Environmental Fluid Mechanics

, Volume 12, Issue 4, pp 301–319 | Cite as

Formation of tidal starting-jet vortices through idealized barotropic inlets with finite length

  • Duncan B. Bryant
  • Kerri A. Whilden
  • Scott A. Socolofsky
  • Kuang-An Chang
Original Article


This paper presents a surface particle image velocimetry study to investigate the dynamics of shallow starting-jet dipoles formed by tidal flow through inlets and their interaction with vorticity formed at the inlet channel lateral boundaries. Vortical structure in the flow field is identified using a local swirl strength criterion evaluated from the two-dimensional flow field. The starting jet dipole vortices and vortices formed as the lateral boundary layers are expelled during flow reversal are characterized by their trajectory, size, and circulation. Using these quantities, a model is developed to predict the size and strength of the expelled lateral boundary layer vortices based on the inlet velocity, channel length, and width of the lateral boundary layer. The expelled boundary layer vortices are found to disrupt the formation of the primary tidal jet dipole through two mechanisms. First, because the boundary layer vortices themselves form a dipole with each half of the starting-jet dipole, the starting-jet vortices are pulled apart and advected away from the inlet mouth early in the tidal cycle, resulting in a reduction in the spin-up time and the amount of vorticity input during starting-jet vortex formation. Second, the advection of each dipole away from the inlet disconnects each starting-jet vortex from the starting jet; hence, the vortices are not fed by fluid in the jet or energized by shear in the jet boundary layers. These influences of the lateral boundary layer on the starting-jet vortices’ formation and propagation are found to be a function of the channel length L, maximum velocity U, and tidal period T, resulting in a predictive value to characterize their trajectory, strength, and evolution.


Vortex dynamics Tidal exchange Vortex interaction Shallow waterflow 

List of symbols


Boundary layer width


Lateral displacement


Boundary layer circulation


Starting-jet vortex circulation




Kinematic viscosity


Velocity gradient tensor


Turbulent diffusion coefficient


Water depth


Inlet strouhal number


Channel length


Vortex radius


Sink length scale


Jet excursion length scale


Tidal period


Vortex spin-up time


Reynolds Number


Maximum tidal velocity


Inlet Width


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Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Duncan B. Bryant
    • 1
  • Kerri A. Whilden
    • 2
  • Scott A. Socolofsky
    • 2
  • Kuang-An Chang
    • 2
  1. 1.Coastal and Hydraulics LaboratoryUS Army Engineers Research and Development CenterVicksburgUSA
  2. 2.Zachry Department of Civil Engineering, Coastal and Ocean Engineering DivisionTexas A&M UniversityColleamge StationUSA

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