Communicated by Y. BazilevsFluid-structure interaction (FSI) modeling of spacecraft parachutes involves a number of computational challenges beyond those encountered in a typical FSI problem. The stabilized space-time FSI (SSTFSI) technique serves as a robust and accurate core FSI method, and a number of special FSI methods address the computational challenges specific to spacecraft parachutes. Some spacecraft FSI problems involve even more specific computational challenges and require additional special methods. An example of that is the impulse ejection and parachute extraction of a protective cover used in a spacecraft. The computational challenges specific to this problem are related to the sudden changes in the parachute loads and sudden separation of the cover with very little initial clearance from the spacecraft. We describe the core and special FSI methods, and present the methods we use in FSI analysis of the parachute dynamics and cover separation, including the temporal NURBS representation in modeling the separation motion. Math. Models Methods Appl. Sci. 2013.23:307-338. Downloaded from www.worldscientific.com by UNIVERSITY OF PITTSBURGH on 03/16/15. For personal use only. 308 K. Takizawa et al.the fluid mechanics equations in a computational domain with moving interfaces and accurate and robust coupling between the equation blocks representing the fluid and structural mechanics. When FSI problems are computed with movingmesh methods, which are definitely more desirable compared to nonmoving-mesh methods in terms of accurately resolving the fluid mechanics boundary layers near solid surfaces, a third equation block, representing the mesh-moving equations, is coupled to the first two. The arbitrary Lagrangian-Eulerian (ALE) finite element formulation 1 is the basis of many moving-mesh methods used in FSI computations (see, for example, Refs. 2-15). Parachute FSI modeling has all the computational challenges of a typical FSI problem. The fluid mechanics of the parachute depends on its shape and motion, and deformation of the parachute structure, which is made of membranes and cables, depends on the fluid mechanics forces. In addition, because the parachute is a light structure compared to the air masses involved in the parachute dynamics, the response of structure is very sensitive to the changes in the fluid mechanics forces. This makes it essential to have a robust coupling method to handle the coupling between the equation blocks representing the fluid mechanics, structural mechanics, and mesh-moving equations.The deforming-spatial-domain/stabilized space-time (DSD/SST) formulation, 16-22 was introduced as a general-purpose moving-mesh method for flow problems with moving interfaces, including FSI. Its stabilization components are the streamline-upwind/Petrov-Galerkin (SUPG) 23 and pressure-stabilizing/Petrov-Galerkin (PSPG) 16,24 methods. The DSD/SST formulation is used with the mesh update methods 25,26 developed to complement the formulation. The mesh update includes moving the mesh for as long ...
Communicated by Y. BazilevsDeforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation was developed for flow problems with moving interfaces and has been successfully applied to some of the most complex problems in that category. A new version of the DSD/SST method for incompressible flows, which has additional subgrid-scale representation features, is the space-time version of the residual-based variational multiscale (VMS) method. This new version, called DSD/SST-VMST and also Space-Time VMS (ST-VMS), provides a more comprehensive framework for the VMS method. We describe the ST-VMS method, including the embedded stabilization parameters, and assess its performance in computation of flow problems at high Reynolds numbers by comparing the results to experimental data. The computations, which include those with 3D airfoil geometries and spacecraft configurations, signal a promising future for the ST-VMS method.
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