The Shock and Gas Dynamics Laboratory performs research on thermal-fluid dynamics
problems with specialites in optical diagnostics and explosively-driven flows. The
research laboratory is supervised by Dr. Michael Hargather. The lab employs both
graduate and undergraduate students, who work with Dr. Hargather on funded research
projects.
Research overview
The primary research interests of the SGDL include:
Explosively-driven fragmentation: fragment size, velocity, shape distribution measurement,
optical arena test characterizations, fragment aerodynamics
Optical diagnostic development: 3D shock wave and fragment tracking, focusing schlieren,
background oriented schlieren (BOS), high-speed imaging in harsh environments
General fluid dynamics and high-speed gas dynamics
Current research is funded by:
Sandia National Laboratories
Defense Threat Reduction Agency (DTRA)
US Air Force and the Air Force Office of Scientific Research (AFOSR)
Lawrence Livermore National Laboratory
National Nuclear Security Agency
Optical Diagnostics Overview
The SGDL specializes in the application and development of optical diagnostics for
studying refractive flowfields. Any flow with refractive index differences originating
from temperature, pressure, density, or species gradients can be visualized and studied
with these techniques. The general class of techniques was recently reviewed in a paper coauthored by Dr. Hargather.
Schlieren imaging is the standard laboratory method for visualizing refractive index
gradients. The technique uses precision lenses or mirrors to create a region in which
refractive index gradients can be directly imaged. This technique produces images
which clearly show shock waves, expansion fans, turbulent gases, and small variations
in refractive index. A schlieren image of a small firework explosion is shown here,
with the shock wave and product gases produced clearly visible.
Retroreflective shadowgraphy is used to visualize the second-derivative of refractive index fields in the imaged
area. This technique reveals sharp changes in refractive index, allowing visualization
of shock waves and turbulent structures as well as contact surfaces. The image shown
is of a sabot-launched rifle projectile, showing the oblique shock waves on the projectile
and sabot pieces, circular muzzle blast, and product gas cloud. The retroreflective
shadowgraph system was designed to be used outdoors and provides detailed visualizations
at sizes in excess of 1m field of view in outdoor conditions.
The background oriented schlieren (BOS) technique is a digital method used to visualize
refractive disturbances via their distortion of a background pattern. The technique
is used here to visualize large-scale explosion phenomena like the car bomb shown. High-speed images of the explosion process are
recorded, then processed using a range of digital image processing techniques to reveal
locations where the background has apparently changed due to a refractive disturbance.
The processing method here visualizes the shock wave from the explosion as well as
fragments produced. The techniques is optically equivalent to schlieren and has a
broad range of applications across the laboratory and field scales.
The optical techniques used by the SGDL can be applied in many unique methods to extract
quantitative information from density fields, to object motions, to measurement of
velocity fields. One example is the schlieren image velocimetry (SIV) technique which
is used to measure velocity fields similar to the more conventional approach of particle
image velocimetry (PIV). The SIV technique tracks "particles" that are the naturally-occurring
refractive-turbulent eddies in the flow which are made visible through schlieren imaging.
A sequence of schlieren images are recorded then image processing tracks the motion
of the flow features to determine the local velocity fields. This technique works
well for turbulent flows where density, temperature, or species gradients exist, as
in compressible and combustion flows. By using the naturally-occurring refractive-turbulent
eddies, we are able to obtain seedless velocimetry with SIV.
Facilities
The SGDL laboratory space is located at the Energetic Materials Research and Testing Center (EMRTC), located adjacent to campus in Socorro, NM. The laboratory includes EMRTC Lab 4
and Lab 7, which are attached to the main EMRTC building. These labs are used for
the development of optical techniques and small-scale explosive research. Additional
laboratory space is also maintained on the EMRTC Field Lab for larger-scale explosive
testing including, ballistic research, rocket testing, and free-air-blast research.
The EMRTC field lab includes over 40 square miles of space with more than 30 individual
test sites to conduct explosive research and testing. The EMRTC is a part of New
Mexico Tech and assists with all energetic testing in the SGDL.
Publications
For copies of Dr. Hargather's publications, please check here.
For APS Division of Fluid Dynamics Gallery of Fluid Motion posters, check here.
Current and previous students
The SGDL currently employs 7 graduate students and 2 undergraduate students.
Graduate students that have previously worked in the SGDL include: