148 research outputs found
Stability analysis of second-order time accurate schemes for ALE-FEM
In this work we will introduce and analyze the Arbitrary Lagrangian Eulerian formulation for a model problem of a scalar advection-diffusion equation defined on a moving domain. Moving from the results illustrated in our previous work [J. Num. Math. 7 (1999) 105], we will consider first and second-order time advancing schemes and analyze how the movement of the domain might affect accuracy and stability properties of the numerical schemes with respect to their counterpart on fixed domains. Theoretical and numerical results will be presented, showing that stability properties are not, in general, preserved, while accuracy is maintained. (C) 2004 Elsevier B.V. All rights reserved
Comparative assessment of drivers' stress induced by autonomous and manual driving with heart rate variability parameters and machine learning analysis of electrodermal activity
12openopenZontone, P; Affanni, A; Bernardini, R; Brisinda, D; Del Linz, L; Formaggia, F; Minen, D; Minen, M; Savorgnan, C; Piras, A; Rinaldo, R; Fenici, RZontone, P; Affanni, A; Bernardini, R; Brisinda, D; Del Linz, L; Formaggia, F; Minen, D; Minen, M; Savorgnan, C; Piras, A; Rinaldo, R; Fenici,
Three-dimensional CFD simulations with large displacement of the geometries using a connectivity-change moving mesh approach
This paper deals with three-dimensional (3D) numerical simulations involving 3D moving geometries with large displacements on unstructured meshes. Such simulations are of great value to industry, but remain very time-consuming. A robust moving mesh algorithm coupling an elasticity-like mesh deformation solution and mesh optimizations was proposed in previous works, which removes the need for global remeshing when performing large displacements. The optimizations, and in particular generalized edge/face swapping, preserve the initial quality of the mesh throughout the simulation. We propose to integrate an Arbitrary Lagrangian Eulerian compressible flow solver into this process to demonstrate its capabilities in a full CFD computation context. This solver relies on a local enforcement of the discrete geometric conservation law to preserve the order of accuracy of the time integration. The displacement of the geometries is either imposed, or driven by fluidâstructure interaction (FSI). In the latter case, the six degrees of freedom approach for rigid bodies is considered. Finally, several 3D imposed-motion and FSI examples are given to validate the proposed approach, both in academic and industrial configurations
Generalized Navier Boundary Condition and Geometric Conservation Law for surface tension
We consider two-fluid flow problems in an Arbitrary Lagrangian Eulerian (ALE)
framework. The purpose of this work is twofold. First, we address the problem
of the moving contact line, namely the line common to the two fluids and the
wall. Second, we perform a stability analysis in the energy norm for various
numerical schemes, taking into account the gravity and surface tension effects.
The problem of the moving contact line is treated with the so-called
Generalized Navier Boundary Conditions. Owing to these boundary conditions, it
is possible to circumvent the incompatibility between the classical no-slip
boundary condition and the fact that the contact line of the interface on the
wall is actually moving. The energy stability analysis is based in particular
on an extension of the Geometry Conservation Law (GCL) concept to the case of
moving surfaces. This extension is useful to study the contribution of the
surface tension. The theoretical and computational results presented in this
paper allow us to propose a strategy which offers a good compromise between
efficiency, stability and artificial diffusion
Reconstructing Haemodynamics Quantities of Interest from Doppler Ultrasound Imaging
The present contribution deals with the estimation of haemodynamics
Quantities of Interest by exploiting Ultrasound Doppler measurements. A fast
method is proposed, based on the PBDW method. Several methodological
contributions are described: a sub-manifold partitioning is introduced to
improve the reduced-order approximation, two different ways to estimate the
pressure drop are compared, and an error estimation is derived. A test-case on
a realistic common carotid geometry is presented, showing that the proposed
approach is promising in view of realistic applications.Comment: arXiv admin note: text overlap with arXiv:1904.1336
Reduced-order semi-implicit schemes for fluid-structure interaction problems
POD-Galerkin reduced-order models (ROMs) for fluid-structure interaction problems (incompressible fluid and thin structure) are proposed in this paper. Both the high-fidelity and reduced-order methods are based on a Chorin-Temam operator-splitting approach. Two different reduced-order methods are proposed, which differ on velocity continuity condition, imposed weakly or strongly, respectively. The resulting ROMs are tested and compared on a representative haemodynamics test case characterized by wave propagation, in order to assess the capabilities of the proposed strategies
Dimension reduction in heterogeneous parametric spaces with application to naval engineering shape design problems
We present the results of the first application in the naval architecture field of a methodology based on active subspaces properties for parameter space reduction. The physical problem considered is the one of the simulation of the hydrodynamic flow past the hull of a ship advancing in calm water. Such problem is extremely relevant at the preliminary stages of the ship design, when several flow simulations are typically carried out by the engineers to assess the dependence of the hull total resistance on the geometrical parameters of the hull, and others related with flows and hull properties. Given the high number of geometric and physical parameters which might affect the total ship drag, the main idea of this work is to employ the active subspaces properties to identify possible lower dimensional structures in the parameter space. Thus, a fully automated procedure has been implemented to produce several small shape perturbations of an original hull CAD geometry, in order to exploit the resulting shapes and to run high fidelity flow simulations with different structural and physical parameters as well, and then collect data for the active subspaces analysis. The free form deformation procedure used to morph the hull shapes, the high fidelity solver based on potential flow theory with fully nonlinear free surface treatment, and the active subspaces analysis tool employed in this work have all been developed and integrated within SISSA mathLab as open source tools. The contribution will also discuss several details of the implementation of such tools, as well as the results of their application to the selected target engineering problem
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