Numerical study of gas mixture separation in curved nozzles

Species separation can be produced by imposing a pressure gradient in gaseous mixtures, which induces different molecular velocities depending on the molar weight. Pressure gradients can be achieved by centrifugal forces brought about by the passage of the gas through a curved nozzle at supersonic velocity. The efficiency of this process depends on the geometry of the nozzle as well as the flow operating conditions. The numerical solver Fluent was used in order to produce a model of the aerodynamics and the oxygen diffusion of a steady-state flow of air in a curved nozzle. The development of the pressure and O2 concentration profiles along the nozzle were analyzed for different pressure boundary conditions at the inlet and the exit, testing several nozzle sizes. Optimum values of the cut and the inlet pressure were found which maximize the separation efficiency. The effect of the exit pressure was associated with the axial pressure distribution along the inner wall of the nozzle. The results were compared with measurements showing good agreement.Fil: Guozden, Tomas Manuel. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Clausse, Alejandro. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Supersonic cracks in lattice models

We have studied cracks traveling along weak interfaces. We model them using harmonic and anharmonic forces between particles in a lattice, both in tension (Mode I) and antiplane shear (Mode III). One of our main objects has been to determine when supersonic cracks traveling faster than the shear wave speed can occur. In contrast to subsonic cracks, the speed of supersonic cracks is best expressed as a function of strain, not stress intensity factor. Nevertheless, we find that supersonic cracks are more common than has previously been realized. They occur both in Mode I and Mode III, with or without anharmonic changes of interparticle forces prior to breaking, and with or without dissipation. The extent and shape of the supersonic branch of solutions depends strongly on details such as lattice geometry, force law anharmonicity, and amount of dissipation. Particle forces that stiffen prior to breaking lead to larger supersonic branches. Increasing dissipation also tends to promote the existence of supersonic states. We include a number of other results, including analytical expressions for crack speeds in the high-strain limit, and numerical results for the spatial extent of regions where particles interact anharmonically. Finally, we note a curious phenomenon, where for forces that weaken with increasing strain, cracks can slow down when one pulls on them harder. © 2009 Springer Science+Business Media B.V.Fil: Guozden, Tomas Manuel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Jagla, Eduardo Alberto. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Marder, M.. University of Texas at Austin; Estados Unido

An experimental study of the aerodynamic dispersion of loose aggregates in an accelerating flow

The dispersion of powders in gas flows is relevant in some powder processing techniques, in dry powder inhalers and in particle size analysers, among others. When using small particle sizes, the powder tends to form stronger aggregates and the dispersion becomes more difficult. There are many approaches to the dispersion process but most include collisions as one of the possible agglomerate break-up mechanisms. This is not always a satisfactory solution as particles may get contaminated or reduced. In the present work we explore the dispersion of powder aggregates in an accelerating flow with no particle-wall collisions. We built a fluid-dynamic device with a simple geometry consisting of a sharp slit, producing a rapidly converging flow at the entrance and a planar jet at the exit. A powder feeder exited with an ultrasonic actuator was used to generate single powder aggregates. The stationary flow field was calculated numerically and the velocity and degree of aggregate dispersion were assessed based on imaging results. In all the cases tested, erosion of the aggregates could be observed. In the case with the highest suction pressure, a different mechanism arises, which leads to the disintegration of the aggregate and a significantly better dispersion of the powder.Fil: Silin, Nicolas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Tarrio, Juan José. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Universidad Nacional de Cuyo; ArgentinaFil: Guozden, Tomas Manuel. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Universidad Nacional de Río Negro; Argentina. Universidad Nacional de Cuyo; Argentin

Spatiotemporal variability of the wind power resource in Argentina and Uruguay

The spatiotemporal variability of the wind power resource over Argentina and Uruguay is assessed based on the Modern-Era Retrospective Analysis for Research and Applications 2 (MERRA2) dataset. Hourly wind speeds were interpolated to 100-m height, and then, wind power outputs were computed using power curves of three International Electrotechnical Commission (IEC) wind classes. The time series of wind power outputs were filtered using a fast Fourier transform (FFT) to separate regular (annual and daily) from irregular (interannual and synoptic scale) cycles. An empirical orthogonal function analysis was applied to the resulting datasets to obtain the main modes of variability. The results show that the combination of wind power outputs from southern and northern Patagonia broadly follows the average annual electric load. Patagonia exhibits the highest variability on the interannual, annual, and synoptic timescales. On the interannual and synoptic timescales, the variability modes are associated with known and distinct atmospheric circulation modes. The interannual modes of variability are associated with opposite surface level pressure (SLP) anomalies between middle and high latitudes.Fil: Bianchi, Emilio. Universidad Nacional de Rio Negro. Sede Andina. Laboratorio de Procesamiento de Señales Aplicadas y Computacion de Alto Rendimiento.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Solarte Casanova, Edinson Andrés. Universidad Nacional de Rio Negro. Sede Andina. Laboratorio de Procesamiento de Señales Aplicadas y Computacion de Alto Rendimiento.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Guozden, Tomas Manuel. Universidad Nacional de Rio Negro. Sede Andina. Laboratorio de Procesamiento de Señales Aplicadas y Computacion de Alto Rendimiento.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentin

Optimized balance between electricity load and wind-solar energy production

One of the greatest obstacles in the exploitation of wind and solar resources is the uncertainty in their availability, usually known as intermittence. These effects can be greatly diminished by combining wind and solar resources from different locations. In this article we propose a numerical optimization of future renewable capacity additions aimed to minimize the dispersion of the residual power, which is the remaining electricity load after subtracting the contribution of renewables. Results show that penetration of wind and solar power may increase in another 10% of energy share while keeping the dispersion of the residual power constant, by adding capacity at sites most positively correlated with electricity load. For further increments, an optimized distribution of wind and solar facilities compensates variations between renewables. In this situation, wind sites that anticorrelate with solar cycle play an important role.Fil: Guozden, Tomas Manuel. Universidad Nacional de Río Negro; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); ArgentinaFil: Carbajal, Juan Pablo. Swiss Federal Institute of Aquatic Science and Technology; Suiza. University of Applied Sciences Rapperswil; SuizaFil: Bianchi, Emilio. Universidad Nacional de Río Negro; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Agencia de Extensión Rural El Bolsón; ArgentinaFil: Solarte Casanova, Edinson Andrés. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geología Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centro EspacialTeofilo Tabanera. Comision Nacional de Actividades Espaciales ; Argentin