Optimal Control of Shock Wave Attenuation using Liquid Water Droplets with Application to Ignition Overpressure in Launch Vehicles
Author
Moshman, Nathan D.
Sritharan, Sivaguru S.
Hobson, Garth V.
Date
2011Metadata
Show full item recordAbstract
This paper presents the first solution of an optimal control problem concerning unsteady
blast wave attenuation where the control takes the form of the initial distribution of liquid
water droplets. An appropriate two-phase flow model is adopted for compressible
homogeneous two-phase flows. The dynamical system includes an empirical model for
water droplet vaporization, the dominant mechanism for attenuating the jump in pressure
across the shock front. At the end of the simulation interval, an appropriate target state is
defined such that the jump in pressure of the target state is less than that of the simulated
blast wave. Given the nature of the non-linear system, the final time must also be a free
variable. A novel control algorithm is presented which can satisfy all necessary conditions
of the optimal system and avoid taking a variation at the shock front. The adjoint-based
method is applied to NASA’s problem of Ignition Overpressure blast waves generated
during ignition of solid grain rocket segments on launch vehicles. Results are shown for a
range of blast waves that are plausible to see in the launch environment of the shuttle.
Significant parameters of effective droplet distributions are identified.
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.Collections
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