Combination Of Air Lubrication And Super Hydrophobic Frictional Drag Reduction

Tech ID: 29227 / UC Case 2018-118-0

Patent Status

Country Type Number Dated Case
United States Of America Published Application 20210309321 10/07/2021 2018-118
European Patent Office Published Application 3833878 06/16/2021 2018-118
Patent Cooperation Treaty Published Application WO2020101769 05/22/2020 2018-118

Brief Description

This technology combines air layer frictional drag reduction (ALDR) with super hydrophobic surfaces (SHS) to achieve frictional drag reduction of ALDR with significantly reduced gas flux. Thus, enabling increased net energy savings. The stable air layer is achieved with lesser gas flux when utilizing a SHS.

Periodic air layers may replenish SHS, enabling drag reduction with reduced energy cost.

Combinations of SHS and regular or other non-SHS surface may be used to control spreading of gas, thus facilitating formation of ALDR using discrete gas injection points better than previously achievable. Such surface variations could also be used to preferentially guide gas towards or away from propulsion, depending on desired outcome.

By controlling ALDR regionally or globally on a surface, with or without SHS, this technology modifies flow around a hull. This mediates forces on partially or fully submerged objects, enabling control of flow patterns, resistance, steering, and/or dynamics.

Suggested uses

Ship owners could potentially save 100k to 1M per year per ship in fuel, if this works as planned. Compared to ALDR alone, would significantly reduce cost to retrofit ship as smaller piping and compressors required. Savings of ~500k to ~2M per ship. 
Can enable increased ship speed (e.g. pleasure yacht and military applications). 
Control of air flow to propulsor region can be used to reduced vibrations and noise. 
For pipelines and chemical plants etc, potential for >10% pumping cost savings. For large pipelines, millions in USD and much reduction in carbon footprint (similar to benefit for ships). Also, reduced pumping cost and lower dp means can have lower p_max and have big safety impact. 
Can be used for any vehicle/device operating in liquid or transferring liquid (UUV, ROV, WEC, tidal turbine, ship, torpedo, submarine, pipeline, etc.)


Frictional drag accounts for approximately 60% of a typical cargo ship's propulsive power requirements. By combining two previously studied frictional drag reduction techniques, this technology significantly reduces a ship's frictional resistance, offering substantial economic and environmental advantages.   

By itself, air layer frictional drag reduction (ALDR) can save a ship about 20% in propulsive power, but the net energy savings are typically less than 10% due to energy required to supply the gas. 

Super hydrophobic surfaces (SHS) also do not robustly reduce the frictional drag in turbulent flows over extended periods of time. Among the challenges, gas trapped on an SHS is lost over time and needs to be supplemented. 

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Other Information


frictional drag reduction, friction, drag reduction, hydrophobic

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