A computational methodology to account for the liquid film thickness evolution in Direct Numerical Simulation of prefilming airblast atomization

Prefilming airblast atomization is widely used in aero engines. Fundamental studies on the annular configuration of airblast atomizers are difficult to realize. For this reason, researchers focused on planar configurations. In this regard, the Karlsruhe Institute of Technology (KIT) developed a test rig to conduct experimental activities, conforming a large database with results for different conditions. Such data allow validation of two-phase flow calculations concerning primary atomization on these devices. The present investigation proposes a Direct Numerical Simulation (DNS) on the KIT planar configuration through the Volume of Fluid (VOF) method within the PARIS code. The novelty compared to DNS reported in the literature resides in the use of a boundary condition that accounts not only for the gas inflow turbulence but also for the spatio-temporal evolution of the liquid film thickness at the DNS inlet and its effect on turbulence. The proposed methodology requires computing precursor single-phase and two-phase flow Large-Eddy Simulations. Results are compared to DNS that only account for a constant (both timewise and spanwise) liquid film thickness at the domain inlet, validating the workflow. The proposed methodology improves the qualitative description of the breakup mechanism, as its different stages (liquid accumulation behind the prefilmer edge, bag formation, bag breakup, ligament formation and ligament breakup) coexist spanwise for a given temporal snapshot. This implies more continuous atomization than the one predicted by the constant film thickness case, which showed the same breakup stage to be present along the prefilmer span for a given instant and led to a more discretized set of atomization events. The proposed workflow allows quantifying the influence of the liquid film flow evolution above the prefilmer on primary breakup frequency and atomization features.Comment: Preprint submitted to International Journal of Multiphase Flo

Plan de Acción Tutorial en la Facultad de Educación: percepciones del alumnado sobre sus tutores

El acceso a la universidad es un momento en el que el alumnado de primer curso de grado precisa cierta orientación para resolver sus dudas y conocer todos los servicios que tiene a su disposición en la universidad. La Facultad de Educación de la Universidad de Alicante ofrece el Plan de Acción Tutorial (PAT), iniciativa desarrollada por diversos tutores que aumenta anualmente el interés entre el alumnado. El objetivo de esta investigación fue conocer las percepciones que presenta parte del alumnado que asiste al PAT en cuanto a la función que ejercen sus tutores. La muestra estuvo compuesta por 26 alumnos del grado de Maestro de Educación Primaria e Infantil quienes cumplimentaron un cuestionario de elaboración propia acerca de sus percepciones respecto a la labor de sus tutores universitarios. Los resultados obtenidos señalan que entre las funciones más valoradas por los alumnos se encuentran: la obtención de información acerca de las salidas profesionales, el funcionamiento del Prácticum y los itinerarios educativos y cursos. No obstante, se precisa considerar la intervención de los tutores en el área emocional del alumnado (autoestima, confianza personal, emociones negativas y relaciones sociales entre compañeros) ya que es una de las funciones menos valoradas

Characterization and prediction of the discharge coefficient of non-cavitating diesel injection nozzles

An experimental and theoretical study about the characterization of the discharge coefficient of diesel injection nozzles under non-cavitating conditions is presented in this paper. A theoretical development based on the boundary layer equations has been performed to define the discharge coefficient of a convergent nozzle. The discharge coefficient has been experimentally obtained for a standard diesel fuel under a wide range of Reynolds numbers by two different techniques: mass flow rate measurements and permeability measurements. Five different nozzles have been used: two multi-hole nozzles that have been tested in the frame of this work, and three other single-hole nozzles, the data of which have been taken from previous studies. The experimental results show good agreement with the theoretical expressions, proving that it is possible to predict the discharge coefficient of a non-cavitating nozzle with the equations shown in this paper.The authors would like to thank different members of the CMT-Motores Termicos team of the Universitat Politecnica de Valencia for their contribution to this work, specially to R. Payri, F.J. Salvador, J. Gimeno and G. Bracho. This work was partly sponsored by "Ministerio de Economia y Competitividad" in the frame of the project "Comprension de la influencia de combustibles no convencionales en el proceso de inyeccion y combustion tipo diesel", reference TRA2012-36932. The equipment used in this work has been partially supported by FEDER project funds "Dotacion de infraestructuras cientifico tecnicas para el Centro Integral de Mejora Energetica y Medioambiental de Sistemas de Transporte (CiMeT), (FEDER-ICTS-2012-06)", in the frame of the operation program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain. This support is gratefully acknowledged by the authors. Finally, the authors would like to thank the Spanish Ministry of Education for financing the PhD. studies of Dario Lopez-Pintor (grant FPU13/02329).Desantes Fernández, JM.; López, JJ.; Carreres Talens, M.; López-Pintor, D. (2016). Characterization and prediction of the discharge coefficient of non-cavitating diesel injection nozzles. Fuel. 184:371-381. https://doi.org/10.1016/j.fuel.2016.07.02637138118

An Open-set Recognition and Few-Shot Learning Dataset for Audio Event Classification in Domestic Environments

The problem of training a deep neural network with a small set of positive samples is known as few-shot learning (FSL). It is widely known that traditional deep learning (DL) algorithms usually show very good performance when trained with large datasets. However, in many applications, it is not possible to obtain such a high number of samples. In the image domain, typical FSL applications are those related to face recognition. In the audio domain, music fraud or speaker recognition can be clearly benefited from FSL methods. This paper deals with the application of FSL to the detection of specific and intentional acoustic events given by different types of sound alarms, such as door bells or fire alarms, using a limited number of samples. These sounds typically occur in domestic environments where many events corresponding to a wide variety of sound classes take place. Therefore, the detection of such alarms in a practical scenario can be considered an open-set recognition (OSR) problem. To address the lack of a dedicated public dataset for audio FSL, researchers usually make modifications on other available datasets. This paper is aimed at providing the audio recognition community with a carefully annotated dataset for FSL and OSR comprised of 1360 clips from 34 classes divided into pattern sounds and unwanted sounds. To facilitate and promote research in this area, results with two baseline systems (one trained from scratch and another based on transfer learning), are presented.Comment: To be submitted to Expert System with Application

Profesorado novel y tutoría entre iguales en innovación tutorial

El trabajo que se presenta es una de las propuestas objeto de estudio de la Red PAT-Educación: acompañamiento tutorial en la formación universitaria. Tomando como punto de partida el trabajo colaborativo y coordinado que supone llevar a cabo procesos de innovación en docencia universitaria y teniendo en cuenta que una parte del profesorado que en la actualidad realiza tareas de tutoría en el Programa de Acción Tutorial de la Facultad de Educación (PAT/EDU), es profesorado novel, se pretende con este estudio analizar la relación y la eficacia del acompañamiento tutorial con un perfil de profesorado tutor así como también la inclusión de alumnado tutor para realizar modalidad tutorial entre iguales. El procedimiento realizado y la elaboración de un cuestionario sobre percepciones del alumnado, nos ha permito conocer a través de los resultados obtenidos, grados de satisfacción del alumnado en las actuaciones realizadas de acompañamiento tutorial. Una vez concluido el proceso de desarrollo y seguimiento de la acción tutorial durante este curso, se plantearán propuestas de mejora que incidan en la eficacia y aprovechamiento de la tutoría entendida como acompañamiento tutorial a lo largo del proceso de aprendizaje del estudiante universitario

Evaluation of diurnal responses of Tetradesmus obliquus under nitrogen limitation

Tetradesmus obliquus is an oleaginous microalga with high potential for triacylglycerol production. We characterized the biochemical composition and the transcriptional landscape of T. obliquus wild-type and the starchless mutant (slm1), adapted to 16:8 h light dark (LD) cycles under nitrogen limitation. In comparison to the nitrogen replete conditions, the diurnal RNA samples from both strains also displayed a cyclic pattern, but with much less variation which could be related to a reduced transcription activity in at least the usually highly active processes. During nitrogen limitation, the wild-type continued to use starch as the preferred storage compound to store energy and carbon. Starch was accumulated to an average content of 0.25 g·gDW−1, which is higher than the maximum observed under nitrogen replete conditions. Small oscillations were observed, indicating that starch was being used as a diurnal energy storage compound, but to a lesser extent than under nitrogen replete conditions. For the slm1 mutant, TAG content was higher than for the wild-type (average steady state value was 0.26 g·gDW−1 for slm1 compared to 0.06 g·gDW−1 for the wild-type). Despite the higher TAG content in the slm1, the conversion efficiency of photons into biomass components for the slm1 was only half of the one obtained for the wild-type. This is related to the observed decrease in biomass productivity (from 1.29 gDW·L−1·day−1 for the wild-type to 0.52 gDW·L−1·day−1 for the slm1). While the transcriptome of slm1 displayed clear signs of energy generation by degrading TAG and amino-acids during the dark period, no significant variation of these metabolites could be measured. When looking through the diurnal cycle, the photosynthetic efficiency was lower for the slm1 mutant compared to the wild-type especially during the second half of the light period, where starch accumulation occurred in the wild-type.publishedVersionPaid Open Acces

Comparison of microsac and VCO diesel injector nozzles in terms of internal nozzle flow characteristics

A computational study focused on the inner nozzle flow and cavitation phenomena has been reported in this paper in order to investigate the two most common types of diesel injector nozzles at the present: microsac and valve covered orifice (VCO). The geometrical differences among both types of nozzles are mainly located at the needle seat, upstream of the discharge orifices. In the case of microsac nozzles there is a small volume upstream of the discharge orifices which is not present in VCO nozzles. Due to these geometrical differences among both type of nozzles, differences in the inner flow and the cavitation development have been found and analysed in this research. For the study, two cylindrical nozzles with six orifices and the same outlet diameter have been experimentally characterized in terms of mass flow rate. These measurements have been used to validate the CFD results obtained with the code OpenFOAM used for the analysis of the internal nozzle flow. For the simulations, two meshes that reproduce the microsac and VCO nozzles seat geometry while keeping the same geometry at the orifices have been built. The simulations have been carried out with a code previously validated and able to simulate cavitation phenomena using a homogeneous equilibrium model (HEM) and with RANS approach for the turbulence modelling (RNG k-epsilon). For the computational study, three injection pressures and different geometries simulating different needle lifts have been used. The comparison among nozzles has been made in terms of mass flow, momentum flux and effective velocity and in terms of other non-dimensional parameters which are useful for describing the inner nozzle flow: discharge coefficient (C-d), area coefficient (C-alpha) and velocity coefficient (C-v). The analysis performed by studying and comparing the particularities of the flow in each nozzle has been useful in order to explain the experimental differences found in terms of mass flow rate and critical cavitation conditions. One of the main conclusions of this study is the higher influence of the needle on the mass flow, momentum and injection velocity results for the VCO nozzle as compared to the microsac one. Hence, whereas in the first one these variables scale with the needle lift value, in the second one there is an intermediate needle lift from which they stop being influenced by the presence of the needle. Furthermore, the study has also revealed important differences in the proneness to produce cavitation and its morphology. For the VCO nozzle, cavitation phenomenon occurs only in the upper part of the orifice inlet. However, for the microsac nozzle cavitation appears both at the upper and the lower part of the nozzle orifice entrance.This work was partly sponsored by "Ministerio de Economia y Competitividad" in the frame of the project "Comprension de la influencia de combustibles no convencionales en el proceso de inyeccion y combustion tipo diesel", Reference TRA2012-36932. This support is gratefully acknowledged by the authors.Salvador Rubio, FJ.; Carreres Talens, M.; Jaramillo Císcar, D.; Martínez López, J. (2015). Comparison of microsac and VCO diesel injector nozzles in terms of internal nozzle flow characteristics. Energy Conversion and Management. 103:284-299. https://doi.org/10.1016/j.enconman.2015.05.062S28429910

Un trabajo colaborativo y de acompañamiento tutorial: el Plan de Acción Tutorial en la Facultad de Educación

El trabajo que se presenta refleja el trabajo colaborativo de la RED PAT-Educación en la que ha participado el profesorado integrante del Programa de Acción Tutorial (PAT) de la Facultad de Educación, dentro del Programa de REDES de investigación en docencia universitaria del ICE de la Universidad de Alicante. El objetivo del mismo es describir el Programa de acción tutorial (PAT) llevado a cabo durante el curso 2013/2014 en la Facultad de Educación así como analizar el desarrollo del mismo, desde la perspectiva de trabajo colaborativo entre el profesorado tutor participante y la puesta en práctica de un proceso de acompañamiento tutorial hacia el alumnado tutorado. Al mismo tiempo, se ha generado un trabajo conjunto con la inclusión de las TIC tanto para el profesorado tutor como para el alumnado tutorado a través de la creación del blog: http://edupatua.blogspot.com.es/ como recurso didáctico en el desarrollo de las tareas tutoriales, permitiéndonos conocer y analizar las necesidades y demandas del alumnado en este proceso de implementación del PAT. Los resultados obtenidos constatan fortalezas y debilidades que nos hacen reflexionar sobre las posibles propuestas de mejora que favorecerían el proceso de acompañamiento tutorial implementado