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Title: Assessment of fluidic control effectors using computational fluid dynamics
Author: Hoholis, G. A.
ISNI:       0000 0004 6058 7499
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2016
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The work discussed in this thesis uses computational uid dynamics to evaluate the performance of circulation control as a control effector for manoeuvring aircraft. As an outcome of this work, it has been shown that circulation control could potentially replace conventional control surfaces as a manoeuvre effector. Two test cases were simulated to validate the computational uid dynamics solver used throughout this work. The �rst, a circulation control aerofoil, which demonstrated that the solver was capable of predicting the pressure distribution over the aerofoil surface and the boundary layer velocities near the slot. The level of grid re�nement and the choice of turbulence model were also investigated showing that the results depended signi�cantly on the model used. The second, a generic unmanned combat air vehicle which exhibits highly nonlinear ow topologies at high angles of attack. The integrated loads were well predicted while the ow remained attached. There were some discrepancies in the loads at higher angles of attack due to the unsteady nature of the ow however the overall ow topology was captured accurately throughout the angle of attack range of zero to twenty �ve degrees. This demonstrated that the vortical ow encountered by typical combat aircraft can be predicted. Modi�cations were then made to the generic unmanned combat air vehicle used as a test case. The conventional control surfaces were replaced by circulation control and the performance of two operations was investigated. The two operations are, one for generating a rolling moment and the other for generating a yawing moment. The yawing moment operation was able to perform independently of the angle of attack, whilst the performance of the rolling moment operation dropped off signi�cantly when trailing edge ow separation occurred. Two con�gurations were tested, one with a single slot and one with three slots along the span. A increase in efficiency for the rolling moment operation was demonstrated by using multiple slots with a gap in between each. A tabular model for a two dimensional aerofoil employing circulation control was constructed to investigate whether these types of models are suitable for predicting unsteady loads. All loads are expressed as combinations of functions depending on a selection of the input parameters, i.e. angle of attack. The effects of decoupling the input parameters from each other were investigated. At high angles the performance of the circulation control decreases. The stall angle also decreases as there is an increase in the control parameter for the circulation control. As a result of this, these two parameters must be coupled within the model to obtain accurate predictions of the integrated loads. Overall, the lift and pitching moment were predicted accurately with some hysteresis. The drag was over and underpredicted during rapid changes of the control parameter and there was a signi�cant amount of hysteresis observed. A discussion of how a tabular model may be constructed for a full aircraft employing circulation control was also conducted.
Supervisor: Badcock, K. J. ; Steijl, R. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral