Ship design is a complex engineering process in which numerous variables must be optimised simultaneously. Among the most determining parameters in this process is the resistance of the ship moving through water. The accurate estimation of this resistance value directly determines the success of the design.
What is Ship Resistance?
As a ship moves through water, it pushes the water aside and creates turbulence along its path. The sum of the forces arising from this interaction constitutes the ship's resistance. To overcome this resistance force and move the vessel, the propulsion system must produce sufficient thrust. Resistance therefore directly determines the required engine power and fuel consumption.
Resistance is composed of multiple components — wave resistance, frictional resistance, form drag, and additional components — each carrying different weights depending on the vessel's speed, form, and water conditions.
Why Are Model Tank Tests Conducted?
Model-scale experiments are used to determine the resistance characteristics of a vessel before it is launched at full scale. Models scaled according to Froude similarity laws are towed under controlled laboratory conditions to obtain resistance–speed curves.
These experiments allow critical decisions to be validated during the design phase, reduce risks before transitioning to full scale, and lay the groundwork for the experimental validation of numerical results obtained through computational methods (CFD).
The Complementarity of Digital and Experimental Methods
Computational fluid dynamics (CFD) makes it possible to predict ship resistance through numerical simulation. However, a CFD model that has not been validated against experimental data cannot serve as a reliable basis for design decisions. For this reason, model tank tests remain an indispensable validation tool that complements numerical methods.
Contribution to Autonomous Systems
For autonomous marine vehicles, energy management and route optimisation depend on the vessel's energy consumption profile at different speeds. Constructing this profile reliably requires that the resistance–speed relationship be modelled using experimentally validated data. Model tank tests therefore contribute directly to the design process of autonomous systems as well.