Nuestros investigadores

Gorka Sánchez Larraona

Líneas de investigación
Flujos Multifásicos, Dinámica de Fluidos Computacional (CFD) aplicada a procesos de tratamiento de aguas
Índice H
6, (WoS, 16/04/2019)
7, (Scopus, 16/04/2019)

Publicaciones científicas más recientes (desde 2010)

Autores: Ramos González, Juan Carlos; Antón Remírez, Raúl; Aramburu Montenegro, Jorge; et al.
Revista: DYNA
ISSN 0012-7361  Vol. 95  2020  págs. 640-645
The air conditioning systems used in transport vehicles (railway passenger cars) are constrained by two issues: the consumed energy and the occupied space. In order to assess how both restrictions can be fulfilled a parametric analysis and an optimization have been carried out by means of Design of Experiments (DoE) techniques applied to a mathematical model of a real AC system. To evaluate the energy efficiency of the system four parameters have been used: the COP (Coefficient of Performance), the refrigeration power of the system and its dimensionless expression and the effectiveness of the evaporator. The occupied space of the AC system has been characterized through the dimensionless volume of the evaporator. The same compressor has been used in the analysis and the input parameters varied have been the dimensionless evaporator volume and four operating conditions: the evaporator inlet air temperature and mass flow rate, the condenser inlet air temperature and the air temperature increment in the condenser. Through a Central Composite Surface Response design, the regression equations of the four output energy efficiency parameters have been obtained in a wide range of operating conditions. Results show that the dimensionless refrigeration power is the best parameter because is independent of the operating conditions and only depends on the dimensionless volume of the evaporator: the lower the latter, the higher the former. An optimal dimensionless volume has been identified for the simultaneous optimization of the four output variables of the system that provides an increase of 26% in the dimensionless refrigeration power with respect to the baseline system.
Autores: Ortega Calderón, Julio; Antón Remírez, Raúl (Autor de correspondencia); Ramos González, Juan Carlos; et al.
ISSN 2040-7939  Vol. 36  Nº 6  2020  págs. e3337
In the last decades, the numerical studies on hemodynamics have become a valuable explorative scientific tool. The very first studies were done over idealized geometries, but as numerical methods and the power of computers have become more affordable, the studies tend to be patient specific. We apply the study to the numerical analysis of tumor-targeting during liver radioembolization (RE). RE is a treatment for liver cancer, and is performed by injecting radiolabeled microspheres via a catheter placed in the hepatic artery. The objective of the procedure is to maximize the release of radiolabeled microspheres into the tumor and avoid a healthy tissue damage. Idealized virtual arteries can serve as a generalist approach that permits to separately analyze the effect of a variable in the microsphere distribution with respect to others. However, it is important to use proper physiological boundary conditions (BCs). It is not obvious, the need to account for the effect of tortuosity when using an idealized virtual artery. We study the use of idealized geometry of a hepatic artery as a valid research tool, exploring the importance of using realistic spiral-flow inflow BC. By using a literature-based cancer scenario, we vary two parameters to analyze the microsphere distribution through the outlets of the geometry. The parameters varied are the type of microspheres injected and the microsphere injection velocity. The results with realistic inlet velocity profile showed that the par
Autores: Elduayen Echave, Beñat (Autor de correspondencia); Lizarralde Aguirrezabal, Izaro; Sánchez Larraona, Gorka; et al.
ISSN 0043-1354  Vol. 155  2019  págs. 26-41
Mathematical models describing precipitation processes in one step need to be upgraded. Particle size distribution is a crucial variable and its inclusion in the modelling libraries is necessary if the technology wants to be optimized through simulation. With this objective, a mass based population balance model is presented in this contribution. The model has been constructed using a stoichiometric matrix and a kinetic vector and using mass as the internal coordinate, as it is usually done in wastewater treatment modelling. Identifiability of the parameters of the model was evaluated using a sensitivity and a collinearity analysis for six simulation case studies of struvite precipitation. In addition, parameters in the model were calibrated to represent data from two batch tests in the laboratory. The results of the analysis showed that the identifiability of the parameters depends on the available experimental data and explored scenarios. Identifiability of the parameters could be the reason behind the shifting parameter values describing mechanisms of precipitation in the literature. This contribution helps to understand the possibilities and limitations that the population balance model approach offer.
Autores: Aramburu Montenegro, Jorge (Autor de correspondencia); Antón Remírez, Raúl; Rivas Nieto, Alejandro; et al.
ISSN 1025-5842  Vol. 22  Nº 5  2019  págs. 518 - 532
Balloon-occluded transarterial chemoembolisation (B-TACE) is an intraarterial transcatheter treatment for liver cancer. In B-TACE, an artery-occluding microballoon catheter occludes an artery and promotes collateral circulation for drug delivery to tumours. This paper presents a methodology for analysing the haemodynamics during B-TACE, by combining zero-dimensional and three-dimensional modelling tools. As a proof of concept, we apply the methodology to a patient-specific hepatic artery geometry and analyse two catheter locations. Results show that the blood flow redistribution can be predicted in this proof-of-concept study, suggesting that this approach could potentially be used to optimise catheter location.
Autores: Martin-Martin, L.; Gastelurrutia, J. , (Autor de correspondencia); Sánchez Larraona, Gorka; et al.
ISSN 1359-4311  Vol. 147  2019  págs. 155 - 166
A simple battery thermal management system's control strategy based on reliable battery-pack-level CFD models and numerical optimization methodologies is proposed for vertical elevation applications powered by lithium-ion batteries. A new devised heat generation model named as False Steady has been successfully used to calculate the heat density generated in each cell of the battery pack in a steady simulation without losing the thermal coupling and hence prediction accuracy. The best placement for the temperature sensors to evaluate the thermal dispersion has been decided based on the CFD model results. When the predefined thermal limits are crossed the fans will start operating and they will be regulated depending on the ambient temperature and the measured charge or discharge current level. The optimal values of fans' pulse width modulation level are determined from response surfaces obtained from the simulations.
Autores: Aramburu Montenegro, Jorge (Autor de correspondencia); Antón Remírez, Raúl; Rivas Nieto, Alejandro; et al.
ISSN 2040-7939  Vol. 34  Nº e2983  2018 
Autores: Aramburu Montenegro, Jorge; Antón Remírez, Raúl; Borro Yagüez, Diego; et al.
ISSN 2057-1976  Vol. 2  Nº 1  2016  págs. 015001
The analysis of the progression of cardiovascular diseases is an active area of ongoing research. This paper develops an image registration-based methodology to quantify the patient-specific local blood vessel shape variations that occur in the radial direction (i.e. expansion or shrinkage) over an imaging follow-up period, and an example is presented as proof of principle. The methodology can be used for complex vessels with bifurcations, and it is able to identify and address vessel deformations if changes in tortuosity or longitudinal direction are small. The methodology consists of (a) overlapping the baseline and follow-up vessel surfaces by matching the lumen centerline, (b) dividing the region of interest into slices perpendicular to the centerline and centering each slice, and (c) dividing each centered slice into sectors. The local approach consists of analyzing a representative point in each sector of each slice (i.e. each patch). In this paper the algorithm is applied to a patient-specific abdominal aortic aneurysm (AAA) as a proof of principle of the method. Six patient-specific image reconstructions from a single subject followed for 28 months are analyzed in pairs, yielding five time spans to which the algorithm was applied. The algorithm was able to quantify the AAA radial growth. The average AAA radial growths for the five case studies are ¿2.13 mm, 3.43 mm, ¿0.25 mm, 1.41 mm, and 0.84 mm, whereas the maximum local growths are 4.76 ± 0.15 mm, 9.30 ± 1.13 mm, 2.08 ± 0.05 mm, 4.10 ± 0.14 mm, and 4.16 ± 0.45 mm. The tolerance of the geometric local measurements is related to the matching processes (i.e. overlapping the geometries and centering each slice) because of the vessel deformation that took place over time. Thus, this methodology has been used to quantify the average AAA growth and the maximum local AAA growth (± the tolerance) as metrics of the vessel's radial growth.
Autores: Ruiz de Galarreta Moriones, Sergio; Antón Remírez, Raúl; Cazón Martín, Aitor; et al.
ISSN 1350-4533  Vol. 38  Nº 12  2016  págs. 1505 - 1512
An Abdominal Aortic Aneurysm (AAA) is a permanent focal dilatation of the abdominal aorta at least 1.5 times its normal diameter. The criterion of maximum diameter is still used in clinical practice, although numerical studies have demonstrated the importance of other biomechanical factors. Numerical studies, however, must be validated experimentally before they can be clinically implemented. We have developed a methodology for manufacturing anisotropic AAA replicas with non-uniform wall thickness. Different composites were fabricated and tested, and one was selected in order to manufacture a phantom with the same properties. The composites and the phantom were characterized by biaxial tensile tests and a material model was fit to the experimental data. The experimental results were compared with data from the literature, and similar responses were obtained. The anisotropic AAA replicas with non-uniform wall thickness can be used in benchtop experiments to validate deformations obtained with numerical simulations or for pre-intervention testing of endovascular grafts. This is a significant step forward considering the importance of anisotropy in numerical simulations.
Autores: Sesma Gotor, Ignacio; Sánchez Larraona, Gorka; Viñolas Prat, Jordi; et al.
ISSN 0954-4097  Vol. 229  Nº 2  2015  págs. 186 - 200
In a crosswind scenario, the risk of high-speed trains overturning increases when they run on viaducts since the aerodynamic loads are higher than on the ground. In order to increase safety, vehicles are sheltered by fences that are installed on the viaduct to reduce the loads experienced by the train. Windbreaks can be designed to have different heights, and with or without eaves on the top. In this paper, a parametric study with a total of 12 fence designs was carried out using a two-dimensional model of a train standing on a viaduct. To asses the relative effectiveness of sheltering devices, tests were done in a wind tunnel with a scaled model at a Reynolds number of 1x10(5), and the train's aerodynamic coefficients were measured. Experimental results were compared with those predicted by Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations of flow, showing that a computational model is able to satisfactorily predict the trend of the aerodynamic coefficients. In a second set of tests, the Reynolds number was increased to 12x10(6) (at a free flow air velocity of 30m/s) in order to simulate strong wind conditions. The aerodynamic coefficients showed a similar trend for both Reynolds numbers; however, their numerical value changed enough to indicate that simulations at the lower Reynolds number do not provide all required information. Furthermore, the variation of coefficients in the simulations allowed an explanation of how fences modified the flow around the vehicle to be proposed. This made it clear why increasing fence height reduced all the coefficients but adding an eave had an effect mainly on the lift force coefficient. Finally, by analysing the time signals it was possible to clarify the influence of the Reynolds number on the peak-to-peak amplitude, the time period and the Strouhal number.
Autores: Cazón Martín, Aitor; González Prada, Jorge (Autor de correspondencia); García, E.; et al.
ISSN 1745-2759  Vol. 10  Nº 3  2015  págs. 149 - 162
Formula Student is an international competition governed by the Society of Automotive Engineers (SAE) which challenges university students to design and build a racing car that will subsequently be compared against other cars from universities around the world on homologated racing circuits by non-professional drivers. This study focuses on the design, analysis and manufacturing process of a new oil sump for a Formula Student car - which involves combining a main ABS-plastic core created by an additive manufacturing (AM) printing process and a manual lay-up process with carbon fibre - in order to reduce the sloshing effect due to the movement of the oil during racing. The new oil sump and the original sump were modelled with computer-aided design (CAD) software and five computational fluid dynamics (CFD) simulations were performed to compare the sloshing effect in both designs in three driving scenarios: acceleration, braking and changing direction. The simulations showed that acceleration is not a critical situation since the new internal design of the sump was capable of delaying the immersion time of the oil pick-up pipe from 0.75 seconds to 2 seconds during braking and from 0.4 seconds to 0.8 seconds during lateral acceleration. The new design was physically manufactured and subsequently integrated into an internal combustion engine for testing for 45 minutes. During this test, the engine was started and put at 9600 RPM, so the oil worked under realistic temperature condi
Autores: Bengoechea García, Asier; Antón Remírez, Raúl; Sánchez Larraona, Gorka; et al.
ISSN 0142-727X  Vol. 46  2014  págs. 43 - 60
A perforated plate placed behind an axial fan (push cooling) is a common assembly in electronic systems. The flow approaching the screen will have a swirling component, and therefore, there is uncertainty in the prediction of the flow pattern at the outlet of the screen and the pressure drop through the screen. Correctly predicting the flow field is important in order to properly place the electronic components. This work tries to give some insight into these issues. A wind tunnel was manufactured in order to produce the typical flow field at the outlet of an axial fan and to measure the field at the inlet and at the outlet of the perforated plate using the Particle Image Velocimety (PIV) technique; the pressure drop through the screen was also measured. The velocity contours measured at the screen inlet were used as boundary conditions for computational fluid dynamics (CFD) simulations. Several turbulence models (k-epsilon, k-omega and RSTM) and their variations were used for the simulations and the results at the outlet of the perforated plate are compared with the Particle Image Velocimetry results. Two screens with very different geometrical characteristics were used. Results show that if k-e models are used a significant error is made in the prediction of the velocity field and in the pressure drop. Although the k-omega models predicted better than the k-e models, the RSTM were shown to be the most reliable. (C) 2014 Elsevier Inc. All rights reserved.
Autores: Bengoechea García, Asier; Antón Remírez, Raúl; Sánchez Larraona, Gorka; et al.
ISSN 1994-2060  Vol. 8  Nº 4  2014  págs. 623 - 638
A perforated plate placed downstream of an axial fan in order to avoid electromagnetic interferences (push cooling) is a common assembly in electronic systems. Because of the swirling component that the flow approaching the screen has, there is no accuracy in knowing how the screen affects the flow pattern downstream of the screen and the pressure drop through the screen. Since cooling capacity is related to velocity, the placement of the components downstream of the screen will be related to the velocity magnitude. Thus, properly predicting the flow pattern is highly important, and the results of this work may serve a good guideline for thermal designers to surmount this challenge. In order to establish how the screen affects the flow pattern, a parametric study is carried out. This study is performed by a central composite face-centered (CCF) Design of Experiment (DoE), which demanded 81 Computational Fluid Dynamics (CFD) simulations and for which the Reynolds Stress Transport Model was used as a turbulence model. Thanks to the numerical results, the influence that different operational and geometrical parameters have on the flow pattern downstream of a screen and on the total pressure drop is analyzed. The swirl that the flow has at the inlet is found to be related to the screen's capacity to homogenize the flow downstream of the screen, as its thickness plays an important role in the flow's tangential component destruction. The main effects of the parameters and the interactions between them are shown. At the same time, through DoE techniques, different reduced models that predict how the flow pattern changes because of the screen are presented as useful tools for thermal designers.
Autores: Beiza Silva, Maximiliano Patricio; Ramos González, Juan Carlos; Rivas Nieto, Alejandro; et al.
ISSN 1359-4311  Vol. 62  Nº 1  2014  págs. 215 - 228
An algebraic thermal zonal model of the ventilation of underground transformer substations during a standardised temperature rise test is presented in this paper. The development and adjustment of the proposed model rely on the analysis of the air flow pattern and temperature distributions obtained by a more complex model numerically solved by means of CFD techniques. The flow domain of the model represents a section of the substations divided into several interrelated zones where the mass and the energy conservation equations are formulated and the generated system of nonlinear algebraic equations is solved. The model is validated by comparing its results with the ones obtained by the CFD model and with the experimental results of eight temperature rise tests under different conditions. A parametric analysis was carried out on the model to prove its utility as an efficient tool to improve and optimise the thermal performance of transformer substations during the design process. From the parametric study it has been inferred that the main parameters affecting the ventilation of the substations are the pass area between the LV-MV zone and the transformer zone, the surface area of the ventilation grilles in the substation with horizontal ventilation, and the perimeter of the protruding ventilation vents in the substation with vertical ventilation. (c) 2013 Elsevier Ltd. All rights reserved.
Autores: Sánchez Larraona, Gorka; Rivas Nieto, Alejandro; Antón Remírez, Raúl; et al.
ISSN 1359-4311  Vol. 52  Nº 2  2013  págs. 428 - 438
A parametric study based on design of experiments (DoE) techniques was carried out by computational simulation in order to evaluate the effect that design parameters have on heat transfer and pressure loss of an impinging jet in a cross-flow configuration. The main effects of each parameter and the interactions between parameters were analyzed in detail through the Response Surface Methodology (RSM). Additionally, the potential of the impinging jet in a cross-flow configuration was assessed by calculating the optimal values of the parameters and comparing the cooling efficiency of the resulting configuration with the efficiency of the conventional cross-flow configuration. It was found that the degree to which the average heat transfer coefficient is enhanced as the result of adding an impinging jet depends on the height of the cooled component. Specifically, it was found that the higher the component, the more significant the enhancement. (C) 2013 Elsevier Ltd. All rights reserved.
Autores: Ramos González, Juan Carlos; Beiza Silva, Maximiliano Patricio; Gastelurrutia Roteta, Jon; et al.
ISSN 1359-4311  Vol. 51  Nº 1-2  2013  págs. 852 - 863
Ventilation by natural convection of two underground transformer substations has been numerically modelled. The model has been verified in terms of discretization errors and it has been validated with the experimental results of eight temperature rise tests carried out under different conditions of ventilation and transformer power losses. The results of the simulations serve to analyse the air flow pattern and the air temperature distributions inside the substation. A correlation for the air mass flow rate as a function of the ventilation conditions (discharge coefficient and area of the grilles) and the heat dissipated by the transformer has been fitted. The heat transfer coefficients on the surfaces of the transformer and the walls of the enclosure can also be obtained from the simulations of the model. All this information will be used in a future paper to develop a zonal thermal model of the ventilation of the substations that can be employed as a design and optimisation tool. (C) 2012 Elsevier Ltd. All rights reserved.
Autores: Antón Remírez, Raúl; Bengoechea García, Asier; Rivas Nieto, Alejandro; et al.
ISSN 1043-7398  Vol. 134  Nº 1  2012  págs. 011004 - 011004-8.
The performance of axial fans in close proximity to the electromagnetic compatibility (EMC) screens was analyzed by means of an experimental parametric study. The following geometrical parameters were studied: the hub-to-tip ratio, the ratio between fan thickness and fan diameter, the porosity and thickness of the perforated plate, and finally, the distance between the perforated plate and the inlet and the outlet of the fan. Screen porosity was found to be the most important parameter. Fan performance degradation is expressed by means of two correlations: one for the deterioration in the fan pressure at the no-flow point and the other for the flow rate reduction at the free delivery point. Both correlations were formulated as functions of screen porosity and the distance between the fan and the screen. We believe that the correlations can serve as a good guide for correct fan placement in a telecommunications cabinet. [DOI: 10.1115/1.4005913]
Autores: Masip Macia, Yunesky; Rivas Nieto, Alejandro; Sánchez Larraona, Gorka; et al.
ISSN 0142-727X  Vol. 38  2012  págs. 50 - 71
The air flow around a cubic obstacle mounted on one wall of a rectangular channel was studied experimentally. The obstacle represents an electronic component and the channel the space between two parallel printed circuit boards (PCBs). The flow was produced by the combination of a channel stream and a jet which issued from a circular nozzle placed at the wall opposite from where the component is mounted. With this aim, a test rig was designed and built to carry out experiments with both the above mentioned configurations and other cooling arrangements. Planar Particle Image Velocimetry (PIV) was employed to measure the instantaneous flow velocity on several planes covering the space around the component. The mean velocity and the Reynolds stresses were obtained from averaging the instantaneous velocity, and the mean flow showed a complex pattern with different features such as recirculation bubbles, vortices, detachment and reattachment zones. The influence of two parameters, namely the channel Reynolds number and the jet-to-channel Reynolds number ratio, on these flow features was studied considering nine cases that combined three values of the channel Reynolds number (3410, 5752 and 8880) and three values of the ratio (0.5, 1.0 and 1.5). The results show that the Reynolds number ratio determines the drag produced on the jet and the deflection from its geometric axis due to the channel stream. In all the cases corresponding to the lowest value of the ratio, the jet was dragged and did not impact the component. This fact accounts for the non-existence of the Upper Horseshoe Vortex and changes in the flow characteristics at the region over the component. (C) 2012 Elsevier Inc. All rights reserved.
Autores: Gastelurrutia Roteta, Jon; Ramos González, Juan Carlos; Sánchez Larraona, Gorka; et al.
ISSN 1359-4311  Vol. 31  Nº 4  2011  págs. 493 - 505
The thermal behaviour of several ONAN (Oil Natural Air Natural) distribution transformers has been numerically modelled. A simplified differential model has been developed with the aim of reducing the computational cost that would require a model with the complete geometrical description. This model has been capable of reproducing the expected oil flow and the thermal distribution inside the transformer. The influence of turbulence modelling in the obtained results has been evaluated and the model has been verified in terms of discretization errors. The thermal boundary conditions have been thoroughly analysed searching for the most appropriate expressions for this particular case instead of using inadequate mean values obtained from bibliography. The devised model has been validated by comparing the numerical results with the experimental ones obtained for different transformers and power losses. This mathematical tool can be used to study the natural convection of the oil inside the transformers and allows the manufacturers to optimise their designs from a thermal point of view. (C) 2010 Elsevier Ltd. All rights reserved.
Autores: Antón Remírez, Raúl; Gastelurrutia Roteta, Jon; Ramos González, Juan Carlos; et al.
ISSN 0949-149X  Vol. 27  Nº 4  2011  págs. 805 - 812
A Multiple Approach Competing Practical Exercise (MACPE), is an open exercise that confronts a group of students with a practical engineering problem using their own resources and choosing among multiple approaches in a competing environment. A case study with a teacher's assessment and a student's assessment has shown that this sort of exercise is able to motivate the students' learning process. It has also been found that it is a fun way to foster team work and constitutes an open door to innovation.
Autores: Gastelurrutia Roteta, Jon; Ramos González, Juan Carlos; Rivas Nieto, Alejandro; et al.
ISSN 1359-4311  Vol. 31  Nº 17-18  2011  págs. 4024 - 4035
The present paper proposes an algebraic zonal model describing the cooling process, via internal oil and external air natural convection, of distribution transformers during a standardised heating test. The conception and adjustment of the presented algebraic zonal model rely on the oil flow and thermal results obtained by a more complex numerical differential model that has been verified and validated by the authors. The domain of the original differential model is divided into several interrelated control volumes or zones where mass and energy conservation laws are applied in conjunction with the necessary boundary conditions. The generated nonlinear algebraic equation system is solved, obtaining in the process the top oil temperature, the internal and external surface temperatures and the heat dissipation distribution. The results of the zonal model have been validated using the previous results from the differential model as well as experimental measurements from heating tests with three different transformers under various power loads. The model developed has proven to be an efficient tool in improving and optimising the thermal design of these devices. (C) 2011 Elsevier Ltd. All rights reserved.
Autores: Elduayen Echave, Beñat; Ochoa de Eribe, A.; Lizarralde Aguirrezabal, Izaro; et al.
Libro:  Frontiers in Wastewater Treatment and Modelling. Lecture Notes in Civil Engineering
Vol. 4  2017  págs. 614 - 621
Struvite precipitation has raised as a promising solution to recover phosphorous in wastewater treatment plants (WWTP). Struvite is a fertilizer that varies its performance depending on its size. This shows the need to upgrade one-step classic kinetic precipitation models by new frameworks as the Population Balance Model (PBM). In this abstract a mass-based Discretized Population Balance Model (DPBM) used to predict struvite precipitation is presented. The model includes primary nucleation, growth and aggregation mechanisms as a function of supersaturation index and kinetic parameters. Main advantage of the mass-based definition is that mass continuity is guaranteed and that it is fully compatible with other chemical and physicochemical reactions. A sensitivity analysis performed reveals exponents of nucleation and growth as the most relevant parameters in the pH evolution during precipitation and final Particle Size Distribution (PSD). Experimental data was used to calibrate the model employing Bayesian Inference. Selected values of the parameters showed good agreement with reality.
Autores: Masip Macia, Yunesky; Rivas Nieto, Alejandro; Bengoechea García, Asier; et al.
Libro:  Advances in Fluid Mechanics VIII
2010  págs. 569 - 584