[Thesis]. Manchester, UK: The University of Manchester; 2016.
Numerical models of insect flapping flight have previously been developed and used
to simulate the performance of insect flight. These models were commonly developed
via Blade Element Theory, offering efficient computation, thus allowing them to be
coupled with optimisation procedures for predicting optimal flight. However, the models
have only been used for simulating hover flight, and often neglect the presence of
the induced flow effect. Although some models account for the induced flow effect,
the rapid changes of this effect on each local wing element have not been modelled.
Crucially, this effect appears in both axial and radial directions, which influences
the direction and magnitude of the incoming air, and hence the resulting aerodynamic
forces.This thesis describes the development of flapping wing models aimed at advancing
theoretical tools for simulating the optimum performance of insect flight. Two models
are presented: single and tandem wing configurations for hawk moth and dragonfly,
respectively. These models are designed by integrating a numerical design procedure
to account for the induced flow effects. This approach facilitates the determination
of the instantaneous relative velocity at any given spanwise location on the wing,
following the changes of the axial and radial induced flow effects on the wing. For
the dragonfly, both wings are coupled to account for the interaction of the flow,
particularly the fact that the hindwing operates in the slipstream of the forewing.A
heuristic optimisation procedure (particle swarming) is used to optimise the stroke
or the wing kinematics at all flight conditions (hover, level, and accelerating flight).
The cost function is the propulsive efficiency coupled with constraints for flight
stability. The vector of the kinematic variables consists of up to 28 independent
parameters (14 per wing for a dragonfly), each with a constrained range derived from
the maximum available power, the flight muscle ratio, and the kinematics of real insects;
this will prevent physically-unrealistic solutions of the wing motion. The model developed
in this thesis accounts for the induced flow, and eliminates the dependency on the
empirical translation lift coefficient. Validations are shown with numerical simulations
for the hover case, and with experimental results for the forward flight case. From
the results obtained, the effect of the induced velocity is found to be greatest in
the middle of the stroke. The use of an optimisation process is shown to greatly improve
the flapping kinematics, resulting in low power consumption in all flight conditions.
In addition, a study on dragonfly flight has shown that the maximum acceleration is
dependent on the size of the flight muscle.