Exam Question
Q5
Describe the relation between frictional resistance and
(a) Ship speed
(b) The wetted area
(c) The surface roughness
(d) The length of the vessel
Class 2 (2nd Engineer)
SC&S
📅 Jan 2026
Reference Answer
### Introduction to Frictional Resistance
Frictional resistance ($$R_f$$) is a component of the total resistance experienced by a ship moving through water. It arises from the shear forces created by the viscosity of the water as it flows over the submerged surface of the hull, known as the wetted surface. This resistance is heavily influenced by the properties of the boundary layer, which is the thin layer of fluid in the immediate vicinity of the hull surface. The total frictional resistance can be expressed by the general formula:
$$ R_f = C_f \times \frac{1}{2} \rho S V^2 $$
Where:
Frictional resistance ($$R_f$$) is a component of the total resistance experienced by a ship moving through water. It arises from the shear forces created by the viscosity of the water as it flows over the submerged surface of the hull, known as the wetted surface. This resistance is heavily influenced by the properties of the boundary layer, which is the thin layer of fluid in the immediate vicinity of the hull surface. The total frictional resistance can be expressed by the general formula:
$$ R_f = C_f \times \frac{1}{2} \rho S V^2 $$
Where:
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