Two-dimensional Hydrodynamic Model Research Articles

Two-Dimensional Hydrodynamic Simulation of the Effect of Stormwater Inlet Blockage on Urban Waterlogging

The drainage capacity of stormwater inlets, which serve as the connection between the surface and the underground drainage system, directly affects surface runoff and the drainage capacity of underground drainage systems. However, in reality, stormwater inlets are often blocked due to the accumulation of leaves, human waste disposal and other factors, resulting in a greatly reduced drainage capacity of the drainage network and, in turn, urban waterlogging disasters. In view of the problem of stormwater inlet blockage, employing a typical waterlogging point in the Lianjiang Middle Road area of Fuzhou city as the research object, the stormwater inlet equivalent drainage method was adopted in this paper to characterize the drainage capacity of the pipe network and enable the control of the stormwater inlet blockage state. Coupled with the stormwater inlet drainage equation, an improved ITF-FLOOD two-dimensional hydrodynamic model was constructed, and the influence of stormwater inlet blockage on urban waterlogging under different rainfall return periods was simulated and analyzed. With increasing rainfall return period, the influences of stormwater inlet blockage on both the maximum area and the depth of accumulated water in the study area gradually decreased compared with those of a nonblocked stormwater inlet, and the growth proportions decreased from 43.35% and 34.58% under the 1-year rainfall scenario to 3.34% and 9.76% under the 50-year rainfall scenario, respectively. However, in terms of the change in the accumulated water level, stormwater inlet blockage will cause an increase, and the influence will always be significant. Overall, stormwater inlet blockage aggravated the waterlogging risk and the extent of waterlogging. Therefore, the results provided a reference for the construction of an urban waterlogging model and have certain guiding significance for waterlogging prevention and control in the study area prone to stormwater inlet blockage.

A Simple Approach to Simulate Logjams in Two-Dimensional Hydrodynamic Models

A Simple Approach to Simulate Logjams in Two-Dimensional Hydrodynamic Models

Hydrodynamical simulations favour a pure deflagration origin of the near-chandrasekhar mass supernova remnant 3C 397

ABSTRACT Suzaku X-ray observations of the Type Ia supernova remnant (SNR) 3C 397 discovered exceptionally high mass ratios of Mn/Fe, Ni/Fe, and Cr/Fe, consistent with a near MCh progenitor white dwarf (WD). The Suzaku observations have established 3C 397 as our best candidate for a near-MCh SNR Ia, and opened the way to address additional outstanding questions about the origin and explosion mechanism of these transients. In particular, subsequent XMM–Newton observations revealed an unusually clumpy distribution of iron group elemental (IGE) abundances within the ejecta of 3C 397. In this paper, we undertake a suite of two-dimensional hydrodynamical models, varying both the explosion mechanism – either deflagration-to-detonation (DDT), or pure deflagration – WD progenitors, and WD progenitor metallicity, and analyse their detailed nucleosynthetic abundances and associated clumping. We find that pure deflagrations naturally give rise to clumpy distributions of neutronized species concentrated towards the outer limb of the remnant and confirm DDTs have smoothly structured ejecta with a central concentration of neutronization. Our findings indicate that 3C 397 was most likely a pure deflagration of a high central density WD. We discuss a range of implications of these findings for the broader SN Ia progenitor problem.

Simulating sea level extremes from synthetic low-pressure systems

Abstract. In this article we present a method for numerical simulations of extreme sea levels using synthetic low-pressure systems as atmospheric forcing. Our simulations can be considered to be estimates of the high sea levels that may be reached when a low-pressure system of high intensity and optimal track passes the studied region. We test the method using sites located along the Baltic Sea coast and simulate synthetic cyclones with various tracks. To model the effects of the cyclone properties on sea level, we simulate internal Baltic Sea water level variations with a numerical two-dimensional hydrodynamic model, forced by an ensemble of time-dependent wind and air-pressure fields from synthetic cyclones. The storm surges caused by the synthetic cyclones come on top of the mean water level of the Baltic Sea, for which we used a fixed upper estimate of 100 cm. We find high extremes in the northern Bothnian Bay and in the eastern Gulf of Finland, where the sea level extreme due to the synthetic cyclone reaches up to 3.5 m. In the event that the mean water level of the Baltic Sea has a maximal value (1 m) during the cyclone, the highest sea levels of 4.5 m could thus be reached. We find our method to be suitable for use in further studies of sea level extremes.

Short-Term Early Warning Method for Algal Bloom Risk Based on a Neural Network and a Two-Dimensional Hydrodynamic Model

Short-Term Early Warning Method for Algal Bloom Risk Based on a Neural Network and a Two-Dimensional Hydrodynamic Model

Flood Propagation Characteristics in a Plain Lake: The Role of Multiple River Interactions

Plain lakes play a crucial role in the hydrological cycle of a watershed, but their interactions with adjacent rivers and downstream water bodies can create complex river–lake relationships, often leading to frequent flooding disasters. Taking Poyang Lake as an example, this paper delves into its interaction with the Yangtze River, revealing the spatiotemporal patterns of flood propagation within the lake and its impact on surrounding flood control measures. The aim is to provide insights for flood management in similar environments worldwide. This study employs a comprehensive approach combining hydrological statistical analysis and two-dimensional hydrodynamic modeling, based on extensive hydrological, topographic, and socio-economic data. The results indicate that the annual maximum outflow from Poyang Lake is primarily controlled by floods within the watershed, while the highest annual lake water level is predominantly influenced by floods from the Yangtze River. The peak discharge typically reaches the lake outlet within 48 h, with the peak water level taking slightly longer at 54 h. However, water storage in the lake can shorten the time that it takes for the peak discharge to arrive. When converging with floods from the Yangtze River, the peak water level may be delayed by up to 10 days, due to the top-supporting interaction. Furthermore, floods from the “Five Rivers” propagate differently within the lake, affecting various lake regions to differing degrees. Notably, floods from the Fu River cause the most significant rise in the lake’s water level under the same flow rate. The top-supporting effect from the Yangtze River also significantly impacts the water surface slope of Poyang Lake. When the Yangtze River flood discharge significantly exceeds that of the “Five Rivers” (i.e., when the top-supporting intensity value, f, exceeds four), the lake surface becomes as flat as a reservoir. During major floods in the watershed, the water level difference in the lake can increase dramatically, potentially creating a “dynamic storage capacity” of up to 840 million cubic meters.

Analysis of the water temperature and quality characteristics of the Daheiting Reservoir based on coupled hydrology–hydrodynamic–water quality simulations

To analyse the influence of nonpoint source pollution on the water quality in the Daheiting Reservoir, based on measured hydrological and water quality data, a coupled hydrological model for the Panjiakou-Daheiting interval basin and a two-dimensional vertical hydrodynamic and water quality model for the Daheiting Reservoir were constructed. The water quantity and water quality output results of the upstream hydrological model (Soil and Water Assessment Tool, SWAT) were input into the reservoir hydrodynamic-water quality model (CE-QUAL-W2) as boundary conditions. The annual distribution of pollutants in the reservoir was simulated and analysed. The results showed that nutrients such as nitrate nitrogen and phosphate in the reservoir area were stratified, and there were seasonal differences due to the water temperature, dissolved oxygen and upstream inflow. After lowering upstream pollution emissions, the water quality in the reservoir was improved significantly, and compared to that of reducing point source pollution, the effect of reducing nonpoint source pollution is more obvious.

Relationship between vorticity near the surface and a long-lived vortex raised above it

The ability to predict the behavior of vortices is valuable for solving various scientific problems. One such problem is the evolution of tornado-like vortices near the surface and their connection with the original vortex located at a certain height above the surface. This article considers a two-dimensional axisymmetric hydrodynamic model in which the initial vorticity is maintained by an external force. Using the model, the influence of external force and temperature field on the evolution of vorticity near the surface is studied. It is shown that at relatively short times, the behavior of the resulting tornado-like vortices near the surface is universal and weakly depends on the external force and temperature field. However, over time, this influence becomes significant. It is shown that, depending on the presence of an anomaly in the temperature distribution, the vortex formed at the surface can exist for a long time.

Managing photon flux in a miniaturized photoionization detector

Miniaturized photoionization detectors (PIDs) are used in conjunction with gas chromatography systems to detect volatile compounds in gases by collecting the current from the photoionized gas analytes. PIDs should be inexpensive and compatible with a wide range of analyte species. One such PID is based on the formation of a He plasma in a dielectric barrier discharge (DBD), which generates vacuum UV (VUV) photons from excited states of He to photoionize gas analytes. There are several design parameters that can be leveraged to increase the ionizing photon flux to gas analytes to increase the sensitivity of the PID. To that end, the methods to maximize the photon flux from a pulsed He plasma in a DBD-PID were investigated using a two-dimensional plasma hydrodynamics model. The ionizing photon flux originated from the resonance states of helium, He(3P) and He(21P), and from the dimer excimer He2*. While the photon flux from the resonant states was modulated over the voltage pulse, the photon flux from He2* persisted long after the voltage pulse passed. Several geometrical optimizations were investigated, such as using an array of pointed electrodes. However, increasing the capacitance of the dielectric enclosing the plasma chamber had the largest effect on increasing the VUV photon fluence to gas analytes.

Water Quality of Lake Erhai in Southwest China and Its Projected Status in the near Future

The water quality of Lake Erhai has deteriorated in recent decades due to socioeconomic development in the lake basin. After the massive implementation of water environmental protection measures in Lake Erhai in 2016, the trend of water quality deterioration has been curbed and the intensity and frequency of algal blooms has decreased. However, water quality monitoring data show that pollutant concentrations in Lake Erhai still exceed acceptable values, and there is a risk of water quality standard limits being further exceeded in the future. Therefore, it is urgent to systematically study the variability characteristics of water quality in Lake Erhai to provide practical methods to predict the future evolution of water quality. Based on water quality monitoring data from 2009 to 2019, the current water quality characteristics of Lake Erhai were analyzed, and a two-dimensional hydrodynamic and water quality mathematical model was built to predict the water quality in 2025. The results showed that the total phosphorus (TP) concentration declined after 2016, mainly due to the significant reduction of TP entering the lake due to pollution interception. However, the concentrations of the potassium permanganate index (CODMn) and total nitrogen (TN) increased after 2016, demonstrating that the pollution control measures have had little effect on the improvement of CODMn and TN. The spatial and temporal distribution of pollutants showed that the water quality in winter and spring was better than in summer and autumn, and the water quality in the southern lake was better than in the northern lake. This analysis indicates that non-point source pollution remains the main source of pollution in Lake Erhai, and that rainfall is the main driving force of pollutants exceeding the water quality standard. According to the water quality predictions, without additional pollution control measures, pollutant concentrations in Lake Erhai will exceed the Class II water quality standard by 2025. This study analyzes the water quality characteristics, predicts the direction of future water quality changes, and provides a theoretical basis for the future water quality protection of Lake Erhai.

Study of the hydrologic and hydrodynamic coupling model (HHDCM) and application in urban extreme flood systems

Based on urban flood hydrology processes and hydrodynamic principles, the stormwater management model (SWMM) was improved upon. The coupling and implementation methods of the SWMM and two-dimensional hydrodynamic model are proposed. The improved SWMM was coupled with the hydrodynamic model both from the vertical and horizontal directions. The hydrology and hydrodynamic coupling model (HHDCM) was constructed and verified by using extreme rainstorm data. Taking July.20 extreme rainstorms (from July 17 to July 20, 2021, i.e., July.20 extreme rainstorm) in Zhengzhou city, Henan Province, China, as an example and using the HHDCM model, the flood disaster caused by July.20 extreme rainstorm was simulated. Based on the simulation results, an inundation distribution map was drawn for the urban area. A comparison between the simulated and measured results reveals that the maximum relative error in the simulated results is 12.5%. Therefore, the HHDCM model proposed in this paper has desirable accuracy and reliability for simulating extreme urban rainstorms and flood disasters.

Hydrodynamic response of a large river–lake system under flow regulation: A numerical study of Hongze lake

The hydrodynamic processes in large river–lake systems and their responses to flow regulation represent regionally unique and highly significant issues. This study presents the implementation, validation and application of a two-dimensional hydrodynamic model to a system comprising a section of the Huai River and Hongze Lake, China. The validated model enabled the identification of hydrodynamic characteristics by analysing the flow patterns under the influence of the local flow regulation. Effective flow regulation measures during flood period reduced the retention time of floodwater in the lake and contributed to a low-velocity current field in the northern part of the river–lake system. Throughout the non-flood period, a distinctive flow pattern emerged due to persistent easterly winds, resulting in a dual circulation pattern in the interconnected region between the northern and central segments of the system. The investigation of flow patterns revealed the creation of stagnant water zones in the northern sector of Hongze Lake. Distributing a substantial portion of outflow discharge to the Erhezha gate could lead to an expansion of the flood passing area by scenario analysis. Simultaneously, implementing intermittent control over the Erhezha gate drainage effectively heightened the current velocities in the stagnant water zone. The deliberate allocation of outflow discharge has a substantial impact on the flow dynamics within a vast river–lake system during the flood season, which carries significant research potential in enhancing the local water self-purification capacity and water quality.

Construction and validation of C3F8 electron impact and heavy particle reaction scheme for modeling plasma discharges

This work presents the results of developing a set of electronic and chemical reactions for a plasma discharge in octafluoropropane (C3F8). Electronic reactions were obtained using the most relevant set of cross sections at the moment, taking into account experimentally known dissociation and ionization channels. Based on the dissociation products obtained during electronic reactions, a set of chemical reactions was adapted by analogy with the C4F8 reaction scheme from the literature. Next, the resulting complete set of reactions was tested against published experimental data on the concentration of electrons, negative ions, and electronegativity in a capacitive plasma discharge at different gas pressures and discharge input powers. For this purpose, a one-dimensional hydrodynamic drift-diffusion model was used. Reasonable agreement was obtained between the model and experimental data on electronegativity. Eventually, the resulting set of reactions was adapted for a two-dimensional hydrodynamic drift-diffusion model of an ICP discharge. The results of the calculations are two-dimensional distributions of radicals and ions, radical and ion composition of fluxes onto the substrate under conditions typical for industrial reactors.

Analyzing urban form influence on pluvial flooding via numerical experiments using random slices of actual city data

Diversified urban forms resulting from urbanization is a pivotal factor influencing urban pluvial flooding. A systematic analysis of the influence of urban forms on the surface flow of urban pluvial flooding was conducted. We obtained 1,000 sets of 1 km × 1 km urban form data that met quality control requirements using a random slicing method, based on actual urban underlying surface data, with nine spatial characteristic parameters used to tabulate the urban forms. A two-dimensional hydrodynamic model was employed to simulate the surface flow of the urban flood inundation. Scenario simulations and analyses were conducted for three slopes (1, 2, and 3 %) and three rainfall scenarios (with return periods of 5, 20, and 100 yr). The results showcased that, in different scenarios, the urban forms had some impact on urban flow variables and their processes, although the impact patterns were relatively complex. Regarding the process of urban flow variables, the urban forms affected the rate of decline in flood variables during the descending stage. The correlation analysis highlighted that road density, road area proportion, spread contact among various patch types, and uniformity across patches have important impacts on the maximum flood volume and maximum inundated area. The research results could help deepen our understanding of the formation mechanisms of urban pluvial flooding, flood-sensitive urban design, and flood risk management.

Effects of urban drainage inlet layout on surface flood dynamics and discharge

Drainage inlets, the primary conduits for surface floodwater into underground facilities, significantly influence the performance of a drainage system. This study employs a two-dimensional hydrodynamic model to investigate how drainage inlet distribution affects urban flood dynamics and drainage flow discharge. We first validate the model with dataset obtained in a dedicated experiment observing urban surface and drainage flows. We identified two common layouts of drainage inlets, namely straight-line distribution (SLD) and surround type distribution (STD), and based on the two layouts, we simulated detailed surface flood dynamics and drainage discharge under various urban flood conditions and inlet spacing scenarios. The results indicate that SLD exhibits higher drainage capacity in shorter time and greater total drainage volume under urban peripheral flood condition, while STD consistently outperforms in draining urban surface flooding induced by intense rainfall. It is also found that inlet spacing plays a crucial role in affecting drainage efficiency. To be specific, both layouts with medium spacing (l0 = 0.53 for SLD and 0.93 for STD) near flood-prone areas perform better when a sudden-onset peripheral flooding occurred; however, in the case of rainfall-induced flooding, maximizing inlet spacing and strategically distributing them across urban streets proves to be a more effective strategy for draining floodwater. Individual inlets near the ends of SLD and inlets at far-corners of STD shoulder higher drainage loads. This study provides valuable insights for optimizing inlet layout strategies under various urban flood conditions and improving floodwater collection.

A two-dimensional hydrodynamic urban flood model based on equivalent drainage of manholes

Abstract Numerical simulations of urban flood events are of great significance in flood control and disaster reduction. An important part of these numerical investigations concerns drainage, which is crucial to the accuracy of the simulation results. To overcome the difficulty of obtaining underground pipe network data and improve the traditional equivalent drainage simulation method, an equivalent drainage model based on manholes is proposed, to simulate urban flooding based on a two-dimensional hydrodynamic model. The new model is applied to a classic case and the simulation results are compared with those from the MIKE URBAN model to verify the simulation accuracy of the proposed formulation. The submerged areas given by the two models are compared under different rainfall conditions, with an average relative error of 6%. The differences in water depths at various nodes are statistically analyzed, and the average Nash–Sutcliffe efficiency and average root mean square error are found to be 96% and 0.03 m, respectively. The results of this research provide effective urban flood simulation in areas lacking pipe network data and have important significance for promoting the practical application of refined numerical simulations of urban flooding.

Exploring the Sensitivity of Water Temperature Models for High Dams and Large Reservoirs: A Case Study of the Nuozhadu Reservoir in China

The parameters governing a water temperature model play a pivotal role in determining the uncertainties associated with the model’s outcome. In this study, a two-dimensional (2D) hydrodynamic and water temperature coupling model is constructed, focusing on the Nuozhadu Reservoir situated along the Lancang River. Employing a single-factor analysis approach, the sensitivity of the thermal balance parameters and hydrodynamic parameters in the model is assessed. This study overcomes the shortcomings of previous sensitivity analyses of hydrodynamic parameters in reservoir water temperature models. The findings reveal that the attenuation parameters of light and Beer’s law parameter exhibit minimal sensitivity to the vertical temperature structure. Conversely, radiation parameter A and radiation parameter B exert tenfold disparate influences on the surface and bottom temperatures of the reservoir. Among the hydrodynamic parameters considered, the horizontal viscosity factor shows no sensitivity to the vertical temperature structure, whereas the vertical viscosity factor serves as a crucial determinant, directly influencing the intensity of vertical temperature stratification. An increased vertical viscosity factor promotes heat exchange between the upper and lower water layers, thereby reducing the vertical temperature gradient and weakening stratification. Conversely, diminishing this factor intensifies stratification. Thus, when conducting water temperature simulations in high dams and large reservoirs, careful attention should be given to calibrating vertical viscosity factor.

Changes in Population Exposure to Rainstorm Waterlogging for Different Return Periods in the Xiong’an New Area, China

In the context of global climate change and urban expansion, urban residents are encountering greater rainstorm waterlogging risk. Quantifying population exposure to rainstorms is an important component of rainstorm waterlogging risk assessments. This study utilized a two-dimensional hydrodynamic model to simulate the inundation water depth and inundation area resulting from rainstorms, with return periods of 5, 10, 50, and 100 years, in the Xiong’an New Area, and overlaid the gridded population data in 2017 and in 2035 under SSP2 to assess the change in population exposure. The results show that the average inundation depth and area increase were from 0.11 m and 207.9 km2 to 0.18 m and 667.2 km2 as the rainstorm return period increased from once in 5 years to once in 100 years. The greatest water depths in the main urban areas were mainly located in the low-lying areas along the Daqing River. The total population exposed to rainstorm waterlogging for the 5-, 10-, 50-, and 100-year return periods was 0.31, 0.37, 0.50, and 0.53 million, respectively, in 2017. However, this is projected to rise significantly by 2035 under SSP2, increasing 2–4-fold compared with that in 2017 for the four return periods. Specifically, the projected population exposure is expected to be 0.7, 1.0, 1.8, and 2.0 million, respectively. The longer the return period, the greater the increase in population exposure. The proportion of the population exposed at the 0.05–0.2 m water depth to the total population exposure decreases as the return periods increases, whereas the proportion changes in the opposite direction at the 0.2–0.6 m and >0.6 m depth intervals. Spatially, high-exposure areas are concentrated in densely populated main urban regions in the Xiong’an New Area. In the future, more attention should be paid to densely populated low-lying areas and extreme recurrence rainstorm events for urban flood-risk management to ensure population safety and sustainable urban development.

Two Dimensional Hydrodynamics Model with Evaporation for Coastal Systems

Introduction. The use of two-dimensional (2D) hydrodynamic models is relevant, despite the development of numerical methods of marine hydrodynamics focused on the use of three-dimensional spatial models. This is due to the modelling of hydrodynamic processes in shallow and coastal systems in solving practically important problems of predicting the transport of pollutants in suspended and dissolved forms. Evaporation for the Southern of Russia marine coastal systems (the Azov Sea, the Northern Caspian, etc.), and even more so in the coastal areas of the Red Sea, is a significant factor that affects not only the balance of water masses, but also makes changes in the momentum of the system and the distribution of the velocity vector of the aquatic environment. This effect is significant for coastal currents and shallow-water systems.Materials and Methods. The traditional method of converting the terms of the Navier-Stokes equations containing differentiation by horizontal spatial variables was used, involving the rearrangement of differentiation operations by horizontal spatial coordinates and integration by vertical coordinate when constructing a spatially two-dimensional model of hydrodynamics of marine coastal systems when integrated by vertical coordinate. This made it possible to avoid the appearance of non-physical sources of energy and momentum in the spatially two-dimensional model, which can be essential in traditional 2D models with significant depth differences characteristic of coastal systems. The implementation of the analogue of the law of conservation of the total mechanical energy of the system for the constructed 2D model is investigated.Results. Using the correct transformation of the 3D model (integration of the Navier-Stokes equations and continuity along a vertical coordinate, taking into account evaporation from a free surface), spatially two-dimensional models of hydrodynamics are constructed, for which the basic conservation laws, including mass and total mechanical energy of the system, are fulfilled. The implementation of an analogue of the law of conservation of total mechanical energy for various types of boundary conditions, including at the bottom, is investigated. The evaporation from the free surface is correctly accounted for not only in the continuity equation, but also in the equations of motion taking into account wind and waves.Discussion and Conclusion. 2D model of hydrodynamics has been constructed and studied, taking into account evaporation not only in the mass balance equation (continuity), but also in the Navier-Stokes equations of motion. The proposed model can be used for predictive modelling of hydrophysical processes, including the spread of pollutants in the aquatic environment of coastal systems and shallow reservoirs in relation to marine systems such as the Sea of Azov, the Northern Caspian Sea, coastal areas of the Red Sea, etc. Spatially two-dimensional models of marine hydrodynamics, without replacing three-dimensional models, can serve as a model basis for operational forecasting of situations in coastal systems and shallow-water objects using computing systems with relatively low performance and a moderate amount of RAM (5–10 Tflops, 2–4 TB, respectively).

Dynamic planning method of evacuation route in dam-break flood scenario based on the ACO-GA hybrid algorithm

As the major water storage infrastructure, the failure of a reservoir dam will cause significant losses to people's lives and property. A scientific and reasonable evacuation route is one of the essential measures to reduce casualties. Thus, it is of great significance to realize the dynamic planning of evacuation routes in dam-break flood scenarios to reduce the risk of dam failure. This study employed a physically based mathematical model (Breach model) and a two-dimensional hydrodynamic model to simulate dam-break flood routing. Further, a road network construction method was proposed based on the graph theory and flood routing information. The ant colony optimization algorithm (ACO) was improved by the backtracking, the improved heuristic function, and the elite ants, and the genetic algorithm (GA) was optimized according to the characteristics of flood avoidance route planning. Accordingly, an improved ant colony-genetic optimization hybrid algorithm (ACO-GA) was proposed. Compared with the basic ACO algorithm, the correct rate of simulation results of the ACO-GA hybrid algorithm was improved by 34 %, the average number of iterations was reduced by 18.3 times, and the optimization ability was markedly enhanced. Based on the constructed dam-break flood scenario and the ACO-GA hybrid algorithm, the novel dynamic planning method for evacuation routes in the dam-break flood scenario was proposed. Moreover, this method was applied to a typical water conservancy engineering project, and the planned optimal evacuation routes accurately avoided the flood influence, and the calculation results were reasonable and accurate. The real-time dynamic planning of flood avoidance routes based on flood routing information was realized. This study provides effective guarantee for the emergency transfer of downstream people, which has valuable implications for the theoretical research and engineering practice of reservoir dam safety and management.