Spatially varying bottom friction

[BAN]

I'm a happy user of the new spatially varying bottom friction. This option will make it possible to get better agreement between tidal simulations and measurements. . . but this option is also suited to simulate 2D current energy drain in specific areas e.g. simulating the effect of a tidal stream farm (current speed to electric power).

The only problem seems to be that the old policy of allowing the user to activate several types of bottom friction simultaneously has been prohibited with this new option.

It is commonly accepted that quadratic bottom friction is a better than linear bottom friction when modeling tides or turbulent friction around static objects; but when modeling energy loss due to a rotating turbine G.I. Shapiro (Ocean Science, 2011 http://www.ocean-sci.net/7/165/2011/os-7-165-2011.html) argues that linear friction is better. So when modeling the impact of a tidal stream farm it would be best to have quadratic bottom friction for the model area and a added linear bottom friction for the tidal stream farm area.

As modeling environmental impact of tidal farms will be a hot topic for some time (i.e. several users might have this problem), I suggest/recommend that more than one type of spatially varying bottom frictions can be activated at the same time in the main version of ROMS.

[m.hadfield]

The only problem seems to be that the old policy of allowing the user to activate several types of bottom friction simultaneously has been prohibited with this new option.

It's been prohibited for the last year or two, since before the spatially varying option was introduced. (Or so I recall.) But I agree with you that it would be nice to be able to activate linear plus quadratic bottom friction.