Publications
Following publications have been announced by our department Hydrodynamics and Data Assimilation. For further information please contact Dr Joanna Staneva:
Nam, P.T., Staneva, J., Thao, N.T., & Larson, M. (2020): Improved Calculation of Nonlinear Near-Bed Wave Orbital Velocity in Shallow Water: Validation against Laboratory and Field Data. J. Mar. Sci. Eng. 2020, 8, 81, doi:10.3390/jmse8020081
Abstract:
A new parameterization for calculating the nonlinear near-bed wave orbital velocity in the shallow water was presented. The equations proposed by Isobe and Horikawa [1] were modified in order to achieve more accurate predictions of the peak orbital velocities. Based on field data from Egmond Beach in the Netherlands, the correction coefficient and maximum skewness were determined as functions of the Ursell number. The obtained equations were validated against measurements from Egmond Beach, and with laboratory data from small-scale wave flume experiments at Delft University of Technology and from large-scale wave flume experiments at Delft Hydraulics. Inter-comparisons with other previously developed parameterizations were also carried out. The model simulations by the present study were in good agreement with the measurements and have been improved compared to the previous ones. For Egmond Beach, the root-mean-square errors for the peak onshore (uc) and offshore (ut) orbital velocities were approximately 21%. The relative biases were small, approximately 0.013 for uc and −0.068 for ut. The coefficient of determination was in the range between 0.64 and 0.68. For laboratory experiments, the root-mean-square errors in a range of 7.2%–24% for uc, and 7.9%–15% for ut.
Haid, V., Stanev, E.V., Pein, J., Staneva, J., & Chen, W. (2020): Secondary circulation in shallow ocean straits: Observations and numerical modeling of the Danish Straits. Ocean Modelling, Volume 148, 101585, doi:10.1016/j.ocemod.2020.101585
Abstract:
In this paper, we explore the secondary flows in the Danish Straits using observations and numerical simulations performed with the unstructured-grid hydrodynamic model SCHISM covering the North Sea and Baltic Sea. The straits are resolved on scales of up to ∼100 m. Given that large-scale atmospheric variability dominates the transport in these straits, we focus on the processes with subtidal time scales. Similarities and differences between the in- and outflows in the straits and flood and ebb flows in estuaries are analyzed. Contrary to the tidal straining in estuaries, the Danish Straits feature substantial differences in the stratification stability during the outflow and inflow phases. With a resolution of ∼100 m, new transport and mixing pathways that were previously unresolved appear fundamental to the strait dynamics. The variety of the strait morphology leads to high variability in the appearance of secondary circulation. Helical cells, often with a horizontal extension of ∼1 km, develop in the deep parts of the channels. A comparison between the high-resolution simulation and a simulation with a coarse grid of ∼500 m in the straits suggests that the coarser resolution overestimates the stratification and misrepresents the transport balance; the axial velocities and transport through the Sound are underestimated by ∼12%. These differences are explained by the missing secondary circulation when the coarse resolution is used (approximately two grid-points per cell instead of ten grid-points per cell in the fine resolution model), along with the resulting changes in mixing along the straits. In conclusion, the use of ultrafine resolution grids is essential to adequately resolve secondary flow patterns and two-layer exchange. Thus, the problems caused by the failure to resolve the secondary circulation in straits appear similar to the problems caused by the failure to resolve mesoscale eddies in ocean models.
Staneva, J., Behrens, A., Ricker, M., & Gayer, G. (2020): Black Sea Waves Analysis and Forecast (CMEMS BLK-Waves 2016-present) (Version 1) [Data set]. Copernicus Monitoring Environment Marine Service (CMEMS), doi:10.25423/CMCC/BLKSEA_ANALYSIS_FORECAST_WAV_007_003
Staneva, J., Behrens, A., Ricker, M., & Gayer, G. (2020): Black Sea Waves Reanalysis (CMEMS BLK-Waves) (Version 1) [Data set]. Copernicus Monitoring Environment Marine Service (CMEMS), doi:10.25423/CMCC/BLKSEA_REANALYSIS_WAV_007_006
