Generation and Adaptive Modification of Anisotropic Meshes

The ability to quickly and reliably simulate high-speed flows over a wide range of geometrically complex configurations is critical to many of NASA's missions. Advances in CFD methods and parallel computing have provided NASA the core flow solvers to perform these simulations. However, the ease of use of these flow solvers and the reliability of the results obtained are a strong function of the technologies used to discretize the domain. Many applications involve solutions with highly anisotropic features: boundary layers, shear layers, wakes, shocks etc. Efficient resolution of those features motivates matching the mesh resolution/anisotropy to the solution's anisotropy but, in the more challenging applications, the location and strength of those features is difficult to precisely estimate prior to solution. Currently available meshing tools are not capable of producing and controlling the required initial meshes, nor adapting the mesh to match evolving anisotropic features. This project will combine Simmetrix Inc. expertise in the development of meshing components for flow simulations, and Rensselaer's Scientific Computation Research Center expertise in the development of adaptive mesh control technologies, to provide NASA the mesh generation and adaptation technologies needed. New techniques will be developed to create highly anisotropic semi-structured and unstructured meshes suitable for CFD simulations with high Reynolds number flow features (e.g., boundary layers, bow shocks, free shear layers, wakes, contact surfaces). Techniques to adapt these meshes based on mesh correction indicators will be developed to enable fully automated adaptive simulations. All procedures to be developed will work effectively in parallel on large-scale parallel computers and will support a wide range of flow solvers. The overall capabilities will be demonstrated through execution of fully automated parallel adaptive simulations on problems relevant to NASA.

High speed flow simulations are also of interest to many organizations outside of NASA thus the majority of the NASA applications also apply to non-NASA organizations. Moreover, the generality of these procedures proposed to be developed will allow them to apply them for other flow applications such as cardiovascular flows to accurately predict wall shear stress, flow over wind turbines to obtain better designs, two-phase annular flows to predict liquid film thickness to avoid dry out conditions, etc. In addition there are other types of physics such as electromagnetics and heat transfer that have solutions with high gradients that can also utilize these types of meshes for simulations.

NASA applications of this technology include any type of computational fluid dynamics simulations that involve complex geometry and/or complex flow features whose solution resolution needs cannot be precisely defined before starting the solution process. Applications in the aeronautics area include airflow around aircraft and engines. Applications to astronautics include propulsion, liftoff and reentry aerodynamics, and energy generation systems in space. Problems with a wide range of spatial scales resulting from complex geometry and flow features will benefit most from the proposed developments. Specific examples may include passive and/or active flow control devices, inlet configurations for blended wing body with boundary layer ingestion, hypersonic flight vehicles with scramjet engines, crew launch and exploration vehicles, launch vehicles, re-entry capsules, tethered ballute configurations. In addition to these "high speed" aerodynamics applications, there are also NASA commercial applications related to power generation and other spacecraft systems in a low gravity environment. The mesh resolution needs of two phase flow systems in such environments can also be addressed by the proposed developments. Finally, there are also biomedical applications of CFD such as the effects of low gravity on the cardiovascular system and the respiratory system.

This is a mature technology (TRL 7) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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