Chen Changsheng

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Chen
First Name
Changsheng
ORCID
0000-0001-8715-6101

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A dike–groyne algorithm in a terrain-following coordinate ocean model (FVCOM) : development, validation and application

2012-01 , Ge, Jianzhong , Chen, Changsheng , Qi, Jianhua , Ding, Pingxing , Beardsley, Robert C.

A dike-groyne module is developed and implemented into the unstructured-grid, three dimensional primitive equation Finite-Volume Coastal Ocean Model (FVCOM) for the study of the hydrodynamics around human-made construction in the coastal area. The unstructured-grid finite-volume flux discrete algorithm makes this module capable of realistically including narrow-width dikes and groynes with free exchange in the upper column and solid blocking in the lower column in a terrain-following coordinate system. This algorithm used in the module is validated for idealized cases with emerged and/or submerged dikes and a coastal seawall where either analytical solutions or laboratory experiments are available for comparison. As an example, this module is applied to the Changjiang Estuary where a dike-groyne structure was constructed in the Deep Waterway channel in the inner shelf of the East China Sea (ECS). Driven by the same forcing under given initial and boundary conditions, a comparison was made for model-predicted flow and salinity via observations between dike-groyne and bed-conforming slope algorithms. The results show that with realistic resolution of water transport above and below the dike-groyne structures, the new method provides more accurate results. FVCOM with this MPI-architecture parallelized dike-groyne module provides a new tool for ocean engineering and inundation applications in coastal regions with dike, seawall and/or dam structures.

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Surface circulation in Block Island Sound and adjacent coastal and shelf regions : a FVCOM-CODAR comparison

2016-02-29 , Sun, Yunfang , Chen, Changsheng , Beardsley, Robert C. , Ullman, Dave , Butman, Bradford , Lin, Huichan

CODAR-derived surface currents in Block Island Sound over the period of June 2000 through September 2008 were compared to currents computed using the Northeast Coastal Ocean Forecast System (NECOFS). The measurement uncertainty of CODAR-derived currents, estimated using statistics of a screened nine-year time series of hourly-averaged flow field, ranged from 3-7 cm/s in speed and 4°-14° in direction. The CODAR-derived and model-computed kinetic energy spectrum densities were in good agreement at subtidal frequencies, but the NECOFS-derived currents were larger by about 28% at semi-diurnal and diurnal tidal frequencies. The short-term (hourly to daily) current variability was dominated by the semidiurnal tides (predominantly the M2 tide), which on average accounted for ~87% of the total kinetic energy. The diurnal tidal and subtidal variability accounted for ~4% and ~9% of the total kinetic energy, respectively. The monthly-averaged difference between the CODAR-derived and model-computed velocities over the study area was 6 cm/s or less in speed and 28° or less in direction over the study period. An EOF analysis for the low-frequency vertically-averaged model current field showed that the water transport in the Block Island Sound region was dominated by modes 1 and 2, which accounted for 89% and 7% of the total variance, respectively. Mode 1 represented a relatively stationary spatial and temporal flow pattern with a magnitude that varied with season. Mode 2 was characterized mainly by a secondary cross-shelf flow and a relatively strong along-shelf flow. Process-oriented model experiments indicated that the relatively stationary flow pattern found in mode 1 was a result of tidal rectification and its magnitude changed with seasonal stratification. Correlation analysis between the flow and wind stress suggested that the cross-shelf water transport and its temporal variability in mode 2 were highly correlated to the surface wind forcing. The mode 2 derived onshore and offshore water transport, and was consistent with wind-driven Ekman theory. The along-shelf water transport over the outer shelf, where a large portion of the water flowed from upstream Nantucket Shoals, was not highly correlated to the surface wind stress.

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