The isolation of rare cells (those infrequently seen in the medium of interest) is important in diagnostic medicine. The use of antibody-coated surfaces to bind and capture cells of specific types has been extensively studied but collision frequency and probability of detachment before capture is complete are less studied and more important for the capture of rare cells. For surface capture to be effective, cells need to make physicochemical contact with the antibody coated entities. Because cells suspended in medium cannot be considered as point masses due to their large volumes, the usual computational fluid dynamics (CFD) techniques of tracking particle movement are insufficient to predict the frequency and duration of contact. The novel Macroscopic Particle Model (MPM) recently proposed by developers of the Fluent CFD package is used and extended to relate its parameters to collision frequencies and patterns known to occur in experimentally observed systems. This study explores and evaluates many of MPM’s parameters according to their effects on the numerical accuracy and overall similarity of the simulations to experimentally observed systems. The current MPM model shows some limitations when simulating real three dimensional systems; nevertheless, with the ongoing revisions to MPM by Fluent developers, we are optimistic about its accuracy and utility in the future.