An experimental study of flow regimes of a gravity current over a Cape in a stratified environment


Properties of the flow generated by a buoyancy source are investigated by a number of laboratory experiments. Experiments are carried out in a tank with a Cape to simulate the features of a gravity current when moving and separating over a delta Cape as in a real marine flow. Of the many experiments performed, 63 are recorded and analyzed in detail. Most of the experiments are carried out under 0.01 < Fr < 3 and 0.03 < Ro < 0.45 (where Fr and Ro are the flow Froude and Rossby numbers respectively). Dimensionless parameters of the simulations of the flow in a laboratory are comparable with those of the real flow in the Caspian Sea. Based on the behavior of flow upstream of the Cape, three regimes can occur in these experiments: laminar, eddy, and laminar-eddy regimes. The eddy regime is found for values of the Rossby number less than 0.05. For the moving flow on the bottom slope, an empirical relation between CNof, the Nof speed, and u, the current speed, is found from which CNof is predicted from u using oceanographic data. Based on the Rossby number of the flow in the Caspian Sea, the laminar-eddy regime is more likely to occur. The flow shows a different behavior when moving over the Cape which is categorized by the Cape upstream behavior of the flow. Under  = 0.02 m/s2, f = 0.72 s−1 (T = 17 s) Ro = 0.17, and Fr = 0.24, one cyclone eddy and one anticyclone eddy are formed similar to those seen in nature (here the Caspian Sea). In the eddy regime, the cascade process occurs with a timescale of longevity tL < 6T for each eddy. The results indicate that the geometry of the Cape and the features of the flow (, Fr, and Ro) upstream can be effective in the shape, size, and location of eddy formation. The experimental results also show that the radius of the eddy is about two times larger than the Rossby deformation radius of the flow in upstream of the Cape, while having a timescale tf between T/2 and 2T. In nature, the eddy formation and development time scale are about 1 to 2 years with 10 and 15 months for Seddy (cyclone eddy) and Anseddy (anticyclone eddy) respectively. Because of the ability of an eddy to transport and spread pollutants such as oil in the southern Caspian Sea, this work can also be important for the marine dispersion estimations.

This is a preview of subscription content, log in to check access.

Access options

Buy single article

Instant unlimited access to the full article PDF.

US$ 39.95

Price includes VAT for USA

Subscribe to journal

Immediate online access to all issues from 2019. Subscription will auto renew annually.

US$ 99

This is the net price. Taxes to be calculated in checkout.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Fig. 12
Fig. 13
Fig. 14
Fig. 15
Fig. 16


  1. Alpers W, Brandt P, Lazar A, Dagorne D, Sow B, Faye S, Brehmer P (2013) A small-scale oceanic eddy off the coast of West Africa studied by multi-sensor satellite and surface drifter data. Remote Sens Environ 129:132–143

  2. Apel JR (1987) Principles of ocean physics (Vol. 38). Academic Press

  3. Armi L, Zenk W (1984) Large lenses of highly saline Mediterranean water. J Phys Oceanogr 14(10):1560–1576

  4. Babagoli J, Bidokhti AA, Shieh M (2018) Some aspects of the deep abyssal overflow between the middle and southern basins of the Caspian Sea. Ocean Sci Discuss.

  5. Baey JM (1997) Instabilite’s d’un courant d’eauinterme’diaire. Ph.D. dissertation, Universite´ Joseph Fourier, Grenoble, France, 201 pp

  6. Baines PG (2008) Mixing in downslope flows in the ocean-plumes versus gravity currents. Atmosphere-Ocean 46(4):405–419

  7. Bidokhti AA (2017) Fundamentals of fluid dynamics. 2nd edn. University of Tehran, Press

  8. Bidokhti AA, Ezam M (2009) The structure of the Persian Gulf outflow subjected to density variations. Ocean Sci 5:1–12

  9. Bower AS, Armi L, Ambar I (1997) Lagrangian observations of meddy formation during a Mediterranean undercurrent seeding experiment. J Phys Oceanogr 27(12):2545–2575

  10. Bower AS, Hunt HD, Price JF (2000) Character and dynamics of the Red Sea and the Persian Gulf outflows. Journal of Geophysical Research: Oceans 105(C3):6387–6414

  11. Cenedese C (1998) Baroclinic eddies over topography (Doctoral dissertation, University of Cambridge)

  12. Cenedese C, Linden PF (1999) Cyclone and anticyclone formation in a rotating stratified fluid over a sloping bottom. J Fluid Mech 381:199–223

  13. Cenedese C, Whitehead JA (2000) Eddy shedding from a boundary current around a Cape over a sloping bottom. J Phys Oceanogr 30(7):1514–1531

  14. Cenedese C, Whitehead JA, Ascarelli TA, Ohiwa M (2004) A dense current flowing down a sloping bottom in a rotating fluid. J Phys Oceanogr 34(1):188–203

  15. Chia F, Griffiths RW, Linden PF (1982) Laboratory experiments on fronts: part II: the formation of cyclonic eddies at upwelling fronts. Geophys Astrophys Fluid Dyn 19(3–4):189–206

  16. Ellison TH, Turner JS (1959) Turbulent entrainment in stratified flows. J Fluid Mech 6(3):423–448

  17. Ezam M, Bidokhti AA, Javid AH (2010) Numerical simulations of spreading of the Persian Gulf outflow into the Oman Sea. Ocean Sci 6(4):887–900

  18. Flierl GR (1987) Isolated eddy models in geophysics. Annu Rev Fluid Mech 19(1):493–530

  19. García-Lafuente J, Naranjo C, Sammartino S, Sánchez-Garrido JC, Delgado J (2017) The Mediterranean outflow in the Strait of Gibraltar and its connection with upstream conditions in the Alborán Sea. Ocean Sci 13(2):195–207

  20. Gill AE 1983 Eddies in relation to climate. In: Robinson AR (ed) Eddies in marine science. Springer Velag

  21. Girton JB, Sanford TB (2003) Descent and modification of the overflow plume in the Denmark Strait. J Phys Oceanogr 33(7):1351–1364

  22. Grant HL, Stewart RW, Moilliet A (1962) Turbulence spectra from a tidal channel. J Fluid Mech 12(2):241–268

  23. Griffiths RW, Hopfinger EJ (1986) Experiments with baroclinic vortex pairs in a rotating fluid. J Fluid Mech 173:501–518

  24. Griffiths RW, Hopfinger EJ (1987) Coalescing of geostrophic vortices. J Fluid Mech 178:73–97

  25. Griffiths RW, Linden PF (1981) The stability of vortices in a rotating, stratified fluid. J Fluid Mech 105:283–316

  26. Hopfinger EJ, Heijst GJFV (1993) Vortices in rotating fluids. Annu Rev Fluid Mech 25(1):241–289

  27. Jacobs P, Guo Y, Davies PA (1999) Boundary currents over shelf and slope topography. J Mar Syst 19(1–3):137–158

  28. Knauss JA (1997) Introduction to physical oceanography. Prentice Hall Press

  29. Lane-Serff GF, Baines PG (1998) Eddy formation by dense flows on slopes in a rotating fluid. J Fluid Mech 363:229–252

  30. Lane-Serff GF, Beal LM, Hadfield TD (1995) Gravity current flow over obstacles. J Fluid Mech 292:39–53

  31. Manucharyan GE, Moon W, Sévellec F, Wells AJ, Zhong JQ, Wettlaufer JS (2014) Steady turbulent density currents on a slope in a rotating fluid. J Fluid Mech 746:405–436

  32. Ottolenghi L, Cenedese C, Adduce C (2017) Entrainment in a dense current flowing down a rough sloping bottom in a rotating fluid. J Phys Oceanogr 47(3):485–498

  33. Paterson AR (1983) A first course in fluid dynamics. University Press, Cambridge 528 p

  34. Pingree RD, Le Cann B (1993) Structure of a meddy (Bobby 92) southeast of the Azores. Deep-Sea Res I Oceanogr Res Pap 40(10):2077–2103

  35. Price JF, Baringer MON (1994) Outflows and deep water production by marginal seas. Prog Oceanogr 33(3):161–200

  36. Privett DW (1959) Monthly charts of evaporation from the N. Indian Ocean (including the Red Sea and the Persian Gulf). Q J R Meteorol Soc 85(366):424–428

  37. Reynolds RM (1993) Overview of physical oceanographic measurements taken during the Mt. Mitchell Cruise to the ROPME Sea Area (No. BNL--49194; Conf-9301123--1). Brookhaven National Lab., Upton, NY (United States)

  38. Rhines PB (2001) Mesoscale eddies. Encyclopedia of ocean sciences, pp 1717–1730

  39. Robinson AR (ed) (2012) Eddies in marine science. Springer Science and Business Media

  40. Sadoux S, Baey JM, Fincham A, Renouard D (2000) Experimental study of the stability of an intermediate current and its interaction with a cape. Dyn Atmos Oceans 31(1–4):165–192

  41. Saunders PM (1973) The instability of a baroclinic vortex. J Phys Oceanogr 3(1):61–65

  42. Seim KS, Fer I, Avlesen H (2012) Stratified flow over complex topography: a model study of the bottom drag and associated mixing. Cont Shelf Res 34:41–52

  43. Serra N, Sadoux S, Ambar I, Renouard D (2002) Observations and laboratory modeling of meddy generation at Cape St. Vincent. J Phys Oceanogr 32(1):3–25

  44. Shapiro GI, Zatsepin AG (1997) Gravity current down a steeply inclined slope in a rotating fluid. In Annales Geophysics, vol 15, No. 3. Springer-Verlag, pp 366–374

  45. Shiea M, Chegini V, Bidokhti AA (2016) Impact of wind and thermal forcing on the seasonal variation of three-dimensional circulation in the Caspian Sea

  46. Spitz YH, Nof D (1991) Separation of boundary currents due to bottom topography. Deep Sea Res A Oceanogr Res Pap 38(1):1–20

  47. Sutherland BR, Nault J, Yewchuk K, Swaters GE (2004) Rotating dense currents on a slope. Part 1. Stability. J Fluid Mech 508:241–264

  48. Whitehead JA, Stern ME, Flierl GR, Klinger BA (1990) Experimental observations of baroclinic eddies on a sloping bottom. J Geophys Res Oceans 95(C6):9585–9610

  49. Yang Z, Voke PR (2001) Large-eddy simulation of boundary-layer separation and transition at a change of surface curvature. J Fluid Mech 439:305–333

Download references


The experiments were performed in the GFD laboratory in the Institute of Geophysics at the University of Tehran. This work has been supported by a grant funded from the University of Tehran (number: 6202018/1/03). We thank Dr. Maryam Shieh for the help in the estimations of some parameters of the eddy in the Caspian Sea using numerical simulations.

Author information

Correspondence to Abbasali Aliakbari Bidokhti.

Additional information

Responsible Editor: Alejandro Orfila

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Babagoli Matikolaei, J., Aliakbari Bidokhti, A. An experimental study of flow regimes of a gravity current over a Cape in a stratified environment. Ocean Dynamics 69, 769–786 (2019) doi:10.1007/s10236-019-01272-4

Download citation


  • Density driven flow
  • Rotating fluid
  • Eddy shedding
  • SefidRud Delta Cape
  • Cyclonic and anticyclonic eddies