Papers by Alberto Beltran
Magnetohydrodynamics, 2015
Bulletin of the American Physical Society, Nov 23, 2014
We study numerically the duct flow of an electrically conducting incompressible viscous fluid (a ... more We study numerically the duct flow of an electrically conducting incompressible viscous fluid (a liquid metal) past a a localized magnetic field, namely, a magnetic obstacle. We use a quasi-two-dimensional model based on a formulation that includes the induced magnetic field as electromagnetic variable (B-formulation) and analyze the stability of the flow in the parametric space of the Hartmann and Reynolds numbers. We find that even though for a given strength of the localized braking Lorentz force (characterized by the Hartmann number) the flow may become unstable and give rise to a time-periodic wake, when a critical Reynolds number is reached, a further increase in the Reynolds number may result in the flow becoming steady again. Evidently, this behavior is not observed in the flow past a solid obstacle. Experimental observations carried out in a liquid metal (GaInSn) duct flow suggest that this prediction is correct.
Angeles-The concept of a magnetic obstacle in an electrically conducting fluid flow refers to the... more Angeles-The concept of a magnetic obstacle in an electrically conducting fluid flow refers to the opposing Lorentz force induced by a localized magnetic field that is in relative motion with the surrounding fluid. The name stems from some similarities that occur between the flow past a rigid obstacle and that generated by a localized magnetic field. In this work, the stability of a flow past a magnetic obstacle is described in terms of the Hartmann and Reynolds numbers of the imposed flow (the Hartmann number squared estimates the ratio of magnetic to viscous forces). We find that for a given Hartmann number the flow is steady for small Reynolds numbers and becomes time-dependent, shedding vortices periodically as the Reynolds number grows. But in sharp contrast to the case of a rigid obstacle, for even larger Reynolds numbers, the flow may become steady again. The dependence of the Strouhal number on the governing parameters is also explored.
Journal of Energy Storage
Journal of the Brazilian Society of Mechanical Sciences and Engineering
Sustainability
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Journal of Porous Media, 2020
The contributions of microporosity (φ micro) and micropermeability (k micro) to the total (Darcy)... more The contributions of microporosity (φ micro) and micropermeability (k micro) to the total (Darcy) permeability (k) were estimated for limestones from Sierra de Chiapas region. To achieve this purpose, microporosity (φ micro) was measured using scanning electron microscopy (SEM) image analysis and compared to experimental permeability. Moreover, k micro was estimated using the modified Kozeny-Carman equation, whose parameters were also determined from SEM image analysis of the porous network. The obtained equations that establish the correlations k micro-k and φ micro-k were in excellent agreement with experimental permeabilities, demonstrating their efficacies. Besides, the importance of the use of SEM as complementary tool for the analysis of small pores was demonstrated.
Submitted for the DFD13 Meeting of The American Physical Society On the open/close performance of... more Submitted for the DFD13 Meeting of The American Physical Society On the open/close performance of prosthetic heart valves at high frequencies A. BELTRAN, R. ZENIT, Universidad Nacional Autonoma de Mexico-We report experimental observations of the performance of mechanical and biological prosthetic heart valves. The valves are mounted in a test circular channel conected to a flow system that emulates accelerated human-like conditions. The flow is generated by a high frequencie pulsative pump (in the range of 7 to 18 Hz). The objective of the investigation is to find the treshold conditions for which the open/close performance fails. Preliminary results show that for the mechanical valve the failure starts at 436 pulses/min, while for the biological valve, it starts a failing performance is observed for frequencies higher that 462 pulses/min. Even though these values are far from the heart rate in the human body, we use these measurements to further understand the structure-fluid interaction mechanics of the flow through heart valves.
Journal of Structural Geology, 2017
Among all the rock parameters measured by modern well logging tools, the formation factor is esse... more Among all the rock parameters measured by modern well logging tools, the formation factor is essential because it can be used to calculate the volume of oil-and/or gas in wellsite. A new mathematical model to calculate the formation factor is analytically derived from first principles. Given the electrical properties of both rock and brine (resistivities) and tortuosity (a key parameter of the model), it is possible to calculate the dependence of the formation factor with porosity with good accuracy. When the cementation exponent ceases to remain constant with porosity; the new model is capable
Journal of the Brazilian Society of Mechanical Sciences and Engineering
PLoS ONE, 2014
Electrical transmission signals have been used for decades to characterize the internal structure... more Electrical transmission signals have been used for decades to characterize the internal structure of composite materials. We theoretically analyze the transmission of an electrical signal through a composite material which consists of two phases with different chemical compositions. We assume that the temperature of the biphasic system increases as a result of Joule heating and its electrical resistivity varies linearly with temperature; this last consideration leads to simultaneously study the electrical and thermal effects. We propose a nonlinear conjugate thermo-electric model, which is solved numerically to obtain the current density and temperature profiles for each phase. We study the effect of frequency, resistivities and thermal conductivities on the current density and temperature. We validate the prediction of the model with comparisons with experimental data obtained from rock characterization tests.
Applied Thermal Engineering, 2021
Abstract This paper reports on an experimental and numerical investigation of a modifiable Tesla ... more Abstract This paper reports on an experimental and numerical investigation of a modifiable Tesla turbine driven by compressed air. To study the impact of geometrical parameters like the rotor’s diameter and space between the rotor and the housing, two Tesla turbine prototypes with diameters of 11.25 and 15 cm were designed and built. For both, a 3 mm space between rotor and housing is considered. In particular, for each turbine the effect of disc spacing and pressure flow in the range of real operating conditions is analyzed. Experimental characterization based on a thermodynamic analysis allows estimating optimum values of 0.9 mm and 103.89 kPa for the disc spacing and pressure flow, respectively. Additionally, values for the efficiency and the stall torque are calculated when the pressure flow is varied in the range of 50 to 327 kPa and of 59.34 to 272.46 kPa, maximum efficiencies of 33% and 50% are obtained, and stall torque measurements reach up to 0.304 N · m and 0.448 N · m, for the turbines with small and large diameters, respectively. 3D simulations performed with the open source CFD library OpenFOAM ®, well reproduced the stall torque measurements. Numerical results show that the loss of isentropic power in the space between the rotor and the housing is up to 36.17% and that the largest wall shear stress values are located on the periphery of the rotor’s disc.
Physical Review E, 2010
A numerical simulation and a theoretical model of the two-dimensional flow produced by the harmon... more A numerical simulation and a theoretical model of the two-dimensional flow produced by the harmonic oscillation of a localized magnetic field ͑magnetic obstacle͒ in a quiescent viscous, electrically conducting fluid are presented. Nonuniform Lorentz forces produced by induced currents interacting with the oscillating magnetic field create periodic laminar flow patterns that can be characterized by three parameters: the oscillation Reynolds number, Re , the Hartmann number, Ha, and the dimensionless amplitude of the magnetic obstacle oscillation, D. The analysis is restricted to oscillations of small amplitude and Ha= 100. The resulting flow patterns are described and interpreted in terms of position and evolution of the critical points of the instantaneous streamlines. It is found that in most of the cycle, the flow is dominated by a pair of counter rotating vortices that switch their direction of rotation twice per cycle. The transformation of the flow field present in the first part of the cycle into the pattern displayed in the second half occurs via the generation of hyperbolic and elliptic critical points. The numerical solution of the flow indicates that for low frequencies ͑v.e. Re =1͒, two elliptic and two hyperbolic points are generated, while for high frequencies ͑v.e. Re = 100͒, a more complex topology involving four elliptic and two hyperbolic points appear. The bifurcation map for critical points of the instantaneous streamline is obtained numerically and a theoretical model based on a local analysis that predicts most of the qualitative properties calculated numerically is proposed.
Journal of Computational Physics, 2010
We use the induced electric current as the main electromagnetic variable to compute low magnetic ... more We use the induced electric current as the main electromagnetic variable to compute low magnetic Reynolds number magnetohydrodynamic (MHD) flows. The equation for the induced electric current is derived by taking the curl of the induction equation and using Ampère’s law. Boundary conditions on the induced electric current are derived at the interface between the liquid and the thin conducting
Energy, 2014
ABSTRACT The heat transfer and entropy generation in the parallel plate flow of a power-law fluid... more ABSTRACT The heat transfer and entropy generation in the parallel plate flow of a power-law fluid are analyzed. Asymmetric convective cooling is included in the analysis by considering thermal boundary conditions of the third kind. Using the known velocity profile, the temperature field is analytically derived. Conditions for minimum entropy generation are determined.
Journal of Physics: Conference Series, 2007
The flow in a shallow layer of an electrically conducting fluid past a localized magnetic field i... more The flow in a shallow layer of an electrically conducting fluid past a localized magnetic field is analyzed numerically. The field occupies only a small fraction of the total flow domain and resemblances the magnetic field created by a permanent magnet located close to the fluid layer. Two different physical cases are considered. In the first one, the fluid layer is free from externally injected electric currents, therefore, only induced currents are present. In the second case, an external electric current is injected to the fluid layer, transversally to the main flow direction. It is shown that the Lorentz force created by the interaction of the electric currents with the non-uniform magnetic field acts as an obstacle for the flow and creates different flow patterns similar to those observed in the flow past bluff bodies. A quasi-two-dimensional model that takes into account the existence of the bottom wall through a linear Hartmann-Rayleigh friction term is considered. When inertial and magnetic forces are strong enough, the wake formed behind the zone of high magnetic field is destabilized and a periodic vortex shedding similar to the classical von Kármán street is found. The effect of Hartmann-Rayleigh friction in the emergence of the instability is analyzed.
Sustainability, 2019
This paper introduces a new methodology for the development of appropriate technology that allows... more This paper introduces a new methodology for the development of appropriate technology that allows satisfying energy needs in rural communities. The methodology integrates the technological development, taking particularly into account the assessment of environmental impacts as well as evaluation of the functionality of the technology. Therefore, it is implemented as a case study in the development of a solar wood-dryer in an artisan community in Mexico. Relevant issues were identified for the success of the methodology, which includes identifying key participants in the community, as well as the use of specialized simulation- and computer-based design tools, and a prior evaluation of the potential environmental impacts through Life-Cycle Assessment (LCA) of the solar wood-dryer. Three geometries of a solar wood-dryer prototype were proposed and analyzed with computer-based simulations, which showed better interior heat transfer than the traditional wood brick-dryer. LCA revealed tha...
Bulletin of the American Physical Society, 2008
The concept of a magnetic obstacle in an electrically conducting fluid flow refers to the opposin... more The concept of a magnetic obstacle in an electrically conducting fluid flow refers to the opposing Lorentz force induced by a localized magnetic field that is in relative motion with the surrounding fluid. The name stems from some similarities that occur between the flow past a rigid obstacle and that generated by a localized magnetic field. In this work, the
Bulletin of the American Physical Society, 2014
We report experimental observations of an electromagnetically forced flow in a thin layer of an e... more We report experimental observations of an electromagnetically forced flow in a thin layer of an electrolyte (0.4 cm deep, 30 cm wide, 30 cm long), produced by the interaction of an imposed D.C. Current (0.4 A) and a localized time-dependent magnetic field. The field, generated by a permanent magnet (0.95 cm diameter) placed underneath the electrolyte layer, oscillates harmonically along
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Papers by Alberto Beltran