Rigid Body Collision Modeling for Multiple-Body Proximate Flight Simulation in Loci/CHEM

Currently, there exists a lack of confidence in the computational simulation of multiple body high-speed air delivered systems. Of particular interest is the ability to accurately predict the dispersion pattern of these systems under various deployment configurations. Classical engineering-level methods may not be able to predict these patterns with adequate confidence due primarily to accuracy errors attributable to reduced order modeling. In the current work, a new collision modeling capability has been developed to enable multiple-body proximate-flight simulation in the Loci/CHEM framework. This approach is well suited for simulation of a large number of projectiles, and maintains high-fidelity aerodynamics with six degrees of freedom modeling, and collision response. The Loci/CHEM architecture provides automatic parallelism and has previously demonstrated extreme scalability on thousands of computer nodes. The proposed simulation system is intended to capture the strong interaction phase, which occurs early in the projectile deployment, with subsequent transfer of projectile positions and flight states to the more economical engineering-level methods. Collisions between rigid bodies are modeled using an impulse-based approach with either an iterative propagation method or a simultaneous method. The latter is shown to be more accurate and robust for cases involving multiple simultaneous collisions as it eliminates the need to sort and resolve the collisions sequentially. The implementation of both the collision detection methodology and impact mechanics are described in detail with validation studies which are presented to demonstrate the efficiency and accuracy of the method. The studies chronologically detail the findings for simulating simple impacts and collisions between multiple bodies with aerodynamic interference effects.