Abstract
This paper examines the unsteady lift, drag and moment coefficients experienced by a thin airfoil in high-amplitude pitch ramp motion. Experiments have been carried out in a wind tunnel at moderate Reynolds number ($Re\approx 1.45\times 10^{4}$), using a rigid flat-plate model. Forces and moments have been measured for reduced pitch rates ranging from 0.01 to 0.18, four maximum pitch angles ($30^{\circ },45^{\circ },60^{\circ },90^{\circ }$) and different pivot axis locations between the leading and the trailing edge. Results confirm that for reduced pitch rates lower than 0.03, the unsteady aerodynamics is limited to a stall delay effect. For higher pitch rates, the unsteady response is dominated by a buildup of the circulation, which increases with the pitch rate and the absolute distance between the pivot axis and the $3/4$-chord location. This circulatory effect induces an overshoot in the normal force and moment coefficients, which is slightly reduced for a flat plate with a finite aspect ratio close to 8 in comparison with the two-dimensional configuration. A new time-dependent model has been tested for both the normal force and moment coefficients. It is mainly based on the superposition of step responses, using the Wagner function and a time-varying input that accounts for the nonlinear variation of the steady aerodynamics, the pivot point location and an additional circulation which depends on the pitch rate. When compared with experiments, it gives satisfactory results for $0^{\circ }$ to $90^{\circ }$ pitch ramp motion and captures the main effect of reduced pitch rate and pivot point location.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Reference53 articles.
1. Granlund, K. , Ol, M. & Bernal, L. 2011a Experiments on pitching plates: force and flowfield measurements at low Reynolds numbers. In 49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, Aerospace Sciences Meetings, AIAA 2011-872.
2. State-space representation of the unsteady aerodynamics of flapping flight
3. Experiments to investigate lift production mechanisms on pitching flat plates
4. Recent progress in flapping wing aerodynamics and aeroelasticity
5. Prediction of Dynamic Stall Onset for Oscillatory Low-Speed Airfoils
Cited by
16 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献