This looks up element areas with area() and drag
coefficients with CD(), then computes drag
force (in Newtons) with
\((1/2)*area*rho*CD*u^2\).
drag(m, u, phi = TRUE, rho = 1027)either a mooring object, created by mooring(), or a
mooring-element object, created with anchor(), chain(),
connector(), instrument(), misc(), release(), or wire().
either a non-negative number indicating depth-independent velocity, or a function that returns that velocity as a function of depth (m) below the ocean surface.
passed to area(), so see that function's documentation
for the somewhat subtle details.
a numeric value giving
water density in kg/m^3. The default value of 1027 is
likely to be sufficient for most calculations, given that
oceanographic variations of density are typically well under 1
percent, although it might make sense to use a smaller value
in lake applications. Note that the overall force balance
is more sensitive to other things, as discussed in the “Details”
section of the documentation for buoyancy().
drag returns a numeric vector of horizontal drag force in
Newtons.
Although fluid density rho is a parameter of this
function, the default value is likely to be used in all
practical oceanographic calculations, because neither
the drag coefficient, CD nor the current is easily
constrained to a corresponding tolerance.