Browsing by Author "Tezduyar, Tayfun"
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Item Drogue Parachute Computational Structural and Fluid Mechanics Analysis with Isogeometric Discretization(2017-04-21) Hartmann, Aaron; Tezduyar, Tayfun; Takizawa, KenjiDuring the Orion spacecraft’s return, at higher altitudes drogue parachutes will be used for deceleration. These parachutes are made of ribbons and have 24 gores, with 52 ribbons in each gore, where a gore is the slice of the parachute between two radial reinforcement cables extending from the parachute apex to the skirt. There are hundreds of gaps that the flow goes through, and there are also three wider gaps created by removing ribbons. Computational analysis can help reduce the number of costly drop tests in comprehensive evaluation of the parachute performance. Reliable analysis requires accurate computation of the parachute fluid-structure interaction (FSI) between the drogue and the compressible flow it is subjected to. The FSI computation is challenging because of the geometric and flow complexities and requires first creation of a starting parachute shape and flow field. This is a process that by itself is rather challenging, and that is what we are focusing on here. In our structural and fluid mechanics computations, for spatial discretization, we use isogeometric discretization with quadratic NURBS basis functions. This gives us a parachute shape that is smoother than what we get from a typical finite element discretization. In the flow analysis, we use the NURBS basis functions in the context of the compressible-flow Space-Time SUPG (ST SUPG) method. The combination of the ST framework, NURBS basis functions, and the SUPG stabilization assures superior computational accuracy.Item Main Aspects of the Space-Time Computational FSI Techniques and Examples of Challenging Problems Solved(Japan Society of Mechanical Engineers, 2014-01) Takizawa, Kenji; Tezduyar, Tayfun; Team for Advanced Flow Simulation and ModelingFlow problems with moving boundaries and interfaces include fluid--structure interaction (FSI) and a number of other classes of problems, have an important place in engineering analysis and design, and offer some formidable computational challenges. Bringing solution and analysis to such flow problems motivated the development of the Deforming-Spatial-Domain/Stabilized Space--Time (DSD/SST) method. Since its inception, the DSD/SST method and its improved versions have been applied to a diverse set of challenging problems with a common core computational technology need. The classes of problems solved include free-surface and two-fluid flows, fluid--object and fluid--particle interaction, FSI, and flows with solid surfaces in fast, linear or rotational relative motion. Some of the most challenging FSI problems, including parachute FSI and arterial FSI, are being solved and analyzed with the DSD/SST method as a core technology. Better accuracy and improved turbulence modeling were brought with the recently-introduced variational multiscale (VMS) version of the DSD/SST method, which is called DSD/SST-VMST (also ST-VMS). In specific classes of problems, such as parachute FSI, arterial FSI, aerodynamics of flapping wings, and wind-turbine aerodynamics, the scope and accuracy of the FSI modeling were increased with the special ST FSI techniques targeting each of those classes of problems. This article provides an overview of the core ST FSI technique, its recent versions, and the special ST FSI techniques. It also provides examples of challenging problems solved and analyzed in parachute FSI, arterial FSI, aerodynamics of flapping wings, and wind-turbine aerodynamics.