Accurate Parabolic Navier-Stokes solutions of the supersonic flow around and elliptic cone

Flows of relevance to new generation aerospace vehicles exist, which are weakly dependent on the streamwise direction and strongly dependent on the other two spatial directions, such as the flow around the (flattened) nose of the vehicle and the associated elliptic cone model. Exploiting these characteristics, a parabolic integration of the Navier-Stokes equations is more appropriate than solution of the full equations, resulting in the so-called Parabolic Navier-Stokes (PNS). This approach not only is the best candidate, in terms of computational efficiency and accuracy, for the computation of steady base flows with the appointed properties, but also permits performing instability analysis and laminar-turbulent transition studies a-posteriori to the base flow computation. This is to be contrasted with the alternative approach of using order-of-magnitude more expensive spatial Direct Numerical Simulations (DNS) for the description of the transition process. The PNS equations used here have been formulated for an arbitrary coordinate transformation and the spatial discretization is performed using a novel stable high-order finite-difference-based numerical scheme, ensuring the recovery of highly accurate solutions using modest computing resources. For verification purposes, the boundary layer solution around a circular cone at zero angle of attack is compared in the incompressible limit with theoretical profiles. Also, the recovered shock wave angle at supersonic conditions is compared with theoretical predictions in the same circular-base cone geometry. Finally, the entire flow field, including shock position and compressible boundary layer around a 2:1 elliptic cone is recovered at Mach numbers 3 and

Advances in global instability computations: from incompressible to hypersonic flow

Esta tesis constituye un gran avance en el conocimiento del estudio y análisis de inestabilidades hidrodinámicas desde un punto de vista físico y teórico, como consecuencia de haber desarrollado innovadoras técnicas para la resolución computacional eficiente y precisa de la parte principal del espectro correspondiente a los problemas de autovalores (EVP) multidimensionales que gobiernan la inestabilidad de flujos con dos o tres direcciones espaciales inhomogéneas, denominados problemas de estabilidad global lineal. En el contexto del trabajo de desarrollo de herramientas computacionales presentado en la tesis, la discretización mediante métodos de diferencias finitas estables de alto orden de los EVP bidimensionales y tridimensionales que se derivan de las ecuaciones de Navier-Stokes linealizadas sobre flujos con dos o tres direcciones espaciales inhomogéneas, ha permitido una aceleración de cuatro órdenes de magnitud en su resolución. Esta mejora de eficiencia numérica se ha conseguido gracias al hecho de que usando estos esquemas de diferencias finitas, técnicas eficientes de resolución de problemas lineales son utilizables, explotando el alto nivel de dispersión o alto número de elementos nulos en las matrices involucradas en los problemas tratados. Como más notable consecuencia cabe destacar que la resolución de EVPs multidimensionales de inestabilidad global, que hasta la fecha necesitaban de superordenadores, se ha podido realizar en ordenadores de sobremesa. Además de la solución de problemas de estabilidad global lineal, el mencionado desarrollo numérico facilitó la extensión de las ecuaciones de estabilidad parabolizadas (PSE) lineales y no lineales para analizar la inestabilidad de flujos que dependen fuertemente en dos direcciones espaciales y suavemente en la tercera con las ecuaciones de estabilidad parabolizadas tridimensionales (PSE-3D). Precisamente la capacidad de extensión del novedoso algoritmo PSE-3D para el estudio de interacciones no lineales de los modos de estabilidad, desarrollado íntegramente en esta tesis, permite la predicción de transición en flujos complejos de gran interés industrial y por lo tanto extiende el concepto clásico de PSE, el cuál ha sido empleado exitosamente durante las pasadas tres décadas en el mismo contexto para problemas de capa límite bidimensional. Típicos ejemplos de flujos incompresibles se han analizado en este trabajo sin la necesidad de recurrir a restrictivas presuposiciones usadas en el pasado. Se han estudiado problemas vorticales como es el caso de un vórtice aislado o sistemas de vórtices simulando la estela de alas, en los que la homogeneidad axial no se impone y así se puede considerar la difusión viscosa del flujo. Además, se ha estudiado el chorro giratorio turbulento, cuya inestabilidad se utiliza para mejorar las características de funcionamiento de combustores. En la tesis se abarcan adicionalmente problemas de flujos compresibles. Se presenta el estudio de inestabilidad de flujos de borde de ataque a diferentes velocidades de vuelo. También se analiza la estela formada por un elemento rugoso aislado en capa límite supersónica e hipersónica, mostrando excelentes comparaciones con resultados obtenidos mediante simulación numérica directa. Finalmente, nuevas inestabilidades se han identificado en el flujo hipersónico a Mach 7 alrededor de un cono elíptico que modela el vehículo de pruebas en vuelo HIFiRE-5. Los resultados comparan favorablemente con experimentos en vuelo, lo que subraya aún más el potencial de las metodologías de análisis de estabilidad desarrolladas en esta tesis. ABSTRACT The present thesis constitutes a step forward in advancing the frontiers of knowledge of fluid flow instability from a physical point of view, as a consequence of having been successful in developing groundbreaking methodologies for the efficient and accurate computation of the leading part of the spectrum pertinent to multi-dimensional eigenvalue problems (EVP) governing instability of flows with two or three inhomogeneous spatial directions. In the context of the numerical work presented in this thesis, the discretization of the spatial operator resulting from linearization of the Navier-Stokes equations around flows with two or three inhomogeneous spatial directions by variable-high-order stable finite-difference methods has permitted a speedup of four orders of magnitude in the solution of the corresponding two- and three-dimensional EVPs. This improvement of numerical performance has been achieved thanks to the high-sparsity level offered by the high-order finite-difference schemes employed for the discretization of the operators. This permitted use of efficient sparse linear algebra techniques without sacrificing accuracy and, consequently, solutions being obtained on typical workstations, as opposed to the previously employed supercomputers. Besides solution of the two- and three-dimensional EVPs of global linear instability, this development paved the way for the extension of the (linear and nonlinear) Parabolized Stability Equations (PSE) to analyze instability of flows which depend in a strongly-coupled inhomogeneous manner on two spatial directions and weakly on the third. Precisely the extensibility of the novel PSE-3D algorithm developed in the framework of the present thesis to study nonlinear flow instability permits transition prediction in flows of industrial interest, thus extending the classic PSE concept which has been successfully employed in the same context to boundary-layer type of flows over the last three decades. Typical examples of incompressible flows, the instability of which was analyzed in the present thesis without the need to resort to the restrictive assumptions used in the past, range from isolated vortices, and systems thereof, in which axial homogeneity is relaxed to consider viscous diffusion, as well as turbulent swirling jets, the instability of which is exploited in order to improve flame-holding properties of combustors. The instability of compressible subsonic and supersonic leading edge flows has been solved, and the wake of an isolated roughness element in a supersonic and hypersonic boundary-layer has also been analyzed with respect to its instability: excellent agreement with direct numerical simulation results has been obtained in all cases. Finally, instability analysis of Mach number 7 ow around an elliptic cone modeling the HIFiRE-5 flight test vehicle has unraveled flow instabilities near the minor-axis centerline, results comparing favorably with flight test predictions

High-Frequency Instabilities of Stationary Crossflow Vortices in a Hypersonic Boundary Layer

Hypersonic boundary layer flows over a circular cone at moderate incidence angle can support strong crossflow instability in between the windward and leeward rays on the plane of symmetry. Due to more efficient excitation of stationary crossflow vortices by surface roughness, such boundary layer flows may transition to turbulence via rapid amplification of the high-frequency secondary instabilities of finite-amplitude stationary crossflow vortices. The amplification characteristics of these secondary instabilities are investigated for crossflow vortices generated by an azimuthally periodic array of roughness elements over a 7° half-angle circular cone in a Mach 6 free stream. The analysis is based on both quasiparallel stability theory in the form of a partial-differential-equation-based eigenvalue analysis and plane marching parabolized stability equations that account for the effects of the nonparallel basic state on the growth of secondary disturbances. Depending on the local amplitude of the stationary crossflow mode, the most unstable high-frequency disturbances either originate from the second (i.e., Mack) mode instabilities of the unperturbed boundary layer or correspond to genuine secondary instabilities that reduce to stable disturbances at sufficiently small amplitudes of the stationary crossflow vortex. The predicted frequencies of the dominant secondary disturbances of either type are similar to those measured during wind tunnel experiments at Purdue University and the Technical University of Braunschweig, Germany. Including transverse surface curvature within the quasiparallel predictions does not alter the topology of the unstable modes; however, the resulting changes in both mode shape and disturbance growth rate are rather significant and curvature can be either stabilizing or destabilizing depending on the disturbance frequency and mode type. Nonparallel effects are shown to be strongly destabilizing for secondary instabilities originating from both Mack modes and instabilities of the inclined shear layer bounding the crossflow vortex. Consequently, the two types of instabilities are found to achieve logarithmic amplification factors of up to N=10 and N=7, respectively. Results also reveal possible phase synchronization between a pair of modes that may have a significant influence on their overall amplification

Secondary Instability of Stationary Crossflow Vortices in Mach 6 Boundary Layer Over a Circular Cone

Hypersonic boundary layer flows over a circular cone at moderate incidence can support strong crossflow instability. Due to more efficient excitation of stationary crossflow vortices by surface roughness, such boundary layer flows may transition to turbulence via rapid amplification of the high-frequency secondary instabilities of finite amplitude stationary crossflow vortices. The amplification characteristics of these secondary instabilities are investigated for crossflow vortices generated by an azimuthally periodic array of roughness elements over a 7-degree half-angle circular cone in a Mach 6 free stream. Depending on the local amplitude of the stationary crossflow mode, the most unstable secondary disturbances either originate from the second (i.e., Mack) mode instabilities of the unperturbed boundary layer or correspond to genuine secondary instabilities that reduce to stable disturbances at sufficiently small amplitudes of the stationary crossflow vortex. The predicted frequencies of dominant secondary disturbances are similar to those measured during wind tunnel experiments at Purdue University and the Technical University of Braunschweig, Germany

Herbario Evaldo Buttura, entre caminos y saberes

VII Seminário de Extensão Universitária da UNILA (SEUNI); VIII Encontro de Iniciação Científica e IV Encontro de Iniciação em Desenvolvimento Tecnológico e Inovação (EICTI 2019) e Seminário de Atividades Formativas da UNILA (SAFOR)Un herbario es una colección científica de plantas secas que ejecuta diversas actividades, entre ellas el reconocimiento y levantamiento florístico de un área específica, identificando regiones cruciales para la conservación de la biodiversidad. Un herbario trabaja vinculándose e interactuando con la sociedad es así como se engendran y promueven conocimientos entre academia y comunidad. Sumada a estas labores, el herbario Evaldo Buttura (EVB) de la Universidad Federal de Integración Latinoamericana – UNILA, contempla prácticas universitarias de la carrera de Ciencias Biológicas, Iniciación Científica, Extensión, posgraduación y al público en general. El proyecto de extensión Herbario Evaldo Buttura entre Caminos y Saberes se encuentra realizando capacitaciones en Foz de Iguazú y municipios próximos. Junto a la exposición se realizaron capacitaciones a niños y profesores con el objetivo de divulgar y valorizar el herbario EVB como del trabajo que se realiza en él, fomentar el intercambio de saberes botánicos y promover el interés por la Flora Regional de Foz de Iguazú y proximidades. Una de las estrategias de la capacitación constituyó en el desplazamiento de los participantes por la exposición con los ojos vendados para interactuar con hojas, semillas y frutos, de esa forma el sentido del tacto y olfato se tornó más sensible y la percepción fue única y exclusiva. Retiradas las vendas, los grupos pasaron por todos los paneles de la exposición donde fue explicado la importancia del herbario. El proyecto de extensión viene abasteciendo de interés por la botánica a la comunidad universitaria y a la población, con la troca de conocimientos obtenidos y brindados valorizando el herbario EVB y la flora regionalA la Fundación Araucaria por apoyar, colaborar y permitir que el proyecto siga creciendo y caminando por diferentes lugares. Por incentivarme a la pesquisa, educación y crecimiento académico, profesional y persona

Detailed Study of Amplitude Nonlinearity in Piezoresistive Force Sensors

This article upgrades the RC linear model presented for piezoresistive force sensors. Amplitude nonlinearity is found in sensor conductance, and a characteristic equation is formulated for modeling its response under DC-driving voltages below 1 V. The feasibility of such equation is tested on four FlexiForce model A201-100 piezoresistive sensors by varying the sourcing voltage and the applied forces. Since the characteristic equation proves to be valid, a method is presented for obtaining a specific sensitivity in sensor response by calculating the appropriate sourcing voltage and feedback resistor in the driving circuit; this provides plug-and-play capabilities to the device and reduces the start-up time of new applications where piezoresistive devices are to be used. Finally, a method for bypassing the amplitude nonlinearity is presented with the aim of reading sensor capacitance

BiGlobal and point vortex methods for the instability analysis of wakes

To better understand destruction mechanisms of wake-vortices behind aircraft, the point vortex method for stability (inviscid) used by Crow is here compared with viscous modal global stability analysis of the linearized Navier-Stokes equations acting on a two-dimensional basic flow, i.e. BiGlobal stability analysis. The fact that the BiGlobal method is viscous, and uses a flnite área vortex model, gives rise to results somewhat different from the point vortex model. It adds more parameters to the problem, but is more realistic

Correlation between Anthropometric Measures, Blood Glucose, and Cholesterol Levels in College-Aged Hispanic Males

PURPOSE: To investigate the relationship between anthropometric measures, blood pressure (BP), total cholesterol (TC), fasting blood glucose (FBG), and high density lipoprotein cholesterol (HDL) among Hispanic college-aged males 18 to 30 in the Lower Rio Grande Valley. METHODS: Thirty-five male subjects (age= 23.2 ± 2.8) read and signed the informed consent prior to participation in this study. Subjects had their height, weight, and three circumference measurements taken [waist at umbilicus (WU), waist at smallest point (WSP), and hip at widest point (HWP)] and their body mass index (BMI) calculated. A fasting blood sample was taken to analyze TC, HDL, and FBG; in addition, TC:HDL ratio and non-HDL were calculated. Percent body fat (BF) was also measured using air displacement plethysmography. RESULTS: Age was found to be significantly correlated with weight (r= 0.491, p\u3c 0.01), BF (r= 0.575, p\u3c 0.01), BMI (r= 0.539, p\u3c 0.01), diastolic (DBP) (r= 0.427, p\u3c 0.01), WSP (r= 0.596, p\u3c 0.01), WU (r= 0.638, p\u3c 0.01), and HWP (r= 0.485, p\u3c 0.01), and non-HDL (r= 0.405, p\u3c 0.02). BF and BMI were significantly correlated with HDL (r= −0.370, p\u3c 0.03; r= −0.384, p\u3c 0.03) and correlated with TC:HDL ratio (r= 0.466, p\u3c 0.01; r= 0.441, p\u3c 0.01). WSP, WU, and HWP were significantly correlated with TC:HDL ratio (r= 0.429, p\u3c 0.01; r= 0.449, p\u3c 0.01; r= 0.372, p\u3c 0.03), while only the WU and HWP circumference measurements were significantly correlated with HDL cholesterol (r= −0.369, p\u3c 0.03; r= −0.428, p\u3c 0.01). CONCLUSIONS: The results indicated age had notable correlations across most measures, even within this small 12-year range, which may be due to a decrease in physical activity throughout the college career. The data indicated higher BMI and BF were similarly correlated with lower HDL blood concentration and an increased TC:HDL ratio. This suggests that BMI is still a strong predictor of cholesterol level and can be relied upon when body composition analyzation is not available. Our results also indicated that location of the waist measurements is important and WU may be preferred site for determining negative risk factor regarding cholesterol in college-aged Hispanic males

ACE I/D (Rs1799752), MTHFR C677T (Rs1801133), and CCR5 D32 (Rs333) Genes and their Association with Hypertension and Diabetic Nephropathy in Urban Areas of Costa Rica, Nicaragua, and Mexico

Aim: Type 2 diabetes mellitus (T2DM) is a procoagulant state because it is associated with increased risk of atherosclerosis. The purpose of this study was to investigate the prevalence in thrombotic markers that lead to hypercoagulability and its association with hypertension and diabetic nephropathy (DN)