Altitude Effects - Fluid Flow Transition and Continuum Breakdown

Plume/divert jet interactions on both missile performance and aerothermal effects (seeker window obscuration and heating) are a major concern at higher altitudes where the separation zone produced by these interactions can engulf a large portion of theoverall missile flowfield. Predictive methodology is deficient at these higher altitudes due to the complexity of the physics. The proposed innovation serves to improve our ability to simulate higher altitude missile flows via extending newly developedhypersonic transitional models and hybrid continuum/DSMC methodology. In the altitude regime of 40-60 km, laminar to turbulent transition occurs within this separation zone. Extensions of 3D PDE's for kL (laminar fluctuations) and for G (intermittency havebeen incorporated into the CRAFT CFD Navier-Stokes code in Phase I, and will be extended to analyze plume/divert jet induced separated zones in Phase II. Above 60 km, continuum breakdown occurs and we will improve upon the slip regime extensions andhybrid DSMC coupling (using the DAC97 code) initiated in Phase I. Research will focus on developing advanced coupling techniques at the breakdown surface, thermochemical extensions, and on developing new particulate integration techniques. The resultanthybrid code will provide high fidelity simulations at altitudes up to and beyond 100 km. CRAFT Tech has played a leading role in supporting systems and developmental studies related to missile plume/divert jet interactive flows at altitudes up to about45km. This effort will provide for the extension of such activities to much higher altitudes permitting us to deal with a much broader array of problems. There is no high-fidelity CFD code that contains plume physics and addresses interactive issues andthe Phase II development provides us with a very unique tool. Particular areas where we see major commercialization potential include: (1) support of Army interceptor technology programs; (2) support of MDA/MSIC Boost Phase Intercept studies for detection,discrimination and plume to hardbody handover; (3) Liquid and Solid threat simulant booster design (for target usage) where we have been supporting a number of industrial groups; and (4) varied control jet interactions problems associated with small UAV'sand with space vehicles.