53 research outputs found
Augmented fluid-structure interaction systems for viscoelastic pipelines and blood vessels
[EN] In this work, innovative 1D hyperbolic models able to predict the behavior of the
fluid-structure interaction mechanism that underlies the dynamics of flows in different compliant
ducts are presented. Starting from the study of plastic water pipelines, the proposed tool is then
applied to the biomathematical field to reproduce the mechanics of blood flow in both arteries
and veins. With this aim, various different viscoelastic models have been applied and extended
to obtain augmented fluid-structure interaction systems in which the constitutive equation of
the material is directly embedded into the system as partial differential equation. These systems
are solved recurring to Finite Volume Methods that take into account the recent evolution in the
computational literature of hyperbolic balance laws systems. To avoid the loss of accuracy in
the stiff regimes of the proposed systems, asymptotic-preserving Implicit-Explicit Runge-Kutta
schemes are considered for the time discretization, which are able to maintain the consistency
and the accuracy in the diffusive limit, without restrictions due to the scaling parameters.Bertaglia, G. (2022). Augmented fluid-structure interaction systems for viscoelastic pipelines and blood vessels. En Proceedings of the YIC 2021 - VI ECCOMAS Young Investigators Conference. Editorial Universitat Politècnica de València. 431-438. https://doi.org/10.4995/YIC2021.2021.13450OCS43143
Augmented resolution of linear hyperbolic systems under nonconservative form
Hyperbolic systems under nonconservative form arise in numerous applications
modeling physical processes, for example from the relaxation of more general
equations (e.g. with dissipative terms). This paper reviews an existing class
of augmented Roe schemes and discusses their application to linear
nonconservative hyperbolic systems with source terms. We extend existing
augmented methods by redefining them within a common framework which uses a
geometric reinterpretation of source terms. This results in intrinsically
well-balanced numerical discretizations. We discuss two equivalent
formulations: (1) a nonconservative approach and (2) a conservative
reformulation of the problem. The equilibrium properties of the schemes are
examined and the conditions for the preservation of the well-balanced property
are provided. Transient and steady state test cases for linear acoustics and
hyperbolic heat equations are presented. A complete set of benchmark problems
with analytical solution, including transient and steady situations with
discontinuities in the medium properties, are presented and used to assess the
equilibrium properties of the schemes. It is shown that the proposed schemes
satisfy the expected equilibrium and convergence properties
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Computational haemodynamics in stenotic internal jugular veins
Stenosis in internal jugular veins (IJVs) are frequently associated to
pathological venous circulation and insufficient cerebral blood drainage. In
this work, we set up a computational framework to assess the relevance of IJV
stenoses through numerical simulation, combining medical imaging,
patient-specific data and a mathematical model for venous occlusions.
Coupling a three-dimensional (3D) description of blood flow in IJVs with a
reduced one-dimesional model (1D) for major intracranial veins, we are able
to model different anatomical configurations, an aspect of importance to
understand the impact of IJV stenosis in intracranial venous haemodynamics.
We investigate several stenotic configurations in a physiologic
patient-specific regime, quantifying the effect of the stenosis in terms of
venous pressure increase and wall shear stress patterns. Simulation results
are in qualitative agreement with reported pressure anomalies in pathological
cases. Moreover, they demonstrate the potential of the proposed multiscale
framework for individualbased studies and computer-aided diagnosis
Computational haemodynamics in stenotic internal jugular veins
Stenosis in internal jugular veins (IJVs) are frequently associated to pathological venous circulation and insufficient cerebral blood drainage. In this work, we set up a computational framework to assess the relevance of IJV stenoses through numerical simulation, combining medical imaging, patient-specific data and a mathematical model for venous occlusions. Coupling a three-dimensional (3D) description of blood flow in IJVs with a reduced one-dimesional model (1D) for major intracranial veins, we are able to model different anatomical configurations, an aspect of importance to understand the impact of IJV stenosis in intracranial venous haemodynamics. We investigate several stenotic configurations in a physiologic patient-specific regime, quantifying the effect of the stenosis in terms of venous pressure increase and wall shear stress patterns. Simulation results are in qualitative agreement with reported pressure anomalies in pathological cases. Moreover, they demonstrate the potential of the proposed multiscale framework for individual-based studies and computer-aided diagnosis
Numerical modelling of open channel junctions using the Riemann problem approach
The solution of an extended Riemann problem is used to provide the internal
boundary conditions at a junction when simulating one-dimensional flow through
an open channel network. The proposed approach, compared to classic junction
models, does not require the tuning of semi-empirical coefficients and it is
theoretically well-founded. The Riemann problem approach is validated using
experimental data, two-dimensional model results and analytical solutions. In
particular, a set of experimental data is used to test each model under
subcritical steady flow conditions, and different channel junctions are
considered, with both continuous and discontinuous bottom elevation. Moreover,
the numerical results are compared with analytical solutions in a star network
to test unsteady conditions. Satisfactory results are obtained for all the
simulations, and particularly for Y-shaped networks and for cases involving
variations in channels' bottom and width. By contrast, classic models suffer
when geometrical channel effects are involved
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