Results of a 3-day Simulation (6/12/80 to 6/15/80) 



The same basic model and parameters are used to simulate the tidal 

 currents during a 3-day period during 12 June to 15 June 1980. This period 

 corresponds to a spring tide and hence the surface displacements, as shown in 

 Figure 5.10, are much higher than those during the previous simulation period. 

 Again, good agreement exists at all the stations. Surface contours 

 (Figure 5.11) indicate variation from -9 cm to -24 cm. 



The horizontal currents at selected stations throughout the 3-day period 



are quite strong and compare well with data (Figure 5.12). The velocity field 



at a constant depth of 1 m, at the end of the simulation period, is shown in 



Figure 5.13. The relatively stronger currents lead to a stronger bottom 



stress field as shown in Figure 5.14. Over much of the shallow waters, the 



bottom shear stress exceeds the critical shear stress for entrainment of 



2 

 sediment (0.8 dyne/cm ). Velocity field along a transect across the Mobile 



Bay is shown in Figure 5.15. 



Vertical eddy viscosity along a transect across the Horn Island Pass, 

 shown in Figure 5.16, indicates an almost twofold increase from that in 

 Figure 5.9. 



Results During a Five-Day Simulation (9/1/80 to 9/6/80) 



The ability of the hydrodynamic model to simulate the tidal circulation 

 in the Mississippi Sound has been demonstrated in the two previous 

 simulations. We will now present another 5-day simulation during 1 Sept. to 6 

 Sept. 1980. The model computed surface displacements at four stations are 

 shown in Figure 5.17. Diurnal tides are dominant during this time period with 

 variation in surface displacement on the order of 1 ft. In the following, we 

 will present the detailed results at 6-hour intervals over one complete tidal 

 cycle, from the 72nd hour to the 96th hour. Residual currents over this tidal 

 cycle are also presented. This will enhance our understanding on the detailed 

 tidal dynamics in the Mississippi Sound. In addition, it will provide a basis 

 to better interpret the sediment transport simulations during this time 

 period, which will be presented in a subsequent chapter. 



84 



