Cylinder-Airfoil Interactions and the Effect on Airfoil Performance
| dc.contributor.advisor | Jones, Anya | en_US |
| dc.contributor.author | Lefebvre, Jonathan | en_US |
| dc.contributor.department | Aerospace Engineering | en_US |
| dc.contributor.publisher | Digital Repository at the University of Maryland | en_US |
| dc.contributor.publisher | University of Maryland (College Park, Md.) | en_US |
| dc.date.accessioned | 2021-09-16T05:37:28Z | |
| dc.date.available | 2021-09-16T05:37:28Z | |
| dc.date.issued | 2021 | en_US |
| dc.description.abstract | From micro air vehicles flying in the wake of buildings to aircraft operating in ship airwakes, turbulent flows generate unsteady aerodynamic loads on airfoils that may promote structural failure, loss of flight control, and produce noise radiation. In order to develop engineering solutions capable of mitigating these effects, accurate force prediction of airfoils encountering turbulent wakes is necessary. A barrier to such force prediction techniques is the lack of a fundamental understanding of the aerodynamics of wake-airfoil interactions. The goal of this work is to investigate the cylinder-airfoil configuration by quantifying the effect of cylinder wake turbulence on airfoil force production and identifying the underlying flow physics. Results were obtained from both wind tunnel experiments and numerical simulations using a NASA OVERFLOW solver. Four cylinder-airfoil configuration parameters were evaluated: the gap G/D and offset z/D distances between the cylinder and airfoil, the cylinder-diameter-to-airfoil-chord ratio D/c, and the cylinder cross-sectional geometry. During the investigation of each parameter, the airfoil angle of attack varied from α= -5 to 40 while the Reynolds number based on the airfoil chord c was fixed at Rec =1×10^5. Flow characterization of the region between the cylinder and airfoil revealed that the airfoil encounters a highly unsteady inflow. Turbulence intensity reaches 55% of the freestream velocity upstream of the airfoil's leading edge while the flow oscillates at the cylinder vortex shedding frequency. The influence of the upstream cylinder wake on airfoil performance was quantified by time-averaged force measurements and showed three modifications compared to a clean inflow: (1) lift augmentation, (2) negative drag or thrust, and (3) delay in stall. The unsteady airfoil behavior was also investigated, showing that the amplitude of unsteady airloads increases for small gap and offset distances, while the airfoil frequency response matches the cylinder vortex shedding frequency. Flowfield measurements show that the cylinder-airfoil interaction induces flow separation at the leading edge of the airfoil, generating a leading edge vortex (LEV). The LEV is identified as the main flow structure responsible for modifying airfoil performance as it provides lift enhancement and delays stall at large angles of attack, while at low angles of attack the LEV promotes reverse flow at the surface, contributing to negative drag. The results and analysis from this work advance the fundamental flow physics of the cylinder-airfoil interactions by revealing key flow structures responsible for the unsteady force production on an airfoil in the wake of a cylinder. | en_US |
| dc.identifier | https://doi.org/10.13016/qrs8-qxst | |
| dc.identifier.uri | http://hdl.handle.net/1903/27748 | |
| dc.language.iso | en | en_US |
| dc.subject.pqcontrolled | Aerospace engineering | en_US |
| dc.subject.pqcontrolled | Fluid mechanics | en_US |
| dc.title | Cylinder-Airfoil Interactions and the Effect on Airfoil Performance | en_US |
| dc.type | Dissertation | en_US |
Files
Original bundle
1 - 1 of 1
Loading...
- Name:
- Lefebvre_umd_0117E_21749.pdf
- Size:
- 29.91 MB
- Format:
- Adobe Portable Document Format