Threshold pressure in arbitrary triangular tubes using RSG concept for all wetting conditions

In this paper, we extend the Reduced Similar Geometry (RSG) concept to irregular triangular tubes for arbitrary contact angles. Analytical expressions for the normalized threshold curvatures and the wetting phase saturation in triangular tubes are derived and analyzed. Comparison of the results for triangular tubes with different triangular shapes of the same shape factor shows, for the first time, that these geometrically different triangles have the same capillary behaviour even though they may have different numbers of corners occupied by the wetting phase. A case of rectangular tubes is also demonstrated to show that this concept works well for irregular n-sided polygons.