15 Feb 2023
 | 15 Feb 2023
Status: this preprint is open for discussion.

Observations and modelling of tidally generated high-frequency velocity fluctuations downstream of a channel constriction

Håvard Espenes, Pål Erik Isachsen, and Ole Anders Nøst

Abstract. We investigate data from an ADCP deployed in a constricted ocean channel showing a tidally dominated flow with intermittent velocity extrema during outflow from the constriction but not during inflow. A 2D numerical ocean model forced by tides is used to examine the spatial flow structure and underlying dynamical processes. We find that flow separation eddies generated near the tightest constriction point form a dipole pair which propagates downstream and drives the observed intermittent flow variability. The eddies, which are generated by an along-channel adverse pressure gradient, spin up for some time near the constriction until they develop local low pressures in their centres that are strong enough to modify the background along-channel pressure gradient significantly. When the dipole has propagated some distance away from the constriction, the conditions for flow separation are recovered, and new eddies are formed.

Håvard Espenes et al.

Status: open (until 04 May 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Håvard Espenes et al.

Håvard Espenes et al.


Total article views: 159 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
115 38 6 159 2 2
  • HTML: 115
  • PDF: 38
  • XML: 6
  • Total: 159
  • BibTeX: 2
  • EndNote: 2
Views and downloads (calculated since 15 Feb 2023)
Cumulative views and downloads (calculated since 15 Feb 2023)

Viewed (geographical distribution)

Total article views: 156 (including HTML, PDF, and XML) Thereof 156 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 29 Mar 2023
Short summary
We show that tidally generated eddies generated near the constriction of a channel can drive a strong, and fluctuating flow field far downstream of the channel constriction itself. The velocity signal has been observed in other studies, but this is the first study linking it to a physical process. Eddies such as those we found are generated because of complex coastal geometry, suggesting that – for example – land-reclamation projects in channels may enhance current shear over a large area.