2017 nrl review u


part of a larger program on plasma radiation source


Download 23.08 Mb.
Pdf ko'rish
bet22/28
Sana15.12.2019
Hajmi23.08 Mb.
1   ...   18   19   20   21   22   23   24   25   ...   28
part of a larger program on plasma radiation source 
development involving many scientists from NRL, the 
Sandia National Laboratories, and the Lawrence Liver-
more National Laboratory.
 
[Sponsored by DOE/NNSA] 
References

A. Dasgupta, R.W. Clark, N. Ouart, J. Giuliani, A. Velikovich, 
D.J. Ampleford, S.B. Hansen, C. Jennings, A.J. Harvey-Thomp-
son, B. Jones, T.M. Flanagan, K.S. Bell, J.P. Apruzese, K.B. 
Fournier, H.A. Scott, M.J. May, M.A. Barrios, J.D. Colvin, and 
G.E. Kemp, “A Non-LTE Analysis of High Energy Density Kr 
Plasmas on Z and NIF,” Phys. PlasmasSpecial Issue 23, 101208 
(2016).
2
 C.A. Jennings, D.J. Ampleford, D.C. Lamppa, S.B. Hansen, B. 
Jones, A.J. Harvey-Thompson, M. Jobe, T. Strizic. J. Reneker, 
G.A. Rochau, and M.E. Cuneo, “Computational Modeling of 
Krypton Gas Puffs with Tailored Mass Density Profiles on Z,” 
Phys. Plasmas 22, 056316 (2015). 
3
 K.B. Fournier, M.J. May, J.D. Colvin, M.A. Barrios, J.R. Pat-
terson, and S.P. Regan, “Demonstration of a 13-keV Kr K-shell 
X-ray Source at the National Ignition Facility,” Phys. Rev. E 88
033104 (2013).  
 
  
ª
Supporting Weather Forecasters in 
Predicting and Monitoring Saharan 
Air Layer Dust Events that Impact the 
Greater Caribbean
A.P. Kuciauskas,
1
 P. Xian,
1
 E.J. Hyer,
1
 M.I. Oyola,
2
 and 
J.R. Campbell
1
1
Marine Meteorology Division 
2
American Society for Engineering Education 
 
The U.S. Naval Research Laboratory’s Marine 
Meteorology Division (NRL-MMD) in Monterey, 
California, is in the final phase of a two-year project 
(funded by the National Oceanic and Atmospheric Ad-
ministration) that provides environmental resources in 
monitoring and predicting African dust embedded in 
the Saharan Air Layer (SAL), an elevated air mass that 
passes across the greater Caribbean area. The primary 
consumer of these resources is the National Weather 
Service in San Juan, Puerto Rico (NWS-PR), and out-
reach also extends toward other local agencies, such as 
the Caribbean Institute for Meteorology and Hydrol-
ogy, based in Barbados, West Indies. The overarching 
goal is to protect the public from unhealthy respiratory 
conditions associated with the dust events; Puerto Rico 
currently suffers from historically high asthma rates.
1
 
Additional beneficiaries from this effort include global-
wide human health services and maritime and airline 
operators who rely on accurate air quality and visibility 
reports.
 
Specifically, NRL-MMD provides NWS-PR with 
a publically accessible web-based platform (called 
SAL-WEB) that is designed to monitor these African 
dust events. SAL-WEB consists of satellite imagery, in 
situ air quality measurements, and model fields related 
to aerosol concentrations, covering the extent of dust 
from North African, westward across the Atlantic 
basin, and extending into Mexico. The products in 
SAL-WEB serve to augment the Advanced Weather In-
teractive Processing System-II (AWIPS-II) infrastruc-
ture currently in operation at the NWS-PR. A standard 
product suite available to NWS forecasters, AWIPS-II 
has not been optimized for SAL transport and regional 
observation. 
 
Figure 8 presents a generalized two-dimensional 
isentropic depiction of SAL air mass transport char-
acteristics. Viewing from right to left (East to West), 
the first panel depicts the initialization of the SAL over 
northeastern Africa (Sahel and Sahara regions t
initial

with strong intense desert heating at the surface that 
generates strong sensible heat, associated turbulent 
flux, and convection at the surface. Surface dust is 
often scoured by strong winds and then lifted upward 
to heights reaching 500 hPa. As the SAL eventually 
propagates westward across northwestern Africa and 
into the Atlantic basin, the SAL air mass follows the 
levels of constant air density (i.e., isentropic surfaces). 
Its base becomes decoupled from the surface; just 
offshore, the vertical layer extends between 850 and 
500 hPa. The leading portion of the SAL layer typically 
takes 6–7 days to travel from the African coast to Bar-
bados, where the water vapor mixing ratio is conserved 
at very dry values (~5–10%) and the descent rate of 
the layer is estimated at 7 hPa per day. The associated 
dust throughout the SAL airstream is maintained and 
well mixed in the vertical as a result of weak turbulent 
mixing. By the time the leading edge of the SAL layer 
reaches the Caribbean (t
+7 days
), the lower portion of the 
SAL layer often penetrates well into the marine bound-
ary layer. At this time, much of the dust is impacting 
the surface.
 
Figures 9 and 10 present an overview of how the 
SAL-WEB can facilitate NWS-PR operations. Figure 
9 is a series of image panels captured between June 23 
and June 28, 2014; they track the leading edge of the 
SAL-related dust plume (yellow dashed lines) from its 
source in northwestern Africa (0623: 23 June) through-
out the north tropical Atlantic basin and eventually 
into the Gulf of Mexico. Of operational interest are the 

204
2017 NRL REVIEW
  |  
simulation, computing, and modeling
approaching and passing of the leading dust edge over 
Barbados (BB: 0624) and Puerto Rico (PR: 0625). Fig-
ure 10 shows a model output comparison between the 
current operational version of the Navy Aerosol Analy-
sis and Prediction System (NAAPS, upper left-hand 
panel) with a research testbed version (upper right-
hand panel) that includes the addition of the data from 
the Visible Infrared Imaging Radiometer Suite (VIIRS) 
on the Suomi National Polar-orbiting Partnership satel-
lite. The ground-based aerosol measurements within 
the Aerosol Robotic Network radiometric profile of 
aerosol-induced solar transmission
2
 at La Parguera, 
Puerto Rico (bottom panel), demonstrate how model 
results are improved by including the VIIRS data.
FIGURE 8
Vertical profile of the Saharan Air Layer (SAL) air mass as it is transported via convection and turbulent mixing from its hot 
desert source (right-hand side: Sahel/Saharan region) westward to the northwestern Africa coast, across the north tropical 
Atlantic basin, and finally through the Caribbean Islands. The color shading within the SAL layer represents the transition 
from coarse and large dust particles (red shades) to finer and more diffuse particles further west (yellow shades). The 
vertical brown curved arrows depict larger dust particles settling to the surface. Isentropic contours are annotated in blue
with associated theta labels. The marine boundary layer is shown sloping upwards from East to West.
FIGURE 9
True-color products, derived from Visible Infrared Imaging Radiometer Suite, provide a daily 
sequential look (June 23–28, 2014) at the SAL event propagating from northwestern Africa westward 
to the greater Caribbean. The bold dashed yellow arcs depict the leading edge of the SAL. PR and 
BB locate the positions of Puerto Rico and Barbados, respectively. For each panel, the linear NNW/
SSE oriented features of enhanced radiances across the open water represent sun glint.

205
simulation, computing, and modeling
 
 |  
2017 NRL REVIEW
 
This project was motivated in part during discus-
sions at a symposium on airborne dust and its impacts 
on human health, May 19–21, 2015, in Miami,
3
 and 
on how both scientific and health communities can 
better combine and coordinate efforts in studying SAL 
impacts on human health. The overarching goal is to 
better educate and prepare the Caribbean populace in 
mitigating exposure to SAL’s harmful dusty environ-
ment. Current and near-term plans for NRL-MMD 
include ongoing interactions with NWS-PR, the Carib-
bean Institute for Meteorology and Hydrology, and
Caribbean Aerosol–Health Network agencies to share 
environmental resources, with the goal of hosting a 
more comprehensive set of SAL-related sensing prod-
ucts into SAL-WEB. The website is publically acces-
sible; public feedback is encouraged via the SAL-WEB 
[http://www.nrlmry.navy.mil/SAL.html] feedback tab.
 
[Sponsored by NOAA] 
References

L. Akinbami and J. E. Moorman, “Asthma Prevalence, Health 
Care Use, and Mortality: United States, 2005–2009,” Natl. Health 
Stat. Rep. 32, 1–14 (2011).

B.N. Holben, T.F. Eck, I. Slutsker, D. Tanrés, J.P. Buis, A. Setzer, 
E. Vermote, J.A. Reagan, Y.J. Kaufman, F. Lavenu, I. Jankowiak, 
and A. Smirnov, “AERONET—A Federated Instrument Network 
FIGURE 10
Comparing Navy Aerosol Analysis and Prediction System (NAAPS) with the data assimilation (DA) from the Moderate 
Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Thickness (AOT*) (upper left-hand) versus the NAAPS 
MODIS + VIIRS AOT (upper right-hand) on June 26, 2014, where P.R. represents Puerto Rico. The lower panel is the 
Aerosol Robotic Network (AERONET) AOT plot over La Parguera in southwestern Puerto Rico. The vertical red dashed 
line indicates the corresponding time (18 GMT) with the model outputs. (*Within the figure, aerosol optical depth (AOD) 
and aerosol optical thickness (AOT) are used interchangeably.)
and Data Archive for Aerosol Characterization,” Remote Sens. 
Environ. 66(1), 1–16 (1998).
3
 J. Prospero and H. Diaz, “The Impact of African Dust on Air 
Quality in the Caribbean Basin,” Eos 97 (2016).
     
ª
Reactive Flow Modeling for 
Hypersonic Flight
G.B. Goodwin
1
 and E.S. Oran
2
1
Space Engineering Department 
2
The University of Maryland 
 
Introduction:
 
High-speed fluid dynamics is the 
study of fluid flow in the supersonic or hypersonic 
regimes, in which hypersonic typically refers to flow 
speeds of five times the speed of sound or greater. Re-
active flows may consist of chemically reacting species 
undergoing processes such as combustion, molecular 
dissociation, or ionization. Examples of high-speed 
reactive flows in the context of defense applications 
include the combustion of fuel and air in supersonic 
combustion ramjet (scramjet) engines and detona-

206
2017 NRL REVIEW
  |  
simulation, computing, and modeling
tion of fuel-oxidizer mixtures in detonation engines. 
Airbreathing propulsion systems use oxygen from 
the atmosphere for combustion as opposed to rocket 
engines that must carry oxidizer onboard. Vehicles 
using airbreathing engines benefit from decreased fuel-
mass and increased payload capacity. In the context of 
Department of Defense interests, airbreathing engines 
may be used to power extended range cruise missiles, 
deliver payload to low Earth orbit with single-stage-
to-orbit vehicles, and rapidly deploy personnel and 
materiel across the globe via hypersonic transports.
1
 
Combustion stability in hypersonic airbreathing en-
gines has been one of the predominant technical chal-
lenges in the design of a robust engine that is capable of 
operation across a wide range of altitudes and cruising 
speeds. For the Navy to develop these technologies for 
defense of the surface fleet, the ignition and combus-
tion processes in the engines powering hypersonic 
vehicles must be fully understood.
 
In addition to experimentation in ground test 
facilities and flight tests of proof-of-concept vehicles, 
modeling and simulation are used to increase fun-
damental understanding of the high-speed reactive 
fluid dynamics encountered in hypersonic engines. 
Accurately simulating these flows is a challenge due 
to the small timescales of the macroscopic flow and 
the chemical reactions and the large length scales of 
engines. Simplified chemical models that effectively 
model the physical characteristics of the combustion 
and detonation processes are required to reduce the 
computational expense of the simulations to a thresh-
old that is manageable using modern high performance 
computers. Despite these challenges, computational 
modeling allows researchers to resolve the physics of 
hypersonic propulsion systems at a high level of detail. 
This article presents results from a computational study 
of the acceleration of a turbulent flame and eventual 
transition of the flame to a detonation, in a thin chan-
nel filled with a highly reactive fuel-oxidizer mixture. 
The work was completed as part of a collaborative ef-
fort with the University of Maryland.
 
Shock-Focusing to Detonate Fuel-Oxidizer Mix-
tures: Pulse detonation engines and rotating detonation 
engines rely on the thrust generated by a detonation 
wave to propel a vehicle at supersonic and hypersonic 
speeds. To initiate the detonation wave, a spark is used 
to ignite a flame in a channel filled with a fuel-oxidizer 
mixture. Obstacles are placed in the igniter channel 
to perturb and accelerate the flame as it expands. The 
initially laminar flame accelerates to become a deflagra-
tion, or a turbulent flame traveling at a high subsonic 
speed. Eventually, the fuel-oxidizer mixture detonates. 
The deflagration-to-detonation transition (DDT) has 
been an active area of research for decades. In many 
cases, DDT must be prevented, such as in coal mines, 
but in others it must be controlled in time and space, 
such as in a detonation engine. The mechanism of DDT 
in a channel with obstacles, representative of the igniter 
in a detonation engine, was investigated computation-
ally.
2,3
 The channel dimensions are 0.32 cm in height 
and 21 cm in length. Figure 11 shows temperature 
contour plots at six consecutive timesteps of the two-
dimensional (2D) simulation, beginning with the initial 
condition of a laminar flame ignited by a weak spark. 
Expansion of the flame into the channel produces pres-
sure waves that reflect from the obstacles and channel 
walls. The pressure waves act like a piston, pushing the 
unburned gas ahead of the flame over the obstacles. As 
the flame propagates into the channel, it interacts with 
the reflected pressure waves and vortices shed from the 
obstacles. These interactions cause the flame to become 
turbulent and accelerate. A Rayleigh-Taylor fluid insta-
bility is evident at the turbulent flame front, where the 
fingers of low-density burned gas extend into the high-
density unburned gas. As the flame expands further 
FIGURE 11
Two-dimensional simulation of flame acceleration and deflagration-to-detonation transition in a channel 0.32 cm in height. 
Obstacle height is 0.032 cm. Time is shown in milliseconds in frame corners. Frame length is 3.2 cm and total channel 
length is 21 cm. Flame front is traveling toward right side of frame. Obstacles are numbered.

207
simulation, computing, and modeling
 
 |  
2017 NRL REVIEW
into the channel, pressure waves in the unburned gas 
coalesce into shockwaves that compress and pre-heat 
the unburned gas prior to combustion, as one can see 
by the increased temperature in the region ahead of the 
flame. The shocks reflect against the channel surfaces 
and collide with one another, interacting with the flame 
front, burned gas, and unburned gas. 
 
Shock collisions and reflections against chan-
nel surfaces deposit energy into the unburned gas at 
timescales much smaller than the acoustic timescale 
of the unburned gas. The rate of the energy deposition 
increases as the shocks become stronger. Eventually, 
this rapid increase in the rate of energy deposition is 
significant enough to detonate the unburned gas, as 
shown at 0.2708 milliseconds. To quantify the rate of 
energy deposition required for the detonation, a control 
volume analysis was performed on the volume of un-
burned gas where the detonation initiates, tracking the 
rate of internal and chemical energy deposition into the 
control volume during the shock collision and subse-
quent detonation. Figure 12 shows the energy rates plotted 
as a function of time. There is an increase in the rate of 
internal energy deposition into the control volume as the 
shocks collide, followed by a delay of 0.1 microseconds, 
then chemical and internal energy rates increase dramati-
cally as the gas detonates. Thus, detonation occurs as the 
result of a shock collision focusing a tremendous amount 
of energy in a small volume of unburned gas.
 
Figure 13 shows a three-dimensional (3D) simulation 
that uses the same initial conditions as the 2D case, per-
formed to verify that the shock-focusing DDT mechanism 
is independent of dimensionality. Although the time and 
distance into the channel at which DDT occurs differs 
slightly from the 2D case, detonation in the 3D case is 
initiated by the same mechanism. At 0.102 milliseconds, 
the unburned gas has detonated and the detonation wave 
begins to overtake the turbulent flame front. The detona-
tion wave is fully formed at 0.113 milliseconds, and a 3D 
transverse wave structure is visible along the detonation 
front.
FIGURE 13
Isosurfaces of fuel-mass fractions of 0.2, 0.5, and 0.8 show flame acceleration and DDT in 3D channel. 
Time in milliseconds is shown in frame corners. Obstacles are numbered.
FIGURE 12
Rate of energy deposition in control volume. 
Compression of unburned gas by the shock 
collision begins at (a). Detonation occurs at (b).

208
2017 NRL REVIEW
  |  
simulation, computing, and modeling
 
Significance: These calculations are used to exam-
ine the mechanism that causes DDT in a thin channel 
of a highly reactive fuel-oxidizer mixture. The interac-
tions between the acoustic waves, shocks, boundary 
layers, and channel walls result in the rapid accelera-
tion of the flame and initiation of a detonation due to a 
convergence of shocks on a small volume of unburned 
mixture. An understanding of the complex interactions 
in this system is essential to the design of stable and 
reliable detonation engines.
 
 
[Sponsored by the NRL Base Program (CNR funded) 
and ONR] 
References

D. Sziroczak and H. Smith, “A Review of Design Issues Specific 
to Hypersonic Flight Vehicles,” Prog. Aerosp. Sci. 84, 1–28 
(2016). 

G.B. Goodwin, R.W. Houim, and E.S. Oran, “Effect of Decreas-
ing Blockage Ratio on DDT in Small Channels with Obstacles,” 
Combust. Flame 173, 16–26 (2016). 

G.B. Goodwin, R.W. Houim, and E.S. Oran, “Shock Transition 
to Detonation in Channels with Obstacles,” Proc. Comb. Inst. 
36(2), 2717–2724 (2017).
     
ª

210
  
Mitigation of Spacecraft Communications Blackout via Microparticle Injection
211
  
LASCO: Pioneer of Space Weather
213
  
Slim-Edged Silicon Detectors: Advanced Nano-Fabrication Technology
215
  
Solar Coronal Power Spectra Modeling
Space Research and Satellite T
echnology

210
2017 NRL REVIEW
  |  
space research and satellite technology
Mitigation of Spacecraft 
Communications Blackout via 
Microparticle Injection
E.D. Gillman and W.E. Amatucci 
Plasma Physics Division 
 
Introduction and Motivation: Plasma discharges 
consist of positively charged ions, negatively charged 
electrons, and neutral gas particles. Complex, or 
“dusty,” plasmas contain a fourth species: charged 
microparticles or “dust grains.” When the dust grains 
interact with plasma particles, the dust grains become 
charged and thus subject to electrical and magnetic 
forces that lead to unique phenomena.  
 
There are many examples of naturally occurring 
dusty plasmas. Saturn’s rings and comet tails are com-
posed of microparticles suspended in plasma. Noctilu-
cent clouds formed by ice crystals in the Earth’s polar 
ionosphere are dusty plasmas. Due to the constant 
bombardment by meteors and the presence of debris in 
low Earth orbit, many other regions of the ionosphere 
are also considered dusty plasmas. Dust grains can 
often form as unwanted species in manmade plasmas 
such as semiconductor processing reactors. The mic-
roparticles can collect on these devices after processing, 
resulting in contamination defects that limit feature 
size and result in poor quality control. Dust grains also 
cause significant inefficiencies in plasma fusion reac-
tors.
 
Recent studies in the Plasma Physics Division 
of the U.S. Naval Research Laboratory (NRL) have 
focused on how the controlled release of dust grains 
could mitigate the radio blackout that affects spacecraft 
reentering the Earth’s atmosphere. 
 
The high velocity of spacecraft and frictional heat-
ing during atmospheric reentry causes a dense plasma 
layer to form around the vehicle. Electrons in the plasma 
layer block and attenuate electromagnetic (EM) radio 
waves, preventing the sending and receiving of telem-
etry, communications, and GPS navigation signals. In-
jecting microparticles to absorb a fraction of the plasma 
electron population may mitigate this problem (Fig. 1).   
 
Technical Approach: EM waves interact with plas-
mas differently, depending on the wave frequency and 
plasma electron density. A critical frequency known as 
the cutoff frequency is dependent on the density of free 
electrons in the plasma. At frequencies below the cutoff 
frequency, the free electrons in the plasma are mobile 
enough to react and reflect the incident EM wave. How-
ever, at frequencies above the cutoff frequency, the EM 
wave passes through the plasma with minimal reflection 
or power loss. By inserting microparticles and trans-
forming the plasma layer into a dusty plasma, a substan-
tial portion of the electrons become strongly bound to 
the dust grains. With the reduced free electron density, 
the plasma cutoff frequency is lowered. The electrons 
bound to the microparticles can no longer react to low 
frequency EM signals, and the signal may be able to pass 
through the previously impenetrable layer.
 
While experiments have shown that dusty plasmas 
are depleted of electrons, theory has predicted that the 
interaction of electromagnetic signals with charged 
microparticles may also act as a source of signal 
scattering.
1–4
 
 
FIGURE 1
Microparticle injection into the plasma layer surrounding a reentering spacecraft 
can increase transmission of communications signals, mitigating the radio com-
munications blackout effect.
1   ...   18   19   20   21   22   23   24   25   ...   28




Ma'lumotlar bazasi mualliflik huquqi bilan himoyalangan ©fayllar.org 2020
ma'muriyatiga murojaat qiling