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COMMON PART

Project Number22-11-00295

Project titleHydrophysical and hydrobiological mathematical models and supercomputer technologies for forecasting Southern Russia coastal and shallow-water systems development in conditions of changing climate, natural and technological impacts

Project LeadSukhinov Alexander

AffiliationFederal State-Funded Educational Institution of Higher Education Don State Technical University,

Research area 01 - MATHEMATICS, INFORMATICS, AND SYSTEM SCIENCES, 01-217 - Mathematical simulation of physical environments

KeywordsMathematical model, hydrodynamics and biological kinetics, the pollution propagation process, plastic and microplastic, oil and oil products, coastal system, Earth satellite sensing data, data assimilation methods, boundary-adaptive 3D grids, local-two-dimensional difference scheme, high-performance parallel algorithm, computational decomposition areas

PROJECT CONTENT

Annotation
The high activity of exogenous geological processes has a significant negative impact on the quality of reservoirs in Southern Russia. These reservoirs in the long-term plan are consistently characterized as dirty according to the state report on the state and environmental protection of the Russian Federation. They are characterized by contamination with organic substances, petroleum products, household and industrial effluents, precipitation of atmospheric aerosols on the water surface, microplastics. It should be noted that the salinity of the Don has increased over the past 30 years, as well as exceeding the maximum permissible concentration of petroleum hydrocarbons by 7 times. The salinity of the Taganrog Bay largely depends on the river flow volume. In 2019, the salinity varied from 0,40% to 9,30% and generally increased in subsequent years. The project is dedicated to the creation of 3D hydrodynamics and hydrophysics models with refined mechanisms of turbulent exchange in relation to coastal systems. They can be used to forecast the development of coastal and shallow-water systems in Southern Russia in conditions of changing climate, natural and man-made impacts. High-precision predictive models of the natural and man-made suspensions distribution in coastal systems will be created. Their impact on aquatic ecosystems trophic levels will be assessed. The project will refine and develop models, including long waves, and models of aquatic environment secondary pollution during transport and weighing of bottom sediments. The models will be refined and developed through the use of high-precision schemes for convection-diffusion problems, which are the development of Upwind Leapfrog difference schemes with improved dispersion properties. During the project implementation, computationally efficient parallel algorithms for solving hydrophysics and hydrobiology grid equations will be built. The algorithms are based on the end-to-end application of explicit schemes with regularizing terms – time second order difference derivatives, and two-dimensional-one-dimensional splitting schemes will also be developed. Splitting schemes take into account the multi-scale nature of processes in horizontal directions in comparison with processes in the vertical direction. It is planned to create 3D pollutants transport and transformation models having a diverse nature of origin: domestic and industrial effluents, atmospheric aerosols precipitation on the water surface, oil spills, pollutants containing microplastics, coupled with hydrodynamic models. The most dangerous are microparticles of oil and petroleum products and other pollutants suspensions with long decomposition times. Currently, there are no coupled hydrophysics, biogeochemical cycles and hydrobiology models that take into account the specific features of coastal systems, such as a significant depth difference, desalination zones, the vortex currents near the shore (due to the presence of braids, bays, complex bottom relief, etc.) and other factors that allow for the average- and long-term forecasts of the pollutants spread containing plastic particles, their transformation, absorption of microplastic particles by hydrobionts and harm assessment caused to the food base and ichthyofauna, depending on their species composition and demography. Pollutants enter the Azov Sea, the Tsimlyansk reservoir and other reservoirs in the Southern Russia from the drains of rivers, streams and storm sewers, as well as untreated domestic and industrial effluents. The role of atmospheric aerosols deposited on the water surface is great, which in mass terms can account for up to 25-30% of all coastal systems pollution . Microplastic particles of 1 mm or less in size are especially dangerous, which easily pass into a suspended state and enter the digestive tracts and respiratory systems of representatives of the ichthyofauna; the smallest ones with sizes less than 0,1 mm are highly likely to end up in the zooplankton organisms representatives. In addition to the fact that these processes have a detrimental effect on all living things in the aquatic environment, microparticles of plastic can enter the human body through food chains, causing many dangerous diseases, including cancer. Dredging operations in water bodies in the Southern Russia have a negative impact on coastal aquatic ecosystems. In the Taganrog Bay, this work is constantly being carried out, related to the need to maintain the approach and navigable channels in the required condition, while the extracted bottom sediments volumes amount to many thousands of cubic meters. Extreme aquatic environment pollution by suspended particles occurs at the sites of these works and landfills. The frequency of winds, their strength (speed) and duration in the Southern Russia have increased significantly over the past 3-4 years and there is a tendency for their increase. As a result of the wind impact on the water area of a shallow reservoir, a part of the bottom surface dries up during run-offs, and dust rises into the air, breaking up into fine-dispersed fractions that harm the biogeocenosis of the reservoir: they can get into plankton and fish organisms, thereby impairing the reproduction processes. In addition, the appearance of dust in excess volume in the air environment worsens human living conditions and harms his health. So in November 2019, extreme driving phenomena were observed in the Taganrog Bay – in a few days the coastline shifted towards the sea by almost two kilometers due to strong winds of the north-easterly direction up to 20 meters per second. There was a dust curtain over the city of Taganrog and other coastal settlements for more than a week. The aim of the work is further development of interconnected precision 4D models and parallel algorithms for numerical solution of problems of surface aerodynamics, hydrophysics and hydrobiology, taking into account the specifics of Southern Russia coastal systems to predict the impact of plankton populations and typical coastal systems ichthyofauna representatives pollutants, toxic substances and microparticles, including dust, microplastics, nutrients, heavy metals, air quality, etc. Scientific novelty. To achieve this goal, new classes of models will be built that take into account the mechanisms of primary and secondary coastal systems pollution with dust, microplastics, biogenic substances, heavy metals, taking into account currents, salinity and temperature distribution, solar radiation and biodegradation, the waves influence and storm surges on the secondary pollution and mechanical destruction of pollutants in the form of dust and plastic particles, agitation of bottom sediments and transport of microplastic suspensions. Multi-species interaction models between plankton and commercial fish will be created, including anchovy, mullet, flounder, etc. The developed 4D mathematical models will be more accurate compared to the known ones because they will take into account factors that have a significant impact on the nature of hydrobiological processes in shallow water bodies: advective transport in all coordinate directions, including vertically, parametrisable microturbulent diffusion, including in the vertical direction, gravitational subsidence of microparticles of pollutants and plankton; nonlinear interaction of planktonic and fish populations. The probability of ingress and accumulation of microplastics and small-sized microparticles of pollutants into the organisms of the main commercial fish of the Azov Sea and the Tsimlyansk reservoir will be calculated, depending on the places of their spawning and feeding. The probability will be estimated on the basis of functions describing changes in the microparticles concentrations of the main pollutants, depending on time, the populations concentration and the characteristics of metabolic processes for the ichthyofauna main representatives. To solve the problems of computational aero- and hydrodynamics with large Peclet grid numbers, it is proposed to improve the difference scheme based on a linear combination of the Upwind Leapfrog and Standart Leapfrog difference schemes with weighting coefficients obtained as a result of minimizing the approximation error, and does not have a grid viscosity and, as a result, more accurately describes the behavior of the solution in the case of large grid numbers of the Peclet and allows more accurately describing small-sized vortices arising in the coastal part of shallow reservoirs. Algorithms and complexes of parallel programs will be developed for high-performance computing systems. The project is supposed to build, investigate and apply a complex of interrelated non-stationary, spatially heterogeneous mathematical models describing nonlinear processes of hydrophysics, biogeochemical cycles, transport and transformation of suspensions and bottom sediments containing particles of pollutants, absorption of these particles by zooplankton and fish, microplastic particles movement along the food chain, as well as their impact on the main hydrobionts of coastal systems like the Azov Sea. Continuous suspensions and sediments transport models having a multicomponent nature and containing microplastics, biogeochemical cycles and hydrobiology will be coupled with 3D precision hydrodynamics models of coastal systems developed in the author's team.

Expected results
Complex of interrelated spatial-three-dimensional unsteady hydrodynamics and hydrophysics models with refined turbulent exchange mechanisms in relation to coastal systems will be developed. It can be used to assess hydrophysical changes in the geosystem monitoring of coastal systems in the Southern Russia that are most susceptible to anthropogenic impacts, the formation of scenarios for water purification, strengthening of the coastline, justification of new observations. Planned: development and research of difference schemes for hydrodynamic models discretization, including wave and solid waste transport models, based on modified Upwind Leapfrog schemes with increased accuracy and stability margin in the case of Peclet grid number large values, development and research of two-dimensional – one-dimensional splitting schemes (variable directions and additive), taking into account significantly different spatial-temporal scales and spectral properties of processes in horizontal and vertical directions, as well as significant heterogeneity of the aquatic environment, which will significantly improve the accuracy of modeling and reduce the calculation time on supercomputer systems by reducing the time spent on information exchanges between calculators (when constructing short-term forecasts of changes in the ecological situation of the Azov Sea of and the Tsimlyansk reservoir as a result of the dangerous phenomena occurrence in them, including storm surge, hijacking of the main parts of the reservoir with drying of the bottom surface, water blooming and overseas phenomena), as well as when constructing long-term forecasts (accumulation phenomena in phyto organisms-, zooplankton and fish, toxic and harmful pollutants and particles, including microplastics). Planned: development, research and program implementation of 3D models of transport and transformation of pollutants having a diverse nature of origin: domestic and industrial effluents, precipitation of atmospheric aerosols on the water surface, spills of petroleum products, pollutants containing microplastics, etc., coupled with models of hydrodynamics. Planned: development and research of coupled sediment transport and suspended solids models with models of hydrodynamics contained in river drains (Don, Kuban, etc.), arising from wave action, conducting bottom-deepening works and studying their impact on the state of the aquatic environment and the reshaping of the bottom and shoreline relief, including the processes of erosion and coastal collapse. During the implementation of the project, coupled models of sediment transport and suspended solids contained in river drains (Don, Kuban, etc.), coupled with hydrodynamic models, will be developed and studied, the influence of sediments and suspended solids on the state of the aquatic environment and the reshaping of the bottom and shoreline relief, including the processes of erosion and coastal collapse, will be studied. During the implementation of the project, 3D models of biogeochemical cycles and hydrobiology will be developed and studied, coupled with models of hydrodynamics, transport and transformation of pollutants having a diverse nature of origin, including microplastic particles. Planned: development of methods for linearization of boundary value problems, to study the correctness for systems of nonlinear convection-diffusion equations, to which, basically, the models of hydrophysics and hydrobiology under consideration are reduced. Discrete models will be developed and investigated, including those based on splitting schemes and explicit regularized schemes for subsequent numerical implementation on massively parallel computing systems. It is planned to develop effective iterative algorithms, including those with preconditioners that take into account the spectral properties of convective-diffusion transfer operators due to the specifics of hydrophysics and hydrobiology processes in coastal systems. During the implementation of the project, parallel algorithms and programs will be tested and optimized, taking into account the architectural features of the multiprocessor systems used (with distributed memory, shared memory and hybrid), verification and validation of the constructed models and programs based on available field data, including space sensing data, will be carried out. It is planned to carry out prognostic calculations on a supercomputing system to determine the consequences of the bottom relief evolution, including the erosion and destruction forecast, siltation of channels, destruction of coastal zone objects, forecasting the aquatic environment and the air environment quality, the evolution of planktonic and fish populations in the pollutants presence, including ongoing salinization and an increase in the concentration of microplastic particles for various scenarios of climate change and man-made and anthropogenic impacts. Computational experiment will be conducted based on the developed coupled models of hydrophysics, biogeochemical cycles and hydrobiology on supercomputing systems to study the effect of microparticles of natural and man-made origin, including microplastic particles, on the hydrobiology of coastal systems in the Southern Russia, as a result of which operational forecasts of the distribution of water flow velocities, concentrations of major pollutants, including plastic, oil and petroleum products, as well as biogenic substances will be obtained., distribution of plankton and commercial fish populations; areas of reservoirs with a vortex structure of currents that are potentially dangerous for the accumulation of pollutants, including microplastic; classification of the main sources, types and concentrations of pollutants and microparticles of plastic, oil and petroleum products, as well as biogenic substances (nitrogen, phosphorus, silicon compounds) will be obtained; the calculation of the transfer of multicomponent impurities in the aquatic environment, concentrations of phyto-, zooplankton, biogenic substances, oil and petroleum products, plastics and microplastics under various weather and climatic conditions characteristic of the Azov Sea will be performed; the probability of ingress and accumulation of pollutants and microplastics into the organisms of hydrobionts will be assessed; prognostic modeling of the dynamics of phyto-, zooplankton populations and commercial fish, absorption of nano- and microplastic particles by hydrobionts, taxis, and etc; an assessment of the impact of dredging operations will be made damage from the loss or decrease in the quality and volume of the forage base, deterioration of the quality of the aquatic environment and a decrease in the number of major commercial fish species; proposals and recommended measures will be given to ensure the conservation of biodiversity of fishing resources, ecosystems of shallow water bodies; an assessment and forecast of the state of the ecosystem of the Azov Sea, the forage base and stocks of fishing facilities will be made using the developed software package on supercomputing systems; the effectiveness of the developed software tools for the operational prediction of hazardous and emergency events (emergencies) will be evaluated, including the speed and efficiency of the built parallel algorithms and programs for supercomputing systems, the average time of forecasting the development of emergencies on water bodies, the expected accuracy (error) of predictive modeling and the development of proposals for their further improvement. The constructed grid models will be numerically implemented on the basis of the developed rapidly converging parallel iterative algorithms, will have high efficiency coefficient values for distributed memory systems in cases where it would be advisable to use implicit schemes. The obtained results, as well as the developed methods, can be used by specialists in the field of numerical modeling of continuum mechanics, marine hydraulic engineering, as well as in solving various problems of applied mathematics and mathematical physics. The created parallel algorithms for solving problems of hydrodynamics and biological kinetics can reduce the time for solving problems by tens to hundreds of times; an assessment of the effectiveness of the developed software tools for the operational prediction of dangerous and extreme compared to sequential algorithms will be made. The scientific significance of the work consists in the creation and study of a complex of interrelated models that allow more accurately in comparison with known models to simulate the processes of hydrophysics and biological kinetics, including sediment transport, primary and secondary contamination with impurities when they rise from the bottom of the reservoir under the action of wave processes, eutrophication, distribution of concentrations of pollutants, including dust, microplastics, biogenic substances (nitrogen, phosphorus, silicon compounds), phyto- and zooplankton, blooming waters of coastal zones of shallow reservoirs, similar to the Azov Sea, with complex spatial structures of currents. The project is aimed at developing technologies for monitoring the state of the environment, eliminating its pollution. The results of the work can be used by the employees of the Ministry of Emergency Situations for the operational forecast of the impact of microparticles of natural and man-made origin on the hydrobiology of coastal systems in the Southern Russia. The project will construct and study interrelated models of hydrodynamics and transport of bottom sediments, multi-fraction suspensions, including the study of the correctness of systems of convection-diffusion-reaction equations linearized on a time grid and the proximity of their solutions to the solutions of the original nonlinear boundary value problems in the norms of spaces L1 and L2; construction of discrete models for convection-diffusion-reaction problems, taking into account the diversity of processes occurring in horizontal and vertical directions in relation to marine coastal systems and extended shallow reservoirs, providing effective numerical implementation on supercomputer systems containing many thousands- hundreds of thousands of processors (cores) through the use of two-dimensional-one-dimensional splitting schemes and explicit regularized schemes. The developed models will reliably detect areas of intensive runoff of industrial-polluted waters located in the coastal zone of the reservoir, areas with reduced water exchange (microturbulent exchange coefficient) in the vertical direction, characterized by a shortage or complete absence of oxygen, and their distribution in the water column and in the water area of the reservoir.

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