Examples of secondary flows and lateral variability. S 4. S 4. S 3. S 3. S 2. U+ D U. U- D U. U+ D U. U- D U. U- D U. U- D U. S 2. S 1. S 1. Differential Advection in channel with deep middle and Shallow flanks Producing along channel salinity gradient. Fresh. Fresh. Salty.
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Differential Advection in channel with deep middle and
Shallow flanks Producing along channel salinity gradient
Effects of Differential Advection on Flood Tide
Nunes and Simpson (1985)
What’s the effect on stratification?
What’s the effect on the along channel momentum balance?
What happens on Ebb?
to balance forcing
Kalkwijk and Booij (1986)
From Geyer (1993)
Chant and Wilson (1997)
Seim and Gregg (1997)
NOAA/NOS - PORTS mooring data.
Average ebb-dry period
Average ebb-wet period
No secondary circulation
Red - Surface
Currents during Maximum ebb
Red Surface Blue Bottom
Along Channel Flow
Cross Channel Flow
Cross Channel Flow
Max Ebb vs. Tidal Range Wet Period
Stronger shear in along
channel flow but weaker
cross channel flows.
Max(V)= 2.6 cm/s
Secondary flows decrease
Flood-ebb asymmetry in
g ranges from 1 for weakly
Stratified case and approaces
100 during strongly case
(represents ratio of isopycnal tilting
To differential advection)
Lerczak and Geyer (2004)
Tidally mean vuy+wuz
Is dominated by flood
Note where velocity max
Is on flood (red line)
Figure 4 Salt section along Hudson during moderate to high flow condition during spring tide (upper panel) and neap tide (Lower panel). See figure 2 for timing of transects relative to river flow and tidal range
April May June
Figure 5. (upper panel) along channel currents averaged between 1.35 and 6.1 meters above the bottom water from site 4 (blue line) and its low passed filtered component (green line). (lower panel) surface (green line) and bottom (blue line) salinity during the spring of 2002.
H&R neglected the effect of lateral circulation that becomes more
Important as mixing increases.
Including Coriolis produces lateral asymmetries. This would tend to transport
Sediment to the right (looking seaward) and thus produce a laterally asymmetric
Channel such as the Hudson.
Channel Cross-section at mooring array tend to transport
Laterally Asymmetric Channel in Hudson
In the afternoon we’ll look at aspects of lateral circulation based
On data from the Hudson
Laterally Sheared tend to transport
Figure 3) Schematic showing movement of Hudson and James river estuary through
Kevlin/Ekman number space over the spring neap cycle. Laterally sheared estuaries lie
in the upper right quadrant, while vertically sheared estuaries lie in the lower left quadrant
U2,V2 tend to transport
Full mooring deployment (Lerczak et al. 2006) and locations of
Data used in afternoon experiment