The size and number of corners of a polygonal hydraulic jump depend on various parameters, including fluid flow rate, jet diameter, obstacle height, and physical properties of the fluid. In other words, the size and shape of the polygonal hydraulic jump depend on the Reynolds number, Weber, and Bond numbers. This study investigates the effect of the surface roughness on the shape and region of stability of polygonal hydraulic jumps. Sandpapers of different degrees of roughness are glued on the surface of the target plate to make it rough. The study reveals that, in addition to Reynolds and Weber dimensionless numbers, the surface roughness of the target plate affects the stability of polygonal hydraulic jump. Based on the conditions of this study, including the thin-film flow, surface roughness leads to flow slip on the surface and, consequently, leads to a higher mean velocity and flow momentum. This study demonstrates that, in general, at given values of Reynolds and Weber numbers, a rougher surface leads to a greater number of corners in the polygonal hydraulic jump. Furthermore, the rougher the surface, the smaller the extent of the region of stability of polygonal hydraulic jumps. At last, Taguchi method is used to derive relations to estimate the number of corners of polygonal hydraulic jumps with respect to jet diameter, flow rate, the height of downstream obstacle, and roughness of the target plate for both modes of increasing flow rates and decreasing ones.

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