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|Title: ||Aerodynamics of battle damaged finite aspect ratio wings|
|Authors: ||Samad-Suhaeb, Mujahid|
|Keywords: ||Battle damage|
Low speed wind tunnel
Surface pressure measurements
Finite aspect ratio wing
|Issue Date: ||2005|
|Publisher: ||© M.Samad-Subaeb|
|Abstract: ||When an aircraft is aerodynamically or structurally damaged in battle, it may not able to
complete the mission and the damage may cause its loss. The subject of aircraft battle
survivability is one of critical concern to many disciplines, whether military or civil.
This thesis considered and focused on Computational Fluid Dynamics [CFD] predictions and
experimental investigations into the effects of simulated battle damage on the low-speed
aerodynamics of a fmite aspect ratio wing.
Results showed that in two-dimensional [2d] and three-dimensional [3D] CFD simulations,
Fluent's® models work reasonably well in predicting jets flow structures, pressure distributions,
and pressure-coefficient Cp's contours but not for aerodynamic coefficients. The consequences
were therefore that CFD prediction was poor on aerodynamic-coefficients increments. The
prediction of Cp's achieved good agreement upstream and near the damage hole, but showed
poor agreement at downstream of the hole. For the flow structure visualisation, at both weak and
strong jet incidences, the solver always predicted pressure-distribution-coefficient lower at
upstream and higher at downstream. The results showed relatively good agreement for the case
of transitional and strong jet incidences but slightly poor for weak jet incidences.
From the experimental results of Finite Wing, the increments for Aspect-ratio, AR6, AR8 and
ARIO showed that as damage moves out towards the tip, aerodynamic-coefficients increments
i.e. lift-loss and drag-rise decreased, and pitching-moment-coefficient increment indicated a
more positive value at all incidence ranges and at all aspect ratios. Increasing the incidence
resulted in greater magnitudes of lift-loss and drag-rise for all damage locations and aspect
ratios. At the weak jet incidence 4° for AR8 and in all of the three damage locations, the main
characteristics of the weak-jet were illustrated clearly. The increments were relatively small.
Whilst at 8°, the flow structure was characterised as transitional to stronger-jet. In Finite Wing
tests and for all damage locations, there was always a flow structure asymmetry. This was
believed to be due to gravity, surface imperfection, and or genuine feature. An 'early strong jet'
that indicated in Finite Wing-AR8 at 'transitional' incidence of 8°, also indicated in twodimensional
results but at the weak-jet incidence of 4°.
For the application of 2d data to AR6, AR8, and ARIO, an assessment of 2d force results led to
the analysis that the tests in the AAE's Low Turbulence Tunnel for 2d were under-predicting the
damage effects at low incidence, and over-predicting at high incidences. This suggested
therefore that Irwin's 2d results could not be used immediately to predict three-dimensional.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Aeronautical and Automotive Engineering) |
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