Tidal Hydrodynamic Model Research Articles

Tidal current energy resources assessment in Zhoushan Archipelago, China

ABSTRACT Zhoushan Archipelago, the largest archipelago in China, harbors a significant tidal stream resource due to robust tidal currents coursing through numerous channels between its islands. Nevertheless, the tidal energy resource in the Zhoushan Archipelago has not been systematically characterized considering both topography and energy flow density. This study presents a modeling study aimed at characterizing the tidal energy resource in the whole Zhejiang coast, including Zhoushan Archipelago, employing a high-resolution tidal hydrodynamic model, i.e. MIKE 21. Through a comparison of the model output with observed data from two tidal stations and three current stations, the accuracy of the numerical model was confirmed. The study identified areas with robust currents and suitable water depths, both essential factors for the advancement of tidal current energy. The findings showed that many channels in Zhoushan Archipelago and Wenzhou Bay in Zhejiang experience the highest tidal power density, reaching nearly 5500 W/m2. Furthermore, the study estimated the theoretical tidal current energy production for the whole area, highlighting Loutou channel, Cezi channel, Taohuagang, and the channel between Xiushan island and Daishan island as regions with high potential.

Tidal energy extraction modifies tidal asymmetry and transport in a shallow, well-mixed estuary

Tidal energy extraction is increasingly being studied as a potential renewable energy resource in estuaries worldwide. Although it is understood that energy extraction via tidal stream turbines can modify currents and transport within estuaries, it is not clear how the underlying nonlinear physical mechanisms dictating tidal hydrodynamics are modulated. This research investigates the influence of a hypothetical tidal stream turbine array on barotropic tidal processes in a shallow, well-mixed system: the Piscataqua River – Great Bay (PRGB) estuary, using a numerical model. The modeled turbine farm includes 180 turbines which would extract an estimated 44.7 GWh of energy, annually. The tidal hydrodynamic model for the existing condition is validated with in-situ observations of currents and water level before analyzing tidal asymmetry and transport with and without tidal turbines. Results indicate that the tidal turbine array will decrease tidal elevation and current magnitudes system-wide, but generally reduce ebb currents and transport more than flood over most of the estuary footprint, thereby diminishing tidal asymmetry. The smaller asymmetric distortion compared to the no-turbine case is attributed to reductions in the storage volume of water over the estuary’s extensive tidal flat regions between low and high waters which decreases the associated nonlinear intertidal storage mechanism up to 25%. This leads to weakened ebb dominance over estuary sections from the mouth to mid-reaches, where depths are deep enough to keep the combined nonlinear shallow water and frictional effects from asserting control over the storage mechanism. Even in upstream shallow regions where depth-dependent friction controls asymmetry in both cases, the frictional mechanism is reduced only by 10% with turbines. Some environmental considerations of this work are discussed, with focus on sediment transport, water quality, and ecology.

Evaluating the performance of turbulence closure models for tidal stream resource characterization

Harvesting tidal stream energy from the ocean for electricity generation has been considered as an energy resource alternative to fossil fuels for mitigating the negative impact of climate change and enhancing energy security and coastal resilience. Numerical models have been used extensively to characterize and assess tidal resources at potential tidal energy development sites. Turbulence plays an important role in site selection and tidal turbine farm deployment. However, most of the numerical modeling studies for tidal energy resource characterization do not include turbulence characteristics because of the limitation of Reynolds averaged Navier–Stokes coastal ocean model in resolving the inertial sub-range turbulence scales. However, studies also demonstrated that turbulence properties, such as turbulence intensity and turbulence kinetic energy, simulated by the coastal ocean models based on turbulence closures can be useful in assisting tidal resource characterization at tidal energy sites. In this study, we evaluated four General Ocean Turbulence Model (GOTM) turbulence closure models implemented in a tidal hydrodynamic model –Finite Volume Community Ocean Model (FVCOM) to characterize the tidal energy resource in the Western Passage, Maine, USA – a top ranked tidal energy site. The four turbulence closure models used in this analysis are k–kl (Mellor–Yamada Level 2.5), k-ε, k–ω, and a generic model. Model sensitivities showed that the MY2.5 model performed the best in comparison with the field measurements. In particular, the simulated time series of turbulence intensity and kinetic energy matched the observed data very well in the Western Passage. Detailed analysis was conducted to characterize turbulence properties on the horizontal plane and at selective cross-sections. This study demonstrated that turbulence properties simulated by a coastal ocean model, along with tidal hydrodynamic properties, can be very informative for tidal energy resource characterization and project site selection, as recommended by the International Electrotechnical Commission (IEC) technical specifications (IEC TS 62600-201).

Two-dimensional hydrodynamic tidal model for the coastal zone of Jeddah, eastern coast of the Red Sea

Two-dimensional hydrodynamic tidal model for the coastal zone of Jeddah, eastern coast of the Red Sea

Tidal stream energy resource characterization in the Salish Sea

The Salish Sea, a large estuary on the Pacific Northwest coast, represents a great tidal stream resource because of its strong tidal currents in many tidal channels. However, the tidal energy resource in the Salish Sea has not been systematically characterized. This paper presents a modeling study conducted to characterize the tidal energy resource in the Salish Sea based on a high-resolution tidal hydrodynamic model, which was validated using data derived from 10 tide gauges and 132 current stations. A total of 16 tidal channels with strong currents were identified as hotspots for potential tidal energy development in the Salish Sea. Probability distributions and exceedance of the cross-channel average velocity were calculated at all 16 channels based on international standards for tidal energy resource characterization. The tidal energy resource at the 16 hotspots was also characterized using power density distributions and kinetic energy fluxes. The ranking of the kinetic energy fluxes suggested that Admiralty Inlet, Rosario Strait, and Middle Channel are the top three tidal energy hotspots in the Salish Sea. The study demonstrated the need of a high-resolution modeling framework for accurate simulation of tidal currents in large complex estuarine systems, in the context of tidal resource characterization and assessment.

Spatiotemporal Distribution Characteristics of Nutrients in the Drowned Tidal Inlet under the Influence of Tides: A Case Study of Zhanjiang Bay, China.

The tidal dynamics and the characteristics of pollutant migration in the drowned-valley tidal inlet, a typical unit of coastal tidal inlets, are strongly influenced by geomorphological features. Along with the development of society and the economy, the hydrodynamic and water quality environment of the tidal inlet is also becoming more disturbed by human activities, such as reclamation of the sea and the construction of large bridges. In this study, a typical drowned-valley tidal inlet, Zhanjiang Bay (ZJB), was selected for the establishment of a model via coupling of a tidal hydrodynamic model and water quality numerical model. This model can be used to simulate the migration and diffusion of pollutants in ZJB. The spatial and temporal variation processes of water quality factors of the bay under the influence of special geomorphic units was simulated at the tidal-inlet entrance, the flood/ebb tidal delta, and the tidal basin. The results show that ZJB has strong tidal currents that are significantly affected by the terrain. Under the influence of the terrain and tidal currents, the phosphorus and nitrogen concentration at the flood-tide and ebb-tide moments showed obvious temporal and spatial differences in the ebb-tide delta, tidal-inlet entrance, flood-tide delta, and tidal basin. In this study, we analyzed the response mechanism of the water quality environment to the drowned-valley tidal inlet, and this can provide theoretical guidance and a basis for decision-making toward protecting the ecology and water security of ZJB.

The Characteristics and Mechanism of Changes in the Marine Environmental Capacity of the Estuaries of Haizhou Bay in Northern Jiangsu from 2006 to 2016

To calculate the environmental capacity of the estuaries of Haizhou Bay in northern Jiangsu, China in 2006 and 2016, this study employed the share ratio approach and established a tidal hydrodynamic model and a water quality diffusion model by the Delft 3D software to perform the numerical simulation. The article compared the environmental capacity in 2006 and 2016, and analyzed the changes between these years. The scenario analysis method was used to explore the influence of factors on the environmental capacity and quantify the contribution of each influencing factor. The results show that the theoretical environmental capacity was reduced by 32.718 tons/day (28.56%) from 114.571 tons/day in 2006 to 81.853 tons/day in 2016. The remaining environmental capacity was reduced by 6.955 tons/day (56.92%) from 12.219 tons/day in 2006 to 5.264 tons/day in 2016. The changes in topography and the amount of runoff into the ocean through the estuaries of Haizhou Bay between 2006 and 2016 reduced the total environmental capacity of the estuaries by an influence ratio of 0.363:0.637. The study will provide the management of the marine environment of Haizhou Bay with information to control the aggregate pollutants flowing into the ocean and support the social and economic sustainable development of Haizhou Bay.

The hydrodynamics of the Bons Sinais Estuary: The value of simple hydrodynamic tidal models in understanding circulation in estuaries of central Mozambique

The Bons Sinais Estuary, located in the central Mozambique, with the highest tidal range in the Western Indian Ocean, is shallow (∼10m), long (∼28km) and receives freshwater only during the wet season. These characteristics give the Estuary distinctive hydrodynamics and ecological features. Current measurements and longitudinal CTD profiling were carried out during dry season, July 2011 and November 2012, and wet season, February 2012 and March 2013. The Estuary is partially to well-mixed most of the time, with Simpson Number (Si) ≤0.5. One-D, depth and width integrated, tidal hydrodynamic model, forced by the modelled tides at the mouth, was applied to understand the major mechanisms governing the estuarine dynamics. Barotropic forcing dominated the baroclinic pressure gradient forcing and the currents were found to be mostly tidal driven. Accordingly, the hydrodynamic model described the observed current velocities well in the dry season (R2≈0.95) and to a lesser degree in the wet season (R2≈0.80). The remaining 5%–20% may be attributed to other hydrodynamic forcing that were not captured in the tidal model, requiring further investigation at higher temporal and spatial scales to fully characterize the system dynamics. These may include the identified baroclinic forcing from freshwater inputs and the influence of the complex geometry at the study site. The initial hydrodynamic field study and simple modelling approach that was applied may inform studies of higher-order processes and management tools at the Bons Sinais Estuary, and similar systems (e.g. sediment dynamics and accommodation space, and diagnostic models), and the result can contribute to understanding the drivers of longer-term ecological and geomorphological dynamics of the estuary.

Numerical Modelling of Waves and Surge from Cyclone Mekunu (May 2018) in the Arabian Sea

Natural hazards like cyclones cause significant loss of life and damage to properties, ecosystems and marine structures and facilities. Numerical modelling of cyclones is carried out for deriving robust design conditions for coastal and marine structures and facilities. Cyclone modelling results are also used for emergency planning and decision-making to estimate potential loss of life, damage to properties and marine facilities and to develop rescue and mitigation measures and plan clean-up operations. Royal HaskoningDHV (RHDHV) has set up regional tidal hydrodynamic and wave transformation models covering the Arabian Sea to address the above issues. Cyclone Mekunu is relatively new (May 2018). A quick literature search by Royal HaskoningDHV has suggested that numerical modelling results of waves and surge on Cyclone Mekunu are hardly available in the public domain. Therefore, this paper has concentrated on this event to illustrate the use of numerical modelling to simulate waves and surge generated by cyclones. The MIKE21 model of DHI was used in the study. Sample results of waves and surge from the modelling study are presented in this paper for illustration purposes. Structural design considerations and cyclone risk reduction measures are also provided. The model could be used to simulate any cyclone generated anywhere within the Arabian Sea. The methodology described in this paper for modelling cyclone waves and surge in the Arabian Sea could also be applied to simulate cyclones at other sites around the world. The paper provides valuable information to the researchers and practitioners of the region on this relatively new event.

A Tidal Hydrodynamic Model for Cook Inlet, Alaska, to Support Tidal Energy Resource Characterization

Cook Inlet in Alaska has been identified as a prime site in the U.S. for potential tidal energy development, because of its enormous tidal power potential that accounts for nearly one-third of the national total. As one important step to facilitate tidal energy development, a tidal hydrodynamic model based on the unstructured-grid, finite-volume community ocean model (FVCOM) was developed for Cook Inlet to characterize the tidal stream energy resource. The model has a grid resolution that varies from about 1000 m at the open boundary to 100–300 m inside the Inlet. Extensive model validation was achieved by comparing model predictions with field observations for tidal elevation and velocity at various locations in Cook Inlet. The error statistics confirmed the model performs reasonably well in capturing the tidal dynamics in the system, e.g., R2 > 0.98 for tidal elevation and generally > 0.9 for velocity. Model results suggest that tides in Cook Inlet evolve from progressive waves at the entrance to standing waves at the upper Inlet, and that semi-diurnal tidal constituents are amplified more rapidly than diurnal constituents. The model output was used to identify hotspots that have high energy potential and warrant additional velocity and turbulence measurements such as East Foreland, where averaged power density exceeds 5 kw/m2. Lastly, a tidal energy extraction simulation was conducted for a hypothetical turbine farm configuration at the Forelands cross section to evaluate tidal energy extraction and resulting changes in far-field hydrodynamics.

Study of the Tide and Tidal Currents in the Bay of Bengal Based on Refined Simulations

Wan, W.; Feng, X.; Liu, Q.; Yin, B.; Yang, D., and Gao, G., 2019. Study of the tide and tidal currents in the Bay of Bengal based on refined simulations. Journal of Coastal Research, 35(1), 33–40. Coconut Creek (Florida), ISSN 0749-0208.A high-resolution, two-dimensional, hydrodynamic tidal model of the Bay of Bengal was developed using the Advanced Circulation (ADCIRC) Model to study the tide and tidal currents in the Bay of Bengal. The simulations conformed to the observations, and because of the use of a high-resolution, triangular grid, characteristics of the tide and tidal currents were computed more accurately than in previous studies. The results indicated that tides in most of the Bay of Bengal are semidiurnal, whereas those in the seas SE of Sri Lanka are mixed and predominately semidiurnal. There are two degenerate amphidromic points, one at the NE end of the head of the bay and the other at SE Sri Lanka, whereas there is an amphidromic point at the seas SE of Sri Lanka. The form of the M2 tidal current is rotary on the continental shelf and rectilinear in coastal areas and seas distant from the continental shelf. Four major tidal currents are in a NW–SE direction, in the western part of the head of the bay, and in a NE–SW direction in river estuary areas. Results from the eastern part are the opposite. The amplitudes and major axes of four tides and tidal currents increase upon entering the head of the bay, whereas those of the M2 tide are the largest.

Hydrodynamic Tidal Model of the Persian Gulf Based on Spatially Variable Bed Friction Coefficient

The aim of this study is to develop a two-dimensional hydrodynamic tidal model for the Persian Gulf (PG2017) using 2D-MIKE21 software. The advantages of present study is accounting for the spatial variation of bed friction coefficient besides a precise bathymetry together with a 23-year of combined records of satellite altimetry data. We found that the bed friction coefficient has a significant effect on sea level changes in the region under our modeling consideration. Since the tidal behavior in the northern part of the Qeshm Island is significantly different from the other parts of the Persian Gulf, to present a more accurate hydrodynamic tidal model, the Gulf is divided into two regions where the bed friction coefficient is modeled separately for each region. The root mean square value of the differences between the amplitude of dominant constituents; M2, S2, K1, and O1 derived from the PG2017 model and that of 98 altimetry and coastal tide gauge stations are respectively equal to 1.6, 1.9, 2.8, and 1.3 cm. Moreover, comparing the PG2017 model efficiency with the FES2014, OSU12, EOT11a, DTU10, and Admiralty models shows that the PG2017 model has an improvement of 22.1%, 47.2%, 43.2%, 44.2%, and 57.6% in terms of relative error, respectively.

Numerical modelling of tsunami in the Makran Subduction Zone – A case study on the 1945 event

ABSTRACTTsunamis cause significant loss of life and damage to properties, ecosystems and marine structures and facilities. Tsunami modelling results are used for deriving robust design conditions for coastal and marine structures and facilities. The results are also used for emergency planning and decision-making to estimate the potential loss of life, damage to properties and marine facilities and to develop rescue and mitigation measures and plan clean-up operations. Royal HaskoningDHV (RHDHV) has set up a regional tidal hydrodynamic model covering the Northern Arabian Sea to provide data to address the above issues. The 1945 earthquake in the Makran Subduction Zone generated a tsunami along the coastlines of Iran and Pakistan killing as many as 4,000 people. Furthermore, the tsunami caused catastrophic damage to properties and other coastal facilities. The tsunami modelling in the present study was carried out for this 1945 event. The MIKE21 Flow Model FM of DHI was used to simulate this tsunami event and sample results from the modelling are presented in this paper for illustration purposes. Structural design considerations and tsunami risk reduction measures are also discussed. The model could be used to simulate any tsunami generated within the Arabian Sea. The methodology described in this paper for modelling the 1945 tsunami in the Makran Subduction Zone could also be applied to simulate this type of events at other sites around the world.

Numerical modelling of waves and surge from Cyclone Chapala (2015) in the Arabian Sea

Cyclones cause significant loss of life and damage to properties, ecosystems and marine structures and facilities. Cyclone modelling results are used for deriving robust design conditions for coastal and marine structures and facilities. The results are also used for emergency planning and decision-making to estimate potential loss of life, damage to properties and marine facilities and to develop rescue and mitigation measures and plan clean-up operations. Royal HaskoningDHV (hereafter RHDHV) has set up regional tidal hydrodynamic and wave models covering the Arabian Sea to provide data to address the above issues. Over the course of a number of studies a total of 30 major cyclones have been identified in the Arabian Sea since 1945. Cyclone Chapala (28 October – 4 November 2015) was found to be the second strongest cyclone event since 1945 (the strongest being Cyclone Gonu in 2007). As less information is available on Cyclone Chapala, this paper has concentrated on this event to illustrate the use of numerical modelling to simulate waves and surge generated by cyclones. The MIKE21 model suite has been used to investigate this cyclone and sample results from the wave and surge modelling are presented in this paper for illustration purposes. The models could be used to simulate any cyclone generated within the Arabian Sea. The methodology described in this paper for modelling waves and surge in the Arabian Sea could also be applied to simulate this type of events at other sites around the world.

Cyclone hazards in the Arabian sea–A numerical modelling case study of Cyclone Nilofar

AbstractCyclones cause significant loss of life and damage to properties, ecosystems and marine facilities. To address such issues, Royal HaskoningDHV (RHDHV) has developed regional tidal hydrodynamic and wave models covering the Northern Arabian Sea. A total of 29 major cyclones were identified in the Arabian Sea since 1945. However, as less information is available on Cyclone Nilofar (2014), this paper has concentrated on this event to illustrate the use of numerical modelling to simulate waves and surge generated by cyclones. Sample results from the modelling study are presented in this paper. The methodology described in this paper for modelling cyclone waves and surges in the Arabian Sea could be applied to simulate such natural hazards at other sites around the world.

Improving Modeling of Tides on the Continental Shelf off the West Coast of India

ABSTRACT Testut, L. and Unnikrishnan, A.S., 2016. Improving modeling of tides on the continental shelf off the west coast of India. Global tidal solutions are sometimes inaccurate in coastal regions. This is particularly true in some regions of the northern Indian Ocean, which are characterized by wide continental shelves and large tidal ranges. We show that these global solutions are inaccurate on the shelf region off Mumbai, off the west coast of India. In this region, the shelf is very wide, and it opens into the Gulf of Khambhat, where large tides are observed. Moreover, in regions of large semidiurnal tides in the Bay of Bengal, such as the head Bay, Gulf of Martaban, etc., global tidal solutions are not accurate. In the present work, we focus on the shelf region off the west coast of India. We used a new approach in developing a high-resolution hydrodynamic tidal model for the inner shelf region (8°N to 22°N). The open boundary of the model is aligned to the altimetry tracks, which allowed us to pre...

Hybrid ANN–GA model for predicting turbidity and chlorophyll-a concentrations

The transport and fate of admixtures at coastal zones are driven, or at least modulated, by currents. In particular, in tide-dominated areas due to higher near-bottom shear stress at strong currents, sediment concentration and turbidity are expected to be at maximum during spring tide, while algal growth rate likely is peaking up at slack currents during neap tide. Varying weather and atmospheric conditions might modulate the said dependencies, but the water quality pattern still is expected to follow the dominant tidal cycle. As tidal cycling could be predicted well ahead, there is a possibility to use water quality and hydrodynamic high-resolution data to learn past dependencies, and then use tidal hydrodynamic model for nowcasting and forecasting of selected water quality parameters.This paper develops data driven models for nowcasting and forecasting turbidity and chlorophyll-a using Artificial Neural Network (ANN) combined with Genetic Algorithm (GA). The use of GA aims to automate and enhance ANN designing process. The training of the ANN model is done by constructing input–output mapping, where hydrodynamic parameters act as an input for the network, while turbidity and chlorophyll-a are the corresponding outputs (desired target). Afterward, the prediction is carried out only by employing computed water surface elevation as an input for the trained ANN model. The proposed data driven model has successfully revealed complex relationships and utilized its experiential knowledge acquired from the training process for facilitating the subsequent use of the data driven model to yield an accurate prediction.

Spatial variability of surficial sediments on the northern shelf of the Alboran Sea: the effects of hydrodynamic forcing and supply of sediment by rivers

Alboran Sea, shelf, surficial sediments, backscatter, hydrodynamic modelRecent surficial sedimentary processes led by hydrodynamic forcing and by laterally variable fluvial supplies are investigated in the eastern shelf of the northern Alboran Sea margin. This study highlights the high spatial variability of sedimentary processes in a relatively small area with an abrupt physiography and subjected to a seasonal and strongly fluctuating climate. We correlate seafloor sediments with backscatter distributions extracted from multibeam echo sounder data; in addition, a wind-forced tidal hydrodynamic model provides flow velocity and derived bed shear-stress values under contrasting wind conditions. In the study area, the relative proportions of gravel and muds within a dominantly sandy substratum control surficial backscatter intensities. Across-shelf, the only consistent surficial pattern is depicted by a high backscatter intensity, gravelly sandy infralittoral zone, which is subjected to periodic storm activity. Seaward, significant along-shelf changes of the sediment cover and backscatter intensities appear to be controlled at large by a major physiographic feature (the Carchuna Canyon) which separates a western shelf mostly covered by fluvially-derived sediments and an eastern current-controlled shelf. At a finer scale, the seafloor backscatter response outlines three main shelf environments: storm-dominated, mixed and fluvially-dominated. We found that storm-dominated settings are associated with maximum flow velocities and bed shear stress (during both easterlies and westerlies dominance). The distribution of mixed and fluvially-dominated environments is more complex, as it is related to the interaction of less intense hydrodynamic conditions with laterally changing fluvial supplies from mountainous, short rivers and streams. As a consequence, the surficial sedimentary fingerprints of the two most important regional rivers (Guadalfeo and Adra) are significantly different.

Critical perspectives on the evaluation and optimization of complex numerical models of estuary hydrodynamics and sediment dynamics

AbstractNumerical hydrodynamic and sediment transport models provide a means of extending inferences from direct observation and for advancing our understanding of estuarine processes. However, their parametric complexity invites questions concerning the extent to which model output can be assessed with respect to data. This paper examines the basis for evaluating the performance of complex hydrodynamic and sediment transport models, with reference to a case study of a muddy meso‐tidal estuary. Sophisticated and computationally‐intensive models should be evaluated using robust objective functions, but conventional measures of fit and model efficiency invoke restrictive assumptions about the nature of the errors. Furthermore, they offer little insight into causes of poor performance. Optimization of tidal hydrodynamic models can usefully combine conventional performance measures with harmonic analysis of modelled shallow water tidal constituents that are diagnostic of the interactions between tidal propagation, bathymetry and bottom friction. Models with similar efficiencies can thus be distinguished and likely sources of error pinpointed. Hydrodynamic models have a predictive power that is rooted in a more‐or‐less complete representation of the physical processes and boundary conditions that are well‐constrained with respect to data. In contrast, fine sediment models rely on a less complete conceptualization of a broader set of processes and, crucially, have a parametric complexity that is unmatched by the quantity and quality of observational data. Their performance as measured by conventional objective functions is weaker and it is important to match the structural complexity of model errors with analyses that can localize the scales and times of poor performance. Wavelet analysis is potentially useful here as a means of identifying aspects of the model that need improvement. The context in which such models are deployed is also important. Used heuristically, what might otherwise be dismissed as weak models can still provide mechanistic support for empirically‐derived inferences concerning specific aspects of system behaviour. Copyright © 2009 John Wiley & Sons, Ltd.

Oil Spill Visualization Based on the Numeric Simulation of Tidal Current

This paper proposes an approach to implement the 3D visualization of oil spill based on tidal hydrodynamic model. It simulates tidal current of M2 component tide in Jiaozhou Bay. The simulation results conform to the tidal theory and probably conform to the flow measurement report of crude oil pier Phase III at Qingdao Harbor. Based on tidal current and eye-point related adaptive ocean surface mesh model, by analyzing the drift and diffusion mathematical models of oil spill on the sea, the dynamic visualization of drift and diffusion course of oil on the sea were implemented, the visualization result is satisfactory.