reducing hull friction

More on slip boundary condition:

http://www.mech.northwestern.edu/courses/lichter/nano438/PDF_1/Tretheway.pdf Micron-resolution particle image velocimetry is used to measure the velocity profiles of water flowing through 303300 mm channels. The velocity profiles are measured to within 450 nm of the
microchannel surface. When the surface is hydrophilic ~uncoated glass!, the measured velocity profiles are consistent with solutions of Stokes’ equation and the well-accepted no-slip boundary condition. However, when the microchannel surface is coated with a 2.3 nm thick monolayer of hydrophobic octadecyltrichlorosilane, an apparent velocity slip is measured just above the solid surface. This velocity is approximately 10% of the free-stream velocity and yields a slip length of approximately 1 mm. For this slip length, slip flow is negligible for length scales greater than 1 mm, but must be considered at the micro- and nano scales. ....

http://arxiv.org/PS_cache/cond-mat/pdf/0210/0210154v1.pdf Micron-resolution particle image velocimetry is used to measure the velocity profiles of water flowing through 303300 mm channels. The velocity profiles are measured to within 450 nm of the microchannel surface. When the surface is hydrophilic ~uncoated glass!, the measured velocity profiles are consistent with solutions of Stokes’ equation and the well-accepted no-slip boundary
condition. However, when the microchannel surface is coated with a 2.3 nm thick monolayer of hydrophobic octadecyltrichlorosilane, an apparent velocity slip is measured just above the solid surface. This velocity is approximately 10% of the free-stream velocity and yields a slip length of approximately 1 mm. For this slip length, slip flow is negligible for length scales greater than 1 mm, but must be considered at the micro- and nano scales.

 

Much of the research of the slip boundary condition with hydrophobic surfaces has been at the "nano" level. Relevant questions for boats and ships include:
1) How much drag reduction occurs at the boat and ship size level?
2) How sensitive is the drag reduction to surface roughness?
3) What is a practical hydrophobic surface?

 

Another question would be what is the effect of disolved gases, salt and other contaminates?