Statistical theory of surface contact was used to compare (a) the number of contact points and (b) the average surface area of a single contact in systems of (i) smooth-rough and (ii) rough-rough surfaces.The approach of the rough surfaces was considered in terms of the "depth of penetration".The performed calculations revealed that the topographies of i and ii were too different for the systems to be equivalent in terms of a and b.Hence,capillary adhesion should be modeled individually in each system.All the statistics of real surfaces must be known.The equations given allow to check the criterion for contact's elasticity which is crucial to model capillary adhesion of Geldart's Class C powders (0.1 mm in particle size,hard to fluidize,electrifiable,and liable to capillary adhesion).
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