Browsing by Author "Hartmann, Aaron"

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    Compressible-flow geometric-porosity modeling and spacecraft parachute computation with isogeometric discretization
    (Springer, 2018) Kanai, Taro; Takizawa, Kenji; Tezduyar, Tayfun E.; Tanaka, Tatsuya; Hartmann, Aaron; Mechanical Engineering
    One of the challenges in computational fluid–structure interaction (FSI) analysis of spacecraft parachutes is the “geometric porosity,” a design feature created by the hundreds of gaps and slits that the flow goes through. Because FSI analysis with resolved geometric porosity would be exceedingly time-consuming, accurate geometric-porosity modeling becomes essential. The geometric-porosity model introduced earlier in conjunction with the space–time FSI method enabled successful computational analysis and design studies of the Orion spacecraft parachutes in the incompressible-flow regime. Recently, porosity models and ST computational methods were introduced, in the context of finite element discretization, for compressible-flow aerodynamics of parachutes with geometric porosity. The key new component of the ST computational framework was the compressible-flow ST slip interface method, introduced in conjunction with the compressible-flow ST SUPG method. Here, we integrate these porosity models and ST computational methods with isogeometric discretization. We use quadratic NURBS basis functions in the computations reported. This gives us a parachute shape that is smoother than what we get from a typical finite element discretization. In the flow analysis, the combination of the ST framework, NURBS basis functions, and the SUPG stabilization assures superior computational accuracy. The computations we present for a drogue parachute show the effectiveness of the porosity models, ST computational methods, and the integration with isogeometric discretization.
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    Drogue Parachute Computational Structural and Fluid Mechanics Analysis with Isogeometric Discretization
    (2017-04-21) Hartmann, Aaron; Tezduyar, Tayfun; Takizawa, Kenji
    During 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.