A nice aspect of DPD is its flexibility in modeling flow in other complicated (non-Couette-like) geometries of interest. Such simulations can help provide insight into the important physical mechanisms controlling flow and are useful for the interpretation of measurements. As a simple illustration, consider the flow of a suspension, driven by a body force, between parallel cylinders. This flow scenario is actually quite common when, for example, fresh concrete is poured such that it flows between rebars, which are cylindrical steel bars that are often oriented in a parallel fashion. Figures 14 and 15 shows two cases where in case A the sphere diameter was about ½ the gap spacing between the rebars. For case B, the sphere diameters were about 1/5 the gap spacing. A body force was applied so that the flow was downward. As the simulations progressed, for case A the flow stopped as the spheres became jammed between the rebars. In case B, the simulation showed no indication of jamming. It should be pointed out that, as a practice in the concrete industry, the size of coarse aggregates should be less than a third of the gap spacing between rebars to avoid this very phenomenon. Practice is clearly ahead of theory on this issue.
Figure 14. Flow through rebars: Case A. A suspension of spheres was subject to a body force downward. The sphere's diameter was about ½ the gap spacing between the rebars (the four smaller radii objects represent cylinders). The volume fraction was φ ≈ 50%. After a short period, the flow came to a stop as the spheres became jammed between the rebars.
Figure 15. Flow through rebars: Case B. Here the sphere diameters were about 1/5 the gap spacing. The volume fraction was ≈ 50%. The spheres continued to flow throughout the simulation, which ran several times longer in time than in case A. There was no indication of jamming(note, lubrication forces were not included in this simulation).