Development of the Multi-Purpose Airborne Sensor Carrier MASC-3 and Turbulence Measurements in the Atmospheric Boundary Layer

Abstract

This thesis deals with measurements in the atmospheric boundary layer, which is the lowest part of the earth’s atmosphere. Here, life takes place. Stably stratified turbulence regimes in the atmospheric boundary layer and the wake aerodynamics of wind energy converters are investigated. These topics have one key element in common. The in-situ 3D wind vector mea- surement is crucial for a deeper understanding. Simplified algorithms to es- timate the wind speed and direction are commonly used and the applicability in different meteorological conditions, as well as uncertainties and the tem- poral resolution are investigated. Fixed-wing unmanned aircraft systems us- ing a multi-hole probe in combination with an inertial navigation system are capable of measuring the high resolution 3D wind vector on turbulent scales. Turbulent fluxes of heat and momentum can be estimated. Remaining un- certainties and error sources, such as the influence of a varying airspeed of the UAS during the measurements, or operational constraints due to the cal- ibration of the multi-hole probe, are investigated, quantified and improved. The design and development of the third mark of the Multi-Purpose Airborne Sensor Carrier (MASC-3) is also a major part of this thesis and aims to im- prove the wind measurement, to gain endurance, to allow operations under an enlarged range of environmental conditions and to enable easy imple- mentation of further sensors. A close comparison of the measurements of MASC-3 with established measurement systems, finally allows validation of the turbulent 3D wind vector measurement. MASC-3 in combination with a meteorological measurement tower and a Sodar system, is used for investi- gating the interactive nature of the stable boundary layer over homogeneous terrain in polar conditions. The wake of wind energy converters is investi- gated and the measurements of MASC-3 are able to capture the detaching tip vortices and resolve the complex nature of the flow field in a new and revealing manner.