Flow-induced self-sustained oscillations in a straight channel with rigid walls and elastic supports

This work considers the two-dimensional flow field of an incompressible viscous fluid in a parallel-sided channel. In our study, one of the walls is fixed whereas the other one is elastically mounted, and sustained oscillations are induced by the fluid motion. The flow that forces the wall movement is produced as a consequence that one of the ends of the channel is pressurized, whereas the opposite end is at atmospheric pressure. The study aims at reducing the complexity of models for several physiological systems in which fluid-structure interaction produces large deformation of the wall. We report the experimental results of the observed self-sustained oscillations. These oscillations occur at frequencies close to the natural frequency of the system. The vertical motion is accompanied by a slight trend to rotate the moving mass at intervals when the gap height is quite narrow. We propose a simplified analytical model to explore the conditions under which this motion is possible. The analytical approach considers asymptotic solutions of the Navier-Stokes equation with a perturbation technique. The comparison between the experimental pressure measured at the midlength of the channel and the analytical result issued with a model neglecting viscous effects shows a very good agreement. Also, the rotating trend of the moving wall can be explained in terms of the quadratic dependence of the pressure with the streamwise coordinate that is predicted by this simplified model.Fil: Alviso, Dario. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sciamarella, Denisse. Centre National de la Recherche Scientifique; FranciaFil: Gronskis, Alejandro. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; ArgentinaFil: Artana, Guillermo Osvaldo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Desarrollo sostenible en Paraguay: un enfoque en el potencial de las biorrefinerías y las energías renovables

In Paraguay, the final energy consumption is unsustainable due to a greater participation of petroleum derivatives (39%) and uncertified biomass (41%) compared to electricity (19%). Paraguay is a net importer of petroleum derivatives, where global concern about the volatility of their cost, added to the environmental damage they generate, compromises the scientific community regarding the technological/economic challenges for the exploitation of renewable resources as a productive platform for the country. The objective of this research is to carry out an analysis on the potential development of biorefineries and renewable energies at the country level. The methodology is based on exploratory/descriptive bibliographic research, based on the SWOT analysis. The results reveal the real situation of Paraguay in terms of its potential for sustainable development, as well as the diagnosis of opportunities in research, development and innovation ("R+D+i") and strategies to mitigate possible risks for the implementation of biorefineries in the medium and long term at the national level.En Paraguay, el consumo final de energía es poco sostenible debido a una mayor participación de los derivados de petróleo (39%) y de biomasa no certificada (41%) respecto a la electricidad (19%). Al ser un país importador neto de derivados del petróleo, la preocupación sobre la volatilidad del precio de los mismos, sumado al perjuicio ambiental que generan, compromete a la comunidad científica en cuanto a los desafíos y retos tecnológicos/económicos para la explotación de los recursos renovables como plataforma productiva del país. El objetivo de esta investigación es realizar un análisis sobre el potencial desarrollo de las biorrefinerías y energías renovables a nivel país, a partir de una revisión bibliográfica del tipo exploratoria/descriptiva basada en un análisis FODA. Los resultados presentan un panorama de la situación real del país en cuanto a su potencial para el desarrollo sostenible,, así como un diagnóstico sobre las oportunidades en investigación, desarrollo e innovación (“I+D+i”) y las estrategias para mitigar los posibles riesgos de implementación de biorrefinerías a mediano y largo plazo a nivel nacional

Prediction of the refractive index and speed of sound of biodiesel from its composition and molecular structure

The refractive index and speed of sound can be applied in many biodiesel studies, such as the characterization of biodiesels, their feedstocks, diesel/biodiesel blends, and their adulteration with vegetable oils. They have also been used to monitor the progress and endpoint of the transesterification reaction and the level of oxidation of biodiesel. About 350 oils are considered with potential for the production of biodiesel, and, for most of them, no experimental values of their refractive index and speed of sound are yet available. Regression models allowing an estimation of these two properties can be very useful. Thus, this study proposes regression models to determine the refractive index and speed of sound of biodiesel as a function of its composition and molecular structure (carbon chain length and unsaturation level). Experimental values of the refractive index for several oil-based biodiesels were measured. A regression study was conducted using our results and available experimental databases including a total of 47 data for the refractive index at 313 K and 263 data for the speed of sound in the range of 288-343 K. The equations, which were obtained using multiple linear regression analysis, correctly reproduced the dependencies of these biodiesel properties on carbon chain length and unsaturation level. The results obtained using the regression models proposed were compared with measured and available experimental data, showing very good agreement. The RMSE values of the refractive index and speed of sound models using all the data were lower than 0.0008 and 1.84 m/s, respectively.Fil: Alviso, Dario. Universidad María Auxiliadora; Paraguay. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Romano, Silvia Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; Argentin

Flash point and refractive index measurements of diesel and biodiesel, and their binary blends with n-butanol and n-pentanol

The use of n-butanol (BU) and n-pentanol (PE) as biofuels has gained much attention in recent years. As they have high oxygen content, they could be a future option to be used in Diesel engines for mixing with diesel fuel (DF), biodiesel (BD) and their blends, resulting in lower pollutant emissions. Flash point (FP) is used to regulate fuel handling and storage conditions. Refractive index (RI) has been used for the characterization of BD/DF blends and the estimation of light refraction in several combustion-related studies. Several works focusing on the use of BU and PE in blends with either DF or BD in Diesel engines have been recently carried out. However, less information is available in the literature concerning the measurements of properties such as the FP and the RI of these blends. This paper presents experimental measurements of FP and RI (from 15 to 40 ∘C) for BD and DF, and their binary blends with BU and PE in the full range of composition. The RI and FP of the studied BD and DF, as well as their blends with BU and PE, are also estimated using regression equations as a function of their composition.Fil: Figueroa Semorile, Nicolás. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica; ArgentinaFil: Alviso, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad María Auxiliadora; ParaguayFil: Romano, Silvia Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnologías del Hidrogeno y Energias Sostenibles. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías del Hidrogeno y Energias Sostenibles; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica; Argentin

Prediction of biodiesel physico-chemical properties from its fatty acid composition using genetic programming

This paper presents regression analysis of biodiesel physico-chemical properties as a function of fatty acid composition using an experimental database. The study is done by using 48 edible and non-edible oils-based biodiesel available data. Regression equations are presented as a function of fatty acid composition (saturated and unsaturated methyl esters). The physico-chemical properties studied are kinematic viscosity, flash point, cloud point, pour point (PP), cold filter plugging point, cetane (CN) and iodine numbers. The regression technique chosen to carry out this work is genetic programming (GP). Unlike multiple linear regression (MLR) strategies available in literature, GP provides generic, non-parametric regression among variables. For all properties analyzed, the performance of the regression is systematically better for GP than MLR. Indeed, the RSME related to the experimental database is lower for GP models, from ≈3% for CN to ≈55% for PP, in comparison to the best MLR model for each property. Particularly, most GP regression models reproduce correctly the dependence of properties on the saturated and unsaturated methyl esters.Fil: Alviso, Dario. Universidad Nacional de Asunción; Paraguay. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Artana, Guillermo Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; ArgentinaFil: Duriez, Thomas Pierre Cornil. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Universidad de la Marina Mercante; Argentin

Peak pressures at the throttled flow of oscillating valves

International audiencePressure signals measured at the throttled flow of oscillating valves show a double peak when the closing and reopening of the clearance occur in short times. This phenomenon has been evidenced in spring-loaded valves or in valves of biological flows such as vocal-fold collision upon glottal flow. A comprehensive study of the fluid dynamical causes of this flow behavior is still pending. This work considers a valve with a simple geometry and a prescribed evolution of gap height with time. High performance numerical simulations in two dimensions and simplified models are used to explain experimental results and undertake a parametric study. A reversal of the longitudinal volumetric flow direction near the entrance and exit of the channel at closing and reopening, named suction-cup effect, is shown to be associated to the double peak presence in pressure signals

Flame imaging reconstruction method using high resolution spectral data of OH*, CH* and C2* radicals

This paper focuses on a technique to obtain images of the spatial distribution of ultraviolet OH*, visible CH* and C2* species present in hydrocarbon flames. This is achieved by combining sequentially acquired chemiluminescence spectra along slices defined by the entrance slit of an imaging spectrometer for narrow wavelength bands corresponding to the species of interest. As the analysis has been performed in an axisymmetric conical flame, the Abel inversion procedure has been applied to reduce the effect caused by the line of sight. The images resulting from the proposed reconstruction procedure are compared with the images collected with simple chemiluminescence visualization (detected with an ICCD camera) and respective narrow-band interference filters. Although the technique has been applied only in laminar steady flame condition, it could be interesting for application in more advanced, laser-sheet based diagnostics. The main advantages of the proposed technique are the high spectral resolution of the resulting radical images and the possibility of detecting other species (in the ultraviolet, visible or infrared regions) by combining chemiluminescence spectra at different wavelengths.Fil: Alviso, Dario. Universidad Nacional de Asunción; Paraguay. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mendieta, Miguel. Universidad Nacional de Asunción; ParaguayFil: Molina, Jorge. Universidad Nacional de Asunción; ParaguayFil: Rolón, Juan Carlos. Universidad Nacional de Asunción; Paragua

Modeling of vegetable oils cloud point, pour point, cetane number and iodine number from their composition using genetic programming

Vegetable oils (VOs) are composed of 90–98% of triglycerides, i.e. esters composed of three fatty acids and glycerol, and small amounts of mono- and di-glycerides. Due to their physico-chemical properties, VOs have been considered for uses especially in large ships, in stationary engines and low and medium speed diesel engines, in pure form or in blends with fuel oil, diesel, biodiesel and alcohols. There are about 350 VOs with potential as fuel sources, and for most of them, physico-chemical properties values have not yet been measured. In this context, regression models using only VOs fatty acid composition are very useful. In the present paper, regression analysis of VOs cloud point (CP), pour point (PP), cetane number (CN) and iodine number (IN) as a function of saturated and unsaturated fatty acids is conducted. The study is done by using 4 experimental databases including 88 different data of VOs. Concerning the regression technique, genetic programming (GP) has been chosen. The cost function of GP is defined to minimize the Mean Absolute Error (MAE) between experimental and predicted values of each property. The resulting GP models consisting of terms including saturated and unsaturated fatty acids reproduce correctly the dependencies of all four properties on those acids. And they are validated by showing that their results are in good agreement to the experimental databases. In fact, MAE values of the proposed models with respect to the databases for CP, PP, CN and IN are lower than 4.51 °C, 4.54 °C, 3.64 and 8.01, respectively.Fil: Alviso, Dario. Universidad Nacional de Asunción; Paraguay. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zárate Evers, Cristhian Manuel. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Duriez, Thomas Pierre Cornil. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Experimental and numerical studies of biodiesel combustion mechanisms using a laminar counterflow spray premixed flame

Biodiesel is a mixture of long chain fatty acids such as methyl esters and is mainly used in diesel engines. Its fundamental properties and combustion pathways still need to be analyzed and validated. The present study concerns the creation and development of new data for the combustion of rapeseed methyl ester biodiesel (RME) and methyl decanoate as a surrogate fuel (MD). Experimental and numerical studies are conducted on a laminar counterflow premixed flame configuration where spray biodiesel/air (or MD/air) is injected against methane/air mixture at atmospheric pressure for different strain rates and equivalence ratio conditions. As chemical schemes for methane/air reactions are enough well known, this configuration is suitable to perform validations of chemical schemes for biodiesel/air (or MD/air) combustion, by taking methane/air flame as a reference. Planar Laser-Induced Fluorescence (PLIF) of OH as well as visible and UV chemiluminescence measurements of the excited radicals CH*(A(2)Delta) and OH*(A(2)Sigma+) are employed to experimentally analyze the biodiesel and MD flame structure. The counterflow spray MD flame is simulated by choosing a skeletal reaction mechanism to which we add CH* and OH* reactions. In the case of biodiesel flame simulations, a new surrogate kinetics is developed by combining two existing skeletal kinetics schemes. The new scheme guarantees not only a good prediction of measured radicals but also a good methane/air flame speed which is necessary to well predict the flame front position in the counterflow configuration. CH* and OH* sub-mechanisms are also added to this kinetic scheme. The numerical predictions of the CH* concentration are very close to the experimental profiles along the central axis, for both biodiesel and MD kinetic schemes. However the numerical and experimental results show differences in the OH* production routes between MD and methane flames. (C) 2015 Elsevier Ltd. All rights reserved

Estimation of the rheological curve of HPAM solutions from measurements using the Brookfield viscometer

In recent studies, Jouenne and Levache (2020) proposed a rheological model for polymeric solutions used in enhanced oil recovery, based essentially on a variable obtained as the product of the intrinsic viscosity of the solution and the concentration of the polymer. Using this variable, the authors propose expressions in which is possible to predict the coefficients of Carreau–Yasuda's law that are of interest: the viscosity under zero shear regime η0, the power index n, and the relaxation time λ. In this work, the robustness of this model is improved using a machine learning technique and a larger database than the one previously considered. Based on this enhanced model, a technique is proposed to estimate the intrinsic viscosity of the solutions and the parameters of Carreau–Yasuda's law using only the measurement of viscosity at a shear rate of 7.3 s−1. The results obtained with this approach are compared to those issued from experimental data finding satisfactory results. The use of this strategy is of particular interest for field studies or laboratories that only have as available instruments the Brookfield viscometer.Fil: Pérez, Eduar. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; ArgentinaFil: Alviso, Dario. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Manrique, Eduardo. Ecopetrol S.a. Instituto Colombiano del Petroleo.; ColombiaFil: Artana, Guillermo Osvaldo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin