Jose Ignacio Rojas GregorioUniversitat Politècnica de Catalunya (UPC BarcelonaTECH) · Department of Physics - Division of Aerospace Engineering
Jose Ignacio Rojas Gregorio
PhD-Eng
OpenFOAM computational fluid dynamics simulation of thermally-driven winds in mountains/valleys/slopes on Earth and Mars
About
61
Publications
99,326
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
259
Citations
Citations since 2017
Introduction
Thanks for taking the time to view my profile. I've made research on: 1) CFD analysis of aerodyn perfos of cars & wind tunnels; 2) space technol. & apps. for disaster management; 3) innovative non-destructive testing technique; 4) viscoelastic properties of Al alloys (PhD); 5) wind resource assessment; 6) aircraft repair patches; 7) enroute wave vortex encounters. See scientific production in https://futur.upc.edu/JoseignacioRojasGregorio and personal blog in https://joseirojas.blogspot.com
Additional affiliations
January 2012 - April 2012
Position
- Occupational Trainee
Description
- Analysis of the microstructural evolution of an AlZnMg alloy under continuous heating over the temperature range of 25 to 375ºC by transmission electron microscopy and atom probe tomography.
June 2009 - July 2009
Position
- Intern
Description
- Project on certification of heliports for night operations of helicopters of the UN fleet in peacekeeping operations.
January 2008 - July 2008
Position
- Researcher
Description
- Project on aircraft repair technologies: Comparison of performance of bonded composite joint patches with riveted joint patches
Publications
Publications (61)
An OpenFOAM computational fluid dynamics model setup is proposed for simulating thermally driven winds in mountain–valley systems. As a first step, the choice of Reynolds Averaged Navier–Stokes k−ε turbulence model is validated on a 3D geometry by comparing its results vs. large-eddy simulations reported in the literature. Then, a numerical model o...
Commercial computational fluid dynamics (CFD) codes have often been used for simulation of atmospheric boundary layer (ABL) flows. The present work explores the potential of the open-source CFD software OpenFOAM for simulating thermally-driven winds, by comparing several turbulence models. Indeed, in ABL and other large-scale flows, turbulence is c...
Planetary boundary layer phenomena, such as slope winds and nocturnal low-level jets, are frequent on Mars, e.g., whenever diurnal surface temperature variations are significant, and large-scale winds are weak. In particular, thermally-driven winds are very common over sloping regions; they can reach significantly high speeds for steep slopes, and...
Numerical analysis of thermall-driven winds (and particuarly, slope winds) in Mars
The static strength and fatigue crack resistance of the aircraft skin structures depend on the materials used and joint type. Most of the commercial aircraft’s skin panel structures are made from aluminium alloy and carbon fibre reinforced epoxy. In this study, the fatigue resistance of four joint configurations (metal/metal, metal/composite, compo...
CORRELATION OF VISCOELASTICITY WITH FATIGUE
Objective: to elucidate the relationship between fatigue and mechanical relaxation/internal friction phenomena responsible for viscoelastic behavior of aerospace aluminium alloys
Potential impacts:
1) enable better understanding of underlying physics of fatigue, plastic deformation, and mechanical damp...
supplementary material of article: Rojas, J.I., Melgosa, M., Prats, X., Sensitivity Analysis of Maximum Circulation of Wake Vortex Encountered by En-Route Aircraft, Aerospace 8(7) (2021) 194, doi: 10.3390/aerospace8070194:
Particularly, the supplementary material is Table S1, showing the results from the circulation generator module (CGM) on the...
Wake vortex encounters (WVE) can pose significant hazard for en-route aircraft. We studied the sensitivity of wake vortex (WV) circulation and decay to aircraft mass, altitude, velocity, density, time of catastrophic wake demise event, eddy dissipation rate, wing span, span-wise load factor, and WV core radius. Then, a tool was developed to compute...
The skin structure of modern aircraft is composed of frames, which are complex structures assembled by joining several sub-assemblies. One of the most used methods for joining aircraft structural parts, as well as repair patches, is through rivets. These fasteners are extensively used in the aircraft industry due to many competitive advantages.
For...
http://hdl.handle.net/2117/349249
Exploring novel renewable energy resources such as thermal winds in mountainous areas and valleys is critical to reduce the energy production from fossil fuels and thus mitigating climate change. These winds occur due to thermal gradients and related buoyancy effects. Basically, the latter are mainly associated wi...
Thermal winds appear in mountainous areas and valleys due to temperature gradients caused by the buoyancy effects associated with the diurnal heating-cooling cycle of the lower atmosphere. These winds develop over complex topographies of multiple scales, and reverse their direction twice a day, driven by formation and dissipation of temperature inv...
Praseodymium (Pr2O3) doped PbO-Ro2O3-WO3-B2O3 glasses were prepared by melt quenching method and their optical absorption and emission spectra were characterized, for three different heavy metal oxides (Ro2O3 = Sb2O3, Al2O3, and Bi2O3). The characteristics of the glass matrix are confirmed by X-ray diffraction spectra. Many structural properties ca...
![Figure 1.1: Materials used in Boeing 787 Dreamliner [79].](profile/Jose-Rojas-Gregorio/publication/343306048/figure/fig1/AS:918917979598850@1596098527842/Materials-used-in-Boeing-787-Dreamliner-79_Q320.jpg)
![Figure 1.2: Fatigue life comparison of AA 2024-T3 and 7075-T6 [20].](profile/Jose-Rojas-Gregorio/publication/343306048/figure/fig2/AS:918917979578370@1596098527878/Fatigue-life-comparison-of-AA-2024-T3-and-7075-T6-20_Q320.jpg)
In the present day, the fastest mode of transport is by air. Air transportation demand has increased by two folds in the last decade. Demand for the air transport is increasing because of easy accessibility of airplanes with low flight fares and population growth. Most airlines aim at minimising their operational costs and maximizing aircraft use f...
The influence of modifier oxides (Ro2O3=Sb2O3, Al2O3, and Bi2O3) on the spectral analysis of PbO-Ro2O3–WO3–B2O3 glasses doped with Nd3+ ions is investigated in this work. Samples were prepared by the melt quench method, and their optical, luminescence, and physical properties were examined. From the measured properties, it is observed that the dens...
To increase renewable energy generation in some hydroelectric dams, a solution consisting in installing wind turbines close to dams is proposed. Indeed, dam surroundings are prone to benefit from wind speed-up effect, extra wind generation associated with thermal winds, and existing electrical infrastructure. Identifying the most suitable locations...
In this work, experimental and numerical analyses of repairs on carbon fiber reinforced epoxy (CFRE) substrates, with CFRE and aluminum alloy doublers typical of aircraft structures, are presented. The substrates have a bridge gap of 12.7 mm (simulated crack), repaired with twin doublers joined with riveted, adhesive bonded, and hybrid joints. The...
http://hdl.handle.net/2117/122637
We present numerical investigations on fatigue life analysis of un-repaired and repaired metallic substrate. Most of the engineering structures fail due to fatigue under dynamic loading. While research is mostly focused in experimental fatigue analysis, only few numerical approaches are found in the literature. In...
This paper presents a discussion about risks and hazards of potential wake vortex encounters in the en-route airspace. High-fidelity simulations under realistic conditions have been analysed showing that the current en-route separation standards may be overconservative in some cases –thus enabling a potential reduction that may lead to additional a...
http://hdl.handle.net/2117/122767
In the race for developing aircraft with lighter airframe, aiming at increasing aircraft payload and/or fuel efficiency, the shift from conventional metal structures to light-weight composite structures has attracted attention and competition among the aircraft manufacturers. Apart from fuel consumption, other ope...
The behaviour of various aircraft lap joint repairs is investigated experimentally and numerically under static loading. The lap joints consist of Al alloy 2024-T3 substrates repaired with twin single-sided 2024-T3 or CFRE doublers. Pure riveted, pure bonded and hybrid (riveted and bonded) joints of metal–metal and metal–composite configs are inves...
The viscoelastic response of a novel composite (A356 aluminum alloy matrix with ceramic reinforcement particles developed from colliery shale waste) is measured with dynamic-mechanical analyzer, and is compared to pure aluminum, aluminum alloys A356, 7075 and 2024, and another composite (6061 aluminum alloy matrix reinforced with SiC particles). Th...
Based on the information available in databases from relevant national and international organizations from 1967 to 2010, an Aviation Weather Accidents Database (AWAD) was built. According to AWAD, the weather is the primary cause in a growing percentage of annual aircraft accidents: from ≈40% in 1967 to almost 50% in 2010. While the absolute numbe...
Based on the information available in databases from relevant national and international organizations from 1967 to 2010, an Aviation Weather Accidents Database (AWAD) was built. According to AWAD, the weather is the primary cause in a growing percentage of annual aircraft accidents: from ≈40% in 1967 to almost 50% in 2010. While the absolute numbe...
Free access until December 30, 2017, in this Share Link: https://authors.elsevier.com/a/1W1VD3jWfEmEOf
The microstructural evolution of an Al–Zn–Mg–Cu alloy under continuous heating over the temperature range of 298 to 648 K (25 to 375ºC) is characterized by focused ion beam-scanning electron microscopy, transmission electron microscopy, and atom...
The use of metal matrix composites (MMC) has increased steadily in the last two decades. Conventional MMC are usually produced by addition of either Al2O3 or SiC particles, or their combinations, into molten pure metals or alloys. However, when preparing the MMC through melting routes, there is significant loss of those costly particles, making fab...
One of the major contributions to aircraft operational costs corresponds to maintenance. This is a time consuming and expensive process, but necessary, for instance, to detect early formation of cracks, monitoring crack growth, and for removing or fixing parts with repairs to regain their original strength. Thus, repair technologies play an importa...
Aircraft lap joints play an important role in minimizing the operational cost of airlines. Hence, airlines pay more attention to these technologies to improve efficiency. Namely, a major time consuming and costly process is maintenance of aircraft between the flights, for instance, to detect early formation of cracks, monitoring crack growth, and f...
http://hdl.handle.net/2117/104489
The viscoelastic response of commercial Al–Zn–Mg and Al–Cu–Mg alloys was measured with a dynamic-mechanical analyzer (DMA) as a function of the temperature (from 30 to 425 ∘ C) and the loading frequency (from 0.01 to 150 Hz). The time-temperature superposition (TTS) principle has proven to be useful in studying mec...
This work investigates the potential of the sea breeze for wind energy generation with small wind turbines. For this purpose, we used wind data recorded in the Llobregat Delta (NE of the Iberian Peninsula) from 1993 to 2010 and turbine power curves obtained from QBlade, FAST and AeroDyn freeware tools, and from the manufacturer. The HP-600W turbine...
Aircraft repair technologies play an important role in minimizing the operational costs of airlines. Namely, a major time consuming process is the maintenance of aircraft in between flights, for instance, to detect early formation of cracks, monitoring crack growth and for fixing the corresponding parts with joints, when necessary. This work focuse...
Wind speed data recorded during 18 years (1993-2010) in the Llobregat Delta (15 km south of Barcelona city; northeast of the Iberian Peninsula) were used to assess the wind energy generated by off-grid small scale wind turbines (the IT-PE-100 and the HP-600W) for the whole year and for the sea breeze period. The computations were made using QBlade,...
http://hdl.handle.net/2117/84514
The viscoelastic response of pure Al and 7075 (AlZnMg) and 2024 (AlCuMg) alloys, obtained with a dynamic-mechanical analyzer (DMA), is studied. The purpose is to identify relationships between the viscoelasticity and fatigue response of these materials, of great interest for structural applications, in view of their...
http://hdl.handle.net/2117/84524
An innovative NDT technique is proposed for surface inspection of materials not necessarily magnetic or conductive, based on local magnetic field variations due to ferrofluid deposited in the cracks. The feasibility of the technique is assessed preliminarily, based on signal detectability without applied external ma...
An innovative NDT technique is proposed for surface inspection of materials not necessarily magnetic or conductive, based on local magnetic field variations due to ferrofluid deposited in the cracks. The feasibility of the technique is assessed preliminarily, based on signal detectability without applied external magnetic field, and under applied D...
http://hdl.handle.net/2117/26973
From wind speed data recorded hourly at 2 m high during 18 years (1993-2010) in the Llobregat Delta (15 km south of Barcelona city; northeast of the Iberian Peninsula), wind speed distributions at 10 m high were computed for the whole year and for the sea breeze period (from March 1 to September 30, from 10 to 19 lo...
![Figure 1: Global Deaths and Damage due to Earthquakes (1990-2006) [1][2]](profile/Emily-Coffey-3/publication/33422430/figure/fig3/AS:667677005717506@1536198011384/Global-Deaths-and-Damage-due-to-Earthquakes-1990-2006-12_Q320.jpg)
![Figure 2: Global Earthquake Distribution [18]](profile/Emily-Coffey-3/publication/33422430/figure/fig4/AS:667677005717507@1536198011400/Global-Earthquake-Distribution-18_Q320.jpg)
http://hdl.handle.net/2117/2269
Earthquakes and their after-effects claim thousands of lives and cause enormous property damage each year. Early warning of impending seismological events has the potential to reduce human suffering and physical damage resulting from these natural disasters. Reliable earthquake precursors have yet to be identified, b...
http://hdl.handle.net/2117/23247
This work presents preliminary research on a low-cost meteorological station for measuring in situ Essential Climate Variables (ECV): solar irradiance, surface water vapour, surface air temperature, land surface wind speed/direction, and precipitation. Important benefits can be obtained from these data: 1) optimizat...
http://hdl.handle.net/2117/26927
This work presents preliminary research on a low-cost meteorological station for measuring in situ Essential Climate Variables (ECV): solar irradiance, surface water vapour, surface air temperature, land surface wind speed/direction, and precipitation. Important benefits can be obtained from these data: 1) optimizat...
“Obtenció d'energia mini-eòlica al Delta del Llobregat, i altres zones costaneres, mitjançant petits
aerogeneradors” El projecte pretén avaluar el potencial eòlic del vent de la marinada. Ja es compta amb
un prototip instal·lat a Viladecans per validar les simulacions teòriques. Estan treballant en la implementació
de molinets eòlics d'1.7 metres d...
http://hdl.handle.net/2117/20661
Una experiencia de unificación de asignaturas para desplegar PBL (y las quejas que originó) para otros que se planeen retos similares. Palabras clave: Aprendizaje basado en proyectos, dificultades, organización de los planes de estudio. 1. Introducción Si bien hace ya bastante tiempo que se usa en muchas uni-versida...
http://hdl.handle.net/2117/18490
The viscoelastic response of commercial aluminum alloys 7075-T6 and 2024-T3 as a function of temperature is presented. Experimental data are obtained with a dynamic-mechanical analyzer (DMA) at different loading frequencies and compared with the available transmission electron microscopy (TEM) and differential scann...
Sea breeze is a thermal wind produced as a consequence of land-sea thermal difference. This is the most important wind regime for over 6 months in many coastal areas in the Mediterranean basin, like for instance the Llobregat Delta (15 km South of Barcelona city), where from mid March to mid September the sea breeze is the dominant wind. An automat...
http://hdl.handle.net/2117/26929
A weather station is proposed especially designed for developing countries, and to meet the standards of the international scientific community making research on the Earth system. The station would measure in situ several ECV (Essential Climate Variables). These data may enable an agricultural breakthrough in count...
http://hdl.handle.net/2117/14607
The viscoelastic response of a material offers an alternative method for analyzing its microstructure, phase transformations and fatigue behaviour. In this work, the viscoelastic properties of commercial aluminium alloy (AA) 7075-T6 are studied with a Dynamic-Mechanical Analyzer (DMA), and results are combined with...
http://www.tdx.cat/handle/10803/77907
Historically, much research has been devoted to the characterization of most of the mechanical properties of materials. However, the viscoelastic behaviour of metals, consequence of internal friction when subjected to fluctuating loads, has received much less attention. The comprehension of the underlying physi...
http://hdl.handle.net/2117/7832
The main purpose of this paper is to describe the process by which an initially limited-range practical experience, within the frame of a given subject in an aerospace engineering degree, might be expanded to become the mother-subject itself. Particularly, the practical experience is a Model Rocket Workshop (MRW), wh...
The main purpose of this case is to describe the process by which an initially limited-range practical experience, within the frame of a given course in an aerospace engineering degree, might be expanded to become the mother-course itself. Particularly, the practical experience is a Model Rocket Workshop (MRW), where students design, simulate, buil...
http://hdl.handle.net/2117/1328
One of the main routes to obtain nanostructured materials is through the primary crystallization of metallic glasses. In such transformations, crystallites with a different composition than the amorphous precursor grow with a diffusion-controlled regime. Particle growth is slowed and eventually halted by the impingem...
http://hdl.handle.net/2117/1467
Significant advances are being made in earthquake prediction theory; however, a reliable method for forecasting the occurrence of earthquakes from space and/or ground based technologies remains limited to no more than a few minutes before the event happens. Several claims of earthquake precursors have been put forwar...
A Problem-Based Learning (PBL) experience for undergraduate students of aerospace engineering is described in this paper. The experience allows the students to build a model rocket using materials which can be easily obtained. They also compute all the relevant quantities to design and characterize the rocket and they test the robustness of their d...
http://hdl.handle.net/2117/6829
Problem-Based Learning (PBL) experience for undergraduate students of aerospace engineering is described in this paper. The experience allows the students to build a model rocket using materials which can be easily obtained. They also compute all the relevant quantities to design and characterize the rocket and they...
![Figure 1: Global Deaths and Damage due to Earthquakes (1990-2006) [1][2]](profile/Jose-Rojas-Gregorio/publication/269993155/figure/fig3/AS:667641953927175@1536189654295/Global-Deaths-and-Damage-due-to-Earthquakes-1990-2006-12_Q320.jpg)
![Figure 2: Global Earthquake Distribution [18]](profile/Jose-Rojas-Gregorio/publication/269993155/figure/fig4/AS:667641953914883@1536189654313/Global-Earthquake-Distribution-18_Q320.jpg)
http://hdl.handle.net/2117/2269
Earthquakes and their after-effects claim thousands of lives and cause enormous property damage each year. Early warning of impending seismological events has the potential to reduce human suffering and physical damage resulting from these natural disasters. Reliable earthquake precursors have yet to be identified, b...
![Fig. 1. Occurrence of earthquakes globally [2].](profile/Jose-Rojas-Gregorio/publication/33422462/figure/fig1/AS:277455525957632@1443161960636/Occurrence-of-earthquakes-globally-2_Q320.jpg)
http://hdl.handle.net/2117/2319
Earthquakes represent a major hazard for populations around the world, causing frequent loss of life, human suffering and enormous damage to homes, other buildings and infrastructure. The Technology Resources for Earthquake Monitoring and Response (TREMOR) Team of 36 space professionals analysed this problem over the...
Earthquakes represent a major hazard for populations around the world, causing frequent loss of life, human suffering, and enormous damage to homes, other buildings, and infrastructure. The Technology Resources for Earthquake Monitoring and Response (TREMOR) proposal is designed to address this problem. This proposal recommends two prototype system...
El presente documento constituye el Proyecto Fin de Carrera (PFC) realizado por los alumnos Manuel Delgado Montilla y José Ignacio Rojas Gregorio, de la E.T.S.I. Aeronáuticos, bajo la supervisión del Profesor Rafael Torres Sáenz de Santamaría, del Departamento de Infraestructura, Sistemas Aeroespaciales y Aeropuertos. Dicho Proyecto se adscribe a l...
Questions
Questions (12)
We are studying the generation of thermal winds in mountainous areas, using computational fluid dynamics software. In particular, now we are focusing on the simulation of the full diurnal cycle, with a temperature boundary condition that is periodic with period 24h.
When we check the results, we obtain that the maximum speed of the katabatic wind (nighttime, down-slope flow) is always smaller than the maximum speed of the anabatic wind (daytime, up-slope flow). We think that this is sound, given the actual geometry of the mountain-valley system that we are simulating, and the boundary conditions that we are using (please, see image below) but still we would appreciate some input and confirmation, given that, in some references, we have seen different results.
Projects
Projects (11)
We studied the influence of meteorological phenomena on aircraft accidents according to accidents and incidents data from 1967 to 2010
An innovative NDT technique is proposed for surface inspection of materials not necessarily magnetic or conductive, based on local magnetic field variations due to ferrofluid deposited in the cracks. The feasibility of the technique is assessed preliminarily, based on signal detectability without applied external magnetic field, and under applied DC fields. The signals (local magnetic flux density variations) are quantified analytically, experimentally and numerically. The model agrees well with the tests, showing that the signal increases with the applied field strength, up to the saturation magnetization of the ferrofluid, and decreases with the distance to the crack longitudinal axis, and thus it can provide useful estimations of the signal. The proposed technique, requiring application of external fields to magnetize the ferrofluid to enhance the signal, seems promising: the model suggests that signals associated to cracks significantly smaller than surface cracks in a target application like aircraft skin panel inspection NASA STD-5009 are easily detectable with commercial magnetometers.