Class 1 (Chief Engineer) Engineering Management 📅 Oct 2022

Exam Question

Viscous (frictional) resistance is a major component of overall resistance and hence an important area of attention for energy efficiency improvement of ships. Explain various skin friction reduction methods currently under consideration, with special mention on

the following:

(a) Hull Air Cavity Systems

(b) Hull Surface Texturing

Reference Answer

### Introduction to Viscous (Frictional) Resistance
Viscous resistance, also known as skin friction resistance, is the force that opposes a ship's motion due to the shear stress exerted by the water on the hull's wetted surface. It is a major component of the total resistance, often accounting for 50-80% for slow to medium-speed displacement vessels like tankers and bulk carriers. This resistance arises from the formation of a boundary layer, a thin layer of fluid adjacent to the hull where the fluid velocity changes from zero at the hull surface to the free stream velocity further away.
The magnitude of frictional resistance is primarily influenced by:
1. **Wetted Surface Area (S)**: Larger area means more friction.

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