The focus of the research group in 2018 was the development, testing and usage of research tools for the numerical prediction of flow and sound fields.
Our research dealt with topics in two focus areas, including the numerical and experimental modeling of the wake evolution and radiation of low-frequency sound from wind turbines and tonal noise prediction for a 2-blade pusher propeller. For the wind-turbine flow simulation the in-house code INCA is used with actuator line treatment of rotating blades and LES modeling of the turbulent inflow and wake development over rough ground. For sound prediction the acoustic prediction tool SPYSI, developed at the Friedrich-Alexander Universität Erlangen in the group of Prof. S. Becker, is used. It is a time-domain implementation of the Ffowcs-Williams Hawkings formulation of Lighthills acoustic analogy. For the present studies it has been complemented in order to consider the effect of mean flow advection on the sound propagation. It has also been used to assess the low-frequency noise from wind turbines emerging from the unsteady blade loading due to interaction with atmospheric boundary layer turbulence.
The blade loading for a pusher propeller mounted downstream of the V-tail of the UAV IMPULLS has been predicted using ANSYS CFX in URANS mode. Figure 3 shows a side-view of the tail section. The propeller cuts through the wakes of the two stabilizer fins. As a result of the unsteady blade loading the contributions from higher harmonics of the blade passing frequency to the loading noise increases as shown in Figure 3 for an observer located 45 degrees off the rotor axis.