Synthetic jet actuation for load control

The reduction of wind turbine blade loads is an important issue in the reduction of the costs of energy production. Reduction of the loads of a non-cyclic nature requires so-called smart rotor control, which involves the application of distributed actuators and sensors to provide fast and local changes in aerodynamic performance. This paper investigates the use of synthetic jets for smart rotor control. Synthetic jets are formed by ingesting low-momentum fluid from the boundary layer along the blade into a cavity and subsequently ejecting this fluid with a higher momentum. We focus on the observed flow phenomena and the ability to use these to obtain the desired changes of the aerodynamic properties of a blade section. To this end, numerical simulations and wind tunnel experiments of synthetic jet actuation on a non-rotating NACA0018 airfoil have been performed. The synthetic jets are long spanwise slits, located close to the trailing edge and directed perpendicularly to the surface of the airfoil. Due to limitations of the present experimental setup in terms of performance of the synthetic jets, the main focus is on the numerical flow simulations. The present results show that high-frequency synthetic jet actuation close to the trailing edge can induce changes in the effective angle of attack up to approximately 2.9°

Leading Edge Vortex Formation on a Flapping Wing Robotic Bird

The Robird is an bird-like drone that flies by flapping its wings. It closely resembles a peregrine falcon in appearance, size and weight, but more specifically in its flapping flight performance. Drones like theRobird could might useful purposes such as bird control at airports, but their development is currently hampered by a limited understanding of the aerodynamics involved. The present study aims to identify the role of attached vortical structures on the flight performance of the Robotic bird. Particle Tracking Velocimetry (PTV) measurements were performed on a relatively large volume (200mm × 500mm × 600mm) around the flapping Robird wing. The measurement data shows two significant attached vortical structures: one on the lower side of the wing during the upstroke, and a smaller one on the upper side of the wing during the downstroke. The vortex on the lower side is accompanied by significant spanwise flow near the wing surface. The magnitude of this spanwise flow depends on the Strouhal number, which is a dimensionless measure for the flapping frequency

Detached-Eddy Simulation of the Vortical Flowfield about the VFE-2 DeltaWing

The numerical simulation of the flow around a 65° delta wing configuration with rounded leading edges is presented. For the numerical simulation the Cobalt Code uses a cell-centered unstructured hybrid mesh approach. Several numerical results are presented for the steady RANS equations as well as for DES and DDES hybrid approaches. The simulations are done as part of the NATO RTO/AVT 113 working group focusing on experimental and numerical research on delta wing configurations with rounded leading edges. Within this paper the focus is related to the dual primary vortex flow topology, especially the sensitivity of the flow to angle of attack and Reynolds number effects. Reasonable results are obtained with both steady RANS and SA-DDES simulations. The results are compared and verified by experimental data, including surface pressure and pressure sensitive paint results. The impact of transition is assessed, and recommendations for improving future simulations are made