Resumen | A good understanding of physics in carriage and release of external stores from an aircraft is of primary
concern to military aircraft designers. The flow field encountered on stores in the vicinity of an aircraft is
usually ...
A good understanding of physics in carriage and release of external stores from an aircraft is of primary
concern to military aircraft designers. The flow field encountered on stores in the vicinity of an aircraft is
usually very complex due to mutual interferences. This situation sharpens when transonic fluid flows are
considered. Traditionally, designers have resorted to wind tunnel tests to assess these and other questions.
However, recent years have seen an emergence of application of CFD methods as a cheaper alternative since
they provide accurate results when the appropriate models are applied.
The main aim of this TFM is to validate an inviscid flow solution based on an unstructured grid approach over
a stationary wing/pylon/store configuration. The efficiency of the designed setup is compared, when possible,
against published literature and experimental data. Rigid body aerodynamics and mutual interference effects
are explored to justify the limits of the model. From this ambitious goal, three main constitutive objectives
arise.
First, to design a valid CFD setup to faithfully reproduce the real behaviour of a generic store carried on a
military delta wing at transonic speeds. Along this part, different design methods are evaluated, searching for
their benefits and drawbacks. Thereby, the final geometry, grid approach, and fluid flow solver is found.
Chosen design solution must provide reliable results with an affordable computational cost. As part of this
objective, a parametric study in terms of surface grid resolution is accomplished to determine how this
parameter impacts on results’ accuracy. Additionally, a comparison analysis against a viscous approach is
performed.
Secondly, to validate the final CFD setup by comparing various simulations against published literature and
experimental data. Achieved outcomes include force and moment coefficients and surface pressure
distributions. This allows to determine the limits of the model and to validate its correct operation.
Finally, to theoretically define the fundaments to perform non-stationary store separation simulations. Within
this part, main obstacles, conforming blocks, and interactions among the different elements of the simulation
are described. It is worth mentioning, though, that accomplishing a CFD simulation of a store releasing from
an aircraft requires of enormous computational resources. Currently, this is unaffordable for a personal
computer; therefore, the simulation itself is out of the scope for this TFM.
When working with CFD tools, one must bear in mind that a particular approach may never work the best for
all geometries, flight conditions, and all configurations. However, as it will be demonstrated throughout this
report, the problem assessed during this TFM can be correctly suited by an inviscid approach with
unstructured meshing. The efficiency of the proposed setup provides an acceptable level of accuracy with a
significant savings in time, effort, and computational cost. The fact that this setup is successfully demonstrated
at transonic speeds makes the technique an attractive tool not only for preliminary design but also for more
sophisticated assessments.
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