Institute of Mathematical Machine and System Problems

Kiev, Ukraine

Institute of Mathematical Machine and System Problems

Kiev, Ukraine
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Maderich V.,Institute of Mathematical Machine and System Problems | Jung K.T.,Korea Advanced Institute of Science and Technology | Brovchenko I.,Institute of Mathematical Machine and System Problems | Kim K.O.,Korea Advanced Institute of Science and Technology
Environmental Fluid Mechanics | Year: 2017

A new 3D radioactivity transport model coupled with multiscale circulation and multi-fractional sediment transport modules is presented. The sediment transport module simulates the transport of a mixture of one cohesive sediment fraction and a number of fractions of non-cohesive sediments of different sizes and densities. The model of radionuclide transport describes the key transport and exchange processes in the system of water-suspended and bottom multi-fraction sediments. Two-step kinetics with two successive reversible fast and slow reactions is used in the model. A noticeable feature of the model is approximation of the sediment and contamination profiles in the bed by multiple well-mixed layers to describe the vertical migration of radioactivity within bottom sediments due to erosion/deposition, molecular diffusion and bioturbation. The model accurately reproduced a laboratory experiment on the uptake of radiocesium by lake sediments. An analytical solution describing mutual adjustment of the concentrations of radioactivity in the pore water and in the multi-fraction sediment showed that activity was redistributed between different fractions of sediments far slower than between water and the total concentration in the sediment. The extended one-layer model of bottom contamination of multi-fraction sediments was derived from a general model and compared with a multi-layer model. It was found, however, that the one-layer approximation was not capable of correctly predicting the inventory due to the fact that one-layer averaged concentration can essentially differ from the near-surface value in the multi-layer model. Radionuclide transport in channel with bottom depression was simulated to estimate the effects of erosion/deposition and the multi-fractionality of sediments on the transport process. It was shown that these factors affect the distribution of sediments by forming local maxima and minima of activity at the beginning and end of the depression, respectively, due to the redistribution of contaminated bottom sediments by flow. The developed model can also be used to simulate the transport of a wide class of toxic substances sorbed on sediments. © 2017 The Author(s)

Perianez R.,University of Seville | Bezhenar R.,Ukrainian Center of Environmental and Water Projects | Iosjpe M.,Norwegian Radiation Protection Authority | Maderich V.,Institute of Mathematical Machine and System Problems | And 4 more authors.
Journal of Environmental Radioactivity | Year: 2015

Four radionuclide dispersion models have been applied to simulate the transport and distribution of 137Cs fallout from Chernobyl accident in the Baltic Sea. Models correspond to two categories: box models and hydrodynamic models which solve water circulation and then an advection/diffusion equation. In all cases, interactions of dissolved radionuclides with suspended matter and bed sediments are included. Model results have been compared with extensive field data obtained from HELCOM database. Inventories in the water column and seabed, as well as 137Cs concentrations along 5 years in water and sediments of several sub-basins of the Baltic, have been used for model comparisons. Values predicted by the models for the target magnitudes are very similar and close to experimental values. Results suggest that some processes are not very relevant for radionuclide transport within the Baltic Sea, for instance the roles of the ice cover and, surprisingly, water stratification. Also, results confirm previous findings concerning multi-model applications. © 2014 Elsevier Ltd.

Maderich V.,Institute of Mathematical Machine and System Problems | Bezhenar R.,Ukrainian Center of Environmental and Water Projects | Heling R.,Nuclear Research and Consultancy Group | de With G.,Nuclear Research and Consultancy Group | And 5 more authors.
Journal of Environmental Radioactivity | Year: 2014

The compartment model POSEIDON-R was modified and applied to the Northwestern Pacific and adjacent seas to simulate the transport and fate of radioactivity in the period 1945-2010, and to perform a radiological assessment on the releases of radioactivity due to the Fukushima Dai-ichi accident for the period 2011-2040. The model predicts the dispersion of radioactivity in the water column and in sediments, the transfer of radionuclides throughout the marine food web, and subsequent doses to humans due to the consumption of marine products. A generic predictive dynamic food-chain model is used instead of the biological concentration factor (BCF) approach. The radionuclide uptake model for fish has as a central feature the accumulation of radionuclides in the target tissue. The three layer structure of the water column makes it possible to describe the vertical structure of radioactivity in deep waters. In total 175 compartments cover the Northwestern Pacific, the East China and Yellow Seas and the East/Japan Sea. The model was validated from 137Cs data for the period 1945-2010. Calculated concentrations of 137Cs in water, bottom sediments and marine organisms in the coastal compartment, before and after the accident, are in close agreement with measurements from the Japanese agencies. The agreement for water is achieved when an additional continuous flux of 3.6TBqy-1 is used for underground leakage of contaminated water from the Fukushima Dai-ichi NPP, during the three years following the accident. The dynamic food web model predicts that due to the delay of the transfer throughout the food web, the concentration of 137Cs for piscivorous fishes returns to background level only in 2016. For the year 2011, the calculated individual dose rate for Fukushima Prefecture due to consumption of fishery products is 3.6μSvy-1. Following the Fukushima Dai-ichi accident the collective dose due to ingestion of marine products for Japan increased in 2011 by a factor of 6 in comparison with 2010. © 2013 Elsevier Ltd.

PubMed | Research and Production Association Typhoon, Vinča Institute of Nuclear Sciences, Argonne National Laboratory, Center for Ecology & Hydrology and 9 more.
Type: | Journal: Journal of environmental radioactivity | Year: 2016

We report an inter-comparison of eight models designed to predict the radiological exposure of radionuclides in marine biota. The models were required to simulate dynamically the uptake and turnover of radionuclides by marine organisms. Model predictions of radionuclide uptake and turnover using kinetic calculations based on biological half-life (TB1/2) and/or more complex metabolic modelling approaches were used to predict activity concentrations and, consequently, dose rates of (90)Sr, (131)I and (137)Cs to fish, crustaceans, macroalgae and molluscs under circumstances where the water concentrations are changing with time. For comparison, the ERICA Tool, a model commonly used in environmental assessment, and which uses equilibrium concentration ratios, was also used. As input to the models we used hydrodynamic forecasts of water and sediment activity concentrations using a simulated scenario reflecting the Fukushima accident releases. Although model variability is important, the intercomparison gives logical results, in that the dynamic models predict consistently a pattern of delayed rise of activity concentration in biota and slow decline instead of the instantaneous equilibrium with the activity concentration in seawater predicted by the ERICA Tool. The differences between ERICA and the dynamic models increase the shorter the TB1/2 becomes; however, there is significant variability between models, underpinned by parameter and methodological differences between them. The need to validate the dynamic models used in this intercomparison has been highlighted, particularly in regards to optimisation of the model biokinetic parameters.

Maderich V.,Institute of Mathematical Machine and System Problems | Ilyin Y.,Ukrainian Hydrometeorological Institute | Lemeshko E.,Marine Hydrophysical Institute
Mediterranean Marine Science | Year: 2015

chain of simple linked models is used to simulate the seasonal and interannual variability of the Turkish Straits System. This chain includes two-layer hydraulic models of the Bosphorus and Dardanelles straits simulating the exchange in terms of level and density difference along each strait, and a one-dimensional area averaged layered model of the Marmara Sea. The chain of models is complemented also by the similar layered model of the Black Sea proper and by a one-layer Azov Sea model with the Kerch Strait. This linked chain of models is used to study the seasonal and interannual variability of the system in the period 1970-2009. The salinity of the Black Sea water flowing into the Aegean Sea increases by approximately 1.7 times through entrainment from the lower layer. The flow entering into the lower layer of the Dardanelles Strait from the Aegean Sea is reduced by nearly 80% when it reaches the Black Sea. In the seasonal scale, a maximal transport in the upper layer and minimal transport in the bottom layer are during winter/spring for the Bosphorus and in spring for the Dardanelles Strait, whereas minimal transport in upper layer and maximal undercurrent are during the summer for the Bosphorus Strait and autumn for the Dardanelles Strait. The increase of freshwater flux into the Black Sea in interannual time scales (41 m3s-1 per year) is accompanied by a more than twofold growth of the Dardanelles outflow to the North Aegean (102 m3s-1 per year).

Maderich V.,Institute of Mathematical Machine and System Problems | Brovchenko I.,Institute of Mathematical Machine and System Problems | Jung K.T.,Korea Ocean Research and Development Institute
Environmental Fluid Mechanics | Year: 2012

The effect of the Coriolis force on the oil spill spreading in the gravity-viscous regime is examined. A new shallow water model for the transport and spreading of oil slick of arbitrary shape is described in which the Coriolis force is included in the momentum equations and the oil-water friction is parameterized in a frame of the boundary layer theory including the Ekman friction. The numerical Lagrangian method based on smoothed particle dynamics is described. New similarity solutions of the model equations are obtained for unidirectional and axisymmetric spreading in gravity-viscous, gravity-turbulent and gravity-viscous-rotational regimes for instantaneous as well as continuous releases. The numerical simulation extends these results for the case of continuous release in the presence of currents. It was shown that Coriolis term in the momentum equation can be omitted if slick thickness is much less of the laminar Ekman layer thickness. However, the Ekman friction should be retained for slicks of any thickness for larger times. The Ekman friction results in the essential slowdown of the spreading as well as in the deflection of the oil spreading velocity at 45° from the direction of velocity in the non-rotation case. Numerical simulations of large-scale spills showed that after the 2 days the slick area with the Coriolis effect was approximately less than half of that without rotation. Therefore, the earth rotation can be also important in the oil weathering. © 2012 Springer Science+Business Media B.V.

Maderich V.,Institute of Mathematical Machine and System Problems | Talipova T.,Institute of Applied Physics | Grimshaw R.,Loughborough University | Terletska K.,Institute of Mathematical Machine and System Problems | And 3 more authors.
Physics of Fluids | Year: 2010

This paper is devoted to the study of the transformation of a finite-amplitude interfacial solitary wave of depression at a bottom step. The parameter range studied goes outside the range of weakly nonlinear theory (the extended Korteweg-de Vries or Gardner equation), and we describe various scenarios of this transformation in terms of the incident wave amplitude and the step height. The dynamics and energy balance of the transformation are described. Several numerical simulations are carried out using the nonhydrostatic model based on the fully nonlinear Navier-Stokes equations in the Boussinesq approximation. Three distinct runs are discussed in detail. The first simulation is done when the ratio of the step height to the lower layer thickness after the step is about 0.4 and the incident wave amplitude is less than the limiting value estimated for a Gardner solitary wave. It shows the applicability of the weakly nonlinear model to describe the transformation of a strongly nonlinear wave in this case. In the second simulation, the ratio of the step height to the lower layer thickness is the same as that in the first run but the incident wave amplitude is increased and then its shape is described by the Miyata-Choi-Camassa solitary wave solution. In this case, the process of wave transformation is accompanied by shear instability and the billows that result in a thickening of the interface layer. In the third simulation, the ratio of the step height to the thickness of the lower layer after the step is 1.33, and then the same Miyata-Choi-Camassa solitary wave passes over the step, it undergoes stronger reflection and mixing between the layers although Kelvin-Helmholtz instability is absent. The energy budget of the wave transformation is calculated. It is shown that the energy loss in the vicinity of the step grows with an increase of the ratio of the incident wave amplitude to the thickness of the lower layer over the step. © 2010 American Institute of Physics.

Maderich V.,Institute of Mathematical Machine and System Problems | Konstantinov S.,Institute of Hydromechanics
Fluid Dynamics Research | Year: 2010

The asymptotic behavior of turbulent axisymmetric and plane momentumless wakes was studied using the Reynolds-averaged momentum equations and the second-order model of turbulence. The similarity solutions were obtained analytically and the process of transition to self-similarity was studied numerically. It was found that a single-point spectrum of the solutions of the corresponding eigenvalue problem for turbulent energy and dissipation rate existed. However, the spectra of solutions for the normal components of the anisotropy tensor and for the mean velocity defect were discrete. The numerical solution of a non-self-similar problem shows, in accordance with experiments and analytic solutions, that mean and fluctuating velocities decay with different rates, shear stresses decay faster than normal stresses and the anisotropic component of normal stresses decays faster than the isotropic component. The analysis of solutions for a full system of the Reynolds stress equations showed the presence of 'partial similarity' of the turbulent momentumless wake when some variables (velocity defect and shear stress) remain non-similar in flow that is self-similar as a whole. © 2010 The Japan Society of Fluid Mechanics and IOP Publishing Ltd.

Talipova T.,Nizhny Novgorod State Technical University | Terletska K.,Institute of Mathematical Machine and System Problems | Maderich V.,Institute of Mathematical Machine and System Problems | Brovchenko I.,Institute of Mathematical Machine and System Problems | And 3 more authors.
Physics of Fluids | Year: 2013

In this paper, we extend the numerical study of Maderich et al. ["Interaction of a large amplitude interfacial solitary wave of depression with a bottom step," Phys. Fluids22, 076602 (2010)10.1063/1.3455984] on the interaction of an interfacial solitary wave with a bottom step, considering (i) the energy loss of solitary waves of both polarities interacting with a bottom step and (ii) features of the transformation of a large-amplitude internal solitary waves at the step. We show that the dependence of energy loss on the step height is not monotonic, but has different maximum positions for different incident wave polarities. The energy loss does not exceed 50% of the energy of an incident wave. The results of our numerical modeling are compared with some recent results from laboratory tank modeling. © 2013 American Institute of Physics.

PubMed | International Atomic Energy Agency, Edith Cowan University, Norwegian University of Life Sciences, Bedford Institute of Oceanography and 7 more.
Type: | Journal: Annual review of marine science | Year: 2016

The events that followed the Tohoku earthquake and tsunami on March 11, 2011, included the loss of power and overheating at the Fukushima Daiichi nuclear power plants, which led to extensive releases of radioactive gases, volatiles, and liquids, particularly to the coastal ocean. The fate of these radionuclides depends in large part on their oceanic geochemistry, physical processes, and biological uptake. Whereas radioactivity on land can be resampled and its distribution mapped, releases to the marine environment are harder to characterize owing to variability in ocean currents and the general challenges of sampling at sea. Five years later, it is appropriate to review what happened in terms of the sources, transport, and fate of these radionuclides in the ocean. In addition to the oceanic behavior of these contaminants, this review considers the potential health effects and societal impacts.

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