Sea Technology

NOV 2013

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redevelopment will require cost and effort. Consequently, tremendous research and development efforts have been put into the CAE industry to speed up the application of innovative techniques. In view of the advantages and disadvantages of the above techniques, WCT has successfully developed a hybrid multiscale method that combines the spectral element time domain (SETD) method for the electrical coarse region, e.g., background, the fnite element time domain (FETD) method for electrically small regions that contain fne features of the problem and the second-order accurate enlarged cell technique (ECT), an improved conformal FDTD method for the intermediate region. The above three solvers can be hybridized and can cosimulate with the SPICE circuit simulator to be used for SQIF modeling. The interface between different regions will be treated by the discontinuous Galerkin method, where the fux is correctly updated to ensure stability. Multiscale Method Novelties High-Order Spatial Convergence. The hybrid multiscale simulator uses the FETD method with tetrahedron elements (thus body conforming) in electrically fne regions (including circuits and thin-wire structures), ECT (boundary conformal FDTD method) in intermediate regions and SETD method for coarse regions without circuit and fne structures. This ensures second-order convergence in all regions. Overall, this would be signifcantly more effcient than solving the problem with one very fne grid in the conventional FDTD or FETD methods. Higher Effciency in Time Integration. For multiscale problems, if one uses the explicit FDTD method, the timestep increment will be extremely small because of the stability requirement. On the other hand, if one uses an implicit FETD or FDTD method for the whole domain, the time-step increment can be large because no stability condition is required, but the cost for inverting the system matrix will be prohibitive. Thus, the developed hybrid multiscale scheme uses explicit time integration in the ECT-FDTD and SETD subdomain, but implicit time integration in the FETD subdomain. This is the best combination and is therefore more effcient. Such a subdomain and time integration selection is automatic and seamless to the user. Inherited Parallel Implementation Feature. Since the hybrid method relies on domain decomposition, i.e., different numerical schemes for different regions, it is ideal for parallel computation. The communication among different regions only happens at the region interfaces through the Rie- mann solver, thus minimizing the communication among different computer processors. Conclusion Such enabling CAE technology has been successfully verifed with Space and Naval Warfare Systems Command (SPAWAR) during the Phase II.5 project that WCT has done with the U.S. Navy in April 2013 in Washington, D.C. Practical simulations have been conducted, and a real systemlevel simulation can be performed with the developed technology. WCT is working to commercialize enabling technology and is seeking opportunities to move this project to Phase III, during which SQIF devices will be designed in practical platforms. Acknowledgments The authors of this article wish to express their gratitude to Dr. Qing Huo Liu, who is the founder of WCT and a full professor at Duke University. He has published more than 200 papers in refereed journals. He received the 1996 Presidential Early Career Award for Scientists and Engineers from the White House, the 1996 Early Career Research Award from the Environmental Protection Agency and the 1997 CAREER Award from the National Science Foundation. References For a list of references, contact Bo Zhao at bozhao@ wavenology.com. n Dr. Junho Lee is a research scientist at Wave Computation Technologies. Lee is developing computer simulation software packages for the design of electronic and photonic applications. He served as a research scientist and postdoc at Duke University, where he developed fast and accurate simulation methods in frequency and time domain for high-speed electronic packages. Lee received the Outstanding Postdoc award in 2006 from Duke University. Dr. Mengqing Yuan is a research scientist and manager for product development at Wave Computation Technologies. Yuan received a Ph.D. from Duke University in 2011, where he conducted novel algorithms for time reversal imaging applications. He also has experience with the mechanical design of hydroturbines. His current research interests include computational electromagnetics, microwave circuit designs, and hybrid solvers for electromagnetics and circuit, B-feld antenna and elastic waves. Dr. Bo Zhao is the sales and marketing manager at Wave Computation Technologies. Prior to this, Zhao served as a post-doctoral researcher at the electroscience laboratory at Ohio State University. He was also a core development member of the general electromagnetic framework during his graduate studies at the University of Kentucky. His research interests include computational electromagnetics, microwave circuit designs, hybrid algorithms, and high-performance and multiscale simulations. SYSTEMS AND COMPONENTS FOR SUBMARINES AND SURFACE VESSELS From single sensors to integrated sonar suites, L-3 ELAC Nautik delivers L-3 ELAC Nautik offers more than 80 years of experience in the development and production of hydroacoustic systems. Our product portfolio includes sonar systems and echo sounders, as well as underwater communication systems for a wide range of military and civilian applications. 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