102,156 research outputs found
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
Impact of Cell Microcracks Size and Spatial Distribution on Output Power of PV Modules
No full textIn this paper, we analyze the shape, orientation and spatial distribution of microcracks in 41 different PV-modules with the aim to further investigate the impact of microcracks to the reduction of power output. A first very important result is that there is a good correlation between the percentage of inactive areas (black areas given by electroluminescence test) and the power variation with respect to the nominal power value measured in PV modules. More information has been provided by the position and shape of the microcracks in the PV module
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
BIPAP (bilevel positive airway pressure): Settings and implications during non-invasive ventilation
No full text
Subject-specific multiscale modeling of aortic valve biomechanics
No full textA Finite Element workflow for the multiscale analysis of the aortic valve biomechanics was developed and applied to three physiological anatomies with the aim of describing the aortic valve interstitial cells biomechanical milieu in physiological conditions, capturing the effect of subject-specific and leaflet-specific anatomical features from the organ down to the cell scale. A mixed approach was used to transfer organ-scale information down to the cell-scale. Displacement data from the organ model were used to impose kinematic boundary conditions to the tissue model, while stress data from the latter were used to impose loading boundary conditions to the cell level. Peak of radial leaflet strains was correlated with leaflet extent variability at the organ scale, while circumferential leaflet strains varied over a narrow range of values regardless of leaflet extent. The dependency of leaflet biomechanics on the leaflet-specific anatomy observed at the organ length-scale is reflected, and to some extent emphasized, into the results obtained at the lower length-scales. At the tissue length-scale, the peak diastolic circumferential and radial stresses computed in the fibrosa correlated with the leaflet surface area. At the cell length-scale, the difference between the strains in two main directions, and between the respective relationships with the specific leaflet anatomy, was even more evident; cell strains in the radial direction varied over a relatively wide range (0.36 - 0.87) with a strong correlation with the organ length-scale radial strain (R2= 0.95); conversely, circumferential cell strains spanned a very narrow range (0.75 - 0.88) showing no correlation with the circumferential strain at the organ level (R2= 0.02). Within the proposed simulation framework, being able to account for the actual anatomical features of the aortic valve leaflets allowed to gain insight into their effect on the structural mechanics of the leaflets at all length-scales, down to the cell scale
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