The results of laboratory experiments to examine the influence of the Kelvin numer (K) and fractional depth (h/D) on bulge formation from buoyant outlfows from an estuary or strait perpendicular to the coastline will be discussed. Here K=W/R is the ratio of the width (W) at the mouth of the estuary to the deformation radius (R), and h and D are the buoyant layer and ambient ocean depths respectively. Measurements of velocity and lateral sheer
(≈ relative vorticity ζ) at the baymouth are reported for experiments on a flat-bottomed rotating turntable. The form of the velocity profile across the mouth depends on the value of K. The buoyant outflow flows across the entire width of the estuary for narrow estuaries (i.e., K≤1). In contrast, for wide estuaries (K>2) dense oceanic water inflows on the left and the buoyant waters outflow on the right (looking seaward). Velocity profiles of the inflowing oceanic waters are laterally uniform with velocities (V/C ≈ -0.4), wheras velocity profiles of the outflowing buyoant waters are laterally sheared with peak velocities of V/C ≈ 1. at the right hand exit. The flow pathways when bulges form comprises an anticyclonic turn offshore of the mouth and a downshelf propagating coastal current. Anticyclonic bulges form for surface advected outflows h/D<0.25. Anticyclonic bulges do not form for sufficiently large magnitudes of non-dimensional relative vorticity ζ/f (>0.4), and an additional flow pathway is that buoyant waters recirculate back cyclonically into the estuary at the left hand (upshelf) side of the estuary. The offshore extent of buoyant waters associated with this cyclonic recirculation can be as large as 7R.

Reference: Huq, P., 2009. "The Role of Kelvin Number on Bulge formation from Estuarine Buoyant Outflows." Estuaries and Coasts, 32:709-719.

Dr. Pablo Huq received a B.Sc. in Civil Engineering from the University of Glasgow, Scotland, a M.S. in Environmental Engineering from Cornell University, and a Ph.D. in Fluid Mechanics from the University of Cambridge, UK. He is an associate professor at the University of Delaware's College of Earth, Ocean and Environment and his research focuses on laboratory experiments on density stratified turbulence and rotating flows.

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