We experimentally investigated the turbulent flow in a water channel developing past a two-dimensional array of photovoltaic panels, with varying incidence angle and spacing. Particle image velocimetry revealed two distinct regimes, depending on the incidence angle, while the dependence on inter-panel spacing was weaker. Positive incidence angles produce high turbulence and intense transport above the panels, with strong mixing between the canopy and the external flow. Conversely, negative incidence angles yield a skimming flow with large recirculation vortices that dominate the canopy layer. Vertical profiles, ventilation rates and turbulent statistics indicate that even a modest positive incidence significantly enhances ventilation and scalar transport, whereas they are substantially lower in the case of negative incidence. A Lagrangian analysis using synthetic passive particles allowed the estimation of the residence times and turbulent dispersion coefficients. The latter were more than an order of magnitude larger for positive than for negative incidence. The results demonstrate how panel configuration changes mixing and dispersion processes, providing a fluid mechanics basis for refined microclimate models useful for guiding the design of advanced photovoltaic farms.

In the case of dense and homogeneous canopies, it is well-known that canopy flows are similar to mixing layer flows (so-called mixing layer analogy). When the canopy becomes sparser, a transition between the mixing layer and the boundary layer perturbed by interactions between element wakes occurs. This transition has still to be fully understood and characterized. An experimental work has been developed in order to study this transition for various density canopies.