DITF - MF - Artículos de Revistas Científicas

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Now showing 1 - 20 of 139
  • Publication
    Engineering Lung-Inspired Flow Field Geometries for Electrochemical Flow Cells with Stereolithography 3D Printing
    (American Chemical Society, 2023-08-21) Muñoz Perales, Vanesa; Vand Der Heijden, Maxime; García-Salaberri, Pablo A.; Vera Coello, Marcos; Forner Cuenca, Antonio; European Commission
    Electrochemical flow reactors are increasingly relevant platforms in emerging sustainable energy conversion and storage technologies. As a prominent example, redox flow batteries, a well-suited technology for large energy storage if the costs can be significantly reduced, leverage electrochemical reactors as power converting units. Within the reactor, the flow field geometry determines the electrolyte pumping power required, mass transport rates, and overall cell performance. However, current designs are inspired by fuel cell technologies but have not been engineered for redox flow battery applications, where liquid-phase electrochemistry is sustained. Here, we leverage stereolithography 3D printing to manufacture lung-inspired flow field geometries and compare their performance to conventional flow field designs. A versatile two-step process based on stereolithography 3D printing followed by a coating procedure to form a conductive structure is developed to manufacture lung-inspired flow field geometries. We employ a suite of fluid dynamics, electrochemical diagnostics, and finite element simulations to correlate the flow field geometry with performance in symmetric flow cells. We find that the lung-inspired structural pattern homogenizes the reactant distribution throughout the porous electrode and improves the electrolyte accessibility to the electrode reaction area. In addition, the results reveal that these novel flow field geometries can outperform conventional interdigitated flow field designs, as these patterns exhibit a more favorable balance of electrical and pumping power, achieving superior current densities at lower pressure loss. Although at its nascent stage, additive manufacturing offers a versatile design space for manufacturing engineered flow field geometries for advanced flow reactors in emerging electrochemical energy storage technologies.
  • Publication
    The fluid mechanics of bubbly drinks
    (AIP, 2018-11-01) Zenit, Roberto; Rodríguez Rodríguez, Francisco Javier; Ministerio de Economía y Competitividad (España)
    In most cases, the bubbles in a drink are the result of carbonation. The amount of carbon dioxide gas that dissolves in the liquid is proportional to pressure. And if the pressure is suddenly reduced, such as when a bottle of beer is opened, the gas quickly comes out of solution and forms bubbles that rise to the surface, only to burst after a brief instant or to aggregate into a frothy head of foam.
  • Publication
    Oscillating viscous flow past a streamwise linear array of circular cylinders
    (Cambridge University Press, 2023-03-25) Alaminos Quesada, J.; Lawrence, J. J.; Coenen, Wilfried; Sánchez Pérez, Antonio Luis; Agencia Estatal de Investigación (España)
    This paper addresses the viscous flow developing about an array of equally spaced identical circular cylinders aligned with an incompressible fluid stream whose velocity oscillates periodically in time. The focus of the analysis is on harmonically oscillating flows with stroke lengths that are comparable to or smaller than the cylinder radius, such that the flow remains two-dimensional, time-periodic and symmetric with respect to the centreline. Specific consideration is given to the limit of asymptotically small stroke lengths, in which the flow is harmonic at leading order, with the first-order corrections exhibiting a steady-streaming component, which is computed here along with the accompanying Stokes drift. As in the familiar case of oscillating flow over a single cylinder, for small stroke lengths, the associated time-averaged Lagrangian velocity field, given by the sum of the steady-streaming and Stokes-drift components, displays recirculating vortices, which are quantified for different values of the two relevant controlling parameters, namely, the Womersley number and the ratio of the inter-cylinder distance to the cylinder radius. Comparisons with results of direct numerical simulations indicate that the description of the Lagrangian mean flow for infinitesimally small values of the stroke length remains reasonably accurate even when the stroke length is comparable to the cylinder radius. The numerical integrations are also used to quantify the streamwise flow rate induced by the presence of the cylinder array in cases where the periodic surrounding motion is driven by an anharmonic pressure gradient, a problem of interest in connection with the oscillating flow of cerebrospinal fluid around the nerve roots located along the spinal canal.
  • Publication
    On the stability of piston-driven planar shocks
    (Cambridge University Press, 2023-06-10) Calvo Rivera, Andrés; Velikovich, Alexander L.; Huete Ruiz de Lira, César; Comunidad de Madrid; Universidad Carlos III de Madrid; Agencia Estatal de Investigación (España); Ministerio de Ciencia e Innovación (España)
    We present a theoretical and numerical stability analysis for a piston-driven planar shock against two-dimensional perturbations. The results agree with the well-established theory for isolated planar shocks: in the range of hc < h < 1 + 2M2, where h is the Dyakov-Kontorovich (DK) parameter related to the slope of the Rankine-Hugoniot curve, hc is its critical value corresponding to the onset of the spontaneous acoustic emission (SAE) and M2 is the downstream Mach number, non-decaying oscillations of shock-front ripples occur. The effect of the piston is manifested in the presence of additional frequencies occurring by the reflection of the sonic waves on the piston surface that can reach the shock. An unstable behaviour of the shock perturbation is found to be possible when there is an external excitation source affecting the shock, whose frequency coincides with the self-induced oscillation frequency in the SAE regime, thereby being limited to the range hc < h < 1 + 2M2. An unstable evolution of the shock is also observed for planar shocks restricted to one-dimensional perturbations within the range 1 < h < 1 + 2M2. Both numerical integration of the Euler equations via the method of characteristics and theoretical analysis via Laplace transform are employed to cross-validate the results.
  • Publication
    Initial stage of plate lifting from a water surface
    (Springer, 2017-02) Korobkin, Alexander; Khabakhpasheva, Tatyana; Rodríguez Rodríguez, Francisco Javier; Ministerio de Economía y Competitividad (España)
    This study deals with the flow induced by a rigid flat plate of finite length, initially touching a horizontal water surface, when it starts to move upwards with constant acceleration. In the present model, negative hydrodynamic pressures on the lower (wetted) surface of the plate are allowed, and thus, the water follows the plate due to the resulting suction force. The acceleration of the plate and the plate length are such that gravity, surface tension and viscous effects can be neglected during the early stages of the motion. Under these assumptions, the initial two-dimensional, potential flow caused by the plate lifting is obtained by using the small-time expansion of the velocity potential. This small-time solution is not valid close to the plate edges, as it predicts there singular flow velocities and unbounded displacements of the water-free surface. It is shown that close to the plate edges the flow is nonlinear and self-similar to leading order. This nonlinear flow is computed by the boundary-element method combined with a time-marching scheme. The numerical time-dependent solution approaches the self-similar local solution with time.
  • Publication
    Suppression of thermoacoustic instabilities by flame-structure interaction
    (Elsevier, 2023) Rubio Rubio, Mariano; Veiga López, Fernando; Martínez Ruiz, Daniel; Fernández Tarrazo, Eduardo Antonio; Sánchez Sanz, Mario; Comunidad de Madrid; Agencia Estatal de Investigación (España)
    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 instabilitiesin stoichiometric propane-air premixed flames. A horizontal quasi-two-dimensional Hele-Shaw chamber formed by two parallel plates separated a small distance h is used. The flames are ignited at the open end, in contact with the atmosphere, and propagate towards the opposite closed end. The experiments reveal three distinct propagation regimes determined by the stiffness of the plates and the evolution of the pressure perturbation generated during ignition: (i) for sufficiently rigid plates, we observed secondary acoustic instabilities with large amplitude oscillations in the direction of propagation of the flame; for flexible enough walls to be compliant with ignition-related pressure changes, (ii) the propagation of the flame undergoes small-amplitude oscillations (primary acoustic instabilities) along the channel or (iii) it is smooth with no oscillations whatsoever. The flexural rigidity of the plate is modified experimentally by changing both the widthW and thickness hw of the top plate of the Hele-Shaw cell. The data recorded by the pressure transducer and the accelerometer is used to plot a stability map in the W - hw parametric space to define the combination of structural parameters that triggers the onset of thermoacoustic instabilities. Our experimental measurements, supplemented with results from a theoretical analysis of the walls vibration modes, indicated that deformation-induced volume changes of around 0.1% of the volume of the Hele-Shaw cell are sufficient to suppress thermoacoustic instabilities.
  • Publication
    Bridging scales to model reactive diffusive transport in porous media
    (IOP Science, 2020-01) Liu, Jianjing; García-Salaberri, Pablo A.; Zenyuk, Iryna V.; Ministerio de Economía y Competitividad (España)
    Two novel scale-bridging algorithms to model reaction-diffusion transport in porous media are presented. The algorithms are based on direct numerical simulations and couple the information of a micro-scale model, which accounts for the large field of view provided by micro X-ray computed tomography (X-ray CT), and a nano-scale model, which locally resolves transport in the fine structure extracted from nano X-ray CT. The micro-scale model is discretized in the through-plane direction into a 1D grid, where effective properties and internal boundaries are determined based on the results from the nano-scale model. The validated algorithms are used to examine transport of oxygen in precious group metal-free electrodes considering both zero- and first-order kinetics. Unlike conventional methods, the results show that the effective diffusivity is not a passive property but increases in regions where the reaction-rate coefficient is large. The proposed algorithms account for the multiscale coupling of reaction-diffusion transport and material microstructure, thus improving the predictions compared to conventional methods.
  • Publication
    Probing the Structure-Performance Relationship of Lithium-Ion Battery Cathodes Using Pore-Networks Extracted from Three-Phase Tomograms
    (IOP Publishing Limited, 2020-03-01) Khan, Zohaib Atiq; García-Salaberri, Pablo A.; Heenan, Thomas M. M.; Jervis, Rhodri; Shearing, Paul R.; Brett, Dan J. L.; Elkamel, Ali; Gostick, Jeff T.
    Pore-scale simulations of Li-ion battery electrodes were conducted using both pore-network modeling and direct numerical simulation. Ternary tomographic images of NMC811 cathodes were obtained and used to create the pore-scale computational domains. A novel network extraction method was developed to manage the extraction of N-phase networks which was used to extract all three phases of NMC-811 electrode along with their interconnections Pore network results compared favorably with direct numerical simulations (DNS) in terms of effective transport properties of each phase but were obtained in significantly less time. Simulations were then conducted with combined diffusion-reaction to simulate the limiting current behavior. It was found that when considering only ion and electron transport, the electrode structure could support current densities about 300 times higher than experimentally observed values. Additional case studies were conducted to illustrate the necessity of ternary images which allow separate consideration of carbon binder domain and active material. The results showed a 24.4% decrease in current density when the carbon binder was treated as a separate phase compared to lumping the CBD and active material into a single phase. The impact of nanoporosity in the carbon binder phase was also explored and found to enhance the reaction rate by 16.8% compared to solid binder. In addition, the developed technique used 58 times larger domain volume than DNS which opens up the possibility of modelling much larger tomographic data sets, enabling representative areas of typically inhomogeneous battery electrodes to be modelled accurately, and proposes a solution to the conflicting needs of high-resolution imaging and large volumes for image-based modelling. For the first time, three-phase pore network modelling of battery electrodes has been demonstrated and evaluated, opening the path towards a new modelling framework for lithium ion batteries.
  • Publication
    Lubrication analysis of peristaltic motion in non-axisymmetric annular tubes
    (Cambridge University Press, 2021-08-25) Coenen, Wilfried; Zhang, X.; Sanchez Perez, Antonio Luis; Comunidad de Madrid
    This paper addresses peristaltic flow induced in a non-axisymmetric annular tube by a periodic small-amplitude wave of arbitrary shape propagating axially along its inner surface, assumed to be a circular cylinder. The study is motivated by recent in vivo experimental observations pertaining to the flow of cerebrospinal fluid along the perivascular spaces of cerebral arteries. The analysis employs the lubrication approximation, describing low-Reynolds-number peristaltic flow in the long-wavelength approximation. Closed-form analytic expressions are derived for the average pumping rate in infinitely long tubes and also in tubes of finite length. Consideration is also given to the transverse motion arising in non-axisymmetric tubes. For small-amplitude waves, the solution is reduced to the integration of a parameter-free Stokes-flow problem, which is solved for relevant cross-sectional shapes, with closed-form analytical results derived for thin canals.
  • Publication
    Chiral symmetry breaking and entropy production in Dean vortices
    (AIP Publishing, 2023-04) Herreros Cid, María Isabel; Hochberg, David; Ministerio de Ciencia e Innovación (España)
    In toroidal pipes, the secondary flow in cross section is a mirror symmetric pair of counter-rotating axially oriented Dean vortices. This mirror symmetry is broken in helical pipes. We investigate in detail the mirror symmetry breaking in these secondary flows in going from toroidal to helical geometries. We quantify the degree of mirror symmetry breaking in helical flows by calculating both an (i) order-parameter − 1 ≤ χ ≤ 1 that measures the net integrated chirality of vortices in section and (ii) the entropy production due to both viscous shear forces and convection for Dean vortices as the Dean number and pitch of the helix are varied. We prove that the entropy production due to convective processes is always greater than that due to viscous shear, for stationary incompressible flows in the absence of body forces. For the same pipe radius and pipe curvature, fluid density, viscosity, and entrance flows, the vortex entropy production in the stationary state is minimized for helical conduits (for a given Dean number) with respect to that of toroidal pipes (zero pitch). The dissipation in the fluid flow due to Dean vortices decreases in going from a toroidal to a helical geometry, while the chiral order parameter tends to χ = ± 1 for finite values of the pitch as the Dean number is decreased.
  • Publication
    Minimum ignition energy of hydrogen-ammonia blends in air
    (Elsevier, 2023-04-01) Fernández Tarrazo, Eduardo Antonio; Gomez Miguel, R.; Sánchez Sanz, Mario; Ministerio de Ciencia e Innovación (España)
    We present a numerical analysis to calculate the minimum ignition energy of hydrogen–ammonia blends in air at both under and over atmospheric pressure. Unlike previous calculations, we used the full compressible and reactive Navier–Stokes equations coupled with detailed chemical kinetics (San Diego mechanism for hydrogen, complemented with the San Diego chemistry for nitrogen). The effect of the size of the energy deposition region and the deposition time are considered to determine the most efficient method to ignite the mixture. Our calculations also evaluate the impact of the gas compressibility on the minimum ignition energy after a sudden energy deposition. The results are validated first by comparing the minimum ignition energy of pure hydrogen–air mixtures as a function of the equivalence ratio 𝜙 with available experimental data and previous numerical results. Then, fuel blends made of mixtures of hydrogen and ammonia (NH3) are considered to calculate the minimum ignition energy as a function of fuel composition, equivalence ratio and pressure. The full range of ammonia volumetric content in the blend is varied between the extreme cases of pure hydrogen and pure ammonia. For each fuel blend, we computed a wide range of equivalence ratios 𝜙 that, in the case of pure hydrogen at atmospheric conditions, ranged from 𝜙 = 7 to 𝜙 ≃ 0.07, near the lean flammability limit, to theoretically explain the experimental evidence of ultra-lean flames reported in the literature.
  • Publication
    Ejecta from the DART-produced active asteroid Dimorphos
    (Nature Research, 2023-04-20) Li, Jian Yang; Herreros Cid, María Isabel; European Commission; Ministerio de Ciencia e Innovación (España)
    Some active asteroids have been proposed to be formed as a result of impact events1. Because active asteroids are generally discovered by chance only after their tails have fully formed, the process of how impact ejecta evolve into a tail has, to our knowledge, not been directly observed. The Double Asteroid Redirection Test (DART) mission of NASA2, in addition to having successfully changed the orbital period of Dimorphos3, demonstrated the activation process of an asteroid resulting from an impact under precisely known conditions. Here we report the observations of the DART impact ejecta with the Hubble Space Telescope from impact time T+15 min to T+18.5 days at spatial resolutions of around 2.1 km per pixel. Our observations reveal the complex evolution of the ejecta, which are first dominated by the gravitational interaction between the Didymos binary system and the ejected dust and subsequently by solar radiation pressure. The lowest-speed ejecta dispersed through a sustained tail that had a consistent morphology with previously observed asteroid tails thought to be produced by an impact4,5. The evolution of the ejecta after the controlled impact experiment of DART thus provides a framework for understanding the fundamental mechanisms that act on asteroids disrupted by a natural impact1,6.
  • Publication
    Successful kinetic impact into an asteroid for planetary defence
    (Nature Research, 2023-04-20) Daly, R. Terik; Herreros Cid, María Isabel; European Commission; Ministerio de Ciencia e Innovación (España)
    Although no known asteroid poses a threat to Earth for at least the next century, the catalogue of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation1,2. Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid1,2,3. A test of kinetic impact technology was identified as the highest-priority space mission related to asteroid mitigation1. NASA's Double Asteroid Redirection Test (DART) mission is a full-scale test of kinetic impact technology. The mission's target asteroid was Dimorphos, the secondary member of the S-type binary near-Earth asteroid (65803) Didymos. This binary asteroid system was chosen to enable ground-based telescopes to quantify the asteroid deflection caused by the impact of the DART spacecraft4. Although past missions have utilized impactors to investigate the properties of small bodies5,6, those earlier missions were not intended to deflect their targets and did not achieve measurable deflections. Here we report the DART spacecraft's autonomous kinetic impact into Dimorphos and reconstruct the impact event, including the timeline leading to impact, the location and nature of the DART impact site, and the size and shape of Dimorphos. The successful impact of the DART spacecraft with Dimorphos and the resulting change in the orbit of Dimorphos7 demonstrates that kinetic impactor technology is a viable technique to potentially defend Earth if necessary.
  • Publication
    Solid particles moving parallel to a deformable liquid-liquid interface in a micro-channel: migration forces
    (Cambridge University Press, 2022-10-10) Ruiz Martín, Desirée; Rivero Rodríguez, Javier; Sánchez Sanz, Mario; Ministerio de Ciencia e Innovación (España)
    This work focuses on the dynamics of a train of solid particles, separated by a distance L, flowing near a deformable interface formed by two co-flowing immiscible fluids in a microchannel of height h. Our study includes a systematic analysis of the influence of the governing parameters (fluids viscosity ratio, interface and particle positions, Reynolds Re and capillary Ca numbers and the inter-particle distance L) on the hydrodynamic force f exerted on the particle. In the pure inertial regime with non-deformable interfaces Ca = 0, the particle is driven towards the wall (interface) when the particle is close to the interface (wall). Up to three neutral equilibrium positions f = 0, two of them stable, are found in this limit. The contrary is obtained in the pure capillary regime Re = 0. In this limit, we also carried out an asymptotic analysis in the distinguished limits of very large and very small surface tension. In the latter case, the amplitude of the interface deformation induced by the particle is large, comparable to its diameter, but its influence is limited to a small region upstream and downstream of the particle. In the limit of very large surface tension, the amplitude of the interface deformation is small but the presence of the particle modifies the shape of the interface in a region of length 2 (Lambda), much larger than the particle diameter d. The parameter (Lambda), introduces an additional characteristic length that determines the asymptotic behaviour of the flow properties in the limit of large surface tension.
  • Publication
    Buoyancy-modulated Lagrangian drift in wavy-walled vertical channels as a model problem to understand drug dispersion in the spinal canal
    (Cambridge University Press, 2022-10-25) Alaminos Quesada, J.; Coenen, Wilfried; Gutiérrez-Montes, C.; Sánchez, A. L.; Comunidad de Madrid; Ministerio de Ciencia e Innovación (España)
    This paper investigates flow and transport in a slender wavy-walled vertical channel subject to a prescribed oscillatory pressure difference between its ends. When the ratio of the stroke length of the pulsatile flow to the channel wavelength is small, the resulting flow velocity is known to include a slow steady-streaming component resulting from the effect of the convective acceleration. Our study considers the additional effect of gravitational forces in configurations with a non-uniform density distribution. Specific attention is given to the slowly evolving buoyancy-modulated flow emerging after the deposition of a finite amount of solute whose density is different from that of the fluid contained in the channel, a relevant problem in connection with drug dispersion in intrathecal drug delivery (ITDD) processes, involving the injection of the drug into the cerebrospinal fluid that fills the spinal canal. It is shown that when the Richardson number is of order unity, the relevant limit in ITDD applications, the resulting buoyancy-induced velocities are comparable to those of steady streaming. As a consequence, the slow time-averaged Lagrangian motion of the fluid, involving the sum of the Stokes drift and the time-averaged Eulerian velocity, is intimately coupled with the transport of the solute, resulting in a slowly evolving problem that can be treated with two-time-scale methods. The asymptotic development leads to a time-averaged, nonlinear integro-differential transport equation that describes the slow dispersion of the solute, thereby circumventing the need to describe the small concentration fluctuations associated with the fast oscillatory motion. The ideas presented here can find application in developing reduced models for future quantitative analyses of drug dispersion in the spinal canal.
  • Publication
    Modeling the effect of low Pt loading cathode catalyst layer in polymer electrolyte fuel cells. Part II: Parametric analysis
    (IOP Science, 2022-07) Sánchez Ramos, Arturo; Gostick, Jeff T.; García-Salaberri, Pablo A.; Ministerio de Ciencia e Innovación (España)
    A parametric analysis is presented using a previously validated 1D model for a cathode catalyst layer (CL). The results show that maximum power density at low Pt loading can be maximized with relatively thin CLs (thickness - 2 micrómetros) featuring a high carbon volume fraction (low ionomer-to-carbon weight ratio, I/C) compared to high Pt loading CLs. The shift of the optimal carbon volume fraction (I/C ratio) is caused by the dominant role of the local oxygen transport resistance at low Pt loading, which is lowered by a reduction of the average ionomer film thickness (better ionomer distribution among carbon particles). In contrast, at high Pt loading, higher porosity and pore radius (lower carbon volume fraction) is beneficial due to an increase of bulk effective diffusivity despite thickening of ionomer films. Moreover, the results show that performance at low Pt loading is significantly improved with increasing mass-specific activity. The effect of average saturation and ionomer permeability on performance at low Pt loading is lower compared to dry CL composition and mass-specific activity.
  • Publication
    A one-dimensional model for the pulsating flow of cerebrospinal fluid in the spinal canal
    (Cambridge University Press, 2022-05-25) Sincomb, S.; Coenen, Wilfried; Gutiérrez-Montes, C.; Martínez Bazan, Jesús Carlos; Haughton, V.; Sánchez, A. L.; Comunidad de Madrid; Ministerio de Ciencia e Innovación (España)
    The monitoring of intracranial pressure (ICP) fluctuations, which is needed in the context of a number of neurological diseases, requires the insertion of pressure sensors, an invasive procedure with considerable risk factors. Intracranial pressure fluctuations drive the wave-like pulsatile motion of cerebrospinal fluid (CSF) along the compliant spinal canal. Systematically derived simplified models relating the ICP fluctuations with the resulting CSF flow rate can be useful in enabling indirect evaluations of the former from non-invasive magnetic resonance imaging (MRI) measurements of the latter. As a preliminary step in enabling these predictive efforts, a model is developed here for the pulsating viscous motion of CSF in the spinal canal, assumed to be a linearly elastic compliant tube of slowly varying section, with a Darcy pressure-loss term included to model the fluid resistance introduced by the trabeculae, which are thin collagen-reinforced columns that form a web-like structure stretching across the spinal canal. Use of Fourier-series expansions enables predictions of CSF flow rate for realistic anharmonic ICP fluctuations. The flow rate predicted using a representative ICP waveform together with a realistic canal anatomy is seen to compare favourably with in vivo phase-contrast MRI measurements at multiple sections along the spinal canal. The results indicate that the proposed model, involving a limited number of parameters, can serve as a basis for future quantitative analyses targeting predictions of ICP temporal fluctuations based on MRI measurements of spinal-canal anatomy and CSF flow rate.
  • Publication
    SimEx: A Tool for the Rapid Evaluation of the Effects of Explosions
    (MDPI, 2022-09-10) Sánchez Monreal, Juan; Cuadra Lara, Alberto; Huete Ruiz de Lira, César; Vera Coello, Marcos; Comunidad de Madrid; European Commission
    The dynamic response of structural elements subjected to blast loading is a problem of growing interest in the field of defense and security. In this work, a novel computational tool for the rapid evaluation of the effects of explosions, hereafter referred to as SimEx, is presented and discussed. The classical correlations for the reference chemical (1 kg of TNT) and nuclear ((Formula presented.) kg of TNT) explosions, both spherical and hemispherical, are used together with the blast wave scaling laws and the International Standard Atmosphere (ISA) to compute the dynamic response of Single-Degree-of-Freedom (SDOF) systems subject to blast loading. The underlying simplifications in the analysis of the structural response follow the directives established by UFC 3-340-02 and the Protective Design Center Technical Reports of the US Army Corps of Engineers. This offers useful estimates with a low computational cost that enable in particular the computation of damage diagrams in the Charge Weight-Standoff distance (CW-S) space for the rapid screening of component (or building) damage levels. SimEx is a computer application based on Matlab and developed by the Fluid Mechanics Research Group at University Carlos III of Madrid (UC3M). It has been successfully used for both teaching and research purposes in the Degree in Security Engineering, taught to the future Guardia Civil officers at the Spanish University Center of the Civil Guard (CUGC). This dual use has allowed the development of the application well beyond its initial objective, testing on one hand the implemented capacities by undergraduate cadets with the end-user profile, and implementing new functionalities and utilities by Masters and PhD students. With this experience, the application has been continuously growing since its initial inception in 2014 both at a visual and a functional level, including new effects in the propagation of the blast waves, such as clearing and confinement, and incorporating new calculation assistants, such as those for the thermochemical analysis of explosive mixtures; crater formation; fragment mass distributions, ejection speeds and ballistic trajectories; and the statistical evaluation of damage to people due to overpressure, body projection, and fragment injuries.
  • Publication
    Effects of impact and target parameters on the results of a kinetic impactor: predictions for the Double Asteroid Redirection Test (DART) mission
    (IOP Science, 2022-11) Stickle, Angela M.; Herreros Cid, María Isabel; European Commission; Ministerio de Ciencia e Innovación (España)
    The Double Asteroid Redirection Test (DART) spacecraft will impact into the asteroid Dimorphos on September 26, 2022 as a test of the kinetic impactor technique for planetary defense. The efficiency of the deflection following a kinetic impactor can be represented using the momentum enhancement factor, Beta, which is dependent on factors such as impact geometry and the specific target material properties. Currently, very little is known about Dimorphos and its material properties that introduces uncertainty in the results of the deflection efficiency observables, including crater formation, ejecta distribution, and Beta. The DART Impact Modeling Working Group (IWG) is responsible for using impact simulations to better understand the results of the DART impact. Pre-impact simulation studies also provide considerable insight into how different properties and impact scenarios affect momentum enhancement following a kinetic impact. This insight provides a basis for predicting the effects of the DART impact and the first understanding of how to interpret results following the encounter. Following the DART impact, the knowledge gained from these studies will inform the initial simulations that will recreate the impact conditions, including providing estimates for potential material properties of Dimorphos and Beta resulting from DARTs impact. This paper summarizes, at a high level, what has been learned from the IWG simulations and experiments in preparation for the DART impact. While unknown, estimates for reasonable potential material properties of Dimorphos provide predictions for Beta of 1-5, depending on end-member cases in the strength regime.
  • Publication
    After DART: Using the first full-scale test of a kinetic impactor to inform a future planetary defense mission
    (IOP Science, 2022-10) Statler, Thomas S.; Herreros Cid, María Isabel; European Commission; Ministerio de Ciencia e Innovación (España)
    NASA's Double Asteroid Redirection Test (DART) is the first full-scale test of an asteroid deflection technology. Results from the hypervelocity kinetic impact and Earth-based observations, coupled with LICIACube and the later Hera mission, will result in measurement of the momentum transfer efficiency accurate to ∼10% and characterization of the Didymos binary system. But DART is a single experiment; how could these results be used in a future planetary defense necessity involving a different asteroid? We examine what aspects of Dimorphos's response to kinetic impact will be constrained by DART results; how these constraints will help refine knowledge of the physical properties of asteroidal materials and predictive power of impact simulations; what information about a potential Earth impactor could be acquired before a deflection effort; and how design of a deflection mission should be informed by this understanding. We generalize the momentum enhancement factor β, showing that a particular direction-specific β will be directly determined by the DART results, and that a related direction-specific β is a figure of merit for a kinetic impact mission. The DART β determination constrains the ejecta momentum vector, which, with hydrodynamic simulations, constrains the physical properties of Dimorphos's near-surface. In a hypothetical planetary defense exigency, extrapolating these constraints to a newly discovered asteroid will require Earth-based observations and benefit from in situ reconnaissance. We show representative predictions for momentum transfer based on different levels of reconnaissance and discuss strategic targeting to optimize the deflection and reduce the risk of a counterproductive deflection in the wrong direction.