An improved aerodynamic model for quasi-steady simulations of animal flight at moderate Reynolds numbers
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arXiv
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2023
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| _version_ | 1866909543569555456 |
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| author | Su, Yunxing Fan, Xiaozhou Onoue, Kyohei Vejdani, Hamid Breuer, Kenneth |
| author_facet | Su, Yunxing Fan, Xiaozhou Onoue, Kyohei Vejdani, Hamid Breuer, Kenneth |
| contents | We report on experimental and numerical studies aimed at developing an improved paradigm to model animal flight at moderate Reynolds numbers ($ 20 k - 50k $). A series of experiments were performed to characterize the behaviors of aerodynamic forces and moment associated with a quasi-steady rectangular wing over a range of angle of attack, $α$. We demonstrate that, while the drag coefficient curve, $C_D(α)$, can be accurately modeled solely by a simple trigonometric function, the evolution of lift coefficient curve, $C_L(α)$, is governed by the sum of trigonometric and exponential functions, where the latter captures the linear variation in lift coefficient within the small-angle regime, as predicted by the linear inviscid theory. In addition, we establish an empirical relation between the location of the center of pressure and $α$, which can be used in conjunction with the proposed aerodynamic formulas (i.e., $C_L$ and $C_D$) to evaluate the pitching moment coefficient, $C_M(α)$, about any arbitrary axis. These quasi-steady formulations are then utilized within a previously tested flapping-wing code to simulate the forward flight of a pigeon and a bat at various flight speeds, and the results are compared against previously reported experimental data. We successfully demonstrate that the proposed formulas yield much better agreement with wingbeat frequency for both animals, especially at higher flight speeds. In addition, the small-angle regime proves critical in offering higher $C_L/C_D$, leading to solutions with lower power consumption and body pitching variation, both of which are important aspects in designing future flapping wing robots. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2302_09602 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | An improved aerodynamic model for quasi-steady simulations of animal flight at moderate Reynolds numbers Su, Yunxing Fan, Xiaozhou Onoue, Kyohei Vejdani, Hamid Breuer, Kenneth Fluid Dynamics Biological Physics We report on experimental and numerical studies aimed at developing an improved paradigm to model animal flight at moderate Reynolds numbers ($ 20 k - 50k $). A series of experiments were performed to characterize the behaviors of aerodynamic forces and moment associated with a quasi-steady rectangular wing over a range of angle of attack, $α$. We demonstrate that, while the drag coefficient curve, $C_D(α)$, can be accurately modeled solely by a simple trigonometric function, the evolution of lift coefficient curve, $C_L(α)$, is governed by the sum of trigonometric and exponential functions, where the latter captures the linear variation in lift coefficient within the small-angle regime, as predicted by the linear inviscid theory. In addition, we establish an empirical relation between the location of the center of pressure and $α$, which can be used in conjunction with the proposed aerodynamic formulas (i.e., $C_L$ and $C_D$) to evaluate the pitching moment coefficient, $C_M(α)$, about any arbitrary axis. These quasi-steady formulations are then utilized within a previously tested flapping-wing code to simulate the forward flight of a pigeon and a bat at various flight speeds, and the results are compared against previously reported experimental data. We successfully demonstrate that the proposed formulas yield much better agreement with wingbeat frequency for both animals, especially at higher flight speeds. In addition, the small-angle regime proves critical in offering higher $C_L/C_D$, leading to solutions with lower power consumption and body pitching variation, both of which are important aspects in designing future flapping wing robots. |
| title | An improved aerodynamic model for quasi-steady simulations of animal flight at moderate Reynolds numbers |
| topic | Fluid Dynamics Biological Physics |
| url | https://arxiv.org/abs/2302.09602 |