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The Coandă effect
27th Apr 2026
Khaled Karmous
For most commercial vessels, frictional resistance accounts for between 50 and 92% of total hydrodynamic resistance, a figure that has defined naval architecture for generations. Hull-form refinement, low-friction coatings and reduction of wetted surface area have all pushed that figure down, but each successive gain is harder won. As designs approach established practical limits, the engineering community is looking elsewhere.
The regulatory context sharpens the urgency. The Energy Efficiency Existing Ship Index and the Energy Efficiency Design Index are demanding measurable, demonstrable gains. Even a 5-10% reduction in skin friction translates directly into