Improving hydrodynamic modeling of an estuary in a mixed tidal regime by grid refining and aligning

Abstract

Water levels and flows in the Singapore coastal waters are driven by the complex interactions of the Indian and Pacific Ocean tides, seasonal monsoon-driven contributions and also forced by local winds. The Singapore Regional Model was developed to simulate hydrodynamics in the Strait of Singapore which produces representative sea level variation in this region. However, resolution and alignment of the grid system of the model with respect to depth contours in some of its subregions, i.e., the Johor Estuary area require further improvement. For this, the grid system of the model was modified and compared the simulated results with field measurements. The computed flow velocities agreed better with field observations when the grid resolution was increased. However, improving the alignment of the grid with the channel boundary (with a much lower increase in grid resolution) provided a substantially larger improvement of the model performance. The grid modification greatly influenced the computed salinity in the estuary, while water levels are slightly affected. Further analysis of model results showed a pronounced ebb tidal asymmetry generated by the O1-K1-M2 tidal constituents in the estuary.

Conceptual hydrodynamic-thermal mapping modelling for coral reefs at south Singapore sea

“…However, the improvement in accuracy was usually restricted to only small simulated area (showed in [25,32]) or was not obvious in tidal current and water level simulations (showed in [19]). In comparison, by refining the local mesh resolution according to the local geometry can effectively improve the water levels and tidal currents simulation as proven in various studies (refer to studies by [9,21]), which it is also suggested to be a crucial element in the sensitivity analysis of SCW tidal simulations conducted by Kurniawan et al [22] and Sun et al [27].…”

“…Delft3D, MIKE, POM and FVCOM) have been intensely conducted since last two decades. Among them, most studies were done using either two-dimensional [4,19,27,28] or threedimensional models [3,30,31]. Among those models, the most common meshing method involved orthogonal or regular rectangular grids (as the fully unstructured grid model is computationally too demanding to apply for large-scale coastal flow application as suggested in [29]); and the boundary conditions were usually set by effective water depth.…”

“…Thus an in-depth hydrodynamic understanding of the surrounding sea and coastal area of Singapore Island is crucial in seeking solution to the rising environmental issues. In the research of Singapore coastal waters (SCW) hydrodynamic numerical modelling, there are a numbers of difficulty that were constantly suggested in various studies [3,19,22,25,33], especially for the modelling surrounded Strait of Singapore. They include:…”

“…Some advancements have also been proposed such as boundary-fitted [25,32] and grid-alignment approaches [19] to obtain better accuracy in simulating the 2D tidal currents in SCW. However, the improvement in accuracy was usually restricted to only small simulated area (showed in [25,32]) or was not obvious in tidal current and water level simulations (showed in [19]).…”

“…Those 2D and 3D modelling studies have proven that both local and regional models surrounded SCW can be constructed to precisely capture its tidal situation. The above-mentioned comparison from different studies also further proved that the 2D model can achieve satisfactory results and comparable accuracy with 3D model to reproduce largescale tidal currents simulation, while giving a more efficient and hence practical tidal computational time.Some advancements have also been proposed such as boundary-fitted [25,32] and grid-alignment approaches [19] to obtain better accuracy in simulating the 2D tidal currents in SCW. However, the improvement in accuracy was usually restricted to only small simulated area (showed in [25,32]) or was not obvious in tidal current and water level simulations (showed in [19]).…”