Nina Shokina | Universitätsklinikum Freiburg (original) (raw)
Papers by Nina Shokina
In this video you can see the movement of a swinging lake, including wetting and drying processes.
IEEE Transactions on Medical Imaging
Experiments in Fluids
In this study, the flow through a generic abdominal aneurysm under realistic pulsating flow condi... more In this study, the flow through a generic abdominal aneurysm under realistic pulsating flow conditions is examined with magnetic resonance velocimetry (MRV), laser Doppler velocimetry (LDV) and computational fluid dynamics (CFD). The influence of flow phenomena on the wall shear stress (WSS) is examined. It is seen that a strong vortex ring develops during systole at the proximal end of the aneurysm and subsequently travels downstream and decays. The vortex formation plays a major role in the temporal and spatial distribution of the WSS, which is analyzed in detail. A peak of the WSS is observed for a very limited time and in a very localized region where the vortex ring initially develops. The intrinsic temporal averaging during the acquisition of the MRV data is found to significantly decrease this peak. CFD and LDV results, which are averaged in the same manner, show a similar behavior. This indicates that besides the spatial resolution, the temporal resolution is a crucial facto...
Journal of Magnetic Resonance
Geosciences
In the present article, we describe a few simple and efficient finite volume type schemes on movi... more In the present article, we describe a few simple and efficient finite volume type schemes on moving grids in one spatial dimension combined with an appropriate predictor–corrector method to achieve higher resolutions. The underlying finite volume scheme is conservative, and it is accurate up to the second order in space. The main novelty consists in the motion of the grid. This new dynamic aspect can be used to resolve better the areas with large solution gradients or any other special features. No interpolation procedure is employed; thus, unnecessary solution smearing is avoided, and therefore, our method enjoys excellent conservation properties. The resulting grid is completely redistributed according to the choice of the so-called monitor function. Several more or less universal choices of the monitor function are provided. Finally, the performance of the proposed algorithm is illustrated on several examples stemming from the simple linear advection to the simulation of complex ...
Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 2011
... 107 Kseniya S. Golushko, Sergey K. Golushko, Andrey V. Yurchenko 1 Introduction..... 107 2 St... more ... 107 Kseniya S. Golushko, Sergey K. Golushko, Andrey V. Yurchenko 1 Introduction..... 107 2 StructuralModels of Composite Materials..... 108 Page 11. ... 349 Michael Sladkevich, Anna Levin, Eliezer Kit 1 Introduction..... ...
The equidistribution method for constructing the mo tionless regular grids is considered in the p... more The equidistribution method for constructing the mo tionless regular grids is considered in the present paper. The grids are adapted to the curvilinear boundaries of the domain and to the control function, which is a priori giv en in the domain. Using the general methodology, which is based on the equdistr ibution principle, the nonlinear equations of elliptic type are
Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 2008
ABSTRACT The electromagnetic methods are widely used for solving problems of surveying and defect... more ABSTRACT The electromagnetic methods are widely used for solving problems of surveying and defectoscopy in geophysics. The method of high-frequency induction logging isoparametric sounding (VIKIZ) [1] is directed toward reconstructing resistivity spatial distribution of rock, where oil- and gas-bearing wells are situated.
PAMM, 2010
ABSTRACT The numerical modelling of surface water waves generated by a moving underwater landslid... more ABSTRACT The numerical modelling of surface water waves generated by a moving underwater landslide on irregular bottom is considered. The non-linear shallow water model is used with taking into account bottom mobility. The equations are obtained for an underwater landslide movement under the action of gravity force, buoyancy force, friction force and water resistance force. The predictor-corrector scheme [5], preserving the monotonicity of the numerical solution profiles in a linear case, is used on adaptive grids. The scheme is validated on the problem with a known analytical solution. The analysis is done for the dependencies of wave regimes on bottom slope, initial landslide depth, its length and width. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
PAMM, 2006
ABSTRACT The algorithm is presented for numerical solution of problems on stationary fluid flows ... more ABSTRACT The algorithm is presented for numerical solution of problems on stationary fluid flows with surface gravitational waves in multiply-connected domains with complicated geometry using adaptive grids in the framework of plane shallow water model taking into account bottom irregularities, frictional force and Coriolis force. The stream function - vorticity function statement in curvilinear coordinates is used. The alternating triangular iterative method is developed for solving the system of difference equations for the vorticity function. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PAMM, 2014
ABSTRACT By the example of the 1D transport equation with constant coefficient and the 2D linear ... more ABSTRACT By the example of the 1D transport equation with constant coefficient and the 2D linear transport equation with variable coefficients, the monotonization approach for two-step explicit finite-difference schemes is presented, based on studying scheme differential approximations [1,2]. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 2011
The current work is done in the framework of the BMBF (Bundesministerium für Bildung und Forschun... more The current work is done in the framework of the BMBF (Bundesministerium für Bildung und Forschung -the Federal Ministry of Education and Research) project AdaptHydroMod -Adaptive Hydrological Modelling with Application in Water Industry [1], which is devoted to the development of generic adaptive approach to modelling of coupled hydrological processes: surface and groundwater flows. The surface water flow is modelled by the two-dimensional shallow water equations and the surface flow -by the Richards equation. The implementation is based within DUNE -the Distributed and Unified Numerics Environment [14]. The surface flow, on which we focus in the presented paper, is numerically solved using the Runge-Kutta discontinuous Galerkin method [10] with modifications to render the scheme well-balanced and for handling correctly possible wetting and drying processes. The newly developed limiter is used for the stabilization of the method. The validation of the code is done using several test problems with known exact solutions. The problem with a mass source term, which is a first step to the coupled simulation of the surface and groundwater flows, is solved numerically.
Russian Journal of Numerical Analysis and Mathematical Modelling, 2000
Proceedings, 10th International Meshing Roundtable, …, 2001
The equidistribution method for constructing the mo tionless regular grids is considered in the p... more The equidistribution method for constructing the mo tionless regular grids is considered in the present paper. The grids are adapted to the curvilinear boundaries of the domain and to the control function, which is a priori giv en in the domain. Using the general methodology, which is based on the equdistr ibution principle, the nonlinear equations of elliptic type are obtained for the definition of the node coordinates inside the domai n and on its boundaries.
Russian Journal of Numerical Analysis and Mathematical Modelling, 2012
Equations of a landslide motion over an uneven underwater slope subject to gravity and buoyancy f... more Equations of a landslide motion over an uneven underwater slope subject to gravity and buoyancy forces, water friction and resistance are presented. A simulation of surface waves generated by a landslide in a bounded reservoir with a parabolic bottom profile has been performed within the nonlinear shallow water equations, and the results of that simulation are given. The influence of the parameters of the motion equation on the maximal splashing size is studied numerically.
In this video you can see the movement of a swinging lake, including wetting and drying processes.
IEEE Transactions on Medical Imaging
Experiments in Fluids
In this study, the flow through a generic abdominal aneurysm under realistic pulsating flow condi... more In this study, the flow through a generic abdominal aneurysm under realistic pulsating flow conditions is examined with magnetic resonance velocimetry (MRV), laser Doppler velocimetry (LDV) and computational fluid dynamics (CFD). The influence of flow phenomena on the wall shear stress (WSS) is examined. It is seen that a strong vortex ring develops during systole at the proximal end of the aneurysm and subsequently travels downstream and decays. The vortex formation plays a major role in the temporal and spatial distribution of the WSS, which is analyzed in detail. A peak of the WSS is observed for a very limited time and in a very localized region where the vortex ring initially develops. The intrinsic temporal averaging during the acquisition of the MRV data is found to significantly decrease this peak. CFD and LDV results, which are averaged in the same manner, show a similar behavior. This indicates that besides the spatial resolution, the temporal resolution is a crucial facto...
Journal of Magnetic Resonance
Geosciences
In the present article, we describe a few simple and efficient finite volume type schemes on movi... more In the present article, we describe a few simple and efficient finite volume type schemes on moving grids in one spatial dimension combined with an appropriate predictor–corrector method to achieve higher resolutions. The underlying finite volume scheme is conservative, and it is accurate up to the second order in space. The main novelty consists in the motion of the grid. This new dynamic aspect can be used to resolve better the areas with large solution gradients or any other special features. No interpolation procedure is employed; thus, unnecessary solution smearing is avoided, and therefore, our method enjoys excellent conservation properties. The resulting grid is completely redistributed according to the choice of the so-called monitor function. Several more or less universal choices of the monitor function are provided. Finally, the performance of the proposed algorithm is illustrated on several examples stemming from the simple linear advection to the simulation of complex ...
Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 2011
... 107 Kseniya S. Golushko, Sergey K. Golushko, Andrey V. Yurchenko 1 Introduction..... 107 2 St... more ... 107 Kseniya S. Golushko, Sergey K. Golushko, Andrey V. Yurchenko 1 Introduction..... 107 2 StructuralModels of Composite Materials..... 108 Page 11. ... 349 Michael Sladkevich, Anna Levin, Eliezer Kit 1 Introduction..... ...
The equidistribution method for constructing the mo tionless regular grids is considered in the p... more The equidistribution method for constructing the mo tionless regular grids is considered in the present paper. The grids are adapted to the curvilinear boundaries of the domain and to the control function, which is a priori giv en in the domain. Using the general methodology, which is based on the equdistr ibution principle, the nonlinear equations of elliptic type are
Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 2008
ABSTRACT The electromagnetic methods are widely used for solving problems of surveying and defect... more ABSTRACT The electromagnetic methods are widely used for solving problems of surveying and defectoscopy in geophysics. The method of high-frequency induction logging isoparametric sounding (VIKIZ) [1] is directed toward reconstructing resistivity spatial distribution of rock, where oil- and gas-bearing wells are situated.
PAMM, 2010
ABSTRACT The numerical modelling of surface water waves generated by a moving underwater landslid... more ABSTRACT The numerical modelling of surface water waves generated by a moving underwater landslide on irregular bottom is considered. The non-linear shallow water model is used with taking into account bottom mobility. The equations are obtained for an underwater landslide movement under the action of gravity force, buoyancy force, friction force and water resistance force. The predictor-corrector scheme [5], preserving the monotonicity of the numerical solution profiles in a linear case, is used on adaptive grids. The scheme is validated on the problem with a known analytical solution. The analysis is done for the dependencies of wave regimes on bottom slope, initial landslide depth, its length and width. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
PAMM, 2006
ABSTRACT The algorithm is presented for numerical solution of problems on stationary fluid flows ... more ABSTRACT The algorithm is presented for numerical solution of problems on stationary fluid flows with surface gravitational waves in multiply-connected domains with complicated geometry using adaptive grids in the framework of plane shallow water model taking into account bottom irregularities, frictional force and Coriolis force. The stream function - vorticity function statement in curvilinear coordinates is used. The alternating triangular iterative method is developed for solving the system of difference equations for the vorticity function. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PAMM, 2014
ABSTRACT By the example of the 1D transport equation with constant coefficient and the 2D linear ... more ABSTRACT By the example of the 1D transport equation with constant coefficient and the 2D linear transport equation with variable coefficients, the monotonization approach for two-step explicit finite-difference schemes is presented, based on studying scheme differential approximations [1,2]. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 2011
The current work is done in the framework of the BMBF (Bundesministerium für Bildung und Forschun... more The current work is done in the framework of the BMBF (Bundesministerium für Bildung und Forschung -the Federal Ministry of Education and Research) project AdaptHydroMod -Adaptive Hydrological Modelling with Application in Water Industry [1], which is devoted to the development of generic adaptive approach to modelling of coupled hydrological processes: surface and groundwater flows. The surface water flow is modelled by the two-dimensional shallow water equations and the surface flow -by the Richards equation. The implementation is based within DUNE -the Distributed and Unified Numerics Environment [14]. The surface flow, on which we focus in the presented paper, is numerically solved using the Runge-Kutta discontinuous Galerkin method [10] with modifications to render the scheme well-balanced and for handling correctly possible wetting and drying processes. The newly developed limiter is used for the stabilization of the method. The validation of the code is done using several test problems with known exact solutions. The problem with a mass source term, which is a first step to the coupled simulation of the surface and groundwater flows, is solved numerically.
Russian Journal of Numerical Analysis and Mathematical Modelling, 2000
Proceedings, 10th International Meshing Roundtable, …, 2001
The equidistribution method for constructing the mo tionless regular grids is considered in the p... more The equidistribution method for constructing the mo tionless regular grids is considered in the present paper. The grids are adapted to the curvilinear boundaries of the domain and to the control function, which is a priori giv en in the domain. Using the general methodology, which is based on the equdistr ibution principle, the nonlinear equations of elliptic type are obtained for the definition of the node coordinates inside the domai n and on its boundaries.
Russian Journal of Numerical Analysis and Mathematical Modelling, 2012
Equations of a landslide motion over an uneven underwater slope subject to gravity and buoyancy f... more Equations of a landslide motion over an uneven underwater slope subject to gravity and buoyancy forces, water friction and resistance are presented. A simulation of surface waves generated by a landslide in a bounded reservoir with a parabolic bottom profile has been performed within the nonlinear shallow water equations, and the results of that simulation are given. The influence of the parameters of the motion equation on the maximal splashing size is studied numerically.