Our research, funded by IFPRI, has concentrated on developing physical models for the rapid flow of particles and gas, and exploring the consequences of these models for fully developed and developing flow of the two phases in both vertical and inclined ducts. Experimental studies have shown that solid particles transported by a gas in vertical pipes, such as those encountered in riser reactors, are distributed non-uniformly over the cross section (Bader et al., 1988). Consequently, neither quantitative nor qualitative features of the overall behavior can be represented correctly by one-dimensional flow models, which take into account the presence of the pipe walls only through empirically introduced friction factors. The origin of this segregation has been investigated by us and others over the last decade.
During the past twelve months, we have focused our efforts on understanding the various routes to formation of clusters in rapid flow of gas-particle mixtures. It was apparent from the reactions of some of the industrial representatives during the annual meeting in Nancy that the connection between this work and riser flow modeling is not entirely obvious. Therefore, we begin this report with a discussion of this connection (section 2), then highlight some of the results (section 3) and finally conclude with a summary of the anticipated course of research for the next year (section 4).