Development of a wide-spectrum thermochemical code with application to planar reacting and non-reacting shocks

Mención Internacional en el título de doctorThe recent scientific and technological advancements have underscored the critical necessity for reliable, robust, and efficient numerical codes capable of predicting the chemical composition and properties of complex mixtures at chemical equilibrium. In response to this demand, this thesis presents the development and validation of a novel open-source thermochemical code called Combustion Toolbox (CT). This tool is designed to determine the equilibrium state of multi-species mixtures in gaseous or pure condensed phases, including ions. The code incorporates a comprehensive suite of algorithms, ranging from fundamental chemical equilibrium problems to complex computations of steady shock and detonation waves in various flow configurations, as well as predictions of rocket engine performance. Implemented in MATLAB, CT is accompanied by a user-friendly graphical user interface, ensuring flexibility and accessibility for all users. Extensive validation demonstrates excellent agreement with established codes such as NASA’s CEA, Cantera within Caltech’s Shock and Detonation Toolbox, and the recent Thermochemical Equilibrium Abundances code. CT has been utilized in all of the studies presented in this thesis, demonstrating its reliability and versatility. The second part of the thesis delves into the theoretical analysis of reactive and nonreactive shocks propagating through non-homogeneous conditions. Conducting experiments and high-fidelity simulations in this field can be challenging and computationally expensive. In this context, linear interaction analysis has emerged as a valuable tool to evaluate the hydrodynamical aspects contributing to the amplification of disturbances across the shock. Two prominent cases are investigated. Firstly, the study focuses on detonations with inhomogeneities in the upstream fuel mass fraction. The findings reveal that, in most cases, the detonation propagation speed is higher than in equivalent homogeneous scenarios. Subsequently, the investigation shifts towards the interaction of hypersonic shocks with turbulent flows, incorporating the associated thermochemical effects in single-species diatomic gases. The analysis is further extended to multi-species mixtures using CT, with a particular emphasis on air. These studies demonstrate that thermochemical effects arising at hypersonic velocities significantly enhance turbulent fluctuations in the post-shock gas compared to the simplified thermochemical frozen gas assumption.Los avances científicos y tecnológicos recientes han destacado la necesidad crítica de contar con códigos numéricos fiables, robustos y eficientes capaces de predecir la composición química y las propiedades de mezclas complejas en equilibrio químico. En respuesta a esta demanda, esta tesis presenta el desarrollo y la validación de un novedoso código termoquímico de código abierto llamado Combustion Toolbox (CT). Esta herramienta permite determinar el estado de equilibrio de mezclas multiespecie en fases gaseosas o condensadas puras, incluyendo iones. El código incorpora una amplia gama de algoritmos, desde problemas fundamentales de equilibrio químico hasta complejos cálculos de ondas de choque y detonación estacionarias en varias configuraciones de flujo, así como predicciones del rendimiento de motores cohete. Implementado en MATLAB, CT cuenta con una interfaz gráfica de usuario fácil de usar, que garantiza flexibilidad y accesibilidad para todos los usuarios. Se ha realizado una extensa validación que demuestra una excelente concordancia con códigos establecidos como el CEA de la NASA, Cantera y Shock and Detonation Toolbox del Caltech, así como el reciente código Thermochemical Equilibrium Abundances. CT se ha utilizado en todos los estudios presentados en esta tesis, demonstrando su fiabilidad y versatilidad. En la segunda parte de la tesis, se analizan los choques reactivos y no reactivos que se propagan en condiciones no homogéneas. Realizar experimentos y simulaciones de alta fidelidad en este campo puede ser desafiante y costoso computacionalmente. En este contexto, el análisis de interacción lineal ha surgido como una herramienta valiosa para evaluar los aspectos hidrodinámicos que contribuyen a la amplificación de las perturbaciones a través del choque. Se investigan dos casos destacados. En primer lugar, el estudio se centra en las detonaciones con inhomogeneidades aguas arriba de la fracción másica del combustible. Los resultados indican que, en la mayoría de los casos, la velocidad de propagación de la detonación es mayor que en escenarios homogéneos equivalentes. Posteriormente, la investigación se centra en la interacción de choques hipersónicos con flujos turbulentos, incorporando los efectos termoquímicos asociados en gases diatómicos de una sola especie. El análisis se extiende además a mezclas multiespecie utilizando CT, con un énfasis particular en el aire. Estos estudios demuestran que los efectos termoquímicos que surgen a velocidades hipersónicas aumentan significativamente las fluctuaciones turbulentas en el gas posterior al choque en comparación con la aproximación de gas termoquímicamente congelado.Programa de Doctorado en Mecánica de Fluidos por la Universidad Carlos III de Madrid; la Universidad de Jaén; la Universidad de Zaragoza; la Universidad Nacional de Educación a Distancia; la Universidad Politécnica de Madrid y la Universidad Rovira iPresidente: Francisco José Higuera Antón.- Secretario: Carlos Manuel del Pino Peñas.- Vocal: Bruno Dene

Effect of equivalence ratio fluctuations on planar detonation discontinuities

We propose a linear asymptotic theory to describe the propagation of planar detonation fronts through heterogeneous mixtures of reactive gases consisting of random fluctuations in the fuel mass fraction. The analysis starts with the derivation of the transfer functions that relate the upstream fuel mass fraction inhomogeneities with the burnt-gas perturbations via normal mode analysis. These results are then used in a Fourier analysis of a detonation wave interacting with two- and three-dimensional isotropic heterogeneous fields. This yields integral formulae for the turbulent kinetic energy, sonic energy and averaged vorticity and entropy production rates. Second-order corrections for the turbulent Rankine-Hugoniot conditions are also obtained, along with analytical expressions for the deviation of the detonation velocity with respect to that of the equivalent homogeneous mixture. Upstream inhomogeneities are found to speed up the detonation front in the vast majority of scenarios studied, with a velocity amplification factor that depends on the properties of the fuel-air mixture, particularly on the variation of the density and the heat release with the fuel mass fraction.Work produced with the support of a 2019 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation and project PID2019-108592RB-C41 (MICINN/FEDER, UE). The authors are grateful to Dr. Martinez-Ruiz for the fruitful discussions

Thermochemical effects on hypersonic shock waves interacting with weak turbulence

The interaction between a weakly turbulent free stream and a hypersonic shock wave is investigated theoretically by using linear interaction analysis (LIA). The formulation is developed in the limit in which the thickness of the thermochemical nonequilibrium region downstream of the shock, where relaxation toward vibrational and chemical equilibrium occurs, is assumed to be much smaller than the characteristic size of the shock wrinkles caused by turbulence. Modified Rankine-Hugoniot jump conditions that account for dissociation and vibrational excitation are derived and employed in a Fourier analysis of a shock interacting with three-dimensional isotropic vortical disturbances. This provides the modal structure of the post-shock gas arising from the interaction, along with integral formulas for the amplification of enstrophy, concentration variance, turbulent kinetic energy (TKE), and turbulence intensity across the shock. In addition to confirming known endothermic effects of dissociation and vibrational excitation in decreasing the mean post-shock temperature and velocity, these LIA results indicate that the enstrophy, anisotropy, intensity, and TKE of the fluctuations are much more amplified through the shock than in the thermochemically frozen case. In addition, the turbulent Reynolds number is amplified across the shock at hypersonic Mach numbers in the presence of dissociation and vibrational excitation, as opposed to the attenuation observed in the thermochemically frozen case. These results suggest that turbulence may persist and get augmented across hypersonic shock waves despite the high post-shock temperatures.C.H. was funded by a 2019 Leonardo Grant for Researchers and Cultural Creators awarded by the BBVA Foundation, and by the MICINN Grant No. PID2019–108592RB-C41

Role of age and comorbidities in mortality of patients with infective endocarditis

[Purpose]: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. [Methods]: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015.Patients were stratified into three age groups:<65 years,65 to 80 years,and ≥ 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. [Results]: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 ≥ 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients ≥80 years who underwent surgery were significantly lower compared with other age groups (14.3%,65 years; 20.5%,65-79 years; 31.3%,≥80 years). In-hospital mortality was lower in the <65-year group (20.3%,<65 years;30.1%,65-79 years;34.7%,≥80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%,≥80 years; p = 0.003).Independent predictors of mortality were age ≥ 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI ≥ 3 (HR:1.62; 95% CI:1.39–1.88),and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared,the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. [Conclusion]: There were no differences in the clinical presentation of IE between the groups. Age ≥ 80 years, high comorbidity (measured by CCI),and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

SimEx: A Tool for the Rapid Evaluation of the Effects of Explosions

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.This research was partially funded by UE (H2020-SEC-2016-2017-1) Grant No. SEC-08/11/12-FCT-2016 and by project H2SAFE-CM-UC3M awarded by the Spanish Comunidad de Madrid.Publicad

Cuestionamientos al modelo extractivista neoliberal desde el Sur

Este libro se enmarca en la voluntad de alimentar un diálogo inter-disciplinar entre múltiples esferas sociales, culturales y territoriales en relation al extractivismo, su estudio y vivencia. El libro se constituye en un instrumento que expresa un entrelazamiento entre actores, redes y realidades territoriales que dan forma a la riqueza y a la diversidad de los territorios amenazados actualmente por el extractivismo. Permitiendo una réflexión sobre el présente y el futuro del modelo de desarrollo actual, la présente publicación integra diverso

Contemporary use of cefazolin for MSSA infective endocarditis: analysis of a national prospective cohort

Objectives: This study aimed to assess the real use of cefazolin for methicillin-susceptible Staphylococcus aureus (MSSA) infective endocarditis (IE) in the Spanish National Endocarditis Database (GAMES) and to compare it with antistaphylococcal penicillin (ASP). Methods: Prospective cohort study with retrospective analysis of a cohort of MSSA IE treated with cloxacillin and/or cefazolin. Outcomes assessed were relapse; intra-hospital, overall, and endocarditis-related mortality; and adverse events. Risk of renal toxicity with each treatment was evaluated separately. Results: We included 631 IE episodes caused by MSSA treated with cloxacillin and/or cefazolin. Antibiotic treatment was cloxacillin, cefazolin, or both in 537 (85%), 57 (9%), and 37 (6%) episodes, respectively. Patients treated with cefazolin had significantly higher rates of comorbidities (median Charlson Index 7, P <0.01) and previous renal failure (57.9%, P <0.01). Patients treated with cloxacillin presented higher rates of septic shock (25%, P = 0.033) and new-onset or worsening renal failure (47.3%, P = 0.024) with significantly higher rates of in-hospital mortality (38.5%, P = 0.017). One-year IE-related mortality and rate of relapses were similar between treatment groups. None of the treatments were identified as risk or protective factors. Conclusion: Our results suggest that cefazolin is a valuable option for the treatment of MSSA IE, without differences in 1-year mortality or relapses compared with cloxacillin, and might be considered equally effective

Role of age and comorbidities in mortality of patients with infective endocarditis.

The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015.Patients were stratified into three age groups: A total of 3120 patients with IE (1327  There were no differences in the clinical presentation of IE between the groups. Age ≥ 80 years, high comorbidity (measured by CCI),and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in th