TECHNOLOGY AREA(S): Air Platform

ACQUISITION PROGRAM: PMA-299 (ASW) H-60 Helicopter Program

OBJECTIVE: Develop an innovative software tool capable of performing a rigorous statistical analysis to accurately predict distribution of electromagnetic (EM) fields inside and around large and complex cavities.

DESCRIPTION: Electromagnetic fields inside and around aircraft cockpits and cabins present a hazard to both personnel and equipment, such as avionics systems. The Department of Defense (DoD) and the U.S. Navy in particular have been aware of the effects of long-time exposure to EM radiation [Ref 1] and the need for its mitigation. The Navy seeks development of a modeling and simulation software tool capable of predicting the distribution of EM fields in electrically large cavities that are complex both in geometry and materials. Analyzing EM behavior in electrically large cavities has proven to be a difficult task. Certainly, canonical methods do not work since the cavities in question do not have canonical geometries. High-frequency methods (e.g., physical optics, physical theory of diffraction, shooting and bouncing rays, uniform theory of diffraction), by their very nature, do not work well in an interior environment. Exact-physics approaches do work well, but they require unacceptably long run times and significant computational resources making them unsuitable for routine use. However, recent advances in high-order methods, both in the time domain and frequency domain [Ref 2-4] as well as high-order geometry representation [Ref 5-6] and high-order boundary conditions [Ref 7-9], show potential and promise for fast turnaround for the prediction of electrically large electromagnetic problems of Electromagnetic Environmental Effects (E3) interest to the Navy.

A more robust and computationally efficient code is desired to accurately predict the EM fields inside an aircraft model for which the geometry, materials, and electrical systems are well specified. This code should link directly with detailed computer-aided design (CAD) models and initial graphics exchange specification descriptions through a graphical interface to generate high-order grids with resolution appropriate to both EM accuracy and geometric fidelity requirements. The choice of methods, either time-domain or frequency-domain, to accurately compute the EM fields of cavities should also make optimal use of the latest computing architectures, including graphical processing unit (GPU) clusters, in order to minimize the time required for each run. A reduction in run time by a minimum of one order of magnitude while not compromising on accuracy is required. For example, as a demonstration, the Navy would like to reduce execution time for scattering by a cylindrical cavity of diameter 20 lambda and height 60 lambda for 0 to 90 degree monostatic sweep to well under an hour in a cluster of 128-256 cores.

A graphical user interface (GUI) should intelligently guide the user through any projected application. The design of the GUI should take into account ISO/IEC 25022:2016 usability metrics.

PHASE I: Select and demonstrate capabilities of one or more high-order computational electromagnetics (CEM) codes, including computational resource requirements and accuracy of EM field predictions in cavities of length of at least 100 lambda. Demonstrate CAD/ Initial Graphics Exchange Specification interfaces and high-order gridding tools for the most promising high-order CEM code. The selected code(s) should be able to transition to users for routine use in workstation environments (48 cores) to moderate size, high-performance computing clusters of a few thousand cores. Develop a detailed outline of the requirements and the plan to meet them in Phase II.

PHASE II: Implement the tool(s) with a GUI for problem setup and results analysis. Ensure that the GUI design emphasizes ease-of-use in the context of configuring, visualizing, and executing on arbitrary complex targets with large cavities. Port codes on clusters of central processing units and CPU/GPUs. Test and demonstrate the resulting codes on cases of interest.

PHASE III DUAL USE APPLICATIONS: Refine the methodology and tool developed in Phase II either alone or in partnership with another company and transition to interested DoD and commercial users. This general tool is applicable to a wide range of civilian problems where EM systems are operating within enclosures such as equipment within an enclosed industrial building, a hospital, an automobile, or an aircraft.

REFERENCES:

1. Alpert, B., Greengard, L, and Hagstrom, T.� �Nonreflecting boundary conditions for the time-dependent wave equation�. Journal of Computational Physics, 2002, 180, pp. 270-296. doi:10.1006/jcph.2002.7093

2. Berenger, J.� �A perfectly matched layer for the absorption of electromagnetic waves�. Journal of Computational Physics, 1994, 114(2), pp. 185-200. https://doi.org/10.1006/jcph.1994.1159

3. Darrigrand, E. and Monk, P. �Combining the ultra-weak variational formulation and multilevel fast multiple method�. Applied Numerical Mathematics, 2012, 62(6), pp. 709-719. https://doi.org/10.1016/j.apnum.2011.07.004

4. Hagstrom, T. and Lau, S. �Radiation boundary conditions for Maxwell's equations: a review of accurate time-domain formulations.� Journal of Computational Mathematics, 2007, 25(3), pp. 305-336. https://www.jstor.org/stable/43693369

5. Hesthaven, J. and Warburton, T. �Nodal Discontinuous Galerkin Methods: algorithms, analysis, and applications�. Springer, 2007. ISBN 978-0-387-72067-8. http://www.springer.com/us/book/9780387720654

6. Huttunen, T., Malinen, M., and Monk, P. �Solving Maxwell's equations using the ultra weak variational formulation�. Journal of Computational Physics, 2007, 223(2), pp. 731-758. https://doi.org/10.1016/j.jcp.2006.10.016

7. NAVAIR Integrated Battlespace Simulation and Test. (2013). �Hazards of Electromagnetic Radiation�.� http://www.navair.navy.mil/tande/ibst/03_E3/hero_herp_herf.html

8. Sanjaya, D. and Fidkowski, K. �Improving High-Order Finite Element Approximation Through Geometrical Warping.� AIAA Journal, Vol. 54, No 12 (2016), pp. 3394-4010.� https://doi.org/10.2514/1.J055071

9. Shephard, M., Flaherty, Joseph E., Jansen, K., Li, X., Luo, X., Chevaugeon, N., Remacle, J., Beall, M., and O'Bara, R. �Adaptive mesh generation for curved domains�. Applied Numerical Mathematics, 2005, 52(2-3), pp. 251-271. https://doi.org/10.1016/j.apnum.2004.08.040

KEYWORDS: Electromagnetic Environmental Effects (E3); Computational Electromagnetics; Modeling and Simulation; Cavity Radiation; High-Order Methods; Cavity E3 Statistics