Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1984. / Vita. Bibliography: p. 200-206.

The aim of this study is to compare observational data to data simulated by a one dimensional model. Observational data collected from January to July 2006 at Lake Whitney, Texas, included water current velocities from an Acoustic Doppler Current Profiler, and an Acoustic Doppler Velocimeter from which shear stress, turbulent kinetic energy dissipation rates, and turbulence kinetic energy were computed using several methods. Numerical model experiments, forced by the surface heat and momentum fluxes, velocity profiles, and temperature profiles were conducted to simulate the development of the turbulence parameters. Two equation models, k-epsilon and k-kl, were used to find which model best describes the observed physical processes (turbulence kinetic energy, turbulent kinetic energy dissipation rate and velocity variances). The combined observational and simulated results show a change in stratification levels that consequently leads to variations in turbulent kinetic energy dissipation rate, turbulent kinetic energy, and the velocity variances. In order to investigate the accuracy of the model, we quantitatively compared these parameters to estimates from the observed data in the bottom boundary layer. In general, the model and observational data agree well for the three parameters, with the exception of some time periods, during which the model prediction differed from the observed. This was at times when the Acoustic Doppler Velocimeter measurements were at the noise level of the instrument. Overall, the k-kl model simulation results appear to be closer to the observational results during the weakly and strongly stratified periods than the k-epsilon model.

No description available.

Yes / Laboratory experiments have been carried out to investigate wave damping over the seabed, in which the excess pore pressure and free surface elevations are synchronously measured for examining the wave-induced soil dynamics and wave kinematics. Two types of soil, namely fine sand and silt, are tested to examine the role of soil in the wave damping. Observation of experiments shows that (i) soil liquefaction takes place for some tests with silty bed and soil particles suspend into the water layer when the bed is made of silt; (ii) sand ripples can be generated for experiments with sand bed. Measurements reveal that the wave damping greatly depends on the soil dynamic responses to wave loading and the wave damping mechanism over the silty seabed differs from that over the sand bed. On the one hand, the wave damping rate is greatly increased, when soil liquefaction occurs in the silty bed. On the other hand, the presence of sand ripples generated by oscillatory flow in the sand bed experiments also increases the wave damping to some extent. Furthermore, experimental results show that soil particle suspension in the silt bed test contributes to the wave damping. Theoretical analysis is presented to enhance discussions on the wave damping. The theoretical calculations demonstrate that the wave damping is mainly induced by the shear stress in the boundary layer for the cases when no liquefaction occurs. While for the cases when soil liquefaction takes place, the viscous flow in the liquefied layer contributes most towards to the wave damping. / the National Science Fund for Distinguished Young Scholars (Grant No. 51425901), the National Key Research and Development Program of China (2017YFC1404200), the Marine Renewable Energy Research Project of State Oceanic Administration (GHME2015GC01), and the 111 Project (Grant No. B12032)

Turbulent dynamics at two sites (C and D) in a hypoxic zone on the Texas- Louisiana continental shelf were studied by investigating turbulence quantities i.e. turbulence kinetic energy (TKE), dissipation rate of TKE (E), Reynolds stress (τ ), dissipation rate of temperature variance (χ), eddy diffusivity of temperature (ν't), and eddy diffusivity of density (ν'p). Numerical models were also applied to test their capability of simulating these turbulence quantities. At site D, TKE, E, and τ were calculated from velocity measurements in the bot- tom boundary layer (BBL), using the Kolmogorov’s -5/3 law in the inertial subrange of energy spectra of vertical velocity fluctuations in each burst measurement. Four second-moment turbulence closure models were applied for turbulence simulations, and modeled turbulence quantities were found to be consistent with those observed. It was found from inter-model comparisons that models with the stability functions of Schumann and Gerz predicted higher values of turbulence quantities than those of Cheng in the mid layer, which might be due to that the former stability functions are not sensitive to buoyancy. At site C, χ, E, v’t, and ν’p were calculated from profile measurements throughout the water column, and showed high turbulence level in the surface boundary layer and BBL, as well as in the mid layer where shear stress was induced by advected non-local water above a hypoxic layer. The relatively high dissolved oxygen in the non-local water resulted in upward and downward turbulent oxygen fluxes, and the bottom hypoxia will deform due to turbulence in 7.11 days. Two of the four models in the study at site D were implemented, and results showed that turbulence energy resulting from the non-local water was not well reproduced. We attribute this to the lack of high-resolution velocity measurements for simulations. Model results agreed with observations only for χ and E simulated from the model with the stability function of Cheng in the BBL. Discrepancies between model and observational results lead to the following conclusions: 1) the stability functions of Schumann and Gerz are too simple to represent the turbulent dynamics in stratified mid layers; 2) detailed velocity profiles measurements are required for models to accurately predict turbulence quantities. Missing such observations would result in underestimation,