An improved method and computer system is provided, for analyzing the two- or three-dimensional movement of a fluid in an absorbent article that comprises fluid-swellable composite material, which comprises a fluid-swellable solid material, and that comprises void spaces in the fluid-swellable composite material, the fluid-swellable composite material being defined by a virtual two-dimensional or three-dimensional mesh, to determine the performance or property of at least one feature of the fluid-swellable composite material thereof, or the absorbent article, the method comprising: inputting one or more properties for the fluid-swellable (composite) material into a model and evaluating this to determine the performance of a feature of the absorbent article or fluid-swellable composite material thereof, the virtual model.