NEWPAN2D: Tools for the Analysis and Design of Aerofoils and Wings
A principal area of focus for Flow Solutions, and one in which we
provide industry leading capabilities, is the analysis and design of
aerofoils. These may be purely two-dimensional. More usually however
the sections form a 3D component such as an aircraft or racecar wing,
the hull, keel or rudder of a boat, a propeller or ducted fan. The
area of application is wide, but is concentrated on low-speed
applications, i.e. subsonic Mach numbers.
Broadly speaking, available CFD codes have tended to fall into
one of two camps:
- 3D analysis only, using computationally expensive
methods which are impossible/impractical to use in a direct
- 2D analysis and design (some offering inverse design capability,
but with no coupling or extension to 3D). Whilst it may be attractive
to the CFD code developer to concentrate on 2D-only solutions, it
is rare for a purely two-dimensional result to accurately reflect
the three-dimensional reality.
2D (yellow) and 3D matched (green) results on a front wing section, showing
the dangers of drawing any conclusions from 2D results.
What is much more valuable of course is a 3D design solution, and it
is precisely this requirement which the NEWPAN2D/NEWPAN combination is
designed to provide. By coupling the two codes together, you can gain
access to the inverse design and strong viscous coupling of NEWPAN2D,
applied to the 3D NEWPAN results.
Key Features of NEWPAN2D
- VERY fast and highly interactive; all the functionality described
here executes interactively in one or two seconds at most;
- inviscid analysis of two-dimensional multi-element aerofoils
(e.g. wing sections);
- application of strong viscous coupling to the basic inviscid
results, giving lift, drag and detailed Cp and boundary layer
characteristics up to maximum lift (i.e. with significant areas of
- an inverse aerofoil redesign procedure, which allows the user to
prescribe a sectional pressure distribution, and which returns the
aerofoil profiles required to achieve it;
- redesign by direct profile modification, including rotation, translation
- application of all these features to three-dimensional sectional
data as generated by NEWPAN, allowing redesign and viscous coupling on
sections sitting in a three-dimensional flowfield;
- integration of the method within the VIEWPAN framework, enabling for
example easy generation of 2D sections from 3D wing elements, and
comparison of results generated with existing data;
- integration of the method within the GEMS framework for analysis and
redesign of purely two-dimensional sections.
Strong Viscous Coupling
Both NEWPAN and NEWPAN2D in their basic forms are inviscid
methods. Hence their predicted pressure distributions assume full
attachment, which at high incidences will not be realised; predicted
lift keeps rising beyond the viscous maximum lift value.
Strong inviscid-viscous coupling provides support for accurate
results even in the presence of large areas of flow separation,
up to and beyond maximum lift.
NEWPAN2D provides access to a fully coupled boundary layer (viscous
correction) calculation. It uses quasi-simultaneous coupling to give
converged solutions with separation. The proper boundary solution
is found in cases where separation is present.
It includes calculation of the boundary layer as it flows into the
wake (i.e. it computes the free shear layer in the wake). This is
important as, for example, the wake from a wing element can `burst'
over a downstream flap (after running through the adverse pressure
gradient on the off-body pressure field of the flap). This is an
important stall-inducing mechanism limiting CLmax.
In contrast, other methods capable of being applied to 3D generated
data offer only weak coupling - with no calculation of the wake
free shear layer, and failure to converge in the presence of
Inverse Design: An Aerofoil Redesign Procedure
Although it is undoubtedly useful and important to produce accurate
results for the aerodynamic (or hydrodynamic) properties of your
current design, this is usually only part of the battle. Of even
greater interest is guidance as to how to make the design better.
The skilled aerodynamicist would like to be able to control and
prescribe the aerodynamic properties - such as lift, drag, and
details of the boundary layer behaviour such as transition and
separation, and let the CFD software work out the geometry of the
design necessary to achieve it. This is the inverse design problem,
addressed by NEWPAN2D.
Unconstrained, fully 3D inverse design is feasible, though not yet
possible; instead, through the NEWPAN-NEWPAN2D coupling, Flow
Solutions provides for the redesign of one or more sections sitting in
a NEWPAN-generated 3D flowfield (purely 2D support is also provided).
Multi-element aerofoils may be redesigned as follows. Firstly the
NEWPAN2D pure 2D or 3D derived NEWPAN results for the existing
geometry are computed and displayed. The inverse design method allows
us to directly modify the pressures; hence we graphically edit the
desired target pressures. As we do so, an integral boundary layer
solution is automatically re-evaluated; this allows us to tailor the
pressure gradients to achieve desirable transition and separation
characteristics. When we're ready, NEWPAN2D perturbs the original
aerofoil profiles to achieve a new design which generates a pressure
distribution with the closest feasible match to the target pressures
requested. In this manner, any one or even all of the sections of
a multi-element configuration may be redesigned simultaneously.
We may perform our redesign at one of a number of possible design
points, e.g. attitudes. NEWPAN2D is now able to compute and display
the performance of our new design at all the other design points. We
can evaluate its performance further by applying strong viscous
coupling. Now we are able to refine the design further, by applying
another design iteration, starting either with any of our previous
designs or by returning to the original geometry. In this way a
complete design history may be built up, with a number of branches
down which different possible avenues are explored.
An example and discussion of inverse design applied to the front wing
of a Formula One car is given here.
Redesign by Direct Geometry Modification
Often it is also useful to be able to apply direct geometric changes
within the NEWPAN2D design environment. For example a flap element
could be rotated by 10 degrees, or a mainplane could be scaled along
its chord by 10%. Via a seamless interface to GEMS, its rich toolkit
for geometry editing is also accessible. This allows NURBS editing of
profiles - i.e. fitting a NURBS curve through the points, enabling
smooth perturbation of the profile by moving the control points of the
Uniquely, where the section is part of a 3D model, such
modifications may be evaluated in seconds within the 3D
flowfield. NEWPAN2D provides a means to export the redesigned sections
to GEMS, which in turn provides customised functionality for
reintegration of the sections into the complete 3D model. At this
stage a full 3D NEWPAN rerun may be performed, which serves to
validate the results predicted by NEWPAN2D. Unless huge geometric
changes between configurations have been made, correlation is
highly satisfactory. This technique significantly accelerates the