Ships are subject to increased surface roughness due to the attachment of biofoulings on their hull. When the surface of a ship’s hull is rough, increased frictional resistance can be expected. A ship’s frictional resistance make up almost 80 – 85% of its total resistance. Therefore, it is crucial to maintain the ship’s frictional resistance value to a minimum. In this study, the effects of roughness length scale due to biofouling on friction resistance are investigated. To achieve reliable results, this study used the 3D DTMB 5415 model that was established as a benchmark study by ITTC. Roughness length scales representing biofoulings are applied to the model and analyzed by using the CFD software at a service speed, reaching a Froude Number of 0.28. Results of the simulation are compared and analysed to gain an understanding of the increased friction resistance value due to biofouling. For the smooth case, the results are in agreement with the towing test conducted by ITTC. In addition, friction resistance is found to be increasing along with the rise of the roughness length scale.

Fuel consumption is heavily influenced by ship resistance, which mostly consists of friction resistance. During her operation, a ship is susceptible to the attachment of biofouling to its hull. The arbitrary form of biofouling induces an increase in surface roughness, which is responsible for the increase in friction resistance. This research analyses the increase in skin friction resistance due to biofouling, that is represented by a few variations of roughness length scale, in various orders throughout the models. Two-dimensional models of flat plates are utilized to investigate this issue by means of computational fluid dynamics (CFD) analysis. This study uses models with 0.56 m length to be tested in five Reynolds numbers, to be compared to a similar experiment conducted by using wind tunnel. Other models include 30 m and 60 m length to be tested in two Reynolds numbers each. It is found that the increase in skin friction reaches 3.5 – 31.4% for 0.6 m, 68.1 – 206.9% for 30 m with extreme regular roughness and 117.3 – 129.3% for 30 m with extreme irregular roughness, and 59.5 – 179.6% for 60 m with extreme regular roughness and 123.5 – 128.9% for 60 m with extreme irregular roughness.