| A methodology to simulate purely viscous, creeping, free-surface flows numerically has been developed and compared with experiment. Full two-dimensional and axisymmetric flows are amenable to the methodology; the flows need not conform to the Hele-Shaw thin cavity restrictions and are not limited to simple geometries.;Resin transfer molding processes involve flow through a reinforcing mat. The flow is viewed here on a microscopic scale which observes the process on a length scale comparable to the mean spacing between the reinforcing solids. A determination was made of the extent of microvoidage caused by the front bypassing interstitial volume between the solids. The finite element method was used to simulate the creeping, Newtonian flow without surface tension in a limiting-case geometry with 44% solids loading; experimental verification proved the numerical method to be capable of simulating uneven geometries. The results were extended from the zero surface tension case down to a capillary number of one-half where the interstitial voids were found to represent significant fractions of the volume. The voids left in the interstices between fiber bundles were found to decrease in size with increasing surface forces but were always present in this limiting-case geometry.;Thermoplastic and especially thermoset nonisothermal molding simulation requires a knowledge of the frontal fluid mechanics. Macromolecules are oriented by the "fountain flow" process at the advancing front in homogeneous systems, and reinforcing fillers are oriented in heterogeneous systems. Because the frontal fluid mechanics play an important role in orientation studies, the axisymmetric transient fountain flow has been simulated numerically and studied experimentally as a model geometry for mold filling. The free surface was found to develop in one and one-half channel radii. Numerical simulation showed a similar development rate for the planar fountain flow as occurs in injection molding. Because the front development is rapid, the steady-state fountain flow description is adequate for molding geometries where changes in the surface topology are small in comparison with the size of the channel thickness. |
