Flow Control for Unsteady Aerodynamics of Pitching/Plunging Airfoils
Final Report Abstract
In this project, investigation and control of the leading edge vortex (LEV) detachment from pitching and plunging airfoils is addressed. The investigated scenarios are representative for flapping wing propulsion of Micro Air Vehicles. The phase of high induced lift during the growth of the vortex on the airfoil is supposed to be prolonged by manipulation of its detachment with different flow control devices. Flow manipulation is deployed at topologically critical locations with the overall goal of higher net lift. To allow for a specific and effective manipulation of the LEV detachment, it is studied experimentally over a wide parameter range using complementary parameter space of a water tunnel at the Beihang University and a wind tunnel at TU Darmstadt. Numerical simulations of the uncontrolled and controlled field complement experimental investigations. Based on the validation of comparability of the phenomena between both facilities, with the aid of a common baseline case, a model that allows for the prediction of the occurrence of secondary structures that initiate the vortex detachment is derived and validated. In order to prolong the LEV growth phase on the airfoil and attain higher overall lift, a DBD plasma actuator is deployed to manipulate the flow field at topologically critical locations on different airfoils at TU Darmstadt. The growth phase of the vortex is prolonged, which indicates an enhancement of the vortex induced lift, using the proposed manipulation approach. Transferability of the manipulation approach to different airfoil kinematics of a flat plate and a NACA 0012 airfoil is also validated successfully. Considerations regarding the control authority of the actuator are used to derive and test the minimum effective actuation period, which allows for reduction of the power input to the actuator of more than 40%. In addition to considerations of a pitching and plunging airfoil in steady inflow, transient inflow conditions on a stationary airfoil, representative of gust loads on wind turbine blades or bridge decks, are also adressed within the project. These efforts aim at the experimental validation of aerodynamic transfer functions, known as the Sears and Atassi formulations, which allow for a prediction of unsteady loads. Both functions are found to be capable of load prediction if inflow assumptions are carefully reproduced. It is also shown that no fundamental difference between both functions exists, if they are normalized appropriately. In order to simplify the generation of periodic inflow conditions in a wind tunnel, a gust generation approach utilizing a single pitching and plunging airfoil is derived and experimentally validated. It is demonstrated that high frequency and amplitude gusts can be generated with the aid of optimized airfoil kinematics, derived from the Theodorsen theory, using a single airfoil.
Publications
- Flow mechanism for the effect of pivot point on the aerodynamics characteristics of a pitching airfoil and its manipulation. Physics of Fluids, 31, 087108, 2019
Li, X., Feng, L. and Li, Z.
(See online at https://doi.org/10.1063/1.5114833) - Generation of periodic gusts with a pitching and plunging airfoil. Experiments in Fluids, 2019, 60(11), 166
Wei, N. J., Kissing, J. and Tropea, C.
(See online at https://doi.org/10.1007/s00348-019-2815-1) - Insights into the periodic gust response of airfoils. Journal of Fluid Mechanics, 2019, 876, 237-263
Wei, N. J., Kissing, J., Wester, T. T., Wegt, S., Schiffmann, K., Jakirlic, S., Hölling, M., Peinke, J. and Tropea, C.
(See online at https://doi.org/10.1017/jfm.2019.537) - (2020). Delaying Leading Edge Vortex Detachment by Plasma Flow Control at Topologically Critical Locations. Physical Review Fluids
Kissing, J., Stumpf, B., Kriegseis, J., Hussong, J., & Tropea, C.
(See online at https://doi.org/10.1103/PhysRevFluids.6.023101) - (2020). Investigation and Control of Unsteady Flow Conditions on Airfoils. Technische Universität Darmstadt, Darmstadt, Dissertation
Kissing, J.
(See online at https://dx.doi.org/10.25534/tuprints-00014201) - Experimental investigation on the leading edge vortex formation and detachment mechanism of a pitching and plunging plate. Journal of Fluid Mechanics, 2020, 901, A17
Li, Z., Feng, L., Kissing, J., Tropea, C. and Wang, J.-J.
(See online at https://doi.org/10.1017/jfm.2020.509) - Insights into leading edge vortex formation and detachment on a pitching and plunging flat plate. Experiments in Fluids, 2020, 61, 208
Kissing, J., Kriegseis, J., Li, Z., Feng, L., Hussong, J. and Tropea, C.
(See online at https://doi.org/10.1007/s00348-020-03034-1) - Leading edge vortex formation and detachment on a flat plate undergoing simultaneous pitching and plunging motion: Experimental and computational study. International Journal of Heat and Fluid Flow, 2020, 86
Kissing, J., Kriegseis, J., Wegt, S., Jakirlic, S., Kriegseis, J., Hussong, J. and Tropea, C.
(See online at https://doi.org/10.1016/j.ijheatfluidflow.2020.108726) - Lift enhancement strategy and mechanism for a plunging airfoil based on vortex control. Physics of Fluids, 32, 087116, 2020
Feng, L., and Li, Z. and Chen, Y.
(See online at https://doi.org/10.1063/5.0019317) - On the role of secondary structures during leading edge vortex lift off and detachment on a pitching and plunging at plate. In: New Results in Numerical and Experimental Fluid Mechanics XII, Springer International Publishing, pp 204-213, 2020
Kissing, J., Kriegseis, J. and Tropea C
(See online at https://doi.org/10.1007/978-3-030-25253-3_20)
