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Weapons and Materials Research Directorate Research Areas

Ballistic Modeling and Effects

Electromagnetic Effects in Ballistic Research

Advisor:  JD Powell                            

Key words: electrodynamics, plasma processes (physics), electromagnetic propulsion, ballistics

This opportunity is broadly associated with theoretical and experimental research in electrodynamics and plasma physics, with applications in several areas relevant to ballistic research. Theoretical work emphasizes the development of numerical and analytical models, which can be used to study various electromagnetic effects; while experimental aspects are basically diagnostic. A close collaboration between experimental and theoretical work is also encouraged.

General types of problems under investigation include:

  • current and energy transport in electromagnetic railguns.
  • the investigation of plasma injectors in electrothermal guns.
  • theoretical and experimental studies to evaluate the effects of electromagnetic fields and forces on the motion of solid conductors.
  • the effect of electromagnetic fields on the stability of metallic jets.

These problems are relevant to Army interest in electromagnetic propulsion, electrothermal propulsion, and electromagnetic methods of disrupting threats to armor.

Available laboratory facilities consist of modern high-speed computers, several capacitor-based power supplies, and a wide range of electrical and materials diagnostic equipment.

Interested applicants are encouraged to propose any research within the above guidelines.

Equation-of-State Modeling

Advisor: SB Segletes        

Key words: equations of state, lattice vibrations, crystal lattices, models

Recent research has attempted to tie together models and data, regarding the so-called universal atomic lattice potential, with a thermodynamic approach that uses lattice vibration theory. The result has been an equation-of-state of general form, predicting both compressive and thermal effects of crystalline lattices, and cast in terms of a single independent variable: the characteristics temperature of the lattice (related to the vibrational frequency spectrum).

In addition to providing excellent predictions of cold- and shock-compression for a variety of metals, the formulation also matches the universal lattice expansion potential. By ignoring higher order terms and/or taking limiting cases, the formulation has been shown to reduce to various historical models on the subject, including those of Slater, Dugdale, and MacDonald; the free-volume theory; and the harmonic theory of lattice vibrations.

Further research opportunities exist on the topic of equation-of-state modeling for crystalline solids. Examples include:

  • theoretical underpinnings of a general equation-of-state form for crystalline solids.
  • thermodynamic constraints associated with various aspects of thermodynamic stability.
  • lattice-vibration theory.
  • lattice elasticity under large volumetric strains.

Numerical Modeling of Reacting Multidimensional Gas/Solid Flows

Advisor: M Nusca                             

Key words: fluid dynamics, particle dynamics , h ypergolic fuels , numerical simulation, droplet combustion, solid propellant, reacting flow, turbulence, parallel computing

This opportunity involves the development and application of computational fluid dynamics (CFD) codes that solve the three-dimensional Navier-Stokes equations for chemically reacting gases and solid particles. Applications for CFD codes include flows in which all or some of the following effects are important: solid propellant combustion, gas-phase hypergolic combustion, turbulence, vorticity, droplet combustion, high-temperature plasmas, and radiation.

Emphasis is placed on performing original research and on solving practical problems such as those encountered in modeling novel solid propellant gun charges, as well as rocket engines for next-generation missile systems. We encourage the development of original CFD codes and the enhancement of current ARL codes. Computer resources include PC and SGI workstations, as well as SGI, IBM, and CRAY mainframes. ARL is the site of one of the DOD’s Major Shared Resource Centers for high-performance computing. This vast array of computing resources makes the performance of complex CFD simulations feasible.  Publications in the open literature and the presentation of papers at appropriate meetings and conferences are encouraged.

References
Nusca MJ, et al: Journal of Thermophysics and Heat Transfer 16(1): 157, 2002.

Nusca MJ, et al: Journal of Advanced Oxidation Technologies 4(3): 271, 1999.

Nanoscale Molecular Electronics and Sensors

Advisor: SP Karna             

Key words: molecular electronics, molecular sensors, nanoelectronics, nanodevices, quantum dots and wires, nanophotonics materials, single electron transistor, quantum mechanical theory, surface probe microscopy

This research opportunity focuses on developing a fundamental understanding and functional prototypes of molecular and quantum electron devices for applications in nano-electronics and sensors. Research involves developing device concepts, molecular and quantum architectures, and theoretical and experimental characterization of electron transport and quantum conductance of molecular-scale basic electron device elements.

Theoretical and experimental investigations are performed to understand (1) physical and chemical mechanisms for controlled transport of electron, static, and dynamic electrical response; mechanism and control of current switching, current amplification, and charge retention in molecular electron devices; (2) dynamics of electron transport at the molecule-solid interface; and (3) operation and performance of three-dimensional molecular-scale nano-electronic device architectures and circuits.

The nanosensor research focuses on developing nanoscale molecular sensors for real-time electrical detection of chemical and biological agents. The research involves theoretical and experimental investigation of electrical properties of biotic-abiotic interface, chemical/biological to electrical transduction mechanisms, electrical response of molecule-integrated nanoscale devices, chemical and biological gating of field effect transistors, and interface between molecular and microscopic devices.

A major part of this work focuses on developing and establishing test and evaluation techniques, criteria, and metrics for characterizing and validating molecular-scale nano-electronics and sensor devices. State-of-the-art computational and experimental facilities are available. This research is performed in close collaboration with other teams within ARL and in other DOD laboratories.

References
Woo R, Pati R, Karna SP: Applied Physics Letters 81: 1872, 2002.

Pati R, Karna SP: Chemical Physics Letters 351: 301, 2002.

Theory and Modeling of Nanophotonic Materials

Advisor:  SP Karna                             

Key words: molecular electronics, molecular sensors, nanoelectronics, nanodevices, quantum dots and wires, nanophotonics materials, single electron transistor, quantum mechanical theory, surface probe microscopy

This research focuses on developing theory, computational techniques, and their applications to model electro-optical (EO) and nonlinear optical (NLO) materials. Theoretical methodologies include first-principles quantum mechanics and molecular dynamics simulations. Calculations are performed to investigate the origin and mechanisms of EO and NLO responses; evolution of properties with the size and geometry; and the relationships between chemical, electronic, and geometrical structures and the EO and NLO properties of nanoscale materials.

Materials of interest include functional organic molecules and nanosized atomic clusters of Si, Ge, III-V, and II-IV materials. Excellent facilities exist for algorithm development, testing, and conducting high-performance computations on nanoscale NLO materials.

This research is performed in close collaboration with the experimental groups within ARL, Natick Solider Center, and other DOD laboratories.

Reference
Karna SP: Nonlinear Optics 27: 75, 2001