scholarly journals On the origin of pronounced O3gradients in the thunderstorm outflow region during DC3

2016 ◽  
Vol 121 (11) ◽  
pp. 6600-6637 ◽  
Author(s):  
H. Huntrieser ◽  
M. Lichtenstern ◽  
M. Scheibe ◽  
H. Aufmhoff ◽  
H. Schlager ◽  
...  
Keyword(s):  
Outflow Region ◽  
Thunderstorm Outflow

Dynamics of a Thunderstorm Outflow

1987 ◽  
Vol 44 (15) ◽  
pp. 1879-1898 ◽  
Author(s):  
Cynthia K. Mueller ◽  
Richard E. Carbone
Keyword(s):  
Thunderstorm Outflow

scholarly journals Thunderstorm outflows preceding epidemics of asthma during spring and summer

Thorax ◽  
2001 ◽  
Vol 56 (6) ◽  
pp. 468-471
Author(s):  
G B Marks ◽  
J R Colquhoun ◽  
S T Girgis ◽  
M Hjelmroos Koski ◽  
A B A Treloar ◽  
...  
Keyword(s):  
Pollen Grains ◽  
Ground Level ◽  
Fold Increase ◽  
Underlying Mechanism ◽  
Detailed Examination ◽  
Asthma Exacerbations ◽  
Eastern Australia ◽  
The Difference ◽  
High Concentrations ◽  
Thunderstorm Outflow

BACKGROUNDA study was undertaken to assess the importance of thunderstorms as a cause of epidemics of asthma exacerbations and to investigate the underlying mechanism.METHODSA case control study was performed in six towns in south eastern Australia. Epidemic case days (n = 48) and a random sample of control days (n = 191) were identified by reference to the difference between the observed and expected number of emergency department attendances for asthma. The occurrence of thunderstorms, their associated outflows and cold fronts were ascertained, blind to case status, for each of these days. In addition, the relation of hourly pollen counts to automatic weather station data was examined in detail for the period around one severe epidemic of asthma exacerbations. The main outcome measure was the number of epidemics of asthma exacerbations.RESULTSThunderstorm outflows were detected on 33% of epidemic days and only 3% of control days (odds ratio 15.0, 95% confidence interval 6.0 to 37.6). The association was strongest in late spring and summer. Detailed examination of one severe epidemic showed that its onset coincided with the arrival of the thunderstorm outflow and a 4–12 fold increase in the ambient concentration of grass pollen grains.CONCLUSIONSThese findings are consistent with the hypothesis that some epidemics of exacerbations of asthma are caused by high concentrations of allergenic particles produced by an outflow of colder air, associated with the downdraught from a thunderstorm, sweeping up pollen grains and particles and then concentrating them in a shallow band of air at ground level. This is a common cause of exacerbations of asthma during the pollen season.

Cold Ionospheric Ions in the Magnetic Reconnection Outflow Region

2017 ◽  
Vol 122 (10) ◽  
pp. 10,194-10,202 ◽  
Author(s):  
W. Y. Li ◽  
M. André ◽  
Yu. V. Khotyaintsev ◽  
A. Vaivads ◽  
S. A. Fuselier ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Outflow Region

scholarly journals Erratum: “On the role of separatrix instabilities in heating the reconnection outflow region” [Phys. Plasmas 25, 122902 (2018)]

2019 ◽  
Vol 26 (4) ◽  
pp. 049901
Author(s):  
M. Hesse ◽  
C. Norgren ◽  
P. Tenfjord ◽  
J. L. Burch ◽  
Y.-H. Liu ◽  
...  
Keyword(s):  
Outflow Region

Orifice and Impingement Flow Fields in Confined Jet Impingement

1998 ◽  
Vol 120 (1) ◽  
pp. 68-72 ◽  
Author(s):  
G. K. Morris ◽  
S. V. Garimella
Keyword(s):  
Pressure Drop ◽  
Recirculation Zone ◽  
Jet Impingement ◽  
Flow Fields ◽  
Electronics Packaging ◽  
Target Plate ◽  
Packaging Design ◽  
Numerical Predictions ◽  
Confinement Region ◽  
Outflow Region

The flow fields in the orifice and the confinement region of a normally impinging, axisymmetric, confined, and submerged liquid jet were computationally investigated. Numerical predictions were made for orifice diameters of 3.18 and 6.35 mm at several orifice-to-target plate spacings, with turbulent jet Reynolds number ranging from 8500 to 23,000. The commercial finite-volume code FLUENT was used to solve the flow fields using a modified k–ε model based on renormalization group theory. The predicted characteristics of the separation region at the entrance of the orifice agree with experiments in the literature. The pressure drop across the orifice was predicted to within 5 percent of proposed empirical correlations based on published experimental data. The computed flow patterns in the confinement region of the impinging jet were in good qualitative agreement with flow visualizations; however, a secondary recirculation zone observed in experiments was not predicted by the models. The results presented for the flow (and pressure drop) in the orifice, as well as that in the confined outflow region, influence heat transfer on the impingement surface and are important considerations in electronics packaging design.

Observation of a Sharp Negative Dipolarization Front in the Reconnection Outflow Region

2011 ◽  
Vol 28 (10) ◽  
pp. 109402 ◽  
Author(s):  
Meng Zhou ◽  
Shi-Yong Huang ◽  
Xiao-Hua Deng ◽  
Ye Pang
Keyword(s):  
Dipolarization Front ◽  
Outflow Region

Endwall Contouring and Fillet Design for Reducing Losses and Homogenizing the Outflow of a Compressor Cascade

2014 ◽  
Author(s):  
Oliver Reutter ◽  
Stefan Hemmert-Pottmann ◽  
Alexander Hergt ◽  
Eberhard Nicke
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Leading Edge ◽  
Total Pressure Loss ◽  
Wall Region ◽  
Optimized Design ◽  
Compressor Cascade ◽  
Outflow Region ◽  
Endwall Contouring ◽  
Operating Points

The following paper deals with the development of an optimized fillet and an endwall contour for reducing the total pressure loss and for homogenizing the outflow of a highly loaded cascade with a low aspect ratio. The NACA-65 K48 cascade profile without a fillet and without endwall contouring is used as a basis. Optimizations are performed using the DLR in-house tool AutoOpti and the RANS-solver TRACE. Three operating points at an inflow Mach number of 0.67 with different inflow angles are used to secure a wide operating range of the optimized design. At first only a fillet is optimized. The optimized fillet is small at the leading edge and rather high, wide and thick towards the trailing edge. It reduces the total pressure loss and homogenizes the outflow up to a blade height of 20 %. Following this a combined optimization of the endwall and the fillet is performed. The optimized contour leads to the development of a vortex, which changes the secondary flow in such a way, that the corner separation is reduced, which in turn significantly reduces the total pressure loss up to 16 % in the design operating point. The contour in the outflow region leads to a significant homogenization of the outflow in the near wall region.

scholarly journals One-year observations of carbonaceous and nitrogenous components and major ions in the aerosols from subtropical Okinawa Island, an outflow region of Asian dusts

2014 ◽  
Vol 14 (4) ◽  
pp. 1819-1836 ◽  
Author(s):  
B. Kunwar ◽  
K. Kawamura
Keyword(s):  
Organic Carbon ◽  
Biomass Burning ◽  
Significant Contribution ◽  
Major Ions ◽  
Atmospheric Transport ◽  
Water Soluble ◽  
Anthropogenic Sources ◽  
Marine Biota ◽  
Okinawa Island ◽  
Outflow Region

Abstract. Ambient aerosol samples (TSP, n = 50) were collected for 12 months at subtropical Okinawa Island, Japan, an outflow region of Asian dusts in the western North Pacific and analysed for organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), water-soluble total nitrogen (WSTN), water-soluble organic nitrogen (WSON) and major ions to better understand the formation and transformation of East Asian aerosols during long-range atmospheric transport. Concentration ranges of these components are; OC: 0.76–7.1 μg m−3 (av. 1.7 ± 1.0 μg m−3), EC: 0.07–0.96 μg m−3 (0.28 ± 0.19 μg m−3), WSOC: 0.27–1.9 μg m−3 (0.73 ± 0.38 μg m−3), WSTN: 0.77 to 3.0 μg m−3 (0.58 ± 0.46 μg m−3) and WSON: 0.0–2.2 μg m−3 (0.12 ± 0.23 μg m−3). Higher OC concentrations were obtained in active biota seasons; spring (av. 2.4 μg m−3) and summer (1.8 μg m−3). EC and WSOC concentrations maximized in spring (av. 0.41 μg m−3 and 0.95 μg m−3, respectively) followed by winter (0. 70 and 0.90 μg m−3) whereas they became lowest in summer (0.19 and 0.52 μg m−3). In contrast, WSTN concentrations were highest in winter (0.86 μg m−3) and lowest in summer (0.37 μg m−3) and autumn (0.34 μg m−3). Concentrations of WSON are higher in early summer (av. 0.26 μg m−3) due to the emission from marine biota. The high ratios of OC / EC (av. 7.6) and WSOC / OC (44%) suggest a secondary formation of organic aerosols. Strong correlation between OC and MSA- (0.81) in spring suggests that springtime aerosols are influenced by additional marine and terrestrial biogenic sources. The positive correlation of Ca2+ and TSP in spring (r = = 0.81) demonstrates a significant contribution of Asian dust whereas high abundances of NO3- and nss-SO42- in winter suggest an important contribution from anthropogenic sources including biomass burning, vehicular emission and coal combustion. NH4-N/WSTN ratios peaked in winter (0.56), indicating a significant contribution of biomass burning to WSTN in cold season. In contrast, higher NO3-N/WSTN ratio in spring than winter suggests that the atmospheric transport of vehicular emissions maximizes in spring. Correlation analyses of major ions suggest that NH4+ and Ca2+ play major role in the neutralization of acidic aerosols forming NH4HSO4, (NH4)2SO4 and CaSO4.

First-order effects in time-dependent Petschek-type reconnection

2000 ◽  
Vol 64 (5) ◽  
pp. 547-560 ◽  
Author(s):  
ILYA V. ALEXEEV ◽  
VLADIMIR S. SEMENOV ◽  
HELFRIED K. BIERNAT
Keyword(s):  
Zero Order ◽  
Time Dependent ◽  
Order Effects ◽  
Plasma Velocity ◽  
Plasma Acceleration ◽  
Reconnection Rate ◽  
Initial Current ◽  
First Order ◽  
Potential Trigger ◽  
Outflow Region

The model of time-dependent Petschek-type reconnection is extended to take into account first-order corrections with respect to the reconnection rate. The plasma velocity inside the outflow region turns out to be smaller than the zero-order Alfvén velocity, and therefore strong reconnection is less effective in plasma acceleration. The model is also applied to study the effect of incoming waves on reconnection. We show that incoming waves of Alfvén type, carrying an electric current that is antiparallel to the initial current in the sheet, increase the reconnection rate and cause additional acceleration of the plasma, so that this wave can be considered as a potential trigger.

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