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Open Access
Torsional current - meter for channels
(1997 ASME Fluids Engineering Division Summer Meeting, June 22-26, 1997-06-22) Zarea, Stefan; Rojas-Solorzano, L.
The main objective of this paper is to present the results of the experimental investigation of a Zarea-type torsional velocity-meter. For this, a torsional meter was designed, built and tested in the laboratory. The current meter consists of an axial rotor with blades fixed to a shaft which is in turn fixed to a rigid hub. The force of the water flow produces a torque which deforms the shaft. The current meter has been statically calibrated, thereby establishing the variational curve of the torsion angle as a function of the applied torque. A laboratory facility has been constructed in which tests were run for water speeds of up 3m/s. The torque measurements were taken by using strain gauges. The methodology and the equipment used for the experimental evaluation are shown. Additionally illustrated are the calibration curves, the analysis of obtained results, some advantages and disadvantages, and the range of application of the torsional current-meter are all discussed.
Open Access
Oscillatory momentum transport in cascade transitional boundary layer flows
(DOI: 10.2514/6.1998-2560 Conference: 29th AIAA Fluid Dynamics Conference, At Albuquerque, NM, USA, Volume: 1, 1998) Rojas-Solorzano, L.
The generation and early evolution of boundary layer transitional instabilities, named Tollmien-Schlichting (T-S) waves, in airfoil cascade flows are studied. The energy exchange between the mean flow and the flow instabilities is computed by performing Direct Numerical Simulation of the fluid flow governing equations and by calculating the fluctuating kinetic energy (FKE) budget within the separated boundary layer. The driving role of the FKE production in the wavelength modulation process associated to the receptivity phenomenon, i.e., the generation of T-S waves, is demonstrated. The FKE production largely hastens the wavelength modulation around the inflection point of the mean velocity profile across the boundary layer. Above the inflection point, the fluctuating pressure field favors the energy transport and provides the energy necessary to convect the instabilities out of the boundary layer. The evolution of the T-S waves depicts an asymmetric distribution of the production term in the transverse direction, i.e., in the lower half of the boundary layer the mean flow provides energy to the instabilities while the opposite occurs in the upper half
Open Access
Effects of external disturbances on the momentum transport in cascade transitional boundary layer flows
(Proceedings of FEDSM’98 1998 ASME Fluids Engineering Division Summer Meeting June 21-25, 1998, Washington, DC, 1998-06-21) Rojas-Solorzano, L.
The effects on the boundary layer receptivity in airfoil cascade flow caused by superposed disturbances are studied using an energetic approach. The separated terms in the Fluctuating Kinetic Energy (FKE) budget are calculated. Monotonic time-harmonic disturbances are superposed to the inflow stream using forcing frequencies close to and far from the natural frequency of fluctuation found within the unsteady (supercritical) basic flow. For supercritical regimes, the receptivity is evaluated around the boundary layer separation point, where Tollmien-Schlichting (T-S) waves are naturally generated. For subcritical regimes, the receptivity is explored all over the suction-side of the airfoil since separation does not occur. Within subcritical flows, the superposed perturbation is seen to trigger the generation of T-S-like waves downstream the minimum pressure point only when the forcing frequency is close to n. Within supercritical flows, when the forcing frequency matches n, the FKE budget reflects the energetic interaction between the perturbation and the already existent boundary layer T-S waves
Open Access
Run Life Enlargement Methodology for Ball-and-Seat Check Valves Used in Artificial Lift Pumping Units
(SPE Latin American and Caribbean Petroleum Engineering Conference, Caracas, Venezuela, 21–23 April 1999, 1999-04-21) Zarea, S.; Rojas-Solorzano, L.; Kabboul, F.
Experiments are performed to evaluate the leakage vs. pressure drop, wear and fluid properties, in ball-and-seat valves used in pumping units for artificial oil production. The test facility is constructed to evaluate the operation of several valve sizes, using water, oil and air, subjected to pressure drops up to 5000 psig. Results demonstrated that the currently accepted API vacuum test might be too severe and that more realistic tests may lead to substantial savings in valve replacements. Experimental results in dimensional and dimensionless form are presented, using a new similitude criterion
Open Access
Numerical simulation of the heat penetration in two-plate arc welding
(Conference: h International Congress of Numerical Methods in Engeering and Applied Science (CIMENICS 2000), At Puerto La Cruz, Venezuela, Volume: 5, 2000) Payares, C.; Rojas-Solorzano, L.; Viggiani, P.
A mathematical model and numerical simulation of the three-dimensional and transient metal arc-welding process is presented. The heat source is considered as spatially distributed following a centered Gaussian bell, while the substract material (Al 6063) is assumed homogeneous and isotropic with temperature-dependent thermal properties. Radiation and convection are also calculated through an empirical temperature dependent correlation. Phase-change phenomenon is included as a discontinuity in the material specific heat. Calculations were performed by using a finite volume code (CFX4.2TM). Computed heat penetration and weld metal area are found to be in good agreement with experimental data.
Open Access
Fluid flow hydrodynamic modeling in the passage of an oil artificial lift pumping unit
(Proceeding of ETCE/OMAE2000 Joint Conference Energy for the New Millenium February 14-17, 2000, New Orleans, LA, 2000-02-14) Salazar S., Abraham; Rojas-Solorzano, L.
The study of the two-phase flow through the standing and traveling valves used in an oil artificial-lift pumping unit is presented. The investigation aimed to determine the effects the gaseous phase may cause on the pump volumetric efficiency. Data obtained on a specially designed test facility is presented and analyzed as a first step before developing a semi-empirical model to predict the performance of the pump under two-phase flow conditions. Preliminary results, based on one-phase and two-phase runs, demonstrate important features introduced on the pump performance once the gas-phase is included in the process
Open Access
Numerical simulation of the flow through an intermittent gas lift valve
(Proceeding of ETCE/OMAE2000 Joint Conference Energy for the New Millenium February 14-17, 2000, New Orleans, LA, 2000-02-14) Concho, Maria A.; Gasbarri, Sandro; Rojas-Solorzano, L.
The numerical simulation of the flow through a pilot valve used in the oil intermittent gas lift process is presented.The complexity of the non-isothermal compressible flow is modeled by the solution of the Navier-Stokes, Mass Conservation and Energy equations for the compressible flow. Numerical results and analyses pertaining to the flow dynamics through a 1½-inch pilot valve at an operating condition encountered in typical field operations are presented
Open Access
Design of a large scale flow-meter test and calibration facility
(FEDSM2000 FORUM ON FLUID MEASURENMENT AND INTRUMENTATION BOSTON, MASSACHUSETTS, ON JUNE 11-15, 2000, 2000-06-11) Corrales-Barallobre, C.; Martínez-Huen, R.; Alvarez, Luis; Polanco, G.; Rojas-Solorzano, L.
The design and set up of a large-scale flowmeter calibration and test facility is presented. The facility was designed to handle flowmeters with diameters between 6” and 14”, flow rates up to 0.3 m3/s and to give results less than 1% accurate. The calibration methodology consisted firstly in calibrating the pattern flowmeters, using volume and time primary measurements, and secondly, comparing the pattern to the flowmeters needing calibration. The design and calculation of the primary calibration device is addressed, including numerical simulations of the outflow manifold and the comparison to experimental data. The calibration facility proved to be accurate and reliable in producing renewed calibration data for various tested flowmeters
Open Access
Design of the distribution manifold for a large-scale flowmeter calibration facility
(FEDSM2000 FORUM ON FLUID MEASURENMENT AND INSTRUMENTATION BOSTON, MASSACHUSETTS, ON JUNE 11-15, 2000, 2000-06-11) Corrales-Barallobre, C.; Martínez-Huen, R.; Alvarez, Luis; Polanco, G.; Rojas-Solorzano, L.
The design and test of the distribution manifold for a large-scale flowmeter calibration facility is presented. The design was intended to have an air-free flow operation and a free-surface flow-like towards the downstream half-body discharge. Back of the envelope calculations are presented for the estimation of the preliminary dimensions. Numerical simulations of the flow during manifold steady state operation are utilized to refine the manifold design. No air entrapment is noticed in the flow simulation
Open Access
Design of a flow deflector for an accurate flow meter calibration facility
(FEDSM2000 FORUM ON FLUID MEASURENMENT AND INTRUMENTATION BOSTON, MASSACHUSETTS, ON JUNE 11-15, 2000, 2000-06-11) Corrales-Barallobre, C.; Martínez-Huen, R.; Alvarez, L.; Polanco, G.; Rojas-Solorzano, L.
The design and test of a flow deflector gate used for controlling the flow deviation toward the primary tank in a flow-meter calibration facility is presented. The deflector gate is pneumatically controlled and permits the flow conduction to either the suction tank or to the primary tank. The deflector is designed to approximately compensate the flow deficit towards the primary tank during the opening, with the flow excess while in the shutting process. Numerical simulations are performed to study the flow hydrodynamics during the deflector operation. Results are compared to experimental data, and used to improve the gate design. The enhanced design proved to guarantee the uniformity of the flow through the calibration section and the dramatic reduction of the error in volume measurement during calibration.
Open Access
Study of the transient temperature profiles induced by changes of the welding parameters during aluminium two plate arc butt-welding
(Universidad Simón Bolívar Departamento de Mecánica (*) Departamento de Conversión de Energía, 2001) Urthaler, Yetzirah; Viggiani, Pedro; Payares, Carolina; Rojas-Solorzano, L.
The numerical study and calculation of transient temperatures developing during the arc-welding process of 6063 T5 aluminum plates is presented. The mathematical model is based on the differential energy conservation equation. The governing equation is solved via numerical simulation using the finite control volume method to obtain the three dimensional and transient temperature profiles induced during the welding process. The moving heat source is considered as represented by a centered Gaussian-Bell distribution, while the base material is assumed to be homogeneous and isotropic with temperature-dependent thermal properties. Radiation and convection are computed and introduced into the model through the boundary conditions as an empirical temperature-dependent correlation. Phase-change phenomenon is included as a discontinuity in the material specific heat. Computed results show the influence of the variation of the welding parameters such as the arc power and welding speed on the computed transient temperatures, penetration and process efficiency
Open Access
Two-fluid Mixing Enhancement by Using a Static Turbulence Generator
(SPE International Thermal Operations and Heavy Oil Symposuim, Porlamar, Venezuela, 12–17 March 2001., 2001-03-12) Ortega, P.; McGrath, G.; Rojas-Solorzano, L.
The numerical simulation of a static T-type mixer for turbulent mixing of miscible liquids is reported. The simulation was carried out using CFX, a commercial computational fluid dynamic simulator. The effect of mixing intensification caused by turbulence generators placed downstream of the injection point of the Tee was evaluated in terms of reduction in mixing length for a given mixture quality, uniformity of turbulence intensity and efficiency of energy conversion to useful mixing energy. The mixing quality for an intensified and conventional T-type mixer was compared, and the turbulence generator geometry was optimized. Main stream Reynolds numbers between 50000 and 100000 were considered for additive volume ratios in the range 0.1 - 10%. Selected simulations were validated with experimental data available in the literature for conventional smooth T-type mixers (no ribs). Results were in good agreement with experimental correlations available at high Reynolds numbers. Simulations demonstrated that mixing enhancement was efficient with turbulence generators, extending the Reynolds number range for which compact, low pressure-drop devices may be used for intense mixing. The optimum geometry for turbulence generators was evaluated using criteria based on energetic and spatial efficiency and in all cases the simple Tee was used as the point of reference. Finally, practical design correlations are presented to enable the mixing quality of two miscible streams to be estimated for a simple Tee with and without additional turbulence generators over a range of Reynolds numbers and injection conditions.
Open Access
New borate ester based polymer electrolyte for battery application
(The Electrochemical Society, Inc., 2003-01) Kottegoda, I.R.M.; Bakenov, Zhumabay; Ikuta, H.; Uchimoto, Y.; Wakihara, M.
Safety is an indispensable feature for a battery particularly in large scale applications. In this respect, gel electrolytes are more attractive due to less possibility of electrolyte leakage and safer if abused. Unfortunately, most present gel electrolyte systems are mainly based on polyethers which supposed to be flammable. In addition, PEO and PPO based systems exhibit a low cation transference number. Therefore, the seeking of novel thermally stable and safety polymer electrolytes with improved electrochemical behaviour is crucial. In the present contribution, we propose a series of Li-ion conducting polymer electrolytes based on the poly(ethyleneglycol) (PEG) borate ester (PE-350B) and PEG-methacrylates (PME-400 and PDE-600, respectively) plasticized by M550B100 PEG-borate ester, which can be characterized as a thermally stable solvent with high flash point [1].
Open Access
3D CFD Modeling Investigation of Potential Vortex Formation at the Intakes of Caruachi Powerhouse
(INTERNATIONAL CONFERENCE ONHYDRAULICS OF DAMS AND RIVER STRUCTURES, TEHRAN, IRAN; 04/2004, 2004-04) Marcano, A.; Rojas-Solorzano, L.; Reyes, M.
In this paper, the 3-D CFD simulation of the free-surface flow approaching the intakes of Caruachi Powerhouse is presented. The aim of the investigation is to determine whether or not vortex structures are likely to appear from the water surface through the intakes, as the result of the presence of cofferdams placed few meters upstream of the intakes. The presence of cofferdams was a note of concern with regard to the effects they might have on the turbine intakes once the hydroelectric central starts operating. In all the considered conditions, results did not show neither strong surface vortices in the proximities of the Power House intakes, nor air entrainment-entrapment towards the intakes, which reflects the safe operation of the turbines in the presence of the cofferdams. The latter added in decision taking on leaving the cofferdams submerged instead of removing them, which resulted in cost savings for the project
Open Access
Experimental study of a gas-loquid cylindrical cyclone separator performance
(Proceedings of IMECE2004 2004 ASME International Mechanical Engineering Congress November 13-19, 2004, Anaheim, California, USA, 2004-11-13) Meléndez-Ramírez, Antonio J.; Reyes-Gutiérrez, Miguel A.; Rojas-Solorzano, L.
New data of the experimental performance of a Gas-Liquid Cylindrical Cyclone (GLCC) separator are presented. The data were collected using a 2 3/4” (0.07m) ID GLCC model working with an air-glycerin mixture. The inlet liquid flow rate, the inlet gas flow rate, the tangential liquid velocity inside the separator body and the gas carry under were measured for an operation regime without liquid carry over. The influence of the first three parameters over the gas carry under was established. Results show the separator efficiency is mainly affected by the inlet gas flow rate for the explored conditions with slug flow at the GLCC entrance.
Open Access
Transient Two-Phase-Flow Model for Predicting Column Formation in Intermittent Gas Lift Systems
(SPE Latin American and Caribbean Petroleum Engineering Conference, Rio de Janeiro, Brazil, 20 – 23 June 2005, 2005-06-20) Sandoval, Sarita; Rojas-Solorzano, L.; Gasbarri, Sandro
The major objective of this work is to generate a mathematical model, allowing the prediction of mixture density, liquid holdup, the pressure gradient in the pipe and the real column size. This is useful for optimizing cycle times and the amount of gas required to lift the fluids and to improve the diagnostic and simulation software of IGL wells
Open Access
CFD modeling of porous media in the study of the flow at penstock intake of A 1:30 model of guri hydro-powerhouse
(CIMENICS MF-185-2006, 2006) Arevalo, Angela; Montilla, Gonzalo; Rojas-Solorzano, L.; Reyes, Miguel; Marín, Juan
The transient free surface flow within a 1:30 model of the intake (penstock) to Power House II of Guri Hydro-Power Plant (Venezuela) is studied. The geometry of the model includes a reservoir of 4.31 meters upstream the dam. Geometric details and appropriate boundary conditions were reproduced mathematical and numerically using CFD (Computational Fluid Dynamics) techniques, running the commercial code CFXTM 4.4. The flow features nearby and within the penstock were captured. Special attention was paid to the evaluation of air entrainment that might eventually form due to the presence of free surface vortices. The computational domain included the anti-debris screen at the entrance of the penstock, considering it as a porous medium with equivalent permeability and porosity. Most of simulated cases corresponded to conditions in the prototype Guri´s free surface level of 240 a.s.l. (above sea level), with flow rate of 450 m3/seg. Air and water were considered incompressible fluids with and homogeneous interfacial transport model. Computed velocity profiles at different sections of the reservoir and pressure head along the penstock are compared with experiments. The numerical model captures the influence of the porous medium, used to simulate the anti-debris grill, onto the free-surface and pressure head within the penstock. In order to improve the predictive capabilities of the numerical model and to diminish the instabilities caused by the hydrostatic pressure condition at the entrance of the computational reservoir, preliminary results including a porous wall at the upstream boundary are presented. The porous wall, in fact, mimics the water-calming rock wall placed at the entrance of the experimental reservoir and proved to be a relevant element in improving the CFD predictions
Open Access
Numerical simulation and experiments of the multiphase flow in a liquid-liquid cylindrical cyclone separator
(Proceedings of FEDSM2006 2006 ASME Joint U.S. - European Fluids Engineering Summer Meeting July 17-20, Miami, FL, 2006-07-17) Reyes, Miguel A.; Pacheco, Jorge E.; Marín, Juan C.; Rojas-Solorzano, L.; Rincón, José
A Liquid-Liquid Cylindrical Cyclone separator (LLCC) is a device used in the petroleum industry to separate the oil-water mixture obtained from the well. The use of this device has not been widespread due to the lack of tools for predicting its separation capability. This paper presents a numerical and experimental study of the fluid dynamic performance of this type of cylindrical cyclone separators. The use of numerical simulations would reduce the time and cost necessary to obtain information for predicting the behavior of the equipment. The objective of this study is to determine if CFD (Computational Fluid Dynamics) techniques are able to reproduce the behavior of a LLCC separator. The CFD software examined was ANSYS-CFX 5.6TM and numerical simulations were carried out using the dispersed model with oil as the dispersed phase. The oil and water mixture entering the separator is divided due to centrifugal and buoyancy forces in an upper (oil rich) exit and a bottom (water rich) exit. The separation capability is determined as the maximum amount of water removed from the mixture with the minimum amount of oil content in the water rich exit. The experiments were conducted in a transparent LLCC separator that allows the visualization of the mixture and the measurement of the oil content. Experiments were conducted for three variables: mixture velocity and water content at the entrance, and the split ratio. The split ratio is defined as the bottom exit flow rate divided by the water flow rate at the entrance. The results showed that CFD tools are able to reproduce the oil content obtained from the experiments for all analyzed conditions. Additionally, the mixture distribution images from numerical and experimental data showed good agreement. This study confirms the capacity of CFD tools for the multiphase flow analysis of LLCC separators.
Open Access
Two-dimensional numerical simulation of saltating particles using granular kinetic theory
(Proceedings of FEDSM2007 2007 ASME/JSME Fluids Engineering Division Summer Meeting July 30-August 2, 2007, San Diego, California, USA, 2007-06-30) Marval, Juan P.; Rojas-Solorzano, L.
Most granular flows at environmental conditions are unsteady and exhibit a complex physical behavior. Dune formation and migration in the desert are controlled not only by the flow of saltating particles over the sand bed, but also by turbulent atmospheric airflow. In fact, sediments are transported by the atmospheric airflow within a thin layer only a few centimeters above the sandy surface. These jumping particles reach a maximum sediment mass flux level at a certain delay time (known as the “saturation time”) after the initial movement by sliding and rolling begins. Unlike sediment transport in water where the particles are lifted by the turbulent suspension, the saltating particles are kept alive in the layer mainly due to particle-particle and particle-bed collisions. In order to model this Aeolian transport of sand, Jenkins and Pasini [1] proposed a two-fluid model (one-dimensional and steady state) using Granular Kinetic Theory (GKT) to describe the solid-phase stress. The present work extends the original idea of Jenkins and Pasini [1] by using a more robust model of GKT for the kinetic/collisional contributions to the solid-phase stress tensor, together with a friction model activated for sustained contacts between particles. In addition, a standard k-ε turbulence model for the air and a drag model for the interaction between the phases are employed. A rectangular 2D geometry was chosen with a logarithmic profile for the inlet air velocity, along with an initial amount of sand at rest in the lower part of the simulation domain, resembling the particle saltating flow commonly seen in the vertical middle plane within saltation wind tunnels. This model is validated with experimental data from Liu and Dong [2] and the results given by Pasini and Jenkins [1]. A good estimation for the particle erosion and mass flux in the saltation layer is predicted, even though the profiles of mass flux and concentration within the transport layer are very thin and lower
Open Access
Selection and validation of a turbulence model for the numerical simulation of the flow at hemodialysis cannulas
(III INTERNATIONAL CONGRESS ON COMPUTATIONAL BIOENGINEERING M. Cerrolaza, H. Rodrigues, M. Doublaré, J. Ambrosio, M. Viceconti (Eds.) Isla de Margarita, Venezuela, September 24 to 26, 2007, 2007-09-24) Salazar, Félix A.; Rojas-Solorzano, L.
In recent years, CFD has become an increasingly used tool in the design of blood-based devices. Particularly, the estimation of red blood cell damage (hemolysis) becomes an important challenge to CFD scientists since the blood is a complex fluid present in turbulent regime in most pumping devices. Moreover, previous CFD studies on blood hemolysis lack of reliable relationships between hydraulic results and hematological responses. The objective of this work is to foresee a methodology for performing realistic CFD simulations that lead to reliable hydraulic and hematological correspondence. Cannulae geometries were studied to numerically assess a relatively simple flow with documented hematological data. For the turbulence modeling, a direct numerical simulation (DNS) for a coaxial jet array was used as a benchmark for the selection of an appropriate turbulence model, since the Cannulae approximates the coaxial jet features. Velocity and stress time-averaged profiles were compared between DNS results and the turbulence models. These results, pointed to the Shear Stress Transport with Gamma Theta correlation for transition model as the optimum turbulence model in that geometry. Accurate and reliable hydrodynamic CFD results were obtained for the Cannulae as a previous step to further hematological calculations with a minimum degree of uncertainty