Fernando Veiga Lopez

• Doctor of Engineering
• Researcher at University of Vigo

The relationship between airborne pollen of the invasive species Acacia dealbata Link, climate factors, and its ground expansion is studied using aerobiological data and aerial photography to test if pollen data can be used as a tool to detect changes in the surface area of invasive species. Airborne pollen monitoring was performed over a 31 years...

Purpose This study aims to use dimensionality reduction techniques applied to a detailed wind flow computational fluid dynamics (CFD)-generated database to develop a fast numerical tool that predicts, using the available weather forecast data, the airflow around any urban environment. The tool is aimed for its use in path planning design and optimi...

The deployment of Advanced Air Mobility requires the continued development of technologies to ensure operational safety. One of the key aspects to consider here is the availability of robust solutions to avoid tactical conflicts between drones and other flying elements, such as other drones or birds. Bird detection is a relatively underexplored are...

This work provides an overview of the growing use of drones in both civilian and military domains, highlighting the associated risks to public safety and privacy. It discusses the development of counter-drone systems to mitigate these risks, focusing on detection, tracking, classification, and neutralization technologies. Various sensors such as pa...

This article presents a real-time trajectory calculation system for shore-to-ship operations using Unmanned Aerial Vehicles (UAVs). This is a concept, aimed to improve the efficiency of the transportation system by using UAVs to carry out parcel deliveries to offshore ships. During these operations, the UAVs would need to fly relatively close to ma...

Two types of three-step chain-branching kinetics for gaseous hydrogen–oxygen detonation quenching are proposed. The reaction rates dependency on density and pressure, as well as the change in molecular weight are included and fitted to results of detailed chemistry not only along the Hugoniot curve but also behind transverse waves. The trend of ind...

The proliferation of Unmanned Aerial Vehicles (UAVs) has raised safety concerns due to the potential threats resulting from their misuse or malicious intent. Due to their compact size, high-resolution surveillance systems such as LiDAR sensors are necessary to exert effective control over the airspace. Given the large volume of data that these tech...

Advanced Air Mobility (AAM) is an emerging sector that aims to optimise transportation in urban and interurban environments using Unmanned Aerial Vehicles (UAVs). However, these aircraft are particularly susceptible to adverse weather phenomena, such as turbulence or wind gusts. To ensure the safety of operations, high-resolution real-time atmosphe...

The effect of heat and momentum losses on the steady solutions admitted by the reactive Euler equations with sink/source terms is examined for stoichiometric hydrogen–oxygen mixtures. Varying degrees of nitrogen and argon dilution are considered in order to access a wide range of effective activation energies, $$E_{\textrm{a,eff}}/R_{\textrm{u}}T_{...

Ammonia is a promising compound for chemical storage of renewable energy produced from non-continuous sources. However, the low reactivity of ammonia requires to use ammonia-hydrogen blends as a fuel for combustion applications. The present study corresponds to a first numerical assessment of the potential of ammonia-hydrogen-air mixtures as reacti...

Unmanned Aerial Vehicles (UAVs), commonly known as drones, have experienced a significant surge in both civilian and military applications, owing to their versatility and cost-effectiveness. However, a negligent use or the operation with harmful intent of these aircraft poses a potential risk to public safety and the privacy of individuals. In resp...

The number of species and elementary reactions needed for describing the oxidation of fuels increases with the size of the molecule, and in turn, the complexity of detailed mechanisms. Although the ki-netics for conventional fuels (H2 , CH4 , C3H8 ...) are somewhat well-established, chemical integration in detonation applications remains a major ch...

The influence of low temperature chemistry (LTC) on the locus of steady solutions predicted by a ZND model with curvature losses and detailed kinetics was assessed using undiluted / CO2-diluted stoichiometric DME-O2 mixtures. Results show (i) the existence of an additional critical point at large velocity deficits when the LTC sub-mechanism is incl...

Dendritic combustion in Hele-Shaw cells is investigated qualitatively using a simplified one-dimensional thermo-diffusive model. Formulae for the velocity, size and temperature of the flamelets are derived. The temperature and velocity of the flames increase for small radii to allow for their survival regardless the activation energy. In addition,...

The influence of ozone on quasi-steady curved detonations was numerically studied in stoichiometric H 2-air and DME-O 2 (-CO 2) mixtures with 0%, 0.1% and 1% O 3 addition. Detonation speed-curvature (D-κ) relations were determined for both fuels. The H 2-air mixture has one critical point related to high-temperature chemistry whereas the DME-O 2 (-...

The minimum detonation diameter for methane (CH4) / hydrogen (H2)-air mixtures is numerically evaluated to assess detonation risks in cooktops designed to work with natural gas. A one-dimensional mathematical model that considers heat and friction losses for detonations propagating in pipes is used for that purpose. The initial conditions are selec...

We present here an experimental study of the influence of the aeroelastic coupling between the combustion chamber walls and the acoustic fluid field on the onset and development of thermoacoustic instabilities in stoichiometric propane-air premixed flames. A horizontal quasi-two-dimensional Hele-Shaw chamber formed by two parallel plates separated...

The minimum detonation diameter for methane (CH4)/hydrogen (H2)-air mixtures is numerically evaluated to assess detonation risks in cooktops designed to work with natural gas. A one-dimensional mathematical model that considers heat and friction losses for detonations propagating in pipes is used for that purpose. The initial conditions are selecte...

A methodology to develop more predictive simplified kinetic schemes (1-step/3-step chain branching) is presented in which D-k curves obtained with detailed kinetics are used as the fitting target aiming to capture the turning point of the curve kcrit. This was motivated by the similar trend observed between the kcrit values and the critical reacti...

The problem of the steady propagation of detonation waves with friction losses is revisited including detailed kinetics. The derived formulation is used to study the influence of chemical modeling on the steady solutions and reaction zone structures obtained for stoichiometric hydrogen-oxygen. Detonation velocity-friction coefficient (D − c f) curv...

An experimental study of methane, propane and dimethyl ether (DME) pre-mixed flames propagating in a quasi-two-dimensional Hele-Shaw cell placed horizontally is presented in this paper. The flames are ignited at the open end of the combustion chamber and propagate towards the closed end. Our experiments revealed two distinct propagation regimes dep...

Flame propagation and acceleration in unobstructed channels/tubes is usually assumed as symmetric. A fully optically accessible narrow channel that allows to perform simultaneous high-speed schlieren visualization from two mutually perpendicular directions was built to asses the validity of the aforementioned assumption. Here, we provide experiment...

Very lean hydrogen flames were thought to quench in narrow confined geometries. However, flames with very low fuel concentration undergo an isolated critically-sustained propagation in narrow gaps: H2-air flames can overcome large heat losses and very lean conditions by breaking the reaction surface into isolated flame cells that locally enrich the...

In this paper, a theoretical analysis of the condensation of combustion products in narrow gaps between planar plates is performed. The investigation is motivated by the empirical results shown by Veiga-López [“Flame propagation in narrow channels,” Ph.D. thesis (Carlos III University of Madrid, 2020)] and the lack of a theoretical description dire...

Thermoacoustic instabilities arise for lean hydrogen-air flames propagating in narrow channels. We provide here a detailed experimental analysis of such phenomena in a semi-confined vessel, analyzing the effect of the mixture composition, geometry and gravity on the onset of acoustic-driven flame vibrations. Downward-propagating flames leaner than...

Very lean hydrogen flames were thought to quench in narrow confined geometries. We show for the first time how flames with very low fuel concentration undergo an unprecedented propagation in narrow gaps: H 2-air flames can survive very adverse conditions by breaking the reaction front into isolated flame cells that travel steadily in straight lines...

The physical limits of the unconventional flame propagation regimes recently discovered [Veiga-Lopez et al., Phys. Rev. Lett. 124, 174501 (2020)] are analyzed. These regimes appear in combustible gaseous mixtures approaching the lean quenching limit of hydrogen-air flames in narrow gaps. They are characterized by a split of the flame front into a d...

https://www.investigacionyciencia.es/revistas/investigacion-y-ciencia/grandes-hitos-y-prximos-retos-de-la-ciencia-811/la-sigilosa-combustin-del-hidrgeno-19140

The sudden arrival of the climate change hurries fundamental research on a wide variety of topics trying to slow it down and counteract its effects. One of the examples is the study of alternative fuels (e.g., methane and hydrogen) to replace oil and coal. Furthermore, scientific investigation focusing on combustion in confined geometries is also i...

Very lean hydrogen flames were thought to quench in narrow confined geometries. We show for the first time how flames with very low fuel concentration undergo an unprecedented propagation in narrow gaps: H2-air flames can survive very adverse conditions by breaking the reaction front into isolated flame cells that travel steadily in straight lines...

A series of experiments on hydrogen flame propagation in a thin layer geometry is presented. Premixed hydrogen-air compositions in the range from 6 to 15%(vol.) H2 are tested. Semi-open vertical combustion chamber consists of two transparent Plexiglas side walls with main dimensions of 90x20 cm with a gap from 1 to 10 mm in between. Test mixtures a...

The propagation of low-Lewis-number premixed flames is analyzed in a partially confined Hele–Shaw chamber formed by two parallel plates separated a distance h apart. An asymptotic-numerical study can be performed for small gaps compared to the flame thickness δT . In this narrow-channel limit, the problem formulation simplifies to a quasi-2D descri...

This paper is associated with a video winner of a 2018 APS/DFD Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion. The original video is available online at the Gallery of Fluid Motion, https://doi.org/10.1103/APS.DFD.2018.GFM.V0018

An experimental study of lean hydrogen-air premixed flames propagating in a confined combustion chamber is presented in this paper. Depending on the conditions (both equivalence ratio (Φ) and channel thickness (h) was varied), two different phenomena control the propagation of the flames. Primary and secondary thermoacoustic instabilities appear fo...

An experimental study of lean hydrogen-air premixed flames propagating in a confined combustion chamber ispresented in this poster. All the flames travel from the open end of the chamber towards its closed opposite side. Under such conditions, the interplay between heat losses and viscous friction determines the propagation of the flames. The teste...

An experimental study of methane, propane and dimethyl ether (DME) pre-mixed flames propagating in a quasi-two-dimensional Hele-Shaw cell placed horizontally is presented in this paper. The flames are ignited at the open end of the combustion chamber and propagate towards the closed end. Our experiments revealed two distinct propagation regimes dep...

2018 APS Gallery of Fluid Motion Milton van Dyke Award Winner

Vessel-confinement contributions to thermo-acoustic instabilities of premixed flames

Propagation of premixed flames in closed vessels is a problem of great importance in science and technological applications. The interaction of the acoustic waves with the reacting front is found widely in power-generation devices, which can compromise their structural integrity. A Hele Shaw cell, of very small thickness, has been used to study the...

In this paper, an experimental study of methane-air and propane-air flames propagating in a quasi-two-dimensional, horizontal Hele-Shaw cell is presented. In the configuration considered in this paper, the reactive mixture is ignited at the open end of the combustion chamber and propagates towards the closed end. Our experiments revealed two distin...