Towards High-order Methods for Rotorcraft Applications

This work presents CFD results obtained with an efficient, high-order, finite-volume scheme. The formulation is based on the variable extrapolation MUSCL-scheme, and high-order spatial accuracy is achieved using correction terms obtained through successive differentiation. The scheme is modified to cope with physical and multiblock mesh interfaces, so stability, conservativeness, and high-order accuracy are guaranteed. Results with the proposed scheme for steady flows, showed better wake and higher resolution of vortical structures compared with the standard MUSCL, even when coarser meshes were employed. The method was also demonstrated for unsteady flows using overset and moving grids for the UH-60A rotor in forward flight and the ERICA tiltrotor in aeroplane mode. The present method adds CPU and memory overheads of 47% and 23%, respectively, in performing multi-dimensional problems for routine computations

Tiltrotor CFD part I: validation

This paper presents performance analyses of the model-scale ERICA and TILTAERO tiltrotors and of the full-scale XV-15 rotor with high-fidelity computational fluids dynamics. For the ERICA tiltrotor, the overall effect of the blades on the fuselage was well captured, as demonstrated by analysing surface pressure measurements. However, there was no available experimental data for the blade aerodynamic loads. A comparison of computed rotor loads with experiments was instead possible for the XV-15 rotor, where CFD results predicted the FoM within 1.05%. The method was also able to capture the differences in performance between hover and propeller modes. Good agreement was also found for the TILTAERO loads. The overall agreement with the experimental data and theory for the considered cases demonstrates the capability of the present CFD method to accurately predict tiltrotor flows. In a second part of this work, the validated method is used for blade shape optimisation

Accurate Predictions of Hovering Rotor Flows Using CFD

With work on the S-76 rotor providing encouraging results regarding the prediction of integral loads with CFD in hover, the XV-15 rotor is now analysed. Fully turbulent and transitional results are obtained showing the capability of modern CFD methods. The transition onset and distribution of skin friction are well predicted and were found to have a mild effect on the overall figure of merit. This work also shows the potential of transport-based models for transition prediction in complex 3D flows. Finally, hover simulations for the PSP blade are also shown in terms of surface pressure coefficient and wake visualisation

On the signatures of flare-induced global waves in the Sun: GOLF and VIRGO observations

Recently, several efforts have been made to identify the seismic signatures of flares and magnetic activity in the Sun and Sun-like stars. In this work, we have analyzed the disk-integrated velocity and intensity observations of the Sun obtained from the GOLF and VIRGO/SPM instruments, respectively, on board the SOHO space mission covering several successive flare events, for the period from 11 February 2011 to 17 February 2011, of which 11 February 2011 remained a relatively quiet day and served as a "null test" for the investigation. Application of the spectral analysis to these disk-integrated Sun-as-a-star velocity and intensity signals indicates that there is enhanced power of the global modes of oscillations in the Sun during the flares, as compared to the quiet day. The GOLF instrument obtains velocity observations using the Na I D lines which are formed in the upper solar photosphere, while the intensity data used in our analysis are obtained by VIRGO/SPM instrument at 862~nm, which is formed within the solar photosphere. Despite the fact that the two instruments sample different layers of the solar atmosphere using two different parameters (velocity v/s intensity), we have found that both these observations show the signatures of flare-induced global waves in the Sun. These results could suffice in identifying the asteroseismic signatures of stellar flares and magnetic activity in the Sun-like stars.Comment: 10 pages, 5 figures, 2 table

Metodología de cálculo de NOx en generadores de vapor que queman gas natural

Este trabajo presenta la metodología para el cálculo de emisiones de NOx en un generador de vapor de 350 ton/h quemando gas natural y se investigan los métodos de control de NOx durante la combustión. Hoy en día es uno de los principales problemas de las plantas termoeléctricas puesto que genera un alto nivel de emisiones de óxidos de nitrógeno a la atmósfera. Esta metodología consiste en la determinación de los cuatro parámetros fundamentales que intervienen en la formación de NOx y son los siguientes: coeficiente de exceso de aire en la zona de combustión activa (ZCA) ¿ZCA, la temperatura promedio de la ZCA TZCA, el flujo de calor reflejado en ZCA qrefl ZCA y el tiempo de residencia de los gases en ZCA ¿ZCA. Para poder determinar estos parámetros se tiene que considerar la composición del gas natural, la transferencia de calor en el horno, las condiciones de funcionamiento y las dimensiones del generador de vapor, entre otros factores. Los cuatro parámetros principales se sustituyen en el polinomio experimental para el combustible en cuestión y, de esta forma, se puede determinar la emisión de NOx para los métodos de combustión que se analizarán en el presente artículo: recirculación de gases, diferentes lugares de introducción de gases de recirculación, combustión a dos etapas e inyección de agua

Development of predictive methods for tiltrotor flows

This thesis presents evidence on the ability of grid-based, Computational Fluid Dynamics methods based on the Unsteady Reynolds Averaged Navier-Stokes equations to accurately predict axial flight performance of rotors with modest computer resources. Three well-studied blades, the B0-105, S-76, and PSP main rotor blades, are used and results are compared with experimental data. Likewise, performance analyses of the JORP propeller and XV-15 tiltrotor blades are carried out, respectively, aiming to validate the employed CFD method for such relevant flows. Validation of the HMB3 CFD solver for complete tiltrotors is also presented. The aim is to assess the capability of the present CFD method in predicting tiltrotor airloads at different flight configurations. In this regard, three representative cases of the ERICA tiltrotor were selected, corresponding to aeroplane, transition corridor, and helicopter modes, covering most modes of tiltrotor flight. Aerodynamic optimisation of tiltrotor blades with high-fidelity computational fluid dynamics coupled with a discrete adjoint method is also carried out. This work shows how the main blade shape parameters influence the optimal performance of the tiltrotor in helicopter and aeroplane modes, and how a compromise blade shape can increase the overall tiltrotor performance. Finally, the implementation and validation of an efficient, high-order, finite-volume scheme (up to 4th-order of spatial accuracy) in the HMB3 CFD solver is presented. The scheme shows a higher level of accuracy if compared with the standard-MUSCL, and 4th-order accuracy was achieved on Cartesian grids. Furthermore, a significantly high spectral resolution (dispersion and dissipation) of the new scheme is observed. Two-and three-dimensional test cases were considered to demonstrate the new formulation. Results of the steady flow around the 7AD, S-76, JORP propeller, and XV-15 blades showed a better preservation of the vorticity and higher resolution of the vortical structures compared with the standard MUSCL solution. The method was also demonstrated for three-dimensional unsteady flows using overset and moving grid computations for the UH-60A rotor in forward flight and the ERICA tiltrotor in aeroplane mode. For medium grids, the new high-order scheme adds CPU and memory overheads of 22% and 23%, respectively. The parallel performance of the scheme is fair but can be further improved

La satisfacción del servicio en el transporte público exclusivo para mujeres

Como parte del desarrollo del sistema de transporte público, este ha presentado problemas de sobrecupo, lo cual se ha traducido en impactos negativos particularmente sobre las mujeres, en especial en lo relativo a los niveles de seguridad, en relación con lo que aquellas han reportado diferentes agresiones. Entre las medidas para reducir lo anterior se implementaron los servicios de transporte exclusivos para mujeres (TEPM) –etiquetados como “transporte rosa”–. En este documento se muestran los resultados de cuantificar la satisfacción de las usuarias del TEPM para el caso del Sistema de Transporte Colectivo (metro) de la ciudad de México. Para alcanzar este objetivo, se diseñó y aplicó una encuesta de satisfacción, a partir de la cual se obtuvo información acerca de los niveles de satisfacción de tres factores del TEPM: cobertura, disponibilidad de asientos, y agresiones sufridas. Los resultados muestran que las características del TEPM no están alineadas con las necesidades de las usuarias, y esto lleva a redefinir los objetivos del transporte exclusivo. Palabras clave: satisfacción del servicio, transporte exclusivo para mujere

SISTEMAS DE TRANSPORTE MASIVO .

SÓLO VISIÓN PROYECTABLE

Interregional input-ouptut system for Ecuador, 2007: methodology and results

In this paper, we explore the structural characteristics of the interregional input-output system developed for Ecuador for the year 2007. As part of an ongoing project that aims to develop an interregional CGE model for the country, this database was developed under conditions of limited information. It provides the opportunity to better understand the spatial linkage structure associated with the national economy in the context of its 22 provinces, 15 sectors and 60 different products. This exploratory analysis is based on the description of structural coefficients and the use of traditional input-output techniques. Finally, we further explore the spatial linkage structure by looking at the regional decomposition of final demand. It is hoped that this exercise might result in a better appreciation of a broader set of dimensions that might improve our understanding of the integrated interregional economic system in Ecuador.Interregional input-output model; Ecuador; spatial linkages

MANUAL DE PRáCTICAS DE TERMODINáMICA

Manual para prácticas de laboratorio, taller u otra área de apoyo a la Docenci