|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|
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.
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.
frictional drag reduction, friction, drag reduction, hydrophobic