984) Experimental investigation of jets in a crossflow. J Fluid Mech 138(1):93–127. doi:10.1017/S0022112084000057

    Article  Google Scholar 

  4. 4.

    Roberts PJW, Toms G (1987) Inclined dense jets in a flowing current. J Hydraul Eng 113(3):323–341

    Article  Google Scholar 

  5. 5.

    Mossa M (2004) Experimental study on the interaction of non-buoyant jets and waves. J Hydraul Res 42(1):13–28. doi:10.1080/00221686.2004.9641179

    Article  Google Scholar 

  6. 6.

    Mossa M (2004) Behavior of nonbuoyant jets in a wave environment. J Hydraul Eng 130(7):704–717. doi:10.1061/(ASCE)0733-9429(2004)130:7(704)

    Article  Google Scholar 

  7. 7.

    Gungor E, Roberts PJW (2009) Experimental studies on vertical dense jets in a flowing current. J Hydraul Eng ASCE 135(11):935–948. doi:10.1061/(ASCE)HY.1943-7900.0000106

    Article  Google Scholar 

  8. 8.

    Ben Meftah M, De Serio F, Malcangio D, Mossa M, Petrillo AF (2015) Experimental study of a vertical jet in a vegetated crossflow. J Environ Manag 164:19–31. doi:10.1016/j.jenvman.2015.08.035

    Article  Google Scholar 

  9. 9.

    Malcangio D, Mossa M (2016) A laboratory investigation into the influence of a rigid vegetation on the evolution of a round turbulent jet discharged within a cross flow. J Environ Manag 173:105–120. doi:10.1016/j.jenvman.2016.02.044

    Article  Google Scholar 

  10. 10.

    Van der Zwan S, Pothof IWM, Blankert B, Bara JJ (2012) Feasibility of osmotic power from a hydrodynamic analysis at module and plant scale. J Membr Sci 389:324–333

    Article  Google Scholar 

  11. 11.

    Achilli A, Cath TY, Childress AE (2009) Power generation with pressure retarded osmosis: an experimental and theoretical investigation. J Membr Sci 343:42–52

    Article  Google Scholar 

  12. 12.

    Malcangio D, Ben Meftah M, Chiaia G, De Serio F, Mossa M, Petrillo AF (2016) Experimental studies on vertical dense jets in a crossflow. In: Proc River Flow 2016, USA, St. Louis Mo. 12–15 July

  13. 13.

    Montessori A, Prestininzi P, La Rocca M, Malcangio D, Mossa M. (2016) Two dimensional Lattice Boltzmann numerical simulation of a buoyant jet. In: Proc 4th IAHR Europe Congress, Belgium, Liege 27–29 July, doi:10.1201/b21902-165

  14. 14.

    Pedersen FB (1986) Environmental Hydraulics: stratified flows—lecture notes on coastal and estuarine studies. Springer, Berlin

    Google Scholar 

  15. 15.

    De Serio F, Mossa M (2015) Analysis of mean velocity and turbulence measurements with ADCPs. Adv Water Res. doi:10.1016/j.advwatres.2014.11.006

    Google Scholar 

  16. 16.

    Lai CCK, Lee JHW (2014) Initial mixing of inclined dense jets in perpendicular crossflows. Environ Fluid Mech 14(1):25–49. doi:10.1007/s10652-013-9290-7

    Article  Google Scholar 

  17. 17.

    Choi KW, Lai CCK, Lee JHW (2016) Mixing in the intermediate field of dense jets in cross currents. J Hydraul Eng ASCE. doi:10.1061/(ASCE)HY.1943-7900.0001060

    Google Scholar 

  18. 18.

    Wang RQ, Law AWK, Adams EE (2011) Pinch-off and formation number of negatively buoyant jets. Phys Fluids 23(5):052101. doi:10.1063/1.3584133

    Article  Google Scholar 

  19. 19.

    Wang RQ, Law AWK, Adams EE, Fringer OB (2009) Buoyant formation number of a starting buoyant jet. Phys Fluids 21:125104. doi:10.1063/1.3275849

    Article  Google Scholar 

  20. 20.

    Cipollina A, Bonfiglio A, Micale G, Brucato A (2004) Dense jet modelling applied to the design of dense effluent diffusers. Desalination 167:459–468. doi:10.1016/j.desal.2004.06.161

    Article  Google Scholar 

  21. 21.

    Abessi O, Roberts PJW (2016) Dense jet discharges in shallow water. J Hydraul Eng 142(1):04015033 (1–13). doi:10.1061/(ASCE)HY.1943-7900.0001057

    Article  Google Scholar 

  22. 22.

    Pincince AB, List EJ (1973) Disposal of brine into an estuary. J Water Pollut Control Fed 45:2335–2344

    Google Scholar 

  23. 23.

    Chu VH, Jirka GH (1986) Surface buoyant jets. Encyclopedia of fluid mechanic. Gulf Publishing Company, Houston

    Google Scholar 

  24. 24.

    Abessi O, Saeedi M, Davidson M, Zaker NH (2012) Flow classification of negatively buoyant surface discharge in an ambient current. J Coast Res 278:148–155. doi:10.2112/JCOASTRES-D-10-00131.1

    Article  Google Scholar 

  25. 25.

    Ben Meftah M, De Serio F, Mossa M, Pollio A (2007) Analysis of the velocity field in a large rectangular channel with lateral shockwave. Environ Fluid Mech 7(6):519–536. doi:10.1007/s10652-007-9034-7

    Article  Google Scholar 

  26. 26.

    Ben Meftah M, De Serio F, Mossa M, Pollio A (2008) Experimental study of recirculating flows generated by lateral shock waves in very large channels. Environ Fluid Mech 8(6):215–238. doi:10.1007/s10652-008-9057-8

    Article  Google Scholar 

  27. 27.

    Ben Meftah M, Mossa M, Pollio A (2010) Considerations on shock wave/boundary layer interaction in undular hydraulic jumps in horizontal channels with a very high aspect ratio. Eur J Mech B/Fluids 29:415–429. doi:10.1016/j.euromechflu.2010.07.002

    Article  Google Scholar 

  28. 28.

    Ben Meftah M, Mossa M (2013) Prediction of channel flow characteristics through square arrays of emergent cylinders. Phys Fluids 25(4):045102 (1–21). doi:10.1063/1.4802047

    Article  Google Scholar 

  29. 29.

    Ben Meftah M, Mossa M (2016) A modified log-law of flow velocity distribution in partly obstructed open channels. Environ Fluid Mech 16(2):453–479. doi:10.1007/s10652-015-9439-7

    Article  Google Scholar 

  30. 30.

    Ben Meftah M, De Serio F, Mossa M (2014) Hydrodynamic behavior in the outer shear layer of partly obstructed open channels. Phys Fluids 26(6):065102 (1–19). doi:10.1063/1.4881425

    Article  Google Scholar 

  31. 31.

    Malcangio D, Ben Meftah M, Mossa M (2016) Physical modelling of buoyant effluents discharged into a cross flow. In: Proc IEEE workshop on environmental, energy, and structural monitoring systems, Italy, Bari 13–14 June, doi:10.1109/EESMS.2016.7504838

  32. 32.

    Besalduch LA, Badas MG, Ferrari S, Querzoli G (2013) Experimental studies for the characterization of the mixing processes in negative buoyant jets. EPJ web of conferences, vol 45, p 01012(1–9), doi:10.1051/epjconf/20134501012

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Acknowledgement

This research was supported by a grant from the Italian national project “Hydroelectric energy by osmosis in coastal areas”, PRIN 2010-2011. The experiments were carried out at the Coastal Engineering Laboratory of the Dpt. of Civil, Environmental, Building Engineering and Chemistry, Technical University of Bari, Italy.

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Correspondence to M. Mossa.

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Ben Meftah, M., Malcangio, D., De Serio, F. et al. Vertical dense jet in flowing current. Environ Fluid Mech 18, 75–96 (2018). https://doi.org/10.1007/s10652-017-9515-2

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Keywords

  • Dense jet
  • Shallow flow
  • Salinity
  • Velocity
  • Penetration
  • Dilution
  • Vortices