Myung Eun Lee

Spatially Variable Dispersion Coefficients in Meandering Channels

AbstractTo analyze the spatial variability of two-dimensional dispersion coefficients in meandering channels, an observed dispersion tensor was calculated by applying a theoretical equation to the measured velocity profiles of two laboratory channels. From the observed dispersion tensor, local longitudinal and transverse dispersion coefficients were estimated by the least squares method. In both channels, the spatial variation in the dispersion coefficients was found to be strongly dependent on the specific location within the channel, because alternating bends in channels induces the periodic generation of secondary currents that alter the magnitude of transverse dispersion. Dimensionless transverse dispersion coefficients of each measurement section vary from 0.33 to 1.14 for the M1 channel and from 0.63 to 3.40 in the M2 channel around the entrance and apex of the second bend. The maximum negative correlation occurred near the apex of the channels because of the separation of the point of maximum prima...

Effect of local refinement of unstructured grid on the tidal modeling in the south-western coast of Korea

ABSTRACT Lee, M.E., Kim, G. and Nguyen, V.T., 2013. Effect of local refinement of unstructured grid on the tidal modeling in the south-western coast of Korea. To deal with a very complicated bathymetry in the south-western coast of Korea (SWCK), in this paper a numerical calculation with respect to varying grid and bathymetric resolutions was carried out for M2 barotropic tidal motion using FVCOM. In order to improve the model accuracy, horizontal grid resolutions resolving irregular coastlines and bathymetry together with data accuracy are considered. To do this, three refined horizontal grid resolutions were constructed in the nested local area around SWCK. At each horizontal grid structure, two different bathymetry resolutions were applied; the higher resolution based on a latest survey (2007) is more accurate. Bathymetric data with higher resolution was reconstructed as two different samples of data, to test the effect of resolving basic bathymetric data and the improvement of data accuracy, separately. From the test results, it was found that the accuracy of modeled M2 tidal elevation in this region can be improved dominantly by increasing the accuracy of basic bathymetric data, instead of resolving coastline and islands or increasing the resolution of bathymetry.

2-D numerical model for the analysis of mixing in the meandering stream

Two-dimensional model solving advection-dispersion equation was constructed with modified governing equation using finite element method. This model was testified by the comparison with the experimental results of the mixing in the laboratory S curved channel and also RMA4 was run at the same condition and compared. These results show the improved simulation result for the meandering channel.