The visualization of unsteady flows is an attractive field of research and texture-based techniqu... more The visualization of unsteady flows is an attractive field of research and texture-based techniques seem to pro- vide satisfactory results. In this paper we propose a texture-based method which follows streaklines in order to produce an effective visualization of time-dependent phenomena. Our approach allows to overcome the lack of temporal coherence due to instantaneous methods which depict each frame of
Blood vessel curvature is responsible for the appearance of nonaxial velocity components and for ... more Blood vessel curvature is responsible for the appearance of nonaxial velocity components and for minor changes in the pattern of the axial flow. All the velocity components are expected to contribute to the Doppler signal produced by the ultrasound (US) backscattered by the insonated blood cells, the axial velocity, contributing to the actual volumetric blood flow, and the transverse velocity, causing the recirculating vortices. A detailed, separate analysis of the velocity components is, therefore, mandatory to quantify how vessel curvature can affect results and clinical diagnosis. Both experimental in vitro measures and numerical simulations were performed on a curved tube and the Doppler power spectra so obtained were compared. The satisfactorily agreement of the above spectra shows that the nonaxial velocity components are easily detectable with clinical equipment and that their amplitude, as expected, is not negligible and can bias Doppler measurements and resulting clinical diagnosis.
... Renzo Arina 1, Claudio Canuto 2 ... supplemented by initial and boundary conditions, and by a... more ... Renzo Arina 1, Claudio Canuto 2 ... supplemented by initial and boundary conditions, and by an interface condition which couples w and v at x = b. Since by assumption X(U~,~) =_ 0 in a neighborhood of b, the proper interface condition is of hyperbolic type, namely, each ...
ABSTRACT Supercritical fluids represent an active field of research, interesting from the theoret... more ABSTRACT Supercritical fluids represent an active field of research, interesting from the theoretical point of view, and for industrial applications. We describe a numerical method for the simulation of supercritical fluid flow phenomena, valid for a general real gas equation of state. Three state equations (van der Waals, Carnahan–Starling–De Santis, Redlich–Kwong), describing the thermodynamic behavior of a gas near its critical point are implemented. Numerical tests in the case of the flow through a nozzle and the shock tube problem, show the reliability of the numerical scheme. The response of a supercritical fluid confined into a slab with closed ends, initially at rest in thermodynamic equilibrium, when one boundary is heated, termed Piston effect, is also investigated.
Surface grid-generation algorithms are based on a projection strategy, consisting in generating a... more Surface grid-generation algorithms are based on a projection strategy, consisting in generating a grid on the surface parametric plane, and then to project it on the surface. However during the projection step the grid characteristics, such as point distribution and orthogonality, are often not correctly transported. To overcome these difficulties, a new approach is proposed which can be divided into two main steps: (i) the parameterization of the surface by isothermal coordinates, (ii) the generation of a two-dimensional grid on the conformal parametric plane and its projection on the surface. In this way the projection is based on a conformal map, preserving angles and scale-length ratios.
The visualization of unsteady flows is an attractive field of research and texture-based techniqu... more The visualization of unsteady flows is an attractive field of research and texture-based techniques seem to pro- vide satisfactory results. In this paper we propose a texture-based method which follows streaklines in order to produce an effective visualization of time-dependent phenomena. Our approach allows to overcome the lack of temporal coherence due to instantaneous methods which depict each frame of
Blood vessel curvature is responsible for the appearance of nonaxial velocity components and for ... more Blood vessel curvature is responsible for the appearance of nonaxial velocity components and for minor changes in the pattern of the axial flow. All the velocity components are expected to contribute to the Doppler signal produced by the ultrasound (US) backscattered by the insonated blood cells, the axial velocity, contributing to the actual volumetric blood flow, and the transverse velocity, causing the recirculating vortices. A detailed, separate analysis of the velocity components is, therefore, mandatory to quantify how vessel curvature can affect results and clinical diagnosis. Both experimental in vitro measures and numerical simulations were performed on a curved tube and the Doppler power spectra so obtained were compared. The satisfactorily agreement of the above spectra shows that the nonaxial velocity components are easily detectable with clinical equipment and that their amplitude, as expected, is not negligible and can bias Doppler measurements and resulting clinical diagnosis.
... Renzo Arina 1, Claudio Canuto 2 ... supplemented by initial and boundary conditions, and by a... more ... Renzo Arina 1, Claudio Canuto 2 ... supplemented by initial and boundary conditions, and by an interface condition which couples w and v at x = b. Since by assumption X(U~,~) =_ 0 in a neighborhood of b, the proper interface condition is of hyperbolic type, namely, each ...
ABSTRACT Supercritical fluids represent an active field of research, interesting from the theoret... more ABSTRACT Supercritical fluids represent an active field of research, interesting from the theoretical point of view, and for industrial applications. We describe a numerical method for the simulation of supercritical fluid flow phenomena, valid for a general real gas equation of state. Three state equations (van der Waals, Carnahan–Starling–De Santis, Redlich–Kwong), describing the thermodynamic behavior of a gas near its critical point are implemented. Numerical tests in the case of the flow through a nozzle and the shock tube problem, show the reliability of the numerical scheme. The response of a supercritical fluid confined into a slab with closed ends, initially at rest in thermodynamic equilibrium, when one boundary is heated, termed Piston effect, is also investigated.
Surface grid-generation algorithms are based on a projection strategy, consisting in generating a... more Surface grid-generation algorithms are based on a projection strategy, consisting in generating a grid on the surface parametric plane, and then to project it on the surface. However during the projection step the grid characteristics, such as point distribution and orthogonality, are often not correctly transported. To overcome these difficulties, a new approach is proposed which can be divided into two main steps: (i) the parameterization of the surface by isothermal coordinates, (ii) the generation of a two-dimensional grid on the conformal parametric plane and its projection on the surface. In this way the projection is based on a conformal map, preserving angles and scale-length ratios.
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