progress on aerospace applications of the nimrod code · alfonso g. tarditi nasa johnson space...

Progress on Aerospace Applicationsof the NIMROD Code

Alfonso G. Tarditi

NASA Johnson Space Center, Houston, TX&

University of Houston-Clear Lake, Houston, TX

http://www.go2pdf.com

Plasma MHD Aerospace Applications

Chemical/MHD Propulsion

Lunar Environment

Electric Propulsion

Plasma Aerodynamics

Lightning

MHD/Chemical Prulsion

Plasma-Spacecraft


Introduction

Application interests for MHD simulation in aerospacetechnology• MHD Augmented Propulsion (UHCL)• RF Magnetized Plasma Sources, Atmospheric Plasma

Torches (Propulsion, Re-entry plasma) (UHCL/JSC)• Plasma Actuator/Airfoil for Hypersonic Flight (UHCL)• Plasma Actuator/Airfoil for Hypersonic Flight (UHCL)• FRC-based Electric Propulsion (Fusion/Propulsion)• Lightning Stroke Simulation (JSC)• Magnetic Reconnection (UHCL)


Introduction

NIMROD code developments: latest and in progress• Upgrade of version 3.2.4 with external arrays (n,V,p,B and

grid) input, sources and 0-D neutrals• Externally defined, initial resistivity profile• Grid pre-processor generator for general, curved boundaries• Grid pre-processor generator for general, curved boundaries


Current Developments:Lightning Stroke Plasma Channel


Lightning Stroke Plasma Channel: The Big Picture

Triggered lightning, cloud-to-ground scenario


Launch of ARES I-


Visualization of the Electric Field Enhancement

[Godfrey, 1970]


Model Assumptions

• Attachment already occurred• Lighting stroke with established return current path• Lightning channel path simulated with a given initial density and

temperature distribution, providing a lower resistivity path• Vertical electric field to support the discharge


2D Simulation Domain

x

y


2D Simulation Domain: Gridding Example


y

Higher Resistivity

2D Initial Condition: Plasma Channel

x

Lower Resistivity

Higher Resistivity


3D Simulation Domain

z

r


Further Developments: Swept Stroke

Swept arc channel: current density in region 1 is larger (shorter path) thanin region 2 [Larsson, J. Phys. D: Appl. Phys. 33, 1876 (2000)]


Further Developments: Swept Stroke (II)

Ligthning swept stroke simulation on an aircraft surface [Larsson, J. Phys.D: Appl. Phys. 33, 1876 (2000)]


0-D Plasma-Neutral Model

• Uniform neutral gas component (with given density, flowvelocity and temperature)

• NIMROD equations include plasma-neutral interaction viadensity, momentum and temperature sources

• In progress: time-dependent 0-D Neutral Gas Equations


( ) nSn n D nt

∂+∇ ⋅ = ∇ ⋅ ∇ +

∂V

pt

∂ + ⋅∇ = × −∇ −∇ ⋅ ∇ + ∂

VV V V J V SB

0-D Plasma-Neutral Model (II)

Sources in the n, V, T NIMROD Eqs.

pt

+ ⋅∇ = × −∇ −∇ ⋅ ∇ + ∂ VV V J V SB

11 Tn T p S

tnT Q

γ γ∂ + ⋅∇ = − ∇ ⋅ −∇ ⋅ + + − ∂ −

V V q


n a ioniz e a recomb eS n·n ·v n·n ·vσ σ= −

0-D Plasma-Neutral Model (III)

• For given neutral atom density na and ionization andrecombination cross sections the source/sink term in thecontinuity equation is given by

( )v a collS mn = −V V

• The momentum source term can be expressed in term of the totalelastic (polarization scattering) and anelastic (ionization,recombination, charge exchange) collision frequencies in theform


• The time evolution neutral atom density na can be tracked from

0-D Plasma-Neutral Model (IV)

( )a a e recomb ionizd n n nvd t

σ σ= −

• Similar (0-D) fluid equations can be written for the neutralmomentum and temperature

• Currently the “closure” for the neutral model is simplyVa=constant


Ongoing Applications

• Magnetic nozzle flow• De Laval Magnetic Nozzle• FRC Plasmoid formation in flowing plasma


Plasmoid Thruster Experiment (PTX)

PTX Schematic (NASA MSFC/U. Alabama)


Plasma Flow in Magnetic Nozzle

• The plasma currents in the nozzle: physical analysis andestimates

• Perturbation of the external magnetic field: qualitative picture• Reconnection patterns and detachment: physical picture

Magnetic NozzlePlasma Flow


De Laval Magnetic Nozzle NIMROD Simulation

Mach # contours in t=0

t=0

r

z

r

Density contours

t=0.9 µs

z


t=170 ns

t=18 ns

t=0 r

z

De Laval Magnetic Nozzle NIMROD Simulation

Time evolution of Mach # contours

t=900 ns

t=660 ns


Simulation of Plasmoid Formation in the Nozzle

NIMROD Simulation: density contours and field lines withinduced translating plasmoid in a 10 m long magnetic nozzle


Simulation Hardware

“Columbia” at NASA-Ames: 23 SGI® Altix™ Itaniunm clusters, 14,336Total Cores 88.88 teraflop/s theoretical peak


Conclusions

• MHD/NIMROD has applications in the aerospace sector• 0-D Plasma-neutral interaction model supports a larger spectrum

of applications• NIMROD simulations set to explore innovative propulsion

configurations

progress on aerospace applications of the nimrod code · alfonso g. tarditi nasa johnson space...

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