Post on 07-Apr-2022
Chapter 13
Tidal Hydrodynamics and Inlets
Tidal Inlets
Hydraulically connecting lagoon
with ocean
Tides in lagoons
Navarre Pass, FL
Pensacola Bay, Santa Rosa Sound, and Choctawatchee Bay
Navarre Pass, FL
Tides
The tide in the lagoon lags and is smaller than thetide in the ocean
Tides in the ocean are predicted (except for storms)
Chapter 2
Conservation of Mass and Momentum
Mass:
Island
Linearize:
Planform area of bay
OceanBay
Conservation of Momentum
Add entrance and exit losses
Assume hydrostatic pressure
Integrate across channel
Hydraulic radius:
Note form of shear stress with abs value
Keulegan Method
Neglect inertial term as small
Solve for U
Using Conservation of Mass:
Non-dimensional forms:
Coefficient of Repletion
Nonlinear first order ODE
All of the parameters in $K$ can be determined from navigationalcharts, tide tables, and estimates of frictional losses. Examining theirinfluence on the repletion coefficient directly shows thatincreases in all of the parameters in the numerator (the inlet cross-section) will increase the relative filling of the bay, whereas increasing the parametersin the denominator (bay plan area, frictional lossesin channel) will decrease the relative filling in the bay. For large bays,then, the repletion coefficient is likely to be small.
Keulegan’s Solution
Keulegan’s Solution
Phase Lag Between Ocean and Bay
Bay Response
Linear Problem
From Conservation of Mass:
Conservation of Momentum (with acceleration):
Linear (Forced) Dynamics Equation:
Solution
Assume
Ratios of friction to inertial force
and hydrostatic to inertial force
\sigma_N is the natural frequency in absence of friction and tidal forcing (raise water level in bay and let go
F_0 is the Forcing Magnitude in figure.
Linear Solution
Large \phi_2 gives a_B/a_O of 1, small \phi_2 gives small tide in bay
Effect of Inlet Cross-section on Tidal Prism
Effect of Bay Area on Prism
Effect of Cross-sectional Area on Velocity
Nonlinearities in the Inlet Tides
Inlet Stability
Indian River Inlet, DEand
Ocean City Inlet, MD
Note the bay systems
Ocean City, MD
Ocean City Bathymetry
Why is the shoal asymmetrical? Why is there no connection of the shoal to the island on thenorth side?
Indian River Inlet, DE
Dredging
Bypassing
Cross-sectionalArea
Scour
Indian River Inlet Ebb Shoal
Tidal Prism versus Cross-Section
M.P. O’Brien (1931, 1969)
Tidal Prism versus Cross-section
Jarrett (1976)
Units: Ac [ft2] [ft3]
10^2 to 10^6
Ebb Tidal Shoal Volume
Sedimentary Stability
Bypassing at So.Lake Worth Inlet, FL
Schematic of Weir and Deposition Basin
Weir systems:
Hillsboro Inlet, Fl
Nerang Inlet, Australia