Development and applications of an embedded CSD approach for coupled CFD/CSD modeling of blast/structure interactions

This paper describes recent developments and select applications of a program that couples parallel Computational Fluid Dynamics (CFD) and Computational Structural Dynamics (CSD) methodologies. FEFLO98 is the CFD code used while DYNA3D handles the CSD portion. FEFLO98 solves the time-dependent, compressible Euler and Reynolds-Averaged Navier-Stokes equations on an unstructured mesh of tetrahedral elements. DYNA3D solves explicitly the large deformation, large strain formulation equations on an unstructured grid composed of bricks and hexahedral elements. The initial algorithm constructed to model the coupled processes used the so-called "glued-mesh" approach, where the CFD and CSD faces match identically. Failure of this approach to model severe structural deformations in steel plates, as well as crack growth and propagation in steel and concrete, led us to the development of the so-called "embedded-mesh" approach, where the CSD mesh float through the CFD domain. While each approach has its own advantages, limitations and deficiencies, the embedded approach was proven to be superior for the class of problems modeled here. Critical applications of both approaches are described, including weapon detonation and fragmentation, airblast interaction with a reinforced concrete wall, and fragment/airblast interactions with steel wall structures including a generic steel ship hull and a steel tower.