Front Curvature Analysis and Detonation Shock Dynamics Calibration for Pure and Sensitized Nitromethane

Archival front curvature data for nitromethane in 19.1, 27.6, and 36.8 mm i.d. glass tubes(R. Engelke and J.B. Bdzil, Phys. Fluids, 26) (5) 1983 are re-read from the original films to obtain detonation wave shapes. The data for each profile are fit with an analytic form, and the fitting parameters are tabulated. The basic detonation shock dynamics (DSD) model uses a calibration function relating the local normal wave velocity, D_n, to the local total curvature κ. A (D_n, κ) curve is generated for each charge diameter from the respective wavefront fits. The three curves overlay best for small κ, and diverge as κ increases. This non-uniqueness is similar to that observed in PBX 9502 (95 wt.% TATB) experiments, and is accommodated by extended DSD theory.(T.D. Aslam, J.B. Bdzil, and L.G. Hill, 11th Detonation Symp., 1998) To optimally calibrate the basic theory, a suitable analytic (D_n,κ) function is simultaneously fit to the three detonation wave shapes and to diameter effect data, so as to achieve the best global agreement. The effect of diethylenetriamine sensitizer is estimated by scaling the optimal (D_n,κ) function for pure nitromethane in a manner consistent with sensitized rate stick data. The result is a calibration surface (κ, c, D_n), where c is the sensitizer concentration.