  Offshore wind turbine towers are pre-assembled and temporarily held in close
proximity to each other in group arrangements on port quaysides. Accurate
estimates of the aerodynamic loads on the individual towers and on the overall
group are essential for the safe and economic design of the quayside's
supporting structures and foundations. Wind tunnel tests represent the main way
to address the problem, but results may lead to overconservative designs due to
inevitable mismatches in the Reynolds number. This crucial issue is dealt with
here using an original engineering solution based on concentrated but
discontinuous surface roughness, which allows, for the first time in the case
of finite-height towers arranged in groups and subjected to an atmospheric
boundary layer flow, the successful simulation of the target high Reynolds
number regime. This case study assumes slender wind turbine towers with a
height of 115 m, and for the sake of generality, the investigations focus
principally on a cylindrical shape rather than the more complex real-world
geometry. The constant diameter of the towers is determined based on the
theoretical equivalence of the mean overturning moment. The rationality of this
procedure is verified a posteriori using a set of measurements on the
real-shape towers. The experiments show a regular behavior of the maximum mean
base shear force and moment for towers arranged in double-row groups, while the
results are more complicated for single-row groups, since biased flow sometimes
occurs in symmetric or nearly-symmetric configurations. Dynamic loads are also
inspected, and gust factors in good agreement with Eurocode 1's prescriptions
are found. Several parametric studies are carried out, the most extensive of
which is devoted to assessing the role of tower height. A complicated
non-monotonic pattern of the load coefficients with the tower height is
encountered.
