Figure 4.

The effect of increasing bottom friction on power production by farm with optimal variable drag coefficient. Labels show λ₀ for the three example channels. (a) Average power relative to a constant drag coefficient farm with given ${\lambda }_{\mathrm{F}}^{max}$; (b) velocities relative to the velocity in channel with no farm at given λ₀. Solid lines show peak flow and the dashed lines the flow speed averaged over a tidal cycle. (Online version in colour.)