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Experimental measurements are compared with theoretical predictions for radiative transfer in suspensions of 11.0 μ dia Dow latex particles using 0.6328 μ He-Ne laser light. Both absorbing and nonabsorbing particles are studied with particle volume fraction ranging from 0.01 to 0.7 (close-packed). Predictions based on the classical assumptions that particles act as independent point scatterers are shown to give close agreement with experimental data even for close-packed conditions, as long as the interparticle clearance is greater than about 0.3 wavelengths. Evidence is presented indicating that interparticle spacing measured in wavelengths is the most critical parameter to gauge the importance of dependent scattering and that high particle concentration alone is no indication that scattering is dependent. The results have direct application to the design of packed/fluidized bed systems wherein thermal radiation is a significant heat transfer mode.

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Internal ballistics simulations of solid rocket motors have been conducted with the propellant grain's 3-D burning surface geometry described by a new minimum distance function approach and the internal flowfield represented by 1-D, time-dependent, single-phase compressible flow equations. The combustion model includes erosive burning and unsteady, dynamic burning corresponding to transient energy storage in the heated surface layer of the propellant. The integrated internal ballistics code (Rocballist) is used to investigate the role of these two burning rate augmenting mechanisms in solid rocket motor performance. Two tactical motors are used as test cases. Results indicate that dynamic burning can be the dominant factor in producing a short-duration ignition pressure spike in low-L motors, particularly if the L=D ratio is not too large and the port cross section is nonrestrictive (e.g., center perforated grain). However, when L=D is large and the port cross section is noncircular in the aft section (aft fins/slots), erosive burning can take over in dominating the burning rate to the extent that an otherwise progressive pressure-time trace becomes regressive/neutral. That is, erosive burning can effectively prolong the initial pressure spike in some star-aft motors. The results also show that with sufficiently accurate models of dynamic burning and erosive burning, it is reasonable to expect reliable internal ballistics predictions with suitable simplified flowfield models, thereby realizing significant reductions in computation time compared with 3-D, multiphase reacting flow simulations.

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