UWE Bristol Engineering showcase 2015

Valentin Erb
MEng – Aerospace Engineering (Systems Engineering)
Project Supervisor
Dr. Pritesh Narayan
Assessment of the Me262’s slow flight performance – PART B
Introduction
On the basis of the project concept developed in
PART A of the project, the assessment of the slowflight
characteristics of the Me262 aircraft was
continued.
Based upon the CATIA geometry created in the
first part of the project, a rapid-prototyped scale
wind-tunnel model was created using Fused
Deposition Modelling (FDM), suitable for the UWE
subsonic wind-tunnel.
The same geometry was used in the particle-based
CFD software XFlow to set-up respective
simulations to reflect the wind tunnel tests.
Simulations and tests were run at speed of 15-35
m/s (Re=2e5).
In a final step, the plane was simulated in real
scale to create a basis for the comparison to real
world flight test data at 68 m/s (Re=6e6).
Validation
Before any testing with the Me262 geometry was
done, the wind tunnel and XFlow were validated
using 2D and 3D NACA0012 simulations from
Ansys Fluent. All tests showed a good agreement
between the different tools. The Figure below
shows the validation lift curve from XFlow and the
wind tunnel tests:
Experimental Set-Up 1/18
For the XFlow simulations of the wind tunnel tests
of the Me262, the same set-up was used as in the
NACA0012 validation tests. The two figures below
show the corresponding set-ups:
Besides numerical results, also visual flow
patterns were assessed with woolen threads.
Furthermore, the influence of the surface
roughness of the wind tunnel model was tested,
together with other parameters.
Experimental Set-Up Real Scale
As for the real-scale simulations, an unconstrained
free flow domain was used, which is shown below,
which shows the aircraft in full stall at an angle of
16°:
Results
The scale results from the wind tunnel and XFlow
simulations showed a good agreement in terms of
lift coefficients and also stall angle and zero lift
angle. Also visual flow patterns could be identically
seen in the wind tunnel and the simulations. A
significant influence of surface roughness, speed
dependency or turbulence intensity could not be
identified.
The 1/18 scale model was found to stall at an
angle of 7° and C Lmax of 0.67.
During the real-scale simulations a different
behavior was experienced, as it stalled at 12°
with a C Lmax of 0.9. These differences can be well
explained by the influence of Reynolds-Number
and show the limitations of wind tunnel tests.
The final XFlow simulations showed a good
agreement with historical data, but revealed some
issues with underlying test-flight data.
In the Figure below, the comparison between the
two scales is seen:
All in all the experimental set-up proved to deliver
the desired data and a qualitative statement about
the stalling characteristics could be made.
However, they also revealed some inconsistencies
in the test flight data and suggest a further
analysis of the aircraft and also a consideration of
high lift devices, normally found on the aircraft.
Project summary
The investigation undertaken assesses the
design of the Messerschmitt Me262 aircraft
towards lift generation at high angles of
attack in clean configuration.
Experiments were conducted in XFlow CFD
and a wind tunnel, using a rapid prototyped
model at a scale of 1/18. Finally , the aircraft
was simulated in real scale . The experimental
approach was validated with a NACA0012
wing geometry.
Project Objectives
Besides validating the CFD software against
the UWE wind tunnel, it was targeted to
obtain the lift curve for the basic Me262
aircraft and assess the stalling angle and
maximum lift coefficient. The difference
between scale wind tunnel tests and real
scale simulations were demonstrated.
Furthermore, the capabilities of up-to-date
CFD software were shown and assessed.
Project Conclusion
In terms of experimental approach, the
project showed and demonstrated the
suitability of XFlow and wind tunnel tests for
the assessment of lift generation.
Validation of the approach was achieved and
the geometry of the Me262 could be
assessed and evaluated.
However, particular attention had to be paid
to the simulation set-up to obtain consistent
data.