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Finite Rate Chemistry Effects on the High Altitude Aerodynamics of an Apollo-Shaped Reentry Capsule
No full textAnalysis of aerodynamic performances of experimental flying test bed in high-altitude flight
No full textAn aerodynamic, computational study has been performed on the 3.9.2_FW50 configuration
of the winged experimental flying test bed (FTB-X) of an experimental unmanned space
vehicle in the altitude interval 90–110 km, where the vehicle is in transitional regime. The range of
the angle of attack was 0–40◦ and the side slip angle was 15◦. The flow field has been solved by the
three-dimensional (3D) direct simulation Monte Carlo (DSMC) code: DS3V. The results showed
better aerodynamic behaviour both in symmetric and in side-slip flights, but worst longitudinal
stability in symmetric flight with respect to the previous version of FTB-X (1.1.2). In fact, both
the aerodynamic efficiency and the derivative of pitching moment coefficient in symmetric flight
increased. Furthermore, a preliminary analysis about the possibility of an aerodynamic control
of the vehicle by deflection of a trailing edge flap has been fulfilled. This analysis has been carried
out in terms of the lift and drag forces and pitching moment at the altitude of 70km in the range
of the angle of attack 0–30◦ and flap deflection 0–30◦.The flowfield has been solved by a 2DDSMC
code (DS2V) and computational fluid dynamic code (H3NS). A thermal analysis has been also
carried out for evaluating the heat flux on the flap. This heat flux is comparable with that at the
nose stagnation point, and therefore a thermal protection system should be necessary also on the
flap. The effect of the flap deflection on the flowseparation has been also evaluated. In particular,
at high flap deflection angle, the shock wave boundary layer interaction produces a decrease of
the airfoil aerodynamic efficiency. Therefore, the increases of lift and drag of the aerodynamic
force, as functions of the flap deflection angle, encourage performing similar tests considering
the whole vehicle
Advanced Models for Prediction of High Altitude Aero-Thermal Loads of a Space Re-entry Vehicle
Full text linkThe analysis of the rarefaction effects in predicting the main aero-thermal loads of a Space re-entry vehicle is presented. It is well known that the Navier-Stokes equations fail in rarefied regimes and other approaches must be used.
In the present paper different configurations have been simulated by using the Direct Simulation Monte Carlo method. Moreover, slip flow boundary conditions have been implemented in a Navier-Stokes code in order to extend the validity
of the continuum approach to the transitional flow regime. Finally, bridging formulas for high altitude aerodynamics of winged bodies have been used. Firstly, two simple geometries have been analysed, specifically designed to study the
phenomenon of shock wave boundary layer interaction: a hollow cylinder flare, for which some experiments are available; and a blunt-nosed flat plate/flap model designed and tested at the Italian Aerospace Research Centre. The other
configurations taken into account are, respectively, an experimental winged re-entry vehicle and a capsule, for which global aerodynamic coefficients and local wall heating have been determined with different approaches. The Navier-Stokes code with slip flow boundary conditions has shown good predicting capabilities compared with experiments in the hollow cylinder flare case; however, for the winged vehicle and capsule cases, the CFD results are not fully satisfactory and the Monte Carlo method remains the most reliable approach, together with the bridging formula, that provides good results for the aerodynamic coefficients
Influence of chemical models on heat flux for EXPERT and Orion capsules
No full textThe computation of heat flux on two current re-entry capsules, European eXPErimental Reentry Testbed (EXPERT) and
Orion, has been carried out by a direct simulation Monte Carlo code (DS2V) and by a computational fluid dynamic code
(H3NS) in transitional regime, considering both non-reactive and fully catalytic surface. These capsules have been chosen
for this analysis because they have been characterized by completely different shapes and re-entry trajectories. DS2V and
H3NS use the Gupta and the Park chemical models, respectively. The results showed that the heat flux predicted by
DS2V is always higher than that predicted by H3NS. Therefore, a sensitivity analysis of the chemical models on the heat
flux has been carried out for both capsules. More specifically, the Park model has been implemented in DS2V as well. The
results showed that DS2V and H3NS compute a different chemical composition both in the flow field and on the surface,
even when using the same chemical model (Park); therefore, the different results obtained from the two codes can be
attributed mostly to the different methodology used in handling all chemical processes
Evaluation of radiative heat transfer for interplanetary re-entry under vibrational nonequilibrium conditions
No full textA radiative heat transfer code, based on the Discrete Transfer method, is used in combination with
a spectral radiative database and a thermochemical nonequilibrium Navier–Stokes flowfield solver, to
compute radiative heating under vibrational nonequilibrium conditions for the re-entry test vehicle
FIRE II. The trajectory point under scrutiny refers to a flight velocity of 8.3 km/s, where radiative
equilibrium prevails. Numerical predictions indicate a quite good agreement with experimental data, both
for the radiative intensity along the stagnation streamline and for the total (convective plus absorbed
radiative) heat flux at the stagnation point. The Discrete Transfer method makes the code applicable
to arbitrarily complex geometries, and the vibrational nonequilibrium description allows considering reentry
from lunar or interplanetary return trajectories, as well as from terrestrial orbits
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Analysis of aero-thermodynamic behavior of expert capsule in transitional regime
Full text linkThe aerodynamic behavior of the EXPERT capsule has been already widely studied at low altitudes. In
order to broaden the aerodynamic data base of the capsule, additional computations of the aerodynamic forces and an
evaluation of the longitudinal stability and fluctuation of the pressure center have been carried out in the altitude
interval 80-105 km. The effect of the rolling angle has been also evaluated. As EXPERT, in the considered altitude
interval is in transitional regime, computations have been made by the DSMC code DS3V. Heat flux along the
capsule surface has been also evaluated. This is an important topic because the nose and the frustum are made of low
and high catalyticity materials, respectively. Computations, already performed in continuum regime by the CFD code
H3NS, showed that, at the nose-frustum junction, an abrupt and strong peak of heat flux is present. In this work, this
problem has been analyzed also in transitional regime. For this application, the DSMC 2-D code DS2V, requiring
smaller computer resources, compared with the ones required by DS3V, has been used for making computations at
lower altitudes. Furthermore, using DS2V made possible also to get a more detailed definition of the body surface and
therefore to increase the surface resolution. The launch of the capsule is currently scheduled in 2011; flight data
should be available to verify the results of the present computations
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