**6. Conclusions**

Rough-wall turbulent boundary layer flow is a complex physical phenomenon that increases skin friction drag compared to the smooth wall case. Because the surface roughness of a ship hull fouled with biofoulings or other types of hull imperfections is often found to be inhomogeneous, it is crucial to consider inhomogeneous roughness in addition to homogeneous roughness. In this study, the effects of roughness inhomogeneity on the skin friction drag are investigated by modeling

*The Phenomenon of Friction Resistance Due to Streamwise Heterogeneous Roughness with… DOI: http://dx.doi.org/10.5772/intechopen.99137*

the inhomogeneous roughness pattern in a simplified manner using step changes in the equivalent sand grain roughness heights *ks*, denoted as P, Q, and R.

Some of the findings from this study include:

