Detailed turbulent dynamics of the bottom bounday layer under a pure 

 wave (Sheng, 1982) and current-wave interaction (Sheng and 

 Lewellen, 1982) have also been studied using a Reynolds stress model. 

 Contrary to the general belief, the presence of the wave was found to 

 not always enhance the current-induced stress. 



CONCLUSIONS AND RECOMMENDATIONS 



An efficient three-dimensional numerical model of coastal currents 

 has been developed and is operational. The model is suitable for 

 detailed short-term simulations as well as longer-term simulations. 

 Currents in Mississippi Sound and adjacent offshore waters have been 

 computed with the three-dimensional model. Results obtained during a 

 five-day period in September 1980 agree wery well with the measured 

 data. Large spatial and temporal variation of bottom shear stresses 

 exist within the area. Rate of resuspension of the Mississippi Sound 

 sediments (primarily Smectite) has been determined experimentally and 

 was found to increase with increasing shear stress, decreasing 

 salinity, and shorter time-history of the bottom sediment. Studies are 

 needed to elucidate the effect of turbulence on flocculation the 

 current-wave interaction within the bottom boundary layer, and the 

 inclusion of sediment time-history as a parameter in the mathematical 

 model . 



ACKNOWLEDGEMENT 



This work is supported by the U.S. Army Engineer Waterways 

 Experiment Station under contract DACW 39-80-C-0087. Permission was 

 granted by the Army Chief of Engineers to publish this information. 

 Richard Schmalz and Bob Jensen provided valuable assistance in the 

 study. 



References 



Blumberg, A.F., 1975: "A Numerical Investigation into the Dynamics of 

 Estuarine Circulation," Chesapeake Bay Institute Report No. 91, 

 Baltimore, MD. 



Bowden, K.F. and P. Hamilton, 1975: "Some Experiments with a Numerical 

 Model of Circulation and Mixing in a Tidal Estuary," 

 Estuarine Coastal Marine Sci. , 3^, 281. 



Butler, H.L. and Y.P. Sheng, 1982: "ADI Procedures for Solving the 

 Shallow-Water Equations in Transformed Coordinates," 

 Proc. 1982 Army Num. Anal, and Comp. Conf. , Army Research Office, 



pp. 3feb-38U. 



Donaldson, C.duP., 1973: "Atmospheric Turbulence and the Dispersal of 

 Atmospheric Pollutants," in AMS Workshop on Micrometeorology 

 (D.A. Haugen, ed,). Science Press, Boston, pp. 313-39U. 



Erikson, C.C., 1978: "Measurements and Models of Fine Structure, 

 Internal Gravity Waves and Wave Breaking in the Deep Ocean," 

 J. Geophys. Res., 83, pp. 2989-3009. 



287 



Sheng 



