Experimental measurements of time dependent structure in shock waves and gravitational-collapse of a granular gas

2009 ◽  
Author(s):  
Greg A. Voth ◽  
John A. Perez ◽  
Reuben Son ◽  
Masami Nakagawa ◽  
Stefan Luding
Keyword(s):  
Shock Waves ◽  
Gravitational Collapse ◽  
Time Dependent ◽  
Experimental Measurements ◽  
Granular Gas

scholarly journals NF-κB and FosB mediate inflammation and oxidative stress in the blast lung injury of rats exposed to shock waves

2021 ◽  
Author(s):  
Hong Wang ◽  
Wenjuan Zhang ◽  
Jinren Liu ◽  
Junhong Gao ◽  
Le Fang ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Lung Injury ◽  
Shock Waves ◽  
Time Dependent ◽  
Inflammatory Factors ◽  
Control Group ◽  
Dependent Manner ◽  
Total Antioxidant ◽  
Blast Lung Injury ◽  
And Oxidative Stress

Abstract Blast lung injury (BLI) is the major cause of death in explosion-derived shock waves; however, the mechanisms of BLI are not well understood. To identify the time-dependent manner of BLI, a model of lung injury of rats induced by shock waves was established by a fuel air explosive. The model was evaluated by hematoxylin and eosin staining and pathological score. The inflammation and oxidative stress of lung injury were also investigated. The pathological scores of rats’ lung injury at 2 h, 24 h, 3 days, and 7 days post-blast were 9.75±2.96, 13.00±1.85, 8.50±1.51, and 4.00±1.41, respectively, which were significantly increased compared with those in the control group (1.13±0.64; P<0.05). The respiratory frequency and pause were increased significantly, while minute expiratory volume, inspiratory time, and inspiratory peak flow rate were decreased in a time-dependent manner at 2 and 24 h post-blast compared with those in the control group. In addition, the expressions of inflammatory factors such as interleukin (IL)-6, IL-8, FosB, and NF-κB were increased significantly at 2 h and peaked at 24 h, which gradually decreased after 3 days and returned to normal in 2 weeks. The levels of total antioxidant capacity, total superoxide dismutase, and glutathione peroxidase were significantly decreased 24 h after the shock wave blast. Conversely, the malondialdehyde level reached the peak at 24 h. These results indicated that inflammatory and oxidative stress induced by shock waves changed significantly in a time-dependent manner, which may be the important factors and novel therapeutic targets for the treatment of BLI.

Upstream motions in stratified flow

1988 ◽  
Vol 187 ◽  
pp. 487-506 ◽  
Author(s):  
I. P. Castro ◽  
W. H. Snyder
Keyword(s):  
Body Height ◽  
Three Dimensional ◽  
Time Dependent ◽  
Experimental Measurements ◽  
Two Dimensional ◽  
Towing Tank ◽  
First Order ◽  
Density Perturbations ◽  
Small Obstacle ◽  
Obstacle Height

In this paper experimental measurements of the time-dependent velocity and density perturbations upstream of obstacles towed through linearly stratified fluid are presented. Attention is concentrated on two-dimensional obstacles which generate turbulent separated wakes at Froude numbers, based on velocity and body height, of less than 0.5. The form of the upstream columnar modes is shown to be largely that of first-order unattenuating disturbances, which have little resemblance to the perturbations described by small-obstacle-height theories. For two-dimensional obstacles the disturbances are similar to those found by Wei, Kao & Pao (1975) and it is shown that provided a suitable obstacle drag coefficient is specified, the lowest-order modes (at least) are quantitatively consistent with the results of the Oseen inviscid model.Discussion of some results of similar measurements upstream of three-dimensional obstacles, the importance of towing tank endwalls and the relevance of the Foster & Saffman (1970) theory for the limit of zero Froude number is also included.

Investigation of the stability of boundary layers by a finite-difference model of the Navier—Stokes equations

1976 ◽  
Vol 78 (2) ◽  
pp. 355-383 ◽  
Author(s):  
H. Fasel
Keyword(s):  
Finite Difference ◽  
Stability Theory ◽  
Stokes Equations ◽  
Time Dependent ◽  
Linear Stability Theory ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Navier Stokes Equations ◽  
The Stability ◽  
Small Periodic

The stability of incompressible boundary-layer flows on a semi-infinite flat plate and the growth of disturbances in such flows are investigated by numerical integration of the complete Navier–;Stokes equations for laminar two-dimensional flows. Forced time-dependent disturbances are introduced into the flow field and the reaction of the flow to such disturbances is studied by directly solving the Navier–Stokes equations using a finite-difference method. An implicit finitedifference scheme was developed for the calculation of the extremely unsteady flow fields which arose from the forced time-dependent disturbances. The problem of the numerical stability of the method called for special attention in order to avoid possible distortions of the results caused by the interaction of unstable numerical oscillations with physically meaningful perturbations. A demonstration of the suitability of the numerical method for the investigation of stability and the initial growth of disturbances is presented for small periodic perturbations. For this particular case the numerical results can be compared with linear stability theory and experimental measurements. In this paper a number of numerical calculations for small periodic disturbances are discussed in detail. The results are generally in fairly close agreement with linear stability theory or experimental measurements.

Free Vibration of Continuous Skin-Stringer Panels

1960 ◽  
Vol 27 (4) ◽  
pp. 669-676 ◽  
Author(s):  
Y. K. Lin
Keyword(s):  
Free Vibration ◽  
Boundary Conditions ◽  
Natural Frequencies ◽  
Normal Modes ◽  
Time Dependent ◽  
Experimental Measurements ◽  
Structural Configuration ◽  
Modes Of Vibration ◽  
Fuselage Skin

The determination of the natural frequencies and normal modes of vibration for continuous panels, representing more or less typical fuselage skin-panel construction for modern airplanes, is discussed in this paper. The time-dependent boundary conditions at the supporting stringers are considered. A numerical example is presented, and analytical results for a particular structural configuration agree favorably with available experimental measurements.

On the population of the metastable states behind unstable shock waves in ionizing argon

1986 ◽  
Vol 170 ◽  
pp. 319-337 ◽  
Author(s):  
A. F. P. Houwing ◽  
T. J. Mcintyre ◽  
P. A. Taloni ◽  
R. J. Sandeman
Keyword(s):  
Shock Waves ◽  
Present Model ◽  
Dominant Role ◽  
Metastable States ◽  
Flow Instabilities ◽  
Experimental Measurements ◽  
Excitation Process ◽  
Electron Atom ◽  
Spatially Resolved

Experiments are described in which the populations of metastable levels in ionizing argon are measured through spatially resolved hook interferometry. The results are compared with the present model for shock-induced ionization and a recently proposed mechanism to explain observed flow instabilities. It is found that the experimental measurements support the presently accepted model, which states that electron–atom collisions play the dominant role in the excitation process, but contradicts recent proposals which predict a rapid build-up of anomalously high metastable populations through atom–atom collisions.

scholarly journals Particle acceleration at colliding shock waves

2020 ◽  
Vol 494 (3) ◽  
pp. 3166-3176 ◽  
Author(s):  
T Vieu ◽  
S Gabici ◽  
V Tatischeff
Keyword(s):  
Shock Waves ◽  
High Energy ◽  
Time Dependent ◽  
Shock Acceleration ◽  
Diffusive Shock Acceleration ◽  
Mathematical Methods ◽  
Accretion Flows ◽  
Self Similar Solution ◽  
Self Similar ◽  
Accelerated Particles

ABSTRACT We model the diffusive shock acceleration of particles in a system of two colliding shock waves and present a method to solve the time-dependent problem analytically in the test-particle approximation and high energy limit. In particular, we show that in this limit the problem can be analysed with the help of a self-similar solution. While a number of recent works predict hard (E−1) spectra for the accelerated particles in the stationary limit, or the appearance of spectral breaks, we found instead that the spectrum of accelerated particles in a time-dependent collision follows quite closely the canonical E−2 prediction of diffusive shock acceleration at a single shock, except at the highest energy, where a hardening appears, originating a bumpy feature just before the exponential cut-off. We also investigated the effect of the reacceleration of pre-existing cosmic rays by a system of two shocks, and found that under certain conditions spectral features can appear in the cut-off region. Finally, the mathematical methods presented here are very general and could be easily applied to a variety of astrophysical situations, including for instance standing shocks in accretion flows, diverging shocks, backward collisions of a slow shock by a faster shock, and wind–wind or shock–wind collisions.

scholarly journals Time-dependent line-of-sight extinction tomography for multi-hole GDI injectors

2016 ◽  
Vol 9 (3) ◽  
pp. 199-211 ◽  
Author(s):  
Yudaya Sivathanu ◽  
Jongmook Lim ◽  
Varun Kulkarni
Keyword(s):  
Ambient Temperature ◽  
Direct Injection ◽  
Injection Pressure ◽  
Gasoline Direct Injection ◽  
Time Dependent ◽  
Line Of Sight ◽  
Experimental Measurements ◽  
Fuel Injectors ◽  
Factors Affecting ◽  
Spray Structure

Finely atomized sprays from multi-hole gasoline direct injection (GDI) fuel injectors make them an ideal choice for automobile applications. A knowledge of the factors affecting the performance of these injectors is hence important. In the study presented here, we employ statistical extinction tomography to examine the transient characteristics of two GDI fuel injectors with five and six holes. Two axial locations, 25 mm and 35 mm from the injector exit, are chosen for experimental measurements, and the dependence of injection pressure and ambient temperature on plume locations and angles is examined from these measurements. A pressure chamber with opposing windows is used which permits the nozzle to be rotated 12 times (30° each rotation) to obtain information on the complete spray structure. Additionally, the plume centroid locations are measured and compared with those obtained with a mechanical patternator. The centroid locations from the two instruments compare favorably.

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