Development of an Unmanned Aerial Vehicle for the Measurement of Turbulence in the Atmospheric Boundary Layer

Abstract

This paper describes the components and usage of an unmanned aerial vehicle developed for measuring turbulence in the atmospheric boundary layer. A method of computing the time-dependent wind speed from a moving velocity sensor data is provided. The physical system built to implement this method using a five-hole probe velocity sensor is described along with the approach used to combine data from the different on-board sensors to allow for extraction of the wind speed as a function of time and position. The approach is demonstrated using data from three flights of two unmanned aerial vehicles (UAVs) measuring the lower atmospheric boundary layer during transition from a stable to convective state. Several quantities are presented and show the potential for extracting a range of atmospheric boundary layer statistics.

New Setup of the UAS ALADINA for Measuring Boundary Layer Properties, Atmospheric Particles and Solar Radiation

“…Validation methods used by the ALADINA research team and other authors, e.g., [9,21,26,[35][36][37], are summarized in this section regarding their usefulness before being applied on the dataset.…”

On the Use of Unmanned Aerial Systems for Environmental Monitoring

“…Increasing miniaturization allows multispectral, hyperspectral, and thermal imaging, as well as Synthetic Aperture Radar (SAR) and LiDAR (Light Detection and Ranging) sensing to be conducted from UAS. As examples of recent UAS-based environmental monitoring applications, work has focused on (a) land cover mapping [18,19]; (b) vegetation state, phenology, and health [20,21]; (c) precision farming/agriculture [22][23][24]; (d) monitoring crop growth, and invasive species infestation [25,26]; (e) atmospheric observations [27]; (f) disaster mapping [28]; (g) soil erosion [29,30]; (h) mapping soil surface characteristics [31,32]; and (i) change detection [33].…”

Calibration Procedure and Accuracy of Wind and Turbulence Measurements with Five-Hole Probes on Fixed-Wing Unmanned Aircraft in the Atmospheric Boundary Layer and Wind Turbine Wakes

“…The offset ∆Φ for the roll angle is set to zero and can be, according to Van den Kroonenberg et al [7], neglected, since the influence on the wind components is very small. The offsets ∆Ψ and ∆Θ are applied to the transformation T gb in Equation (5) and the factor f tas is multiplied with the norm of the true airspeed vector | u a | in Equation (4). To ensure comparability between the three calibrations, the correction offsets and factors are determined in the exact same way.…”

“…For environmental science in the atmospheric boundary layer (ABL), airborne measurements supplement the limited coverage of ground-based measurements or tethered balloons. Manned research aircraft have intensively investigated a wide range of processes and phenomena [1][2][3] and unmanned aerial systems (UAS) adopted the measurement techniques of quantities such as temperature, humidity, and the wind vector [4][5][6][7], but are not limited to these, as shown by Bärfuss et al [8] for aerosol and radiation measurements, or by Schuyler and Guzman [9] for gas concentrations. The 3D wind vector using multi-hole probes is calculated by the summation of the ground speed vector of the vehicle and the true airspeed vector.…”

“…For turbulence statistics, flux calculations, and quantitative analysis of turbine wake characteristics, an independent measurement of the true airspeed with a pitot tube and the interpolation of calibration polynomials at different Reynolds numbers of the probe's tip onto the Reynolds number during the measurement, reducing the uncertainty significantly.Atmosphere 2019, 10, 124 2 of 33 attitude, position, and velocity of the vehicle, measured by an inertial navigation system (INS), multiple coordinate transformations finally yield the wind vector. This method is widely used in manned aircraft [1,10] and on fixed-wing UAS [4][5][6][7]. The accuracy of the wind vector measurement is crucial, and the propagation of errors have many influencing factors, originating in the attitude and ground speed measurement of the aircraft, the flow angles and flow magnitude (true airspeed vector) measurement with the multi-hole probe, and also in the measurement of the thermodynamic state of the air.…”