IGA Mid-Processing Modeling Tools for FSI in Vehicle Mobility Applications

The US Army develops, oversees, and deploys a wide variety of vehicles, ranging from rotary-wing aircraft to medium/long-range hypersonic projectiles. These vehicles operate in many flow regimes, from slow-moving rotorcraft to projectiles flying at hypersonic speeds. In addition, the army vehicles are often subjected to extreme events, such as blast, which need to be mitigated to minimize vehicle damage. The US Army has a critical need to not only understand the flight characteristics of its vehicles, which vary greatly depending on the flight regime of interest, but also to reliably predict them. This, in turn, requires the US Army to be equipped with advanced modeling capabilities and tools that enable the simulation of complex-geometry, fixed- and rotary-wing vehicles in flight conditions ranging from subsonic to hypersonic.  Isogeometric Analysis (IGA) is a next-generation computational method that has brought superior accuracy to spatial and temporal discretization in fluid and structural mechanics simulations. IGA, because of its special higher-order nature, has several very desirable features in multiscale computation of flow and fluid–structure interaction (FSI) problems that are ubiquitous in mobility applications. Every computational analysis starts with a suitable definition of the problem geometry followed by mesh generation for that geometry. However, mesh generation in IGA, such as Non-Uniform Rational B-Spline (NURBS) mesh generation, is not as established as in the standard discretizations such as Finite Difference (FD) and Finite Element (FE) methods. Our recent STTR Phase I and II efforts focused on making IGA-based flow and FSI computations more powerful and more practical, by developing core NURBS mesh generation methods and tools that make meshing for IGA less arduous, more straightforward, more automated, and basically as established as it is now for the FD and FE methods.  However, bringing even higher fidelity and higher efficiency to IGA FSI simulations will require the development of IGA mesh generation methods and tools that go beyond the core technology developed in. In the present STTR effort we plan to focus on the next-generation IGA Mid-Processing Tools to support IGA-based aerodynamics and FSI simulations. These tools will include a) Unstructured mesh generation and refinement for IGA (e.g., using T-Splines); b) Mesh moving methods based on advanced fiber-reinforced hyperelasticity concepts; c) Methods that enable computations of IGA-suitable local length scales and stabilization parameters, which play a key role in the accuracy and stability of variational multiscale (VMS) analysis of flows; and d) Methods for efficient visualization of IGA-based solutions. This effort will bring multiscale computational flow and FSI analysis to a new level where it can make a much higher impact and provide the US Army with advanced aerodynamic analysis and design capabilities, which is an area of critical competency.