A Momentum Transfer Measurement Technique Between Contacting Free-Falling Bodies in the Presence of Adhesion

2008 ◽  
Vol 75 (1) ◽  
Author(s):  
M. Benedetti ◽  
D. Bortoluzzi ◽  
S. Vitale
Keyword(s):  
Momentum Transfer ◽  
Inertial Forces ◽  
Noise Sources ◽  
Space Applications ◽  
Interaction Forces ◽  
Measurement Resolution ◽  
Transfer Measurement ◽  
Filtering Technique ◽  
Set Up ◽  
Free Falling

The present paper is aimed at investigating the dynamics of release of objects in free-falling conditions typical of space applications. In the presence of surface interaction forces, a quick separation of the released from the constraining body will result in a momentum transfer, provided that the inertial forces exceed the maximum attractive force. The release conditions as well as the related parameters affecting the momentum acquired by the released body through the adhesion rupture play a fundamental role. Therefore, an analytical model has been set up to predict the imparted momentum in the case of conservative interaction forces. Furthermore, an experimental technique aimed at measuring the momentum transfer has been analyzed. Particular attention has been placed on the capability to accurately reproduce the stress status on the contact patch, on the noise sources affecting the measurement, and on the performances of a noise optimal-filtering technique in terms of achievable measurement resolution.

scholarly journals A Doppler Range Compensation for Step-Frequency Continuous-Wave Radar for Detecting Small UAV

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1331
Author(s):  
Massimiliano Pieraccini ◽  
Lapo Miccinesi ◽  
Neda Rojhani
Keyword(s):  
Short Range ◽  
Continuous Wave ◽  
Range Shift ◽  
Specific Method ◽  
Step Frequency ◽  
Wave Radar ◽  
Small Uav ◽  
The Doppler Effect ◽  
Set Up ◽  
Free Falling

Step-frequency continuous-wave (SFCW) modulation can have a role in the detection of small unmanned aerial vehicles (UAV) at short range (less than 1–2 km). In this paper, the theory of SFCW range detection is reviewed, and a specific method for correcting the possible range shift due to the Doppler effect is devised. The proposed method was tested in a controlled experimental set-up, where a free-falling target (i.e., a corner reflector) was correctly detected by an SFCW radar. This method was finally applied in field for short-range detection of a small UAV.

scholarly journals Fast high-energy X-ray imaging for Severe Accidents experiments on the future PLINIUS-2 platform

2018 ◽  
Vol 170 ◽  
pp. 08003
Author(s):  
L. Berge ◽  
N. Estre ◽  
D. Tisseur ◽  
E. Payan ◽  
D. Eck ◽  
...  
Keyword(s):  
Large Scale ◽  
Spot Size ◽  
High Energy ◽  
Simulation Software ◽  
Small Scale ◽  
Noise Sources ◽  
X Ray ◽  
X Ray Imaging ◽  
The Future ◽  
Set Up

The future PLINIUS-2 platform of CEA Cadarache will be dedicated to the study of corium interactions in severe nuclear accidents, and will host innovative large-scale experiments. The Nuclear Measurement Laboratory of CEA Cadarache is in charge of real-time high-energy X-ray imaging set-ups, for the study of the corium-water and corium-sodium interaction, and of the corium stratification process. Imaging such large and high-density objects requires a 15 MeV linear electron accelerator coupled to a tungsten target creating a high-energy Bremsstrahlung X-ray flux, with corresponding dose rate about 100 Gy/min at 1 m. The signal is detected by phosphor screens coupled to high-framerate scientific CMOS cameras. The imaging set-up is established using an experimentally-validated home-made simulation software (MODHERATO). The code computes quantitative radiographic signals from the description of the source, object geometry and composition, detector, and geometrical configuration (magnification factor, etc.). It accounts for several noise sources (photonic and electronic noises, swank and readout noise), and for image blur due to the source spot-size and to the detector unsharpness. In a view to PLINIUS-2, the simulation has been improved to account for the scattered flux, which is expected to be significant. The paper presents the scattered flux calculation using the MCNP transport code, and its integration into the MODHERATO simulation. Then the validation of the improved simulation is presented, through confrontation to real measurement images taken on a small-scale equivalent set-up on the PLINIUS platform. Excellent agreement is achieved. This improved simulation is therefore being used to design the PLINIUS-2 imaging set-ups (source, detectors, cameras, etc.).

Pseudo-linear-array analysis of passive surface waves based on beamforming

2020 ◽  
Vol 221 (1) ◽  
pp. 640-650
Author(s):  
Ya Liu ◽  
Jianghai Xia ◽  
Feng Cheng ◽  
Chaoqiang Xi ◽  
Chao Shen ◽  
...  
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Urban Areas ◽  
High Efficiency ◽  
Linear Array ◽  
Array Analysis ◽  
Noise Sources ◽  
Set Up ◽  
Wave Methods ◽  
Short Time

SUMMARY Linear arrays are usually deployed for passive surface-wave investigations because of their high efficiency and convenience. In populated urban areas, it is almost impossible to set up a 2-D array in terms of the restriction from the existing infrastructures. The limited azimuthal coverage, however, lacks the ability to attenuate velocity overestimation caused by directional noise sources. We came up with a novel idea to compensate the azimuthal coverage by adding two more offline receivers to a conventional linear array, which is called pseudo-linear-array analysis of passive surface waves (PLAS). We used a beamforming algorithm to capture noise sources distribution and extract accurate dispersion curves. We used array response function to explain the superiority of the pseudo-linear array over the linear array and present the basic workflow of PLAS. Synthetic tests and field examples demonstrated the feasibility of PLAS to measure unbiased dispersion image. Comparison with mostly used passive surface wave methods (refraction microtremor, multichannel analysis of passive surface waves, spatial autocorrelation method, frequency–wavenumber analysis) suggested that PLAS can serve as an alternative passive surface wave method, especially in urban areas with restricted land accessibility and short-time acquisition demands.

scholarly journals Computation of Ice Shedding Trajectories Using Cartesian Grids, Penalization, and Level Sets

2011 ◽  
Vol 2011 ◽  
pp. 1-15 ◽  
Author(s):  
Héloïse Beaugendre ◽  
François Morency ◽  
Federico Gallizio ◽  
Sophie Laurens
Keyword(s):  
Boundary Conditions ◽  
Level Sets ◽  
The Body ◽  
Cartesian Grids ◽  
Falling Sphere ◽  
Proposed Model ◽  
Efficient Alternative ◽  
Ice Shedding ◽  
Set Up ◽  
Free Falling

We propose to model ice shedding trajectories by an innovative paradigm that is based on cartesian grids, penalization and level sets. The use of cartesian grids bypasses the meshing issue, and penalization is an efficient alternative to explicitly impose boundary conditions so that the body-fitted meshes can be avoided, making multifluid/multiphysics flows easy to set up and simulate. Level sets describe the geometry in a nonparametric way so that geometrical and topological changes due to physics and in particular shed ice pieces are straight forward to follow. The model results are verified against the case of a free falling sphere. The capabilities of the proposed model are demonstrated on ice trajectories calculations for flow around iced cylinder and airfoil.

A scattering filter for energy-dispersive optics

1998 ◽  
Vol 5 (3) ◽  
pp. 753-755 ◽  
Author(s):  
Michael Hagelstein ◽  
Ulrich Lienert ◽  
Thorsten Ressler ◽  
Alfonso San Miguel ◽  
Andreas Freund ◽  
...  
Keyword(s):  
European Synchrotron Radiation Facility ◽  
Energy Dispersive ◽  
Double Crystal ◽  
White Line ◽  
Optical Elements ◽  
X Ray ◽  
Angle Scattering ◽  
Filtering Technique ◽  
Set Up ◽  
X Ray Absorption

A filtering technique to remove parasitic scattering from X-ray absorption spectra that are acquired in energy-dispersive mode has been developed and tested at the European Synchrotron Radiation Facility. The improved set-up removes small-angle scattering of the sample or the windows of sample cells which may spoil the energy resolution or reduce the intensity of prominent features in the absorption spectrum, such as the white line at the Pt L III edge. The sample is placed behind the curved monochromator and between two plane perfect crystals in the Bonse–Hart configuration. The dispersion of the Bonse–Hart double-crystal camera is matched to the dispersion of the curved monochromator by inclining the scattering planes of the two optical elements against each other.

scholarly journals Dynamic Analysis on Nonlinear Fluid-Structure Interaction Forces of Rub-Impact Rotor System

2014 ◽  
Vol 8 (1) ◽  
pp. 480-486
Author(s):  
Yuegang Luo ◽  
Songhe Zhang ◽  
Bin Wu ◽  
Wanlei Wang
Keyword(s):  
Numerical Simulation ◽  
Coupling Model ◽  
Rotor System ◽  
Nonlinear Dynamic Model ◽  
Interaction Forces ◽  
Structure Interaction ◽  
Movement Characteristics ◽  
Set Up ◽  
The Stability ◽  
Nonlinear Fluid

Based on the coupling model of nonlinear oil-film force and nonlinear seal fluid force, a nonlinear dynamic model of rotor system with rub-impact fault is set up. The dynamic characteristics of the system were studied with numerical simulation and the effects of airflow excited force, rubbing gap and stiffness parameters on movement characteristics of the rotor were analyzed. The results indicate that the airflow excited force can significantly restrain the stability and amplitude of rubbing rotor. The less rubbing gap and larger rubbing stiffness are in favor of the stability of the system.

A Simple Approach to the Wing Flutter Problem

1933 ◽  
Vol 37 (273) ◽  
pp. 783-792 ◽  
Author(s):  
B. Lockspeiser
Keyword(s):  
Elastic Energy ◽  
Simple Approach ◽  
Inertial Forces ◽  
Initial Displacement ◽  
Wing Flutter ◽  
Wing Section ◽  
Air Damping ◽  
Gain Energy ◽  
Wing Structure ◽  
Set Up

Let us first consider the oscillations, in still air, of a monoplane wing whose aileron is supposed locked to the wing in such a way that it behaves as though it were an integral part of the wing structure. When the wing is displaced from its position of equilibrium and released it will, in general, vibrate both in flexure and torsion. The initial displacement may be purely flexural, but if the inertial forces called into play, over any wing section, produce a twisting moment about the centre of twist (i.e., the centre about which the wing section twists on the application of a pure torque at that section) torsional as well as flexural oscillations will be set up. Inertia, in general, robs the two kinds of oscillation of their independence, and, when they are interdependent, we may conveniently speak of “inertial couplings” between the two motions. In still air these vibrations must, of necessity, die down. One part of the wing may gain energy at the expense of another, but the store of elastic energy given to the wing by the initial displacement must grow progressively less as the wing does work against the viscous air damping and structural hysteresis forces.

scholarly journals Investigation of the Internal Displacement Chamber Pressure of a Rotary Vane Pump

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3341
Author(s):  
Timm Hieronymus ◽  
Thomas Lobsinger ◽  
Gunther Brenner
Keyword(s):  
Cfd Simulation ◽  
Low Noise ◽  
Operating Conditions ◽  
Internal Displacement ◽  
Chamber Pressure ◽  
Vane Pump ◽  
Noise Sources ◽  
Rotary Vane Pump ◽  
Automatic Transmissions ◽  
Set Up

Low noise emissions of vehicle components are today a quality feature in the automotive sector. In automatic transmissions in particular, the hydraulic pump often contributes significantly to noise, which motivates research to clarify the noise sources and transmission pathways in these components. The subject of the present investigation is the generation of noise by the inherently instationary flow in hydraulic pumps. In order to shed some light on these phenomena, a computational fluid dynamics (CFD) simulation model for flow investigations on rotary vane pumps was set up. In this work, first the influence of different simulation parameters on the numerical results is analyzed. Then the pressure in the internal displacement chambers of the pump is examined, as it can be assumed that this is the essential parameter for noise generation. Different operating conditions such as rotational speeds and delivery pressures are investigated. Furthermore, the simulation results are compared to pressure measurements for validation and are used to find optimization potentials.

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