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Open CASCADE and rapid prototyping in human carotid lumen reconstruction
Get PDFImage processing algorithms, CAD-CAM tools and rapid prototyping (RP) techniques are able to produce complex lumen artery replicas. This work presents a system for manufacturing the lumen of human carotid from computed tomography acquisition. The pipe-line of manufacturing process of a human carotid lumen replication is presented. Each stage of the pipe-line is briefly discussed. Technical details of the 3D surface
reconstruction phase, based on the Open Cascade geometric modelling software, and the RP manufaturing process based on Fused Deposition Modelling are presented
Radiosity for highly tessellated models
Get PDFThe radiosity method is one of the methods of choice used in global illumination simulation. It is a finite element technique that is particularly well suited for computing the radiance distribution in an environment exhibiting only diffuse reflection and emission. We discuss a multiresolution implementation of the technique, that has been developed to rapidly compute radiosity solutions for scenes composed of highly tessellated models. The application context is an interactive lighting design tool being developed in the framework of the DIVERCITY project (EU-IST-13365), funded under the European IST programme (Information Society Technologies).2002-05-27Conference held in Chia, CA, ItalySIMAI 2002 Symposium on Adaptive Techniques in Numerical Simulation and Data Processin
Confronto SEM-FEM per un problema di dinamica strutturale
Get PDFIn questo rapporto si è voluto affrontare un problema classico di ingegneria civile, quello di una trave semplicemente appoggiata sollecitata da una forza impulsiva di mezzeria. Il problema in esame, ben noto dal punto di vista sia sperimentale che teorico è stato utilizzato per verificare l’applicabilità delle metodologie ad elementi spettrali, alla risoluzione di un problema di semplice dinamica strutturale. La metodologia SEM (Spectral Element Method) è stata implementata dal gruppo di Meccanica dei Solidi e delle Strutture nella famiglia di codici ELSE, finora queste metodologie sono state impiegate in ambito strutturale, per la risoluzione di problemi statici, e di dinamica transiente “veloce” legata cioè alla propagazione di onde elastiche nelle strutture. I fenomeni dinamici in questo caso sono più lenti, interessano frequenze inferiori, e vengono genericamente definiti come problemi di dinamica strutturale. I risultati ottenibili con la metodologia spettrale saranno confrontati con quelli ottenibili con una specifica metodologia ad elementi finiti, implementata nel codice commerciale ANSYS, di provata affidabilità
Photo-realistic image synthesis in volume rendering for rapid prototyping and CAM applications (draft)
Get PDFThis document describes some preliminary results of the application of direct volume visualization and realistic image synthesis techniques in Computer Aided Manufacturing (CAM) field. The final goal is to analyze the use volume data representation and direct volume visualization techniques respectively as basic geometric element and rendering method for numerical control (NC) process planning and simulation. In particular we want to study their application in the process of human organs replication by rapid prototyping techniques. Volume rendering techniques will be used to evaluate the geometric reconstruction of volumetric data (e.g. parts of human body extracted from a CT scan as the carotid arteries), in order to obtain the best polygonal approximation of a dataset. The polygonal model resulting from this evaluation stage will be used to drive its physical reconstruction via rapid prototyping. A volume rendering program, called VolCastIA, is presented. VolCastIA is a software environment built to evaluate the use of state of the art image synthesis methods in the volume rendering context
CFD simulation of a free-surface isothermal water flow in the myrrha target geometry (MYRRHA benchmark)
Get PDFThe simulation of the MYRRHA free-surface water experiment using an Arbitrary Eulerian-Lagrangian Moving Mesh Algorithm implemented in the Star-CD commercial CFD code is presented.
In spite of the complexity of the surface morphology, relatively to this type of approach for free surfaces modelling, results show that the algorithm is able to give quantitatively correct results in terms of velocity profiles. Although no measurements of the surface shape are available, it can be guessed that it is well predicted.
Better results are obtained without taking into account surface tension, whose effects seem to be overestimated, probably due to the presence of surface discontinuities in the real free surface
Optimisation of the pin cooler design for the megapie target using full 3D numerical simulations
Get PDFThe MEGAwatt PIlot Experiment (MEGAPIE) project has been recently proposed to demonstrate the feasibility of a liquid lead bismuth target for spallation facilities at a beam power level of 1 MW. The target will be put into operation at the Paul Scherrer Institut (PSI, Switzerland) in 2004 and will be used in the existing target block of SINQ. About 650 kW of thermal power has to be removed through a bunch of 12 pin-coolers. In order to improve the heat exchange, it was decided to investigate the possibility of accelerating the oil coolant by introducing a spiral in the oil cylindrical channel. This forces the flow to rotate while rising, thus increasing the Reynolds number and the heat transfer coefficient. We show some numerical simulations, which have supported the dimensioning of the pins as well as the choice of the secondary coolant, that is Diphyl THT. The spiral option has been confirmed.
The spiral diameter must be a little smaller than the channel width, to allow the effective mechanical assemblage of the pin. The existence of a gap between the spiral and the external wall adds complexity to the numerical simulation, being fully 3D with several orders of magnitude of length scales involved.
A single pin has been tested by Enea-Brasimone and entirely simulated by CRS4 for a matrix of various operational settings. Results are shown and compare
Assessment of the boussinesq approximation for buoyancy-driven flows
Get PDFThe numerical simulation of buoyant flows often makes use of the Boussinesq approximation. This is particularly true
when Direct Numerical Simulation is used for the analysis of heat transfer loops or other applications of natural convection flows. Boussinesq approximation consists of considering the density strictly constant, adding the buoyant force to the momentum balance and coupling an equation for the temperature to the incompressible Navier-Stokes system that has to be solved. In this paper, the validity of the Boussinesq approximation is investigated in some details via numerical simulations.
The test cases chosen include a differentially heated cavity and two buoyant heated loops with internal heating. Results
show clearly that the error on some performance parameters depends linearly on the compressibility parameter βΔΤ The
error in some cases can be 20% or higher, but it is drastically reduced to a few percent by the use of a 2ⁿͩ order formulation of the Boussinesq source term. Nevertheless, some flow features are strictly tied to the compressible coupling and are not captured in a Boussinesq framework
Interpol, routines for interpolation
Get PDFA set of C++ classes have been written for finding an interpolated scalar value at any point on a rectangular grid in one, two or three dimensions. The grid is considered to be composed of pixels or voxels and the known values are considered to be defined in one of two ways, either 1) the values of a continuous field measured at the center of each pixel or voxel, or 2) the integrated (averaged) values of the field for each pixel or voxel. (The classes include a method for interpolation using known values defined at arbitrary positions rather than on a rectangular grid, but this part of the package has not been tested.) This packages has implementation of interpolation could be of general use, but the motivation has been for segmentation of medical images, hence, some design choices have been made for that specific application