A Geometrical domain decomposition method in computational fluid dynamics

We present a detailed description of the implementation of the DD methods in the numerical framework of finite elements. We present interpolation techniques for Dirichlet and Neumann data as well as conservation algorithms

Numerical simulation of gear pumps

We present in this paper a complete numerical strategy for the study of two gear pumps. This work includes all the steps to follow from the treatment of the CAD geometry until the analysis of the simulation results. In particular, we treat the CAD simplification, the meshing of the geometry, the numerical strategy and, finally, the analysis of simulation results

A finite element model for the simulation of lost foam casting

In this paper, we present a numerical model to simulate lost foam casting processes. We first introduce this particular casting in order to catch the different physical processes in play during a casting. We also briefly comment on the possible physical and numerical models to envisage the numerical simulation. Next we present a model which aims at solving “part of” the complexities of the casting, together with a simple energy budget that enables to obtain an equation for the velocity of the metal front advance. Once the physical model is established we develop a finite element method to solve the governing equations. The numerical and physical methodologies are then validated through the solution of a two and a three-dimensional example. Finally, we briefly discuss some possible improvements of the numerical model in order to catch more physical phenomena

Transmission conditions with constraints in finite element domain decomposition methods for flow problems

This work presents a conservative scheme for iteration‐by‐subdomain domain decomposition (DD) strategies applied to the finite element solution of flow problems. The DD algorithm is based on the iterative update of the boundary conditions on the interfaces between the subregions, the so‐called transmission conditions. The transmission conditions involve the essential and natural boundary conditions of the weak form of the problem, and should ensure strong continuity of the velocity and weak continuity of the traction. As a first approach, the transmission conditions are interpolated using the classical Lagrange interpolation functions. Conservation problems might arise when two adjacent subdomains have a sensibly different mesh spacing. In order to conserve any desired quantity of interest, an interface constraining is introduced: continuity of the transmission conditions are constrained under a scalar conservation equation. An example of mass conservation illustrates the algorithm.&nbsp

Variational multiscale stabilization for compressible flow

This paper presents a variational multiscale stabilization for the finite element numerical solution of the Euler and Navier-Stokes equations of compressible flow. All the components of the dual operator are considered in the stabilization term and two options are proposed for the computation of the variational multiscale stabilization subscale. The first option that we call diagonal τ subscale, presents the classical form for the subscale as the product of a parameter τ times the residual of the equation. The second option that we call Fourier subscale uses the Fourier transform in order to model the subscale. We compare these two options for the variational multiscale stabilization subscale through several two-dimensional benchmark cases of different complexity in viscous and inviscid flows, covering a wide range of Mach numbers

Development and characterization of semitransparent double skin PV façades

This research aims at developing new standardized typologies of semitransparent double skin façades formed by PV laminates in the outer skin. At present there are many buildings in Europe which incorporate such active façades, but all have been designed as user defined projects and very few accurately evaluate the feasibility of using the heat produced within the air gap. There is actually a lack of effective methodology to allow non-specialist architects to design and evaluate such façades. This research tries to address this situation: the Spanish PV manufacturer ISOFOTON, together with the partners of the PVTBUILDING project: CIMNE, the UdL, PICHAguilera, DOMUS and BSC have begun a collaboration to design industrialized modules constituted by an external semitransparent PV layer, a wide air gap and an internal glass layer. This paper describes the results of four stages of a more wide research: a detailed analysis of the existing double skin façades in office buildings and the definition of a family of standard PV modules and ventilated façades; an intensive evaluation of the existing heat transfer relations for asymmetrical heated vertical air channels; the programming of a dynamic transient solver based on TRNSYS and the validation of the codes with the set up of prototypes and the beginning of an experimental campaign

Parallel Electromechanical model of the heart

In this paper, we present a high performance computational electromechanical model of the heart, coupling between electrical activation and mechanical deformation and running efficiently in up to thousands of processors. The electrical potential propagation is modelled by FitzHugh-Nagumo or Fenton-Karma models, with fiber orientation. The mechanical deformation is treated using anisotropic hyper-elastic materials in a total Lagrangian formulation. Several material models are assessed, such as models based on biaxial tests on excised myocardium or orthotropic formulations. Coupling is treated using the Cross-Bridges model of Peterson. The scheme is implemented in Alya, which run simulations in parallel with almost linear scalability in a wide range computer sizes, up to thousands of processors. The computational model is assessed through several tests, including those to evaluate its parallel performance.Sociedad Argentina de Informática e Investigación Operativ

Heterogeneous CPU/GPU co-execution of CFD simulations on the POWER9 architecture: Application to airplane aerodynamics

High fidelity Computational Fluid Dynamics simulations are generally associated with large computing requirements, which are progressively acute with each new generation of supercomputers. However, significant research efforts are required to unlock the computing power of leading-edge systems, currently referred to as pre-Exascale systems, based on increasingly complex architectures. In this paper, we present the approach implemented in the computational mechanics code Alya. We describe in detail the parallelization strategy implemented to fully exploit the different levels of parallelism, together with a novel co-execution method for the efficient utilization of heterogeneous CPU/GPU architectures. The latter is based on a multi-code co-execution approach with a dynamic load balancing mechanism. The assessment of the performance of all the proposed strategies has been carried out for airplane simulations on the POWER9 architecture accelerated with NVIDIA Volta V100 GPUs

From imaging to simulation: a framework applied to simulate the blood flow in the carotids

In this work we present a methodology to extract information from medical imaging and use it for hemodynamical simulation in arteries. Based on in-vivo magnetic resonance images (MRI), the velocity of the blood flow has been measured at different positions and times. Also, the anatomy of the vessel has been converted into a volume mesh suitable for numerical modeling. This data has been used to solve computationally the dynamics of the fluid inside the artery in healthy and pathologic cases. As an application, we have developed a computational model within the carotids. The next step in the pipeline will be to extend the simulation to fluidstructure interaction (FSI) to find the parameters in an atherosclerotic plaque that could lead to rupture.Peer Reviewe