Panel Discussion 



1-2.25 



'•■a 



Figure 1 



predominant (the closer to the expansion) and the other is finally eliminated. The 

 Reynolds number for this flow, based on Ug , Dp , and v was 200. We have calcu- 

 lated steady annular eddies for higher Reynolds numbers (see J. Fluid Mech., 

 1967, Vol. 28, Part 1), using equations including the local acceleration. In a way 

 this also gives an example of a transient flow. 



Computational Instability 



The numerical calculations were based on an explicit finite-difference 

 scheme, which has the advantage of being very simple to formulate and to treat 

 numerically. It has the disadvantage of becoming unstable outside a region 



1611 



