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HFCP Solver Development

Velodyne is a high fidelity multi-physics multi-numerics hydro-structural solver used to analyze high strain rate large material deformation events. These include target penetration and blast loading by weapons and the resulting damage to the target material such as penetration, perforation, back face spalling, and debris generation. Velodyne contains a wide range of rate-dependent material constitutive and progressive damage routines as well as equations of state to represent the physical behavior of both solid and fluid materials. In addition, Corvid has implemented several unique features that allow us to move beyond the typical limitations of commercial FEA codes and solve complex, high-rate dynamic problems. These features include Smooth Particle Hydrodynamics (SPH), Element to Particle Conversion, Robust Higher Order Auto-Contact, Multi-phase Equations of State (EOS), Thermal/Structural Coupled Solvers, Coupled Lagrangian/Eulerian (CLE) Solvers, and Reaction Kinetics of Energetic Materials.

 

Initial development of Velodyne focused on the needs of the Missile Defense Agency (MDA) to evaluate interceptor effectiveness and provide post-intercept debris scenes for flight test planning and ballistic missile defense system assessments. Because of its ability to accurately model extreme loading conditions, the use of Velodyne was extended to the tactical and combat vehicles, such as the Mine Resistant Ambush Protected (MRAP) family of vehicles and the Medium Tactical Vehicle Replacement (MTVR) vehicle, to assess military crew survivability against underbody blasts by IED/mine explosions. Corvid has also successfully applied Velodyne to the development of innovative light-weight ballistic protection solutions for large diameter solid rocket motors (SRMs) and other high value DoD assets. Another major effort supported by Velodyne is the Insensitive Munitions (IM) program in assessing the response of large rocket motors to IM stimuli, such as cook-off, bullet/fragment impacts, and sympathetic detonation; the success of which has resulted in the development and effective use of a slow cook-off oven designed to meet the stringent requirements for testing large scale rocket motors under US and international IM compliance regulations.

 

Over the last several years, Velodyne has been extensively anchored to test data, both in-house and externally through other contractors or program offices. These comparisons range from simple phenomenological tests to full system level comparisons, showing the breadth of capabilities within Velodyne. Various phenomena modeled across these comparisons include perforation and penetration, failure and fracture, small and large material deformation, and fluid-structural interaction. MDA has even funded the development of a Velodyne Basis of Confidence document which summarizes the operation and usage of Velodyne within the missile defense community in terms of lethality and post-intercept debris This document and the use of Velodyne has undergone extensive peer review by MDA and the DOE.

RavenCFD is a full three-dimensional Navier-Stokes flow solver for compressible viscous flows on unstructured grids. RavenCFD is tailored for robust steady-state and time-accurate solutions for a variety of multi-dimensional flows. Corvid has developed RavenCFD and exercised it extensively over the last ten years, using it to generate tens of thousands of large-scale, high-fidelity flow solutions for a variety of automotive and defense applications. It has been validated through comparison to experimental data for Mach numbers from less than 0.1 to 15. RavenCFD has demonstrated linear to super-linear scalability on thousands of processors, providing an efficient framework for performing large scale calculations. We employ it regularly as a predictive design tool to improve the aerodynamic characteristics of complex configurations. Since RavenCFD development is performed in-house at Corvid, new capabilities are implemented on an as-needed basis.

The main features of RavenCFD include:

 

- Numerical representation of the full three-dimensional conservation equations for fluid flow, including the Euler equations for inviscid flows and the Navier-Stokes equations for laminar or turbulent flows.

- An arbitrary polyhedral formulation, meaning that the solver can accommodate unstructured grids with arbitrary cell shapes. This feature makes RavenCFD well-suited for aerodynamic predictions for complex geometries.

- A variety of upwind flux-splitting schemes, limiters, and turbulence models to provide accurate, stable, and realizable solutions for a broad range of flow conditions.

- Fully implicit time integration with Newton subiterations to recover time accuracy. This combination of features improves the robustness of the solver—providing good solutions even on grids with poor-quality cells—and permit simulation of unsteady flows without excessively small timesteps.

- Multi-species capability, including high-temperature thermodynamic properties for a variety of gases.

- Parallel scalability to permit solutions of large problems on large numbers of processors. While typical problem sizes are in the 50- to 300-million-cell range, we have performed calculations on grids as large as 500 million cells on thousands of processors. These large runs show the same performance as is observed on smaller calculations, and we have demonstrated linear to super-linear scalability on all of our problem sizes.

- Grid deformation, optimization, and adaptation (both h- and r-refinement), embedded into the flow solver itself.