Browsing by Author "Ansari, Salman Ahmad"

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    A Nonlinear, Unsteady, Aerodynamic Model for Insect-like Flapping Wings in the Hover with Micro Air Vehicle Applications
    (Cranfield University, 2004) Ansari, Salman Ahmad; Knowles, Kevin
    The essence of this PhD thesis is the analytical, aerodynamic modelling, as opposed to using grid-based methods such as CFD, of insect-like flapping wings in the hover for micro air vehicle applications. A key feature of such flapping-wing flows is their unsteadiness and the formation of a leading-edge vortex in addition to the conventional wake shed from the trailing edge. What ensues is a complex interaction between the shed wakes which, in part, determines the forces and moments on the wing. In an attempt to describe such a flow, two coupled, nonlinear, wake integral equations are derived and these form the foundation upon which the rest of the work stands. The model so developed is unsteady and inviscid in nature and essentially two-dimensional. It is converted to a 'quasi-three-dimensional' model using a blade-element-type analogy but with radial chords. The governing equations developed in the study are exact but do not have a closed form. Solutions are, therefore, found by numerical methods and implemented in FORTRAN. The model is validated against existing experimental data and remarkable agreement is found both in terms of flow field representation and force prediction. The importance of including the effect of the leading-edge vortex for such problems is also established. The model is then used for a parametric study to analyse the effects of various wing geometry and wing kinematics parameters. From these results, a preferred wing design for a flapping-wing MAV is proposed which is the ultimate aim of this work. The results from the unsteady, aerodynamic model are also compared with earlier work in the PhD using a simple quasi-steady model and good agreement is found in terms of the relative merits of the various wing parameters, thereby establishing the usefulness of using such simple models for initial design studies.