Propagation of Initial Mass Uncertainty in Aircraft Cruise Flight

The propagation of initial mass uncertainty in cruise flight is studied. Two cruise conditions are analyzed: one with given cruise fuel load and the other with given cruise range. Two different distributions of initial mass are considered: uniform and gamma type. The generalized polynomial chaos method is used to study the evolution of mean and variance of the aircraft mass. To compute the mass distribution function as a function of time, two approximate methods are developed. These methods are also applied to study the distribution functions of the flight time (in the case of given fuel load) and of the fuel consumption (in the case of given range). The dynamics of mass evolution in cruise flight is defined by a nonlinear equation, which can be solved analytically; this exact solution is used to assess the accuracy of the proposed methods. Comparison of the numerical results with the exact analytical solutions shows an excellent agreement in all cases, hence verifying the methods developed in this work

Rotational Instability of a Long Liquid Column

A liquid column is. apart from its intrinsic interest from the basic science point of view, a good mechanical model of a crystal growth process known as the floating zone technique. In this technique, rotation of the supporting rods is used to uniformize the usually non-axisymmetric temperature field otherwise produced by the directional heating. The theory of the influence of solid rotation on the stability limit is already available and early experimental results showed the existence of two different kinds of unstable shapes (in absence of other perturbations): the amphora mode and the C-mode. The existence of the amphora mode was realized in SL-D1 experiments but C-mode breakages could not be obtained, probably due to unexpected existence of body forces that always excited the amphora mode breakage. As none of these modes can be realistically simulated on Earth, an experiment in microgravity conditions (TEXUS-23) was performed in order to obtain C-mode deformations (not achieved up to now in a reproducible way). However, experiments on Earth using the Plateau Tank Technique have been performed in order to obtain more insight in the problem and to prepare experiments aboard sounding rockets. Results of the experiment aboard TEXUS-23 show a reasonably good agreement with the theoretical predictions

One-dimensional self-similar solution of the dynamics of axisymmetric slender liquid bridges

In this paper the dynamics of axisymmetric, slender, viscous liquid bridges having volume close to the cylindrical one, and subjected to a small gravitational field parallel to the axis of the liquid bridge, is considered within the context of one-dimensional theories. Although the dynamics of liquid bridges has been treated through a numerical analysis in the inviscid case, numerical methods become inappropriate to study configurations close to the static stability limit because the evolution time, and thence the computing time, increases excessively. To avoid this difficulty, the problem of the evolution of these liquid bridges has been attacked through a nonlinear analysis based on the singular perturbation method and, whenever possible, the results obtained are compared with the numerical ones

On the steady streaming flow due to high-frequency vibration in nearly inviscid liquid bridges

The steady streaming flow due to vibration in capillary bridges is considered in the limiting case when both the capillary Reynolds number and the non-dimensional vibration frequency (based on the capillary time) are large. An asymptotic model is obtained that provides the streaming flow in the bulk, outside the thin oscillatory boundary layers near the disks and the interface. Numerical integration of this model shows that several symmetric and non-symmetric streaming flow patterns are obtained for varying values of the vibration parameters. As a by-product, the quantitative response of the liquid bridge to high-frequency axial vibrations of the disks is also obtained

Sector demand analysis under meteorological uncertainty

- EUCASS 2017, 3-6 Juily, Milan, Italy. - Datos del Proyecto de Investigación: Title: Meteorological Uncertainty Management for Trajectory Based Operations. Acronym: TBO-Met Funding EC | H2020 CallH2020-SESAR-2015-1 Topic: Sesar-04-2015 - Environment and Meteorology in ATM Contract (GA) number 699294 a.. Start Date: 2016/06/01; End Date: 2018/05/31In this paper, a methodology to assess the uncertainty of sector demand when subject to weather uncertainty is presented. The methodology requires the definition of a scenario (in terms of Air Traffic Control sector, flights, and weather forecasts to be considered), the processing of meteorological data (provided by Ensemble Prediction Systems, which are composed of different possible atmosphere realizations), and a trajectory predictor (which, for each flight and for each atmosphere realization, computes a different aircraft trajectory). The computed trajectories, along with the information of the sector, are then used to analyse the sector demand, which is described in terms of entry count (number of flights entering the sector during a selected time period). The analysis is based on the statistical characterization of the entry times of the flights to the sector and of the entry count. The probability of the entry count exceeding the declared capacity of the sector is obtained. A realistic application example is provided to show the potentiality of the methodologyUnión Europea - Horizon2020 - H2020-SESAR-2015-1 - Sesar-04-2015 - Environment and Meteorology in ATM - Contract (GA) number 699294Unión Europea - Horizon2020 - TBO-Me

Probabilistic Aircraft Conflict Detection Considering Ensemble Weather Forecast

In this paper, the effects of wind uncertainty on the problem of conflict detection are analyzed. The wind components are modeled as random variables; the wind uncertainty is obtained from weather forecasts. The case of two en-route aircraft flying at constant altitude, constant airspeed, constant course, and subject to the same wind is considered. The conflict is caracterized by several indicators, such as the minimum distance between aircraft, the time to minimum distance, and the conflict probability. The analysis is based on the transformation of random variables, which evolves the wind probability density functions to obtain the probability density functions of the indicators. Numerical results are presented for a given particular scenario with uniformly-distributed winds.Ministerio de Economía y Competitividad TRA2014-58413-C2-1-

Dynamics of axisymmetric slender liquid bridges in isorotation

The dynamics of axisymmetric slender liquid bridges in isorotation under microgravity conditions is studied. Slendernesses of the bridge very close to the static stability limit for cylindrical bridges are considered. The inviscid three-dimensional problem is solved in the neighborhood of that stability limit following a regular perturbation approach. A nonlinear model where the pressure and velocity fields are coupled with the free-surface deformation is obtained. The free-surface deformation in the case of stable configurations is analyzed. The effect of Coriolis forces in the dynamics of the bridge turns out to be very important: for large values of the rotation speed the movement of the free surface is very irregular, and its amplitude is much smaller than that in the case of small rotation

Metaheuristic Approach to Probabilistic Aircraft Conflict Detection and Resolution Considering Ensemble Prediction Systems

International audienceThis paper presents a methodology to tackle theproblem of strategic aircraft conflict detection and resolution, upto 60 minutes in advance, considering wind and temperatureuncertainties. The problem of hundreds of en-route aircraftflying multi-segmented 2D trajectories is considered. The weatheruncertainty is retrieved from Ensemble Prediction Systems. Theconflict detection is based on ensemble trajectory prediction,and is performed using an efficient grid-based procedure. Ametaheuristic approach is developed to solve the conflicts, basedon simulated annealing, which generates resolution trajectoriesby modifying the location of the route waypoints (vectoring),with the aim of lowering the probabilities of the conflicts whilealso minimising the deviation from the nominal paths. Realisticapplications in scenarios with different traffic densities arepresented

The interaction of thermocapillary convection and low-frequency vibration in nearly-inviscid liquid bridges

The combined effect of thermocapillary stress and steady forcing due to vibrations of the disks in a model-half-zone axisymmetric liquid bridge is considered for low-viscosity liquids (i.e., with a large capillary Reynolds number), and low nondimensional vibration frequencies (i.e., small as compared to the capillary Reynolds number). An asymptotic model is derived for the slowly-varying streaming flow in the bulk (outside the oscillatory boundary layers) resulting from both effects that includes also buoyancy and other thermal expansion effects. This model is used to first analyze the steady streaming flow patterns in isothermal conditions and then to show that mechanical vibrations can annihilate almost completely thermocapillary flows of fairly large Reynolds numbers provided that: (i) the Prandtl number is appropriately small, (ii) both disks are vibrated, and (iii) the vibrating amplitudes, frequency and phases are appropriate (the counterbalancing effect depends crucially on the difference of the vibrating phases of both disks

Presupuesto y control presupuestario en empresas mendocinas

La implementación del control presupuestario en empresas mendocinas resulta de gran importancia debido al contexto inflacionario en el que están inmersas. La presente investigación se propone indagar si la utilización del presupuesto y control presupuestario en un contexto macroeconómico de alta incertidumbre resulta ser una herramienta de utilidad que pueda llevarse a cabo en cualquier tipo de organización con independencia de su estructura, rubro y localización geográfica. La investigación fue abordada con un enfoque cualitativo y cuantitativo a partir de la obtención de datos mediante la realización de entrevistas a empresarios, consultas de estadísticas de la información de cada organización en particular y la recolección de datos macroeconómicos oficiales del Gobierno Nacional. Luego se analizan las ventajas y desventajas que implica la utilización de la herramienta de gestión planteada. Los resultados indican que: 1) Todas las organizaciones pueden aplicar el presupuesto y control presupuestario debido a que son herramientas altamente flexibles pero requieren de una gran dedicación y comprensión del contexto en el que se desarrollan, 2) Aquellas empresas que logran aplicarlas son las que transitan con mayor facilidad los vaivenes económicos del sector y, 3) Las principales ventajas de su aplicación son la reducción de incertidumbre en la toma de decisiones, el logro de políticas empresariales, mayor estabilidad en el tiempo, menor impacto de las consecuencias que genere el contexto inflacionario.Fil: Requelme, Damián Emiliano. Universidad Nacional de Cuyo. Facultad de Ciencias Económicas.Fil: Rivas, Leandro Ricardo. Universidad Nacional de Cuyo. Facultad de Ciencias Económicas