Obtaining 2D surface characteristics from specular surfaces

Today's surface appearance measures often ignore the inherent two-dimensionality. This paper proposes a method to acquire and assess the appearance of larger specular surfaces in 2D. First, we describe a deflectometric setup to obtain a gradient field of the surface microstructure. Hence, we propose an areal measure based on the angular power spectrum, as defined in ISO 25178, to characterize the waviness of coated surfaces in relevant scales. To verify the validity of this measure, we compare it with an 1D industry standard appearance measurement system (wave-scan). While our method shows the same characteristics when mapped to the wave-scan values, we observed differences between both systems. These are mainly caused by the different measurement principles and the resulting information of the surface

Peering into microscale details of mountain winds

A grand challenge from the wind energy industry is to provide reliable forecasts on mountain winds several hours in advance at microscale (similar to 100 m) resolution. This requires better microscale wind-energy physics included in forecasting tools, for which field observations are imperative. While mesoscale (similar to 1 km) measurements abound, microscale processes are not monitored in practice nor do plentiful measurements exist at this scale. After a decade of preparation, a group of European and U.S. collaborators conducted a field campaign during 1 May-15 June 2017 in Vale Cobrao in central Portugal to delve into microscale processes in complex terrain. This valley is nestled within a parallel double ridge near the town of Perdigao with dominant wind climatology normal to the ridges, offering a nominally simple yet natural setting for fundamental studies. The dense instrument ensemble deployed covered a similar to 4 km x 4 km swath horizontally and similar to 10 km vertically, with measurement resolutions of tens of meters and seconds. Meteorological data were collected continuously, capturing multiscale flow interactions from synoptic to microscales, diurnal variability, thermal circulation, turbine wake and acoustics, waves, and turbulence. Particularly noteworthy are the extensiveness of the instrument array, space-time scales covered, use of leading-edge multiple-lidar technology alongside conventional tower and remote sensors, fruitful cross-Atlantic partnership, and adaptive management of the campaign. Preliminary data analysis uncovered interesting new phenomena. All data are being archived for public use

The Perdigão: Peering into Microscale Details of Mountain Winds

During 1 May–15 June 2017, some 70+ scientists, engineers, and support personnel converged on Vale do Cobrão, located in central Portugal within the municipality of Vila Velha de Ródão, for a unique field campaign designed to study microscale details of mountain winds (Fig. 1). Dubbed Perdigão (partridge in Portuguese) after a nearby village, the campaign culminated a decade-long preparation of European Union (EU) scientists to create a New Digital EU Wind Atlas (NEWA) at microscale resolution (see sidebar). The topography of Vale do Cobrão resembles a textbook case of a two-dimensional (2D) valley within parallel ridges, with annual wind climatology perpendicular to the ridges