Three-dimensional Hydrodynamic Model Research Articles

Mechanisms of Advective and Tidal Oscillatory Salt Transport in the Hypertidal Estuary: Yeomha Channel in Gyeonggi Bay

Many estuaries have been damaged by such material movements as marine debris, suspended sediment, and pollutants. Understanding the estuarine circulation system is necessary to solve such problems. Salt transport analysis provides an insight into hydrodynamic processes about material circulation in the estuary. In this study, to understand the mechanisms of salt transport, a three-dimensional hydrodynamic model was applied in the hypertidal estuary system—Yeomha Channel in Gyeonggi Bay. The simulation period of the model was a total of 245 days (20 January to 20 September 2020), including the dry and wet seasons. The model results for the temporal variation in tide, current velocity, and salinity were validated by comparing them with the observed in-situ data. The total salt transport (FS) was calculated in three cross sections of the Yeomha Channel and was decomposed into three components (QfS0: advective salt transport; FE: steady shear dispersion; FT: tidal oscillatory salt transport). During the dry season with strong tidal forces, the total salt transport patterns were mainly dominated by QfS0. During the wet season with high river discharge, the total salt transport patterns were determined by the balance between QfS0, FE, and FT. The long-term tidal constituents (MSf and Mm) were the main mechanisms causing QfS0 with the spring–neap variation during the dry season. The tidal trapping effect, caused by a phase difference of less than 90° between tidal current and salinity, generated landward FT in the dry and wet seasons. In addition, the high river discharge during the wet season decreased the phase difference between tidal current and salinity to less than 70°, resulting in a much stronger landward FT. This study suggests that the long-term tidal constituents and tidal trapping effect are unique characteristics that contribute to material circulation in the hypertidal estuary.

Analysis of the effects of climate change on the gyre in Lake Biwa, Japan

AbstractThe currents of gyre (circulation) flow play an important role in the transportation and mixing of dissolved or suspended nutrients and chemical substances. In recent years, climate change has affected the flow field in Lake Biwa. However, how much climate change can influence the flow field has not been clarified enough yet. In the present study, using a three-dimensional hydrodynamic model, we investigated the effect of changes in air temperature, wind speed, and precipitation on the change of the flow field in Lake Biwa. For sensitivity analysis, numerical simulations were performed for a baseline case using realistic meteorological data from 2007 to 2012, as well as hypothetical cases using meteorological data. The analysis revealed that the changes in air temperature and precipitation changed stratification and vorticity in the surface layer in each season. The strength of the stratification affected the gyre strength in the surface layer. The change in wind speed, on the other hand, changed the wind stress acting on the lake's surface, influencing the strength of gyre significantly. Increased wind speed lengthened the radius of the gyre in Lake Biwa, while decreased wind speed made it weaker above and below the thermocline.

Barotropic response of the Baltic Sea dynamic system to sea level fluctuations in the Kattegat strait

With the help of numerical experiments with a three-dimensional barotropic hydrodynamic model, the response of the level surface of the Baltic Sea to different-scale level disturbances propagating into the Baltic through the Danish straits from the North Sea is studied. For this, 53 harmonic oscillations with amplitudes of 10 cm and periods from 3 hours to 1 year, which in the article are called "external", in contrast to the perturbations of the level inside the sea induced by them. The same amplitudes for all initial oscillations were set so that when analyzing the results, quantitative differences in the amplitude spectra of "external" and "internal" oscillations were clearly visible. It is shown that, with the exception of the frequency range of natural barotropic oscillations of the Baltic Sea, in the Danish Straits there is an almost complete filtration of oscillations specified at the boundary of the region with periods from 3 hours to 10 days. In the range of periods from 15 to 35 hours, there is an increase in "internal" oscillations due to the resonance of the initial oscillations with the natural oscillations of the Baltic. In the mesoscale frequency range (periods from hours to several days), the response of the level surface of the Baltic Sea to the impact of "external" oscillations is manifested in the generation of progressive-standing Kelvin waves with pronounced amphidromic systems and antinodes. For oscillations with periods of more than 10 days, with a decrease in frequency, the filtering effect of the Danish Straits is weakened and for periods of about 60 days, their amplitudes decrease by only 50%. In the range of seasonal variability, hydraulic resistance in the Danish Straits has the least effect on the propagation of "external" sea level fluctuations, reducing their amplitudes by only 6 - 22%. The highest amplitude is observed in semi-annual oscillations, which are amplified due to the influence of the semi-annual overtone in the annual oscillation generated by nonlinear effects.

Development of a Three-Dimensional Hydrodynamic Model Based on the Discontinuous Galerkin Method

Though the discontinuous Galerkin method is attracting more and more applications in many fields due to its local conservation, high-order accuracy, and flexibility for resolving complex geometries, only a few three-dimensional hydrodynamic models based on the discontinuous Galerkin method are present. In this study, a three-dimensional hydrodynamic model with a σ-coordinate system in the vertical direction is developed. This model is discretized in space using the discontinuous Galerkin method and advanced in time with the implicit-explicit Runge–Kutta method. Numerical tests indicate that the developed model is convergent and can obtain better results with a smaller computational time when a higher approximation order is adopted. Other tests with exact solutions also indicate that the developed model can well simulate the vertical circulation under the effect of surface wind stress and the flow under the combined effect of wind stress and Coriolis acceleration terms. The simulation results of tidal flow in part of Bohai Bay, China, indicate that the model can be used for the simulation of tidal wave motion in realistic situations.

Methodological support of verification control of geological and hydrodynamic models and forecast flow rates based on the results of operational drilling of wells

In аrticle we analyze the drilling results based on three-dimensional geological and hydrodynamic models based on data from 115 wells in 28 different fields in the Volga-Ural and Timan-Pechora oil and gas provinces. The analysis of the results of production drilling of wells on the accepted geological and hydrodynamic models was carried out. The confirmation of the main elements of the geological three-dimensional model is considered. To differentiate the reasons for the deviation of the forecast flow rates associated with geological and hydrodynamic modeling, it is suggested to use the graph of comparison of the relative deviation of flow rates and the filtrationcapacitive properties predicted on the geological model. Efficiency and visibility of the separation of geological and technological reasons for the unconfirmed debits on the chart showed that, first of all, the factors related to reservoir development technologies and the forecast of the hydrodynamic model influence the flow rates. The study allows to choose effective measures to reduce the risk of failure to reach the planned production at oil fields, it is proposed to improve the methods of geological and hydrodynamic modeling in the direction of the development of the use of multivariate modeling technologies. Keywords: reservoir; predicted oil production; reservoir simulation modeling; porosity; permeability; reservoir properties.

Development and evaluation of a GPU-based coupled three-dimensional hydrodynamic and water quality model

In this study, a graphics processing unit (GPU)-based three-dimensional coupled hydrodynamic and water quality numerical model (GPUOM-WQ) was developed for the first time, which introduces pollution sources of atmospheric deposition, aquaculture wastewater, and oil platform emission to describe marine pollution comprehensively. A test case with analytical solutions and a real case with measured data were used to validate the accuracy of GPUOM-WQ. Simulation results indicate that the maximum error between the numerical and analytical solutions is 0.9 %, and the average relative error between simulated and measured values of 5 water quality variables at 38 stations in spring, summer, fall and winter is 14.63 %. In the real case simulation, GPUOM-WQ accelerates the computation 62.48 times, which is 3.23 times faster than in 64-core central processing unit (CPU) parallel mode. This study makes it possible to accurately simulate the marine water quality variation and spatiotemporal distribution in a high-resolution and efficient way.

Comprehensive three-dimensional hydrodynamic and thermal modeling of steady-state operation of a flat grooved heat pipe

Mathematical modeling of grooved heat pipes is a challenging task since multiple coupled physical phenomena such as phase change, free-surface flow and heat transfer are involved. Moreover, the fact that the shape of the liquid–vapor interface in the heat pipe is unknown a priori requires simultaneous determination of the interface variation as a part of the solution procedure, a capability currently not addressed in commercially available engineering CFD tools. In this study, a multi-dimensional and multi-scale computational model is presented to gain a comprehensive understanding of the underlying physics of grooved heat pipes. The computational model is based on an iterative scheme for the solution of 3D heat transfer and liquid flow, interface phase change heat transfer (evaporation and condensation) and shape of the interface. The model is implemented using three different methodologies two of which utilize commercial engineering CFD software. The results are verified for a problem previously studied in the literature which indicates the robustness of our computational approach.

Hydrodynamics of a large lake with complex geometry and topography: Lake of the Woods

We developed a high-resolution (250 m) three-dimensional hydrodynamic model of Lake of the Woods (LoW) to study surface seiches, lake circulation, and water temperature. LoW spans over two different geological regions, experiences wind variability, encompasses >14,500 islands and includes twelve hydraulically connected sub-basins. The complex geometry and topography are unique for this large lake that suffers from seasonal algal blooms. The model uses a spatially and temporally variable wind field, heat fluxes, riverine inflows obtained from a watershed model, outflows at Kenora and Norman dams, and was run for the spring-summer of 2017 and 2018. The predominant physical processes in LoW are surface seiches, and wind and rivers drive mean lake-wide circulations and mixing. The observed periods of seiches in the lake are 9.5, 3.4, 2.3, and 1.3 h, attributed to horizontal modes 1, 3, 6, and 12, respectively. Amphidromic structures show that sub-basin seiche's responses to wind may be limited to one sub-basin; however, lake-wide responses were also observed, which suggests the seiche-induced oscillatory velocities can impact transport paths. The mean water temperature is variable spatially, ranging from <15 °C in early June to ∼25 °C in July-August. Sabaskong Bay experienced warmer summer water temperatures with unidirectional mean flows to the lake. Main water transport is towards the northeast. Modelled conservative tracers, consistent with observations, show that the Rainy River plume extent covers Big Traverse, Morson, and Little Traverse Bays. The modelled seasonal hydraulic retention times in southern bays are <150 days and are much longer in northern bays.

Impacts of climate change on estuarine stratification and implications for hypoxia within a shallow subtropical system

Vertical density stratification often plays an important role in the formation and expansion of coastal hypoxic zones through its effect on near-bed circulation and vertical oxygen flux. However, the impact of future climate change on estuarine circulation is widely unknown. Here, we developed and calibrated a three-dimensional hydrodynamic model for Pensacola Bay, a shallow subtropical estuary in the northeastern Gulf of Mexico. Model simulations based on years 2013–2017 were applied to examine changes in salinity, temperature, and density under future climate scenarios, including increased radiative forcing (IR) and temperature (T), increased freshwater discharge (D), sea level rise (SLR), and wind intensification (W). Simulations showed that the impacts of climate change on modeled state variables varied over time with external forcing conditions. The model demonstrated the potential for sea level rise and increased freshwater discharge to episodically increase vertical density gradients in the Bay. However, increased wind forcing destabilized vertical gradients, at times reducing the spatial extent and duration of stable stratification. For time periods with low freshwater discharge, moderate increases in wind speed (10%) can destabilize density gradients strengthened by increased discharge (10%) and sea level rise (0.48 m). In contrast, destruction of strong density gradients that form near the mid-Bay channel following flood events requires stronger wind forcing. These results highlight the importance of considering natural variability in freshwater and wind forcing, as well as local phenomena that are generally unresolved by global climate models.

A Data Assimilation Approach to the Modeling of 3D Hydrodynamic Flow Velocity in River Reaches

The measurement of river discharge is essential for sustainable water resource management. The velocity–area approach is the most common method for calculating river discharge. Although several velocity measurement methods exist, they often have varying degrees of technical issues attributed to their operational complexity, time effectiveness, accuracy, and environmental impact. To address these issues, we propose a three-dimensional (3D) hydrodynamic model coupled with data assimilation (DA) for velocity measurement with improved accuracy and efficiency. We then apply this model to the Lanxi River reach in Zhejiang Province, China. The experimental results confirm that the obtained assimilated velocities using our proposed algorithm are much closer to the observed velocities than the simulated velocities. Our results show that when using the proposed method, the RMSE is decreased by 78%, and the SKILL and DASS values are 0.96 and 0.92, respectively. These confirm that the DA scheme of the flow velocity measurement is effective and capable of significantly improving the accuracy of the velocity with lower computational complexity.

Impact of climate change on coastal water quality and its interaction with pollution prevention efforts

The impact of climate change on nearshore coastal water quality and its interaction with pollution prevention efforts (e.g., the development of green and gray water infrastructure) still lack systematic investigation. This study performed a holistic analysis of the impact of climate change on the salinity and concentrations of total nitrogen (TN), total phosphorus (TP) and chlorophyll a (Chl.a) in Shenzhen Bay between Shenzhen and Hong Kong, the two most developed megacities in South China, based on three-dimensional hydrodynamic and water quality modeling. The major study findings were as follows. First, Chl.a was the most sensitive parameter, and its bay-wide average concentration in 2100 was predicted to be approximately 13% and 46% higher than those in 2015 under mild and rapid climate change scenarios, respectively. Second, sea level rise was found to be a major driver of all four water quality parameters, while temperature and radiation mainly influenced Chl.a and precipitation mainly influenced nutrients. Third, water quality responses to climate change were highly heterogeneous over the bay. Even under a mild climate change scenario, the highest location-specific changes (2100 vs. 2015) in salinity and TN, TP and Chl.a concentrations were projected to be approximately 21%, 19%, 25%, and 65%, respectively. Fourth, changes in seasonal variation due to climate change may lead to an enhanced ecological risk of algal blooms. Finally, the effect of reducing TN and TP concentrations by proposed water infrastructure development was found to be significantly weakened (nearly 40% and 20% for TN and TP, respectively, under a mild climate change scenario), while the negative effect (i.e., increase in the Chl.a concentration) was notably accelerated. Regional cooperation is critical for protecting the water quality of the bay, particularly under climate change. The insights obtained in this study are applicable to other coastal water zones around the world with similar socioeconomic backgrounds and climatic conditions.

A Bayesian data assimilation framework for lake 3D hydrodynamic models with a physics-preserving particle filtering method using SPUX-MITgcm v1

Abstract. We present a Bayesian inference for a three-dimensional hydrodynamic model of Lake Geneva with stochastic weather forcing and high-frequency observational datasets. This is achieved by coupling a Bayesian inference package, SPUX, with a hydrodynamics package, MITgcm, into a single framework, SPUX-MITgcm. To mitigate uncertainty in the atmospheric forcing, we use a smoothed particle Markov chain Monte Carlo method, where the intermediate model state posteriors are resampled in accordance with their respective observational likelihoods. To improve the uncertainty quantification in the particle filter, we develop a bi-directional long short-term memory (BiLSTM) neural network to estimate lake skin temperature from a history of hydrodynamic bulk temperature predictions and atmospheric data. This study analyzes the benefit and costs of such a state-of-the-art computationally expensive calibration and assimilation method for lakes.

Hydrodynamical transport structure and lagrangian connectivity of circulations in the Pearl River Estuary

Using a three-dimensional (3D) hydrodynamic model, this study explored the seasonal hydrodynamic transport structure in the Pearl River Estuary and illustrated the intrinsic connectivity under multiscale motions from a Lagrangian perspective. Generally, the surface Lagrangian residual current (UL) is uniformly southwestward/southeastward in summer/winter, with a stronger intensity in the lower estuary. The bottom UL features in the southeastward direction in the upper estuary and northwest direction in the lower estuary. The fluvial–tide interaction line advances southeastward and northwestward in summer and winter, respectively. The UL captured the major transport processes and was in good agreement with the mean surface sediment transport patterns. In the transition region between Lantau Island and Neilingding Island, where it is largely affected by the interaction between the periodic tidal current and river discharge, the spatially averaged UL showed intensified intratidal variations and had a larger difference with the locally temporally averaged Eulerian residual current. The remarkable Lagrangian coherent structures that illustrated the transport paths and transport convergence regions were identified, which are generally consistent with the bottom sediment depocenters. Based on the Lagrangian connectivity analysis, it was revealed that a barrier between the western and eastern estuaries existed, which was weakened by the strong river discharge during summer. Two convergence regions near the Macau and Hong Kong waters were identified, where the sediment and pollutants easily settled. The study demonstrated the importance of the Lagrangian view in understanding the hydrodynamic process and transport structure in the estuary–shelf regions.

Study of an abnormally strong saltwater intrusion in the Humen Channel of the Pearl River estuary

Saltwater intrusion in estuaries has become a serious environmental problem, such as in the Pearl River estuary (PRE). In this study, we used a fully validated three-dimensional hydrodynamic model EFDC to numerically investigate the saltwater intrusion in the PRE during the dry season of 2007-2008. Based on the measured salinity, an abnormally strong saltwater intrusion occurred in the Humen Channel in February 2008. The saltwater intrusion occurred twice a month to varying extents, with each saltwater intrusion happening 1-3 days before spring tide, and the stronger saltwater intrusion always occurred at the beginning of the month. Our model results show that caused by a long-term northerly wind during the dry season, the increased steady shear term in the salt transport flux were responsible for the abnormally strong saltwater intrusion in the Humen Channel. The abnormally strong saltwater intrusion has features of long duration, far-reaching upstream distance and great hazard to freshwater resources. The wind effects were revealed to mainly influence the bottom salinity in the middle reach of the PRE, especially near the Humen outlet.

A study on the riprap movement based on marine hydrodynamic model and field observation

ABSTRACT The study of mechanisms and the accurate simulation of riprap movement caused by complex hydrodynamics are significant for harbor, channel and coastal engineering. Field measurement of current and riprap drift distance was conducted for a dike project in the port of Lianyungang, Jiangsu Province, China. Meanwhile, a well-validated three-dimensional hydrodynamic model was developed to study and analyze the riprap movement process and the influence of project position combined with the theoretical movement equation of riprap. At the moment of maximum flood, the riprap drift distance is greater than at the moment of maximum ebb. The riprap drift distance increase as the tidal inlet width decreases, which follows a second-order exponential distribution. The riprap mass reduces the riprap drift distance, and the magnitude of the reduction diminishes gradually as the riprap mass increases. Therefore, heavy riprap can reduce the horizontal drift distance in a construction.

Study on dynamic response of underwater towed system in ship propeller wakes using a new hydrodynamic model

The dynamic analysis of underwater towed systems is challenging considering complex flow disturbances such as ship propeller wakes. This paper proposed a new fully-coupled three-dimensional hydrodynamic model for the dynamic analysis of an underwater towed system under complex flow disturbances. The hydrodynamic characteristics of the towed vehicle and the flow field behind the towing ship and propeller were simulated using computational fluid dynamics (CFD). The fluid forces on the towing cable were determined by combining the Morison formula and the CFD method. A dynamic analysis of an underwater towed system in a towing ship propeller wake under typical uncontrolled towing and depth regulation operations was conducted. The simulation results indicated that the proposed method was reasonable. Moreover, the time-averaged position and posture of the underwater towed system and its hydrodynamic characteristics vary with the rotation rate of the ship propeller in uncontrolled towing operation under a fixed towing speed. Furthermore, the fluid forces on the towing system and the cable tension in the depth regulation operation changed more drastically than in the uncontrolled towing operation. The proposed method can be easily extended to simulate other marine cable systems.

A three-part coupled statistical and physical model to monitor water quality parameters governing disinfection byproduct risk at an urban drinking water intake

Extended drought in the twenty-first century has led to loss of volume for lakes and reservoirs across the globe. In the Colorado River Basin, USA, Lakes Powell and Mead have experienced a 68 and 71% decline in volume, respectively, since 2000. Lake Mead is important to the Las Vegas Valley as it accounts for 90–100% of the source water used to serve the 2.2 million residents and 43 million annual tourists. Lake Powell is also vital to maintaining water quality in Lake Mead as it is located upstream and provides 97% of the water entering Mead. As Lakes Powell and Mead are projected to continue decreasing in volume over the next 5 years, it is important to understand the effects of loss of lake volume on water quality in this highly-managed system. Here, the effects of lake drawdown on water quality parameters that affect disinfection byproduct (DBP) formation in the source water for the Las Vegas Valley are projected over the next 5 years using Federal flow projections, regression modeling to project influent temperature from Lake Powell into Lake Mead, and a three-dimensional hydrodynamic and water quality model for Lake Mead. Results from these modeling efforts include projections for changes in values of water temperature, bromide, and total organic carbon (TOC) at the modeled cell that contains the Las Vegas Valley's urban drinking water intake. Raw water bromide was found to have little change across modeled scenarios; however, raw water temperature is projected to increase because of falling lake surface elevations. Raw water TOC is projected to increase three-fold in the simulated scenario that includes the most loss of volume but remains close to historic values in the remaining simulated scenarios. With these raw water quality projections, water managers can better plan for alterations to the water treatment processes, including mitigation of DBP formation.

Three-dimensional hydrodynamic modelling of the Moroccan Atlantic coast: A case study of Agadir bay

Coastal areas are a noteworthy source of commercial and economic fortunes for surrounding municipalities throughout the Moroccan Atlantic coast. Thus, a deep knowledge of local hydrodynamics and environmental processes associated is integral to effective coastal management. 3D hydrodynamic model that includes a Lagrangian particle simulation can participate to this understanding of dynamics. The model was calibrated and validated against meteorological conditions, sea surface level, harmonic tidal constituents, water temperature and salinity using a combination of available in-situ measurements, satellite, and ARGO floats data. Subsequently, it was used to determine the pathway of passive tracers and estimate the local residence time (RT). Despite some discrepancies, the findings revealed a good match between simulations and observations, which underlines the feasibility of the model in predicting the main dynamic features of the Agadir bay. Overall, the hydrodynamics of the area is tidal dominated by semidiurnal tides (M2) and governed by westerly and northwesterly winds. Passive tracer simulations showed strong seasonal and spatial variability, conditioning the obtained RTs, with mean values much shorter during summer (3 to 9 days) than winter (5 to 15 days). The tracers look to be trapped inside a coastal cyclonic eddy that increases the RTs in the southern bay, making it an area with highest likelihood of accumulation of pollutants while favoring the northward transport and decrease RTs in the northern bay.

Effects of Environmental Factors on Suspended Sediment Plumes in the Continental Shelf Out of Danshuei River Estuary

The effects of environmental factors on suspended sediment plumes in the continental shelf out of the Danshuei River estuary were numerically investigated using an unstructured-grid three-dimensional hydrodynamic model (SCHISM) together with a suspended sediment (SS) module. The coupled model (SCHISM-SS) was calibrated and validated against the in situ measurement data in 2016. Consistent with the observation results, the model simulations satisfactorily reproduced the water levels, velocities, salinities, and suspended sediment concentrations. The model was then applied to explore the role of various environmental factors in the dynamics of suspended sediment plumes from the estuary to the adjacent coastal seas. These factors include tidal forcing, salinity, river discharge, and wind stress. Analysis and comparisons of different scenario results indicated that the suspended sediment plume was greatly affected by tides, e.g., a longer plume distance resulted from a larger flux under tidal motions. A higher sediment concentration in the plume in the offshore area was also found during the neap tide, relative to that observed during the spring tide. In addition, salinity affects the movement of density currents and the spread of the sediment plume, i.e., the plume distance is longer due to the residual circulation when a salinity difference is present. Further, an extreme river flow could occur during typhoon periods and would discharge a greater water volume into the coastal region, causing the suspended sediment plume to expand from the near shore. Finally, the directions of prevailing winds can slightly influence the sediment plumes.

Comparative Study on Water Temperature Stratified Flow under Different Vertical Coordinate Systems in Delft3D

Reservoirs often suffer from water blooms, which are likely related to the hydrodynamic and water temperature characteristics of the tributary bays. To obtain the detailed changing process of hydrodynamics and water temperature stratification, it is necessary to choose a suitable vertical coordinate system in order to achieve the required precision. Based on a physical model experiment of cold water flowing into the Generalized Reservoir Hydraulics (GRH) flume, both the σ-coordinate system model and the z-coordinate system model are built for comparison. For the z-coordinate system model, the influences of different grid resolutions and different bottom slopes on the simulation accuracy are also analyzed. The results show that the σ-coordinate system model can simulate cold-water underflow in a reservoir better than the z-coordinate system model, and the numerical errors of the z-coordinate system model can be reduced but not eliminated by increasing the horizontal grid resolution. When the bottom slope of the reservoir is less than 18‰, the z-coordinate system model can also be used to simulate cold-water underflow in a reservoir. The conclusions about vertical coordinate systems can be applied to the development of a three-dimensional hydrodynamic and water temperature model of reservoirs.