Aerodynamics of Low Reynolds Number Rigid Flapping Wing Under Hover and Freestream Conditions.

MAV;Aerodynamics;Flapping Wing;Vortex Dynamics;Surrogate Model;Low Reynolds Number;Aerospace Engineering;Engineering;Aerospace Engineering

Trizila, Patrick ClarkGirard, Anouck Renee ;

University of Michigan

关键词: MAV;    Aerodynamics;    Flapping Wing;    Vortex Dynamics;    Surrogate Model;    Low Reynolds Number;    Aerospace Engineering;    Engineering;    Aerospace Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/86503/ptrizila_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Micro air vehicles (MAVs) are defined by all spatial dimensions being less than 15 cm. Equipped with a video camera or a sensor, these vehicles could perform surveillance and reconnaissance with low rates of detection, or environmental and bio-chemical sensing at remote or otherwise hazardous locations. Its size makes the MAV easily transported and deployed as well as inexpensive and more expendable than alternatives, e.g. an airplane, a satellite, or a human. The ability to hover for an MAV is highly desirable in these contexts. The approach taken in the current studies is to numerically simulate the aerodynamics about flapping wings while controlling the kinematic motions and environmental conditions. Two complementary sets of tools were used in the investigations. Navier-Stokes solvers were used to obtain detailed fluid physics information, instantaneous force data, and to train the surrogate models. The surrogate models were used to estimate the average lift and power required over a flapping cycle while also providing information on the sensitivity of the kinematic variables, to identify trends in lift and power required as a function of the kinematic variables, and to construct a Pareto front showing the trade-offs between the competing objectives. Findings include i) an examination of the competing influences introduced by tip vortices, and it was seen that they could increase lift compared to their analogous 2D cases, counter to classical steady state theory. ii) The highest time averaged lift values were found during kinematics with high angles of attack during advanced rotation as they promoted LEV generation and subsequently took advantage of them during wake capture. iii) Kinematics with synchronized rotation and low angles of attack had surprisingly similar 2D and low-aspect-ratio force histories. iv) Modest environmental perturbations, those a fraction of the translational wing velocity, can have a profound impact on the resulting forces. Closely related open questions regard how the Reynolds number, planform shape, and the flapping about a point, with the resulting centripetal accelerations, affect the LEV and tip vortex development. Particularly what guiding principles should be kept in mind when exploring these degrees of freedom in the context of MAV design?