## AsterStudy

AsterStudy is a new graphical interface for code_aster. It makes the *pre* and *post* processes much more easier, with graphical access to the aster keywords, and much more!

AsterStudy is a new graphical interface for code_aster. It makes the *pre* and *post* processes much more easier, with graphical access to the aster keywords, and much more!

Different industrial applications involve the modeling of flow through porous material, like water filtration, catalyst beds, packing, etc.

Darcy-Forchheimer law can be used on the Porous media to characterize the pressure drop:

Where *S* is a source term added to the Navier-Stokes equations. This term is composed of a viscous loss term and an inertial loss term, creating a pressure drop that is proportional to the velocity and velocity squared, respectively.

The constants *D* and *F* have physical meaning and could be calculated based on permeability and Ergun’s coefficient, but in this work they have been determined by curve fitting of the pressure/velocity curves of the porous material.

This image shows streamlines passing trough the filling material and drift eliminator of a cooling tower:

The simulation has been performed at Idra Simulation on a 3.7 millions elements mesh.

*Topology optimization* determines the distribution of material most suitable to a given objective. It is primarily used to produce a fundamental basis for the engineers at the conceptual design stage, or to generate ideas for new alternatives.

In order to express the distribution of materials in topology optimization, **density variables** of the finite elements created for analysis are used. The element density of 1 represents a part that requires the element, while 0 represents a part that does not require the element. Unlike parametric optimization, the only design variable is the element’s density. As such, the user does not specify separate design variables but composes an optimization problem using only the combinations of objective functions and constraints.

Like any optimization problem, *Topology optimization** *includes the following fundamental elements:

**Objective**: In this problem, the objective is to minimized the static compliance (a function of element density expressed in the form of global deformation energy):

Where:

f : Load vector

u : Global & element displacement vectors

K: Global & element stiffness matrices

**Design variables:** Volume fraction (the n_nodes density values which determine whether material is present (1) or absent (0))

**Geometric constraints**: the initial unoptimized geometry:

**Design evaluator:** the linear elasticity solver of MidasNFX, that calculates deformation energy based on specified loads and boundary conditions.

Since we are looking for general guidelines of an optimal design (in practice, we should say “better design”), the next step consists of modifying the original CAD geometry to remove material when it’s not needed:

Topology optimization often leads to complicated organic-like products that cannot be manufactured using traditional processes (which is not necessarily the case here). Additive manufacturing, like **3D printing**, is sometimes more adapted for this kind of design. Here, a printed version of the optimized part is produced.

This video summarizes the whole process:

A simple model, with a lot of added value! For this project, Midas NFX has been used to control the thickness of the *thermocline* (the layer of fluid where the temperature changes rapidly).

The container is initially filled with warm water, and the inlet of cold water progressively replace it. The shape of the diffusers and the flow rate are adjusted to keep the thickness of the thermocline under a critical value.

**midas NFX 2017** is now available to all our clients. If you still don’t use NFX and you want to try it, contact us to have a free evaluation version.

The **2017** release includes several major improvements for modeling, contact creation, optimization and post processing. For more details, consult the release notes.

There’s more! See the release notes.

This short film presents an original application of HPC, namely *Agent-based social simulation* applied to prehistoric life:

The video is produced by the BSC Scientific Visualization Team. This center is also developing *Alya* (see this previous post about Alya), a multi-physics code designed to run efficiently in supercomputers.

code_aster offers numerous dynamic analysis options: full transient (see “Dynamic stability of 3d-printed device“), modal, spectral and harmonic. This post presents an example of the latest applied to a 8 stories building.

The harmonic analysis can be performed directly in the physical space, or by the modal superposition method – which could be useful for large problems (superposition of modes of the full structure or a series of sub-structures).

The macro commande DYNA_VIBRA gathers many of the dynamic options under a single command, e.g.:

Haro = DYNA_VIBRA( TYPE_CALCUL='HARM', BASE_CALCUL='PHYS', MATR_MASS=M3, MATR_RIGI=K3, MATR_AMOR=C3, LIST_FREQ=listfreq, EXCIT=_F(VECT_ASSE=F3, COEF_MULT=1.0), );

The new DEFI_LIST_FREQ command creates a list a frequencies to sweep with an automatique refinement around the natural modes of the structure.

**For training or consulting using code_aster, contact us.**