Page 16: of Maritime Reporter Magazine (February 2026)

The Path to Zero

A NOVEL COANDA WATER

JET CONCEPT FOR SHIP

RESISTANCE REDUCTION

By Kal Karmous & Mohamed Hussain he maritime sector faces increasingly strict environ- of total resistance, depending on speed and hull type. Even mental regulations such as the Energy Ef? ciency small improvements in skin friction, on the order of 5–10%,

Existing Ship Index (EEXI) and the Energy Ef? - translate into signi? cant fuel savings: lower propulsion power

Tciency Design Index (EEDI). These frameworks are demand, lower speci? c fuel oil consumption (SFOC), reduced compelling ship owners and designers to achieve measurable emissions, greater regulatory margin under EEXI/EEDI, lower gains in energy ef? ciency and fuel economy. While progress operational costs, and reduced environmental footprint. This has been made through improved hull designs, propulsion up- article focuses on and highlights the fuel saving side; however, grades, and energy-saving devices, these solutions are reach- the technology can be used to increase the vessel speed dra- ing practical limits. matically and would help overcome the hydrodynamic barrier.

To meet the rising regulatory and environmental pressure, The innovation uses high-pressure water jets positioned a fundamentally different concept is required. It is within above the waterline. The jets are directed at a small angle to- this context, this article covers a new hydrodynamic vessel ward the ship hull. The jet adheres to the hull via the Coanda skin friction reducing concept: a high-pressure water jet sys- effect, entrains air from the surrounding environment, and car- tem that leverages the Coanda effect to create a stable, self- ries that air below the waterline where it forms a stable sheet sustaining vacuum air sheet along the hull surface, leading to of air along the hull, as long as the vessel is moving forward. a signi? cant reduction in wetted area and viscous drag. The Alternatively, the jets can be below the waterline using a habi- drag is zero wherever an air sheet exists. tat to create an atmospheric environment that allow air supply

This article presents the physics, conceptual system design, that eventually form the vacuum air sheet.

computational results, and operational implications of this This process achieves a form of dynamic air lubricating innovation. The resulting vacuum air sheet and the hydrody- sheet, in a vacuum condition. In essence: namic phenomena have never been observed in other resis- • The jet acts as the “carrier” of air tance reduction devices. • The Coanda adhesion controls trajectory and stability • The entrained air forms a lubricating vacuum air sheet

A New Concept: Coanda-Effect Water Jets • Vessel forward motion and pressure gradients keep the

For most vessels, frictional resistance accounts for 50–92% ? lm attached

Figure 2: Demonstration of the system on VLLC model

Figure 1: Concept of Coanda-Effect Water Jets on ship hull (reproduced from patent, US 12,280,854 B2, System and Method for Reducing Drag on the Hull of a Vessel, 2024).

16 Maritime Reporter & Engineering News • February 2026

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