Jianghao Wu

Bio: Jianghao Wu is an academic researcher from Beihang University. The author has contributed to research in topics: Flapping & Wing. The author has an hindex of 10, co-authored 28 publications receiving 272 citations.

Aerodynamic Analysis of a Flapping Rotary Wing at a Low Reynolds Number

Abstract: A flapping rotary wing is a novel layout for micro air vehicle design. A computational fluid dynamics method is employed to understand the unsteady aerodynamic behavior of such a layout at a low Reynolds number. A comparison of flow between an flapping wing and a typical flapping rotary wing is conducted to evaluate the effect of rotational moment. Although the mean lift of the flapping wing is close to zero, a large mean rotational moment can drive the wing to rotate. A large mean lift coefficient can be obtained when the wing begins to rotate, but the mean rotational moment coefficient starts to decrease. The leading-edge vortex is attached to the wing surface until it moves to the trailing edge, despite the negative spanwise flow near the tip. The aerodynamic force depends on nondimensional variables, including flapping amplitude, mean angle of attack, pitching amplitude, ratio of period of flapping to rotation motion n, and Reynolds number. An analysis of these nondimensional variables shows that only...

Experimental study on the lift generated by a flapping rotary wing applied in a micro air vehicle

Abstract: An experimental study was conducted to further validate whether the newly proposed flapping rotary wing is suitable for micro air vehicle design. First, the effects of two main kinematical parameters (flapping frequency and initial angle of attack) of flapping rotary wing on lift generation were discussed. It was found that a higher lift can be generated by flapping rotary wing through increasing flapping frequency at a proper initial angle of attack. Second, effect of coupled flapping motion with rotating motion on lift generation was analyzed. It is important that a larger lift was generated by flapping rotary wing than the superposition lifts from purely flapping and purely rotating motions when the initial angle of attack was less than a critical value. Finally, the comparison of the capability of lift generation from the flapping rotary wing and conventional rotary wing was given. It was indicated that the lift from flapping rotary wing was larger than that from conventional rotary wing in the range ...

Unsteady aerodynamics of a pitching-flapping-perturbed revolving wing at low Reynolds number

Abstract: Due to adverse viscous effects, revolving wings suffer universally from low efficiency at low Reynolds number (Re). By reciprocating wing revolving motion, natural flyers flying at low Re successfully exploit unsteady effects to augment force production and efficiency. Here we investigate the aerodynamics of an alternative, i.e., a revolving wing with concomitant unsteady pitching and vertical flapping perturbations (a pitching-flapping-perturbed revolving wing). The current work builds upon a previous study on flapping-perturbed revolving wings (FP-RWs) and focuses on combined effects of pitching-flapping perturbation on force generation and vortex behaviors. The results show that, compared with a FR-RW, pitching motion further (1) reduces the external driving torque for rotating at 0° angle of attack (α0) and (2) enhances lift and leads to a self-rotating equilibrium at α0 = 20°. The power loading of a revolving wing at α0 = 20° can be improved using pitching-flapping perturbations with large pitching amplitude but small Strouhal number. Additionally, an advanced pitching improves the reduction of external driving torque, whereas a delayed pitching weakens both the lift enhancement and the reduction of external driving torque. Further analysis shows that pitching effects can be mainly decomposed into the Leading-Edge-Vortex (LEV)-mediated pressure component and geometric projection component, together they determine the force performance. LEV circulation is found to be determined by the instantaneous effective angle of attack but could be affected asymmetrically between upstroke and downstroke depending on the nominal angle of attack. Pitching-flapping perturbation thus can potentially inspire novel mechanisms to improve the aerodynamic performance of rotary wing micro air vehicles.

Aerodynamic Analysis of a Flapping Rotary Wing at a Low Reynolds Number

Abstract: A flapping rotary wing is a novel layout for micro air vehicle design. A computational fluid dynamics method is employed to understand the unsteady aerodynamic behavior of such a layout at a low Reynolds number. A comparison of flow between an flapping wing and a typical flapping rotary wing is conducted to evaluate the effect of rotational moment. Although the mean lift of the flapping wing is close to zero, a large mean rotational moment can drive the wing to rotate. A large mean lift coefficient can be obtained when the wing begins to rotate, but the mean rotational moment coefficient starts to decrease. The leading-edge vortex is attached to the wing surface until it moves to the trailing edge, despite the negative spanwise flow near the tip. The aerodynamic force depends on nondimensional variables, including flapping amplitude, mean angle of attack, pitching amplitude, ratio of period of flapping to rotation motion n, and Reynolds number. An analysis of these nondimensional variables shows that only...

Effects of kinematic parameters on three-dimensional flapping wing at low Reynolds number

Abstract: In nature, creatures such as birds, insects, and fish have excellent flight and mobility capabilities. The prominent flight performance of many creatures employing flapping wings has attracted researchers to study the aerodynamics of bionic flapping wings, which has potential application in designing micro air vehicles and autonomous underwater vehicles. Bionic movements usually have to adapt to the low Reynolds number environment. It is noteworthy that the flow field of a flapping wing at low Reynolds numbers flow state is closely related to the complex non-linear shedding and viscous phenomenon, especially in a three-dimensional (3D) flapping wing. In order to observe the influence of the viscous phenomenon on flapping wing propulsive performance at low Reynolds numbers, the flow field characteristics of the 3D flapping wing under different Reynolds numbers are discussed using the immersed boundary-lattice Boltzmann method with the Chinese supercomputer TianHe-II in this paper. The influence of kinematic parameters on the flow characteristics at low Reynolds number is particularly emphasized, considering that the biological movement involves many kinematic parameters, the unsteady flow field and vortex structure around the flapping wing are analyzed in detail. This study reports that the law of the flapping wing propulsive performance strongly depends on kinematic parameters that affect the vortex changes. The underlying flow mechanism behind flapping wing performance at low Reynolds numbers has been explored, which will make it possible to apply superior kinematic parameters to improve the propulsive performance of a flapping-like new airplane.