High-fidelity electromagnetic modeling of large multi-scale naval structures

Transcription

1 High-fidelity electromagnetic modeling of large multi-scale naval structures F. Vipiana, M. A. Francavilla, S. Arianos, and G. Vecchi (LACE), and Politecnico di Torino 1

2 Outline ISMB and Antenna/EMC Lab overview Electromagnetic virtual prototyping: background Topics of interest High-fidelity multi-scale electromagnetic tool Realistic test cases Conclusions and references 2

3 (ISMB) is a non for profit research center founded in 2000 by Politecnico di Torino and Compagnia di San Paolo. ISMB operates in the ICT field with special focus on wireless technologies, participating with companies in the overall innovation process.

4 Model of Operation

5 Technology Readiness Levels 1. Basic principles observation 2.Technology concepts University ISMB 3. Analytical and experimental proof of concept 4. Component/ subsystem validation in lab 5.System/ subsystem validation in relevant environment 6. System/ subsystem prototyping in relevant environment Industry 7. System prototype demonstration in operational environment 8. Actual system completed 9. Actual system mission proven

6 ISMB research labs All ISMB research labs are managed in partnership with Politecnico di Torino Antenna and EMC Photonics Broadband Wireless Information Systems and Security Short Range Wireless Technologies Satellite Navigation (GPS, Galileo) Miniature Electronic Design System Integration and Applications 6

7 LACE: oratory (1) The (LACE) was created in 2002 as one of the High Quality Laboratory of the Electronics Department of Politecnico di Torino. The LACE offers a world-class expertise in cutting-edge experimental, numerical, and theoretical aspects of antennas, electromagnetic compatibility (EMC), applied electromagnetics, and EM propagation modeling, as well as service to national and international companies with professional consulting and partnership in applied research. The activities of LACE deal with study, design, prototyping and testing of various kinds of antennas, such as antennas for fixed and mobile communications, arrays, printed antennas, reflectarrays, miniaturized antennas, RFID, reconfigurable antennas, metamaterials. 7

8 LACE: oratory (2) The facilities for antenna testing consist of an anechoic chamber for microwave and mmwaves (above 1.5 GHz), with instrumentation for measurements up to 70 GHz, an outdoor antenna test range up to 20 GHz, a spherical near field test range (up to 40 GHz) in a larger anechoic chamber (operating above 700 MHz). 8

9 LACE: oratory (3) The LACE has also a strong expertise in Computational Electromagnetics (CEM), and it has developed several high performance algorithms for computer-assisted design, antenna optimization and synthesis, electromagnetic virtual prototyping, diagnostic tools associated to measurement systems. 9

10 Electromagnetic virtual prototyping: background (1) Frequency domain full wave analysis of arbitrary 3D bodies Maxwell Partial Differential Equations (PDE) are solved with a Boundary Element Method (BEM) where the unknowns are on body surfaces only BEM is the winning technology for large and complex structures such as in naval, aerospace, satellite, and antenna problems Vendors of finite element tools (volume equations) are introducing surface techniques to be able to handle large and complex problems 10

11 Electromagnetic virtual prototyping: background (2) Formulation: Integral Equation (IE) Unknown: field/current on the surface Discretization of IE into a linear system through the Method of Moments (MoM): - the geometry surface is discretized with triangular cells (mesh) - the unknown is described as linear combination known Rao-Wilton-Glisson (1) (RWG) basis functions, defined on the triangular cells source Discretization Solution Geometry surface Triangular mesh Surface current Solution of the linear system through a fast iterative method (e.g. Multi Level Fast Multiple Algorithm - MLFMA) The radiated field (near and far), the antenna circuit parameters, the Radar Cross Section (RCS),... are evaluated as post processing from the solution (1) S.M.Rao, D.R.Wilton, A.W.Glisson, Electromagnetic Scattering by Surface of Arbitrary Shape, IEEE Trans. on Antennas and Propagation, Vol.AP-30, No.3, pp , May

12 Topics of interest: (electrically) large structures with dense meshes complex geometries with large number of unknowns per wavelength non-uniform mesh cell sizes broadband applications low frequency (e.g. VLF, LF,...) Topics of interest Typical examples: antennas and arrays antenna placement on complex platform scattering from complex structures Critical for standard solution schemes (sometimes unable to find a solution) 12

13 Reduction of the gap between the initial mechanical CAD model and the usable mesh model (reduced cleanup phase engineering time decrease) Human cleaning of the original CAD High fidelity modeling (1) Several man-days to clean the geometrical details High fidelity model (original CAD) Low fidelity model 13

14 Only one mesh model for a wide range of frequencies (wide band and time domain phenomena analysis, model reusability) Better accuracy (return loss, near-field) Efficient virtual prototyping High fidelity modeling (2) Many details foreign to EM analysis increase of no. of unknowns and computational requirements Strong multi-scale problem more difficult to handle than a problem with the same number of unknowns but without details 14

15 High fidelity modeling (3) Solution: EM tool user-friendly analysis of antenna placement on realistic platform able to analyze structures rich of fine details together with possibly large smooth sections and large overall sizes with computational requirements comparable to the corresponding low-fidelity model able to converge with multi-scale problems High-fidelity multi-scale electromagnetic tool 15

16 High-fidelity multi-scale EM tool: general scheme Mixed-frequency problem 1 Multi-scale organization of the initial mesh (multi-level grouping) 2 The Multi-Resolution (MR) basis is employed on the DETAIL level meshes where the cell size << λ Low frequency problem The generalized RWG basis plus the Incomplete LU (ILU) preconditioner is employed on the COARSE level mesh (last level) where the cell size is quasi-nyquist (λ/4-λ/8) High frequency problem 16

17 High-fidelity multi-scale EM tool: cell grouping scheme (1) Mesh level 1 Same color = same cell Detail level mesh Cell size << λ MR basis employed 17

18 High-fidelity multi-scale EM tool: cell grouping scheme (2) Mesh level 2 Detail level mesh Cell size << λ MR basis employed 18

19 High-fidelity multi-scale EM tool: cell grouping scheme (3) Mesh level 3 Detail level mesh Cell size << λ MR basis employed 19

20 High-fidelity multi-scale EM tool: cell grouping scheme (4) Mesh level 4 last level λ/4 λ/8 Coarse level mesh Quasi-Nyquist cell size (λ/4-λ/8) Generalized RWG basis employed plus ILU preconditioner 20

21 Numerical results: Low fidelity ship model (1) No. of unknowns = 47,163 max =λ/15 min =λ/200 voltage gap 10 λ 21

22 Numerical results: Low fidelity ship model (2) No. of iterations of the solver to get the unknown surface current with the required accuracy this approach 22

23 Numerical results: Low fidelity ship model (3) Surface density current (dba/m) Freq.= 50 MHz 23

24 Numerical results: High fidelity ship model (1) voltage gap 10 λ No. of unknowns = 113,556 max =λ/15 min =λ/200 24

25 Numerical results: High fidelity ship model (2) this approach 25

26 Numerical results: High Fidelity Ship Model (3) No. of unknowns = 621, λ 26

27 Numerical results: High Fidelity Ship Model (4) Memory occupation Z strong (0.2λ) matrix 15.8 GB LU matrix 1.2 GB GIFFT matrices 1.0 GB Total RAM Memory 18.0 GB no. of unknowns = 621,973 frequency = 150 MHz Iterative solver: BiCGStab MoM fast-solver: GIFFT (double precision) 64-bits workstation DELL Precision T7400 Intel Xeon CPU 2.83GHz 32GB of RAM one-core Other commercial code MLFMA + Sparse Approximate Inverse (SPAI) High-fidelity multiscale EM tool Final residual Iteration count Iteration time 78 s 42 s Solution time 64h 46m 4h 47m Total run time ~ 6 days ~ 15 h 27

28 Numerical results: High Fidelity Ship Model (5) voltage gap Surface density current (dba/m) Freq.= 150 MHz 30 λ 28

29 Numerical results: High Fidelity Ship Model (6) Surface density current (dba/m) Freq.= 150 MHz 29

30 Numerical results: High Fidelity Ship Model (7) Surface density current (dba/m) Freq.= 150 MHz 30

31 Conclusions EM tool to analyze electrically large problems with fine geometrical details High-fidelity EM modeling without human effort to simplify Systematic multi-scale representation of the solution Different preconditioning of different scales Broad-band analysis: same mesh for all the frequency sweep 31

32 Recent references F. Vipiana, M. A. Francavilla, G. Vecchi, EFIE Modeling of High-Definition Multi-Scale Structures, accepted for publication in IEEE Transactions on Antennas and Propagation, Vol. 58, no. 7, July F. Vipiana, G. Vecchi, D. R. Wilton, A Multi-Resolution Moment Method for Wire-Surface Objects, IEEE Transactions on Antennas and Propagation, Vol. 58, No. 5, May 2010, pp F. Vipiana, G. Vecchi, D. R. Wilton, Automatic Loop-Tree Scheme for Arbitrary Conducting Wire- Surface Structures, IEEE Transactions on Antennas and Propagation, Vol. 57, No. 11, Nov. 2009, pp F. Vipiana, G. Vecchi, A novel, symmetrical solenoidal basis for the MoM analysis of closed surfaces, IEEE Transactions on Antennas and Propagation, Vol. 57, No. 4, Apr. 2009, pp F. Vipiana, F. P. Andriulli, G. Vecchi, "Two-tier non-simplex grid hierarchic basis for general 3D meshes", Waves in Random and Complex Media, Special Issue on Wave Interactions with Complex Structures, Vol. 19, No. 1, Feb. 2009, pp F.P. Andriulli, F. Vipiana, G. Vecchi, Hierarchical bases for non-hierarchic 3D triangular meshes, IEEE Transactions on Antennas and Propagation, Special Issue on Large and Multiscale Computational Electromagnetics, Vol. 56, No. 8, Part 1, Aug. 2008, pp