Laboratorio de Plasmas Densos (PLADEMA)

Exposición realizada en el marco del  Encuentro del Ministerio de la Producción, Ciencia y Tecnología de la Provincia de Buenos Aires con autoridades y centros de la Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Exposiciones de los directores de los Centros de Investigación propios, asociados y vinculados

A Python implementation in graphic processing unit of a lattice Boltzmann model for unstable three-dimensional flows in immersed permeable media

The implementation of a lattice Boltzmann model for three-dimensional permeable media with localized drag forces is presented. The model was previously introduced for two-dimensional geometries and follows the basics of the immersed boundary method. Permeable flows are much less stable than their counterparts in porous media and generally produce large coherent flow structures, such as vortex lines, rolls, and wakes. In addition, in permeable media, the small-scale geometry often needs to be represented to a high degree of detail in order to capture certain transport phenomena, such as micro-convection or pollination. Hence, both calculation speed and memory requirements are under strain. The present model was implemented in a graphic processing unit showing excellent performance in the calculation of stable and unstable flows in a rectangular channel partially obstructed by an array of parallel wires. In particular, the model is able to deal with small and medium spatial scales without losing the heterogeneous nature of permeable flows in the homogenization process. The algorithm to manage memory issues is described in detail, and the results of the test case for stable and unstable conditions show the capability of the method to simulate these types of flows.Fil: Boroni, Gustavo Adolfo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Sociales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Silin, Nicolas. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Clausse, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentin

Experimental assessment on the performance of hot wire anemometry in and around a permeable medium by comparison with Particle Image Velocimetry

The air flow through a test section partially obstructed by a permeable array of wires was measured simultaneously by Hot Wire Anemometry (HWA) and Particle Image Velocimetry. The objective ofthe study was the assessment of the suitability of HWA for the measurement of flow velocities amid and adjacent to groups of small obstacles. In the present case the obstacles are set in a regular array configuring a highly permeable structure. The probe was placed at three characteristic positions: in the free flow close to the wire array, inside the permeable medium, and at the interface between the permeable structure and the free flow. The measurements were performed with the hot wire operating under natural convection and mixed convection heat transfer, and operating the hot wire at different overheat ratios. Natural convection plumes extending over several permeable volume elements were detected when the hot wire was under natural convection, in some cases reaching velocities up to 60 mm/s downstream from the hot wire position. For low velocity flows, natural convection can be regarded as a flow velocity offset, which becomes negligible at local velocities higher than 0.03 m/s. For higher velocities, in the mixed convection regime, the intrusivity of the HWA probe becomes relevant. Furthermore, the flow in the test section used in the study presents a linear instability that produces velocity fluctuations. Availing ourselves of this phenomenon we verified the dynamic response of the HWA at the lowest velocity where the flow shows periodic fluctuations; for a local mean velocity of (0.131 ± 0.012) m/s the HWA showed a satisfactory dynamic response up to 20 Hz.Fil: Silin, Nicolas. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Cuscueta, Diego Javier. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Clausse, Alejandro. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Visualización dinámica de campos vectoriales aplicada a escurrimientos hídricos en llanuras

Se describe una aplicación computer graphic para la visualización de campos vectoriales bidimensionales, donde el volumen de datos es muy elevado (de hasta 25 millones de celdas). Se desarrolló una representación gráfica de las trayectorias delineadas por la liberación de partículas dentro del campo vectorial y una adaptación original del concepto de Magic Lens para la visualización dinámica de las propiedades de los campos vectoriales.Eje: Visualizació

Interactive remeshing for navigation over landscape models

The performance of an algorithmic procedure to visualize digital landscapes based in the dynamic control of the size of the model is presented. Approximate representations are produced taking into account criteria relative to the observer position and the local curvature of the terrain. The algorithm leads to substantial reductions of the size of the final meshes, lowering the rendering costs down to 5%. An application of the algorithm is tested on a model of the Colorado Canyon is shown.Fil: Cifuentes, Maria Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires; ArgentinaFil: Venere, Marcelo Javier. Comisión Nacional de Energía Atómica; ArgentinaFil: Clausse, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentina. Comisión Nacional de Energía Atómica; Argentin

Tomography reconstruction by entropy maximization with smoothing filtering

The maximum entropy method (MEM) is a consistent way to treat the problem of tomography reconstruction where an image should be selected from a set of images that fit the measurement data. In this article, MEM is applied to image reconstruction from projections using an entropy formula modified by adding filter terms in order to eliminate the local noise. Numerical experiments were performed showing good results with local mean-square filter terms. The projection error can be used to estimate the weight of the filter term, providing a practical procedure to get improved solutions with limited sets of projections.Fil: Barbuzza, Rosana Graciela. Universidad Nacional del Centro de la Pcia.de Bs.as.. Facultad de Cs.exactas. Departamento de Sistemas; ArgentinaFil: Lotito, Pablo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Departamento de Matemática; ArgentinaFil: Clausse, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Pcia.de Bs.as.. Facultad de Cs.exactas. Departamento de Sistemas; Argentin

Tomografías industriales con el método de máxima entropía

En este artículo se presenta el método de máxima entropía que incorpora información adicional sobre el modelo del objeto, lo cual es aprovechado para mejorar la calidad de la reconstrucción tomográfica. Se muestra la reconstrucción de un conector metálico, a partir de 5 proyecciones con cierto nivel de ruido, tomadas a distinto ángulo. El método tiene en cuenta el error respecto de las proyecciones originales y la textura suave del material para realizar la reconstrucción tomográfica y obtener una imagen de buena calidad. Esta técnica tiene aplicaciones en casos donde la homogeneidad interna del material es conocida a priori desde su diseño y proceso de fabricación.Sociedad Argentina de Informática e Investigación Operativ

A new numerical method for stiff differential equations

A new class of multistep methods for stiff ordinary differential equations is presented. The method is based in the application of estimation functions for the derivatives and the state variables, allowing the transformation of the original system in a purely algebraic system using the solutions of previous steps. From this point of view these methods adopt a semi-implicit scheme. The novelty introduced is an adaptive formula for the estimation function coefficients, deduced from a combined analysis of stability and convergence order. That is, the estimation function coefficients are recomputed at each time step. The convergence order of the resulting scheme is better than the equivalent linear multistep methods, while preserving the properties of stability.Fil: Boroni, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires; ArgentinaFil: Clausse, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires; ArgentinaFil: Lotito, Pablo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentina. Comisión Nacional de Energía Atómica; Argentin

Simulation of phase separation in a Van der Waals fluid under gravitational force with Lattice Boltzmann method

Purpose – This paper aims to assess the accuracy of Lattice Boltzmann method (LBM) for numerical simulation of the stratification of a Van der Waals (VdW) fluid subjected to a gravity field and non-uniform temperature distribution. A sensitivity analysis of the influence of the pseudopotential parameters and the grid resolution is presented. The effect of gravity force on interface densities, density profiles and liquid volume fraction is studied. Design/methodology/approach – The D2Q9 multiple-relaxation-time pseudopotential LBM for two-phase flow is proposed to simulate the phase separation. The analytical solution for density profiles in a one-dimensional problem is derived and used as a benchmark case to validate the numerical results. Findings – The numerical results reproduce the analytical density profiles with great accuracy over a wide range of simulation conditions, including variations of the gravity and temperature fields. Particularly, the numerical simulations are able to represent the effect of gravity on the existence and position of the liquid– vapor boundary of an ideal pure substance in thermodynamic equilibrium. The sensitivity of the results to variations of the calibration parameters of the VdW pseudopotential was assessed. Research limitations/implications – The numerical simulations were performed assuming a VdW fluid in a 2-D cavity with one periodic direction for which analytical solutions for benchmarking purposes are possible to obtain. Originality/value – The following fundamental question is addressed: Is the pseudopotential LBM capable of simulating accurately the liquid–vapor equilibrium under gravity forces and temperature gradients? Moreover, regarding that the pseudopotential model requires the calibration of several internal parameters to achieve thermodynamic consistency, the sensitivity of the results to variations of these parameters is assessed.Fil: Fogliatto, Ezequiel Oscar. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Clausse, Alejandro. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Teruel, Federico Eduardo. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Probabilistic algorithm for computed tomography

A probabilistic algorithm for on-line tomographic reconstruction of ellipse-like images is presented. The algorithm takes advantage of the characteristic preferential direction of the objects, constructing a guidance function to select the angles for subsequent radiographic projections. The simulation results confirm that the technique reduces the number of projections required to achieve a given quality limit.Eje: SimulaciónRed de Universidades con Carreras en Informática (RedUNCI