# Result Charts - Known Flow

When modelling settling slurries, FluidFlow automatically generates a Rosin-Rammler particle size-distribution plot based on the solids data entry in the Input Editor. The graph plot shows Cumulative % Passing vs. Particle Size. Figure 1 provides an illustration of this graph plot. Figure 1: Rosin-Rammler particle size-distribution plot. Note, the Rosin-Rammler (R-R) curve in FluidFlow is curve-fitted to the PSD defined by the user on the Input tab of the Data Palette. The curve is bound by the requirements/limits of the R-R curve equation and as such, if we define a range of PSD data which doesn't fit exactly to the curve, the curve created in FluidFlow may not intersect the data-points. The accuracy of the R-R curve in the software can also be affected if a limited range of % retained PSD data is defined, for instance from 65 to 95%. This means that in FluidFlow, we need a wider range of particle %, i.e. from say 5 or 10% to 100% approx. Particle Data: In the case of defining only a d50 and d85 particle sizes, the same is true, i.e. the Rosin-Rammler curve is bound by the requirements/limits of the R-R curve equation. It's important to note that the modeling approach used is to an extent dependent on the slurry/solid data available. For instance, if you only have d50 data, then the Durand method would be used as this method only uses the d50 value. If you only have d50 and d85 data, then you can use either the Durand or WASC method. WASC uses both d50 and d85 in the solution. Note, when using the above approaches, FluidFlow automatically develops the Rosin-Rammler curve. If the data-points offer a good representation for a Rosin-Rammler curve, this means you have the additional option of using the equations which use PSD data (Liu Dezhong, 4-Component Model, WASP) and the PSD data used would be sourced from the R-R curve developed. If however the Rosin-Rammler curve isn't such a good representation, then we are restricted to using either the Durand or WASC methods. If you want to use the equations which use PSD data (Liu Dezhong, 4-Component Model, WASP), it's recommended that a full range of PSD data is obtained for the slurry/solids. This data can then be used in FluidFlow.