  We present results from novel field, lab and computer studies, that pave the
way towards non-invasive classification of localised surface defects on running
wind turbine rotors using infrared thermography (IRT). In particular, we first
parametrise the problem from a fluid dynamical point of view using the
roughness Reynolds number ($Re_k$) and demonstrate how the parameter regime
relevant for modern wind turbines translate to parameter values that are
currently feasible in typical wind tunnel and computer experiments. Second, we
discuss preparatory wind tunnel and field measurements, that demonstrate a
promising degree of sensitivity of the recorded IRT data w.r.t. the key control
parameter ($Re_k$), which is a minimum requirement for the proposed
classification technique to work. Third, we introduce and validate a local
domain ansatz for future computer experiments, that enables well-resolved
Navier-Stokes simulations for the target parameter regime at reasonable
computational costs.
