Wetting of flat and rough curved surfaces

Wetting of flat and rough curved surfaces is discussed within the general framework of the variational approach. Explicit expressions for Young's and apparent contact angles are obtained by the use of the transversality conditions imposed on the appropriate variational problem. The Young, Wenzel, Cassie-Baxter, and Boruvka-Neumann equations are justified from this point of view. The redefined Young's and apparent contact angles are insensitive to external fields.