Evolution of detonation formation initiated by a spatially distributed, transient energy source

2016 ◽  
Vol 802 ◽  
pp. 305-332 ◽  
Author(s):  
Jonathan D. Regele ◽  
David R. Kassoy ◽  
Mohamad Aslani ◽  
Oleg V. Vasilyev
Keyword(s):  
Time Scale ◽  
Detonation Initiation ◽  
Spatially Resolved ◽  
Initiation Process ◽  
Direct Initiation ◽  
Transient Energy ◽  
Spatially Distributed ◽  
Reactive Euler Equations ◽  
Heated Fluid ◽  
Localized Reaction

Detonations usually form through either direct initiation or deflagration-to-detonation transition (DDT). In this work, a detonation initiation process is introduced that shows attributes from each of these two processes. Energy is deposited into a finite volume of fluid in an amount of time that is similar to the acoustic time scale of the heated fluid volume. Two-dimensional simulations of the reactive Euler equations are used to solve for the evolving detonation initiation process. The results show behaviour similar to both direct initiation and DDT. Localized reaction transients are shown to be intimately related to the appearance of a detonation. Thermomechanical concepts are used to provide physical interpretations of the computational results in terms of the interaction between compressibility phenomena on the acoustic time scale and localized, spatially resolved, chemical energy addition on a heat-addition time scale.

Detonation initiation on the microsecond time scale: DDTs

2008 ◽  
Vol 12 (6) ◽  
pp. 1009-1047 ◽  
Author(s):  
D. R. Kassoy ◽  
J. A. Kuehn ◽  
M. W. Nabity ◽  
J. F. Clarke
Keyword(s):  
Time Scale ◽  
Detonation Initiation

Detonation initiation process using injection from sub-chamber

2017 ◽  
Vol 2017.23 (0) ◽  
pp. 511
Author(s):  
Ryuji OGATA ◽  
Masataka YOSHIDA ◽  
Shinichi MAEDA ◽  
Tetsuro OBARA
Keyword(s):  
Detonation Initiation ◽  
Initiation Process

scholarly journals The spatially resolved star formation history of mergers

2017 ◽  
Vol 607 ◽  
pp. A70 ◽  
Author(s):  
C. Cortijo-Ferrero ◽  
R. M. González Delgado ◽  
E. Pérez ◽  
R. Cid Fernandes ◽  
R. García-Benito ◽  
...  
Keyword(s):  
Star Formation ◽  
Time Scales ◽  
Time Scale ◽  
Star Formation Rate ◽  
Early Stage ◽  
Formation Rate ◽  
Small Sample ◽  
Star Formation History ◽  
Spatially Resolved ◽  
Formation History

This paper presents the spatially resolved star formation history (2D-SFH) of a small sample of four local mergers: the early-stage mergers IC 1623, NGC 6090, and the Mice, and the more advanced merger NGC 2623, by analyzing IFS data from the CALIFA survey and PMAS in LArr mode. Full spectral fitting techniques are applied to the datacubes to obtain the spatially resolved mass growth histories, the time evolution of the star formation rate intensity (ΣSFR), and the local specific star formation rate (sSFR), over three different time scales (30 Myr, 300 Myr, and 1 Gyr). The results are compared with non-interacting Sbc–Sc galaxies, to quantify if there is an enhancement of the star formation and to trace its time scale and spatial extent. Our results for the three LIRGs (IC 1623 W, NGC 6090, and NGC 2623) show that a major phase of star formation is occurring in time scales of 107 yr to few 108 yr, with global SFR enhancements of between approximately two and six with respect to main-sequence star forming (MSSF) galaxies. In the two early-stage mergers IC 1623 W and NGC 6090, which are between first pericentre passage and coalescence, the most remarkable increase of the SFR with respect to non-interacting spirals occurred in the last 30 Myr, and it is spatially extended, with enhancements of factors between two and seven both in the centres (r < 0.5 half light radius, HLR), and in the disks (r > 1 HLR). In the more advanced merger NGC 2623 an extended phase of star formation occurred on a longer time scale of ~1 Gyr, with a SFR enhancement of a factor of approximately two-to-three larger than the one in Sbc–Sc MSSF galaxies over the same period, probably relic of the first pericentre passage epoch. A SFR enhancement in the last 30 Myr is also present, but only in NGC 2623 centre, by a factor of three. In general, the spatially resolved SFHs of the LIRG-mergers are consistent with the predictions from high spatial resolution simulations. In contrast, the star formation in the Mice, specially in Mice B, is not enhanced but inhibited with respect to Sbc–Sc MSSF galaxies. The fact that the gas fraction of Mice B is smaller than in most non-interacting spirals, and that the Mice are close to a prograde orbit, represents a new challenge for the models, which must cover a larger space of parameters in terms of the availability of gas and the orbital characteristics.

scholarly journals Estimation of rheological parameters for unstained living cells

2021 ◽  
Author(s):  
Kirill Lonhus ◽  
Renata Rychtáriková ◽  
Ali Ghaznavi ◽  
Dalibor Štys
Keyword(s):  
Effective Viscosity ◽  
Living Cells ◽  
Original Method ◽  
Velocity Fields ◽  
Rheological Parameters ◽  
Automatic Method ◽  
Human Osteoblast ◽  
Speeded Up Robust Features ◽  
Spatially Resolved ◽  
Spatially Distributed

AbstractIn video-records, objects moving in intracellular regions are often hardly detectable and identifiable. To squeeze the information on the intracellular flows, we propose an automatic method of reconstruction of intracellular flow velocity fields based only on a recorded video of an unstained cell. The basis of the method is detection of speeded-up robust features (SURF) and assembling them into trajectories. Two components of motion—direct and Brownian—are separated by an original method based on minimum covariance estimation. The Brownian component gives a spatially resolved diffusion coefficient. The directed component yields a velocity field, and after fitting the vorticity equation, estimation of the spatially distributed effective viscosity. The method was applied to videos of a human osteoblast and a hepatocyte. The obtained parameters are in agreement with the literature data.

Effect of actuating voltage and discharge gap on plasma assisted detonation initiation process

2018 ◽  
Vol 20 (6) ◽  
pp. 065507
Author(s):  
Siyin ZHOU ◽  
Xueke CHE ◽  
Wansheng NIE ◽  
Di WANG
Keyword(s):  
Detonation Initiation ◽  
Initiation Process ◽  
Discharge Gap

scholarly journals Monthly and spatially resolved black carbon emission inventory of India: uncertainty analysis

2016 ◽  
Vol 16 (19) ◽  
pp. 12457-12476 ◽  
Author(s):  
Umed Paliwal ◽  
Mukesh Sharma ◽  
John F. Burkhart
Keyword(s):  
Black Carbon ◽  
Forest Fires ◽  
Carbon Emission ◽  
Emission Inventory ◽  
Monthly Variation ◽  
Activity Data ◽  
Spatially Resolved ◽  
Spatially Distributed ◽  
Process Level ◽  
Grid Based

Abstract. Black carbon (BC) emissions from India for the year 2011 are estimated to be 901.11 ± 151.56 Gg yr−1 based on a new ground-up, GIS-based inventory. The grid-based, spatially resolved emission inventory includes, in addition to conventional sources, emissions from kerosene lamps, forest fires, diesel-powered irrigation pumps and electricity generators at mobile towers. The emissions have been estimated at district level and were spatially distributed onto grids at a resolution of 40 × 40 km2. The uncertainty in emissions has been estimated using a Monte Carlo simulation by considering the variability in activity data and emission factors. Monthly variation of BC emissions has also been estimated to account for the seasonal variability. To the total BC emissions, domestic fuels contributed most significantly (47 %), followed by industry (22 %), transport (17 %), open burning (12 %) and others (2 %). The spatial and seasonal resolution of the inventory will be useful for modeling BC transport in the atmosphere for air quality, global warming and other process-level studies that require greater temporal resolution than traditional inventories.

Direct initiation of detonation with a multi-step reaction scheme

2003 ◽  
Vol 476 ◽  
pp. 179-211 ◽  
Author(s):  
HOI DICK NG ◽  
JOHN H. S. LEE
Keyword(s):  
Kinetic Model ◽  
Blast Wave ◽  
Chemical Kinetic ◽  
Reaction Scheme ◽  
Chain Branching ◽  
Chemical Kinetic Model ◽  
Initiation Process ◽  
Direct Initiation ◽  
Detonation Instability ◽  
A Chain

The problem of direct initiation of detonation, where a powerful ignition source drives a blast wave into a gaseous combustible mixture to generate a Chapman–Jouguet (CJ) detonation, is investigated numerically by using a three-step chain-branching chemical kinetic model. The reaction scheme consists sequentially of a chain-initiation and a chain-branching step, followed by a temperature-independent chain termination. The three regimes of direct initiation i.e. subcritical, critical and supercritical, are numerically simulated for planar, cylindrical and spherical geometries using the present three-step chemical kinetic model. It is shown that the use of a more detailed reaction mechanism allows a well-defined value for the critical initiation energy to be determined. The numerical results demonstrate that detonation instability plays an important role in the initiation process. The effect of curvature for cylindrical and spherical geometries has been found to enhance the instability of the detonation wave and thus influence the initiation process. The results of these simulations are also used to provide further verification of some existing theories of direct initiation of detonation. It appears that these theories are satisfactory only for stable detonation waves and start to break down for highly unstable detonations because they are based on simple blast wave theory and do not include a parameter to model the detonation instability. This study suggests that a stability parameter, such as the ratio between the induction and reaction length, should be considered and a more complex chemistry should be included in future development of a more rigorous theory for direct initiation of detonation.

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