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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<title>Chonglin Zhang - Research</title>
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<h2>Research(to be updated)</h2>
<div id="bio">
<h3>Research Interests</h3>
<ul>
<li>Kinetic theory, Rarefied gas dynamics, Molecular simulation</li>
<li>Direct simulation Monte Carlo (DSMC) stochastic particle method</li>
<li>Hypersonic non-equilibrium flow, Aerothermodynamics</li>
<li>Plasma physics, Particle-in-cell (PIC) method</li>
<li>Computational fluid dynamics (CFD), Fluid mechanics, Thermal science</li>
<li>High performance computing (HPC)</li>
</ul>
<h3>Direct Simulation Monte Carlo (DSMC) Numerical Algorithms and Code Development</h3>
<ul>
<li>
<h4>A Cartesian Grid DSMC Simulation Code with Adaptive Mesh Refinement</h4>
<p style="text-align: justify">
<p style="text-align: center">
<img src="img/probe_alpha=10_flow_Ttran_Ch_grid.png" width="500 px"></img>
<br><br>
<lab><emph>Fig. 1(a)</emph></lab>
<cap>Flow field temperature and surface heating rate of a Mach 20.2 flow
over a Planetary probe, to demonstrate the capability of the DSMC code.
</cap>
</p>
<p style="text-align: center">
<img src="img/probe_simulation/alpha=0_rho_with_shift.png" width="500 px"></img>
<br><br>
<lab><emph>Fig. 1(b)</emph></lab>
<cap> Flow field density around the probe in the symmetric plane, with 0
degree angle of attack. Density is normalized by the free-stream value.
</cap>
</p>
<p style="text-align: center">
<img src="img/probe_simulation/alpha=0_with_sting.png" width="500 px"></img>
<br><br>
<lab><emph>Fig. 1(c)</emph></lab>
<cap>The surface heat transfer coefficient along the probe surface (in the
symmetric plane).
</cap>
</p>
<p style="text-align: center">
<img src="img/probe_simulation/alpha=10_rho.png" width="500 px"></img>
<br><br>
<lab><emph>Fig. 1(d)</emph></lab>
<cap>Flow field density around the probe in the symmetric plane, with 10
degrees angle of attack. Density is normalized by the free-stream value.
</cap>
</p>
</p>
</li>
<li>
<h4>Robust and Efficient "Cut-Cell" Algorithms for DSMC Simulation with
Complex Geometries</h4>
<p style="text-align:justify">
<p style="text-align: center">
<img src="img/cutcell_whole_process.png" width="600 px"></img>
<br><br>
<lab><emph>Fig. 2</emph></lab>
<cap>The whole process of the "cut-cell" algorithms to handle the
decoupled Cartesian grid flow field mesh and triangulated complex surface
mesh.
</cap>
</p>
<p style="text-align: center">
<img src="img/MIR_flowfield_Mach=20.png" width="500 px"></img>
<br><br>
<lab><emph>Fig. 3</emph></lab>
<cap>Hypersonic flow over a geometry resembling the MIR space state to demonstrate the capability of the
"cut-cell" algorithms to handle very complex geometries.
</cap>
</p>
</p>
</li>
</ul>
<h3>Modeling Hypersonic Non-equilibrium Flows</h3>
<ul>
<li>
<h4>Numerical Assessment of Existing DSMC Models</h4>
<p style="text-align: justify">
<p style="text-align: center">
<img src="img/bluntwall_T_AMR.png" width="550 px"></img>
<br><br>
<lab><emph>Fig. 4</emph></lab>
<cap>Temperature field of a Mach 15 flow over a vertical blunt wall.
Adaptive mesh refinement is used to automatically refine the flow field mesh
to be consistent with the local mean free path.
</cap>
</p>
<p style="text-align: center">
<img src="img/N2_SSL_with_dissociation_no_dissociation_Temp.png" width="400 px"></img>
<br><br>
<lab><emph>Fig. 5</emph></lab>
<cap>Comparison of different modes of temperature (translational, rotational,
vibrational) along the stagnation line for <b>Fig. 4</b> flow configuration. The
results from different DSMC dissociation models are compared (note the results
in this figure are at a higher free stream temperature).
</cap>
</p>
</p>
</li>
<li>
<h4>Nonequilibrium-Direction-Dependent (NDD) Rotational Energy Exchange Model</h4>
<p style="text-align:justify">
<p style="text-align: center">
<img src="img/N2_Shock_T=28_MD_DSMC_1.png" width="400 px"></img>
<br><br>
<lab><emph>Fig. 6</emph></lab>
<cap>Comparison of shock wave profiles between DSMC NDD model and
molecular dynamics (MD) data. The upstream temperature of the shock wave is
T1=28K.
</cap>
</p>
<p style="text-align: center">
<img src="img/N2_Shock_T=300_MD_DSMC_1.png" width="400 px"></img>
<br><br>
<lab><emph>Fig. 7</emph></lab>
<cap>Comparison of shock wave profiles between DSMC NDD model and
molecular dynamics (MD) data. The upstream temperature of the shock wave is
T1=300K.
</cap>
</p>
<p style="text-align: center">
<img src="img/cell-avg-rdfs.png" width="650 px"></img>
<br><br>
<lab><emph>Fig. 8</emph></lab>
<cap>Comparison of the rotational energy distribution function at selected
points within the T1=28.3K shock wave between DSMC, MD results and the
Boltzmann distribution..
</cap>
</p>
</p>
</li>
</ul>
<h3>Applications of the DSMC method</h3>
<ul>
<li>
<h4>Modeling Micro/Nano-scale flow in the transition regime</h4>
<p style="text-align: justify">
<p style="text-align: center">
<img src="img/Case_12_Kn=0.1_0.3_0.8_1_Orient_11_revised.png" width="600 px"></img>
<br><br>
<lab><emph>Fig. 9</emph></lab>
<cap>Flow field velocity and surface pressure of a 5 m/s low Reynold
number flow passing a nano-scale cluster at different Knudsen numbers.
</cap>
</p>
</p>
</li>
<li>
<h4>DSMC Simulation of Jet Flows</h4>
<p style="text-align: justify">
<p style="text-align: center">
<img src="img/jet/jet_flow_T_V_1.png" width="600 px"></img>
<br><br>
<lab><emph>Fig. 9</emph></lab>
<cap>Temperature field around a jet. The jet enters the simulation domain
at the left boundary. A normal shockwave is developed near the jet exit,
in addition to expansion fans and oblique shocks. The position of the
normal shock could be clearly observed by looking at the temperature and
velocity profiles along the jet centerline.
</cap>
</p>
</p>
</li>
</ul>
</div>
<br>
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