VIEWPAN Visualisation and User Interface
Flow Solutions has been able to leverage a decade of investment in
the development of the GEMS pre-processor to the benefit of VIEWPAN.
All the powerful viewing, picking, database and entity management
features found in GEMS are available in VIEWPAN. This provides
significant benefits to the user: 100% compatibility of the user
interface between pre- and post-processors is guaranteed. This
shortens the learning process and increases productivity. See
here for an overview of the GEMS User Interface.
Building on this, VIEWPAN takes 3D visualisation to a new level.
Of course, the usual 3D visualisation styles are supported,
such as displaying variables coloured according to their value
assigned in a colour spectrum. This technique helps provide a
a useful first impression - but invariably we wish to follow
this up with rather more direct plotting of discrete values.
VIEWPAN introduces the Graph Viewer and 3D Graph Viewer components
for X-Y graph-style presentation of data derived from results
plotted along sections (or other paths) of the 3D model. Just like
the other GEMS/VIEWPAN viewers, the graph viewers have intuitive,
mouse-driven operation and display geometry and results in the
same window. The effect is to create a graph plotting viewer
which allows smooth rotation, pan and zoom, with the axes values
translating and rescaling automatically in sympathy. You want to
inspect a region of the plot in more detail? Simply zoom in, and
see the graph axes automatically refine! Overlay results from
different runs and different models simply by selecting them in
the Entity/Run Selector, and choose to distinguish them by colour
or by point marker type.
The 3D Graph Viewer allows screen-vertical axes showing variable
values to be superimposed in the standard 3D view, hence with full
3D "trackball" rotation, pan and zooming. Say for example we wished
to plot values of pressure coefficient along a streamline. We
are able to display the 3D path of the streamline over the model,
view this from any direction, AND bring up a Cp plot, complete
with labelled axis values, in the same view. As we rotate or zoom
the model, the variable plot and axis tick marks move in sympathy.
This capablity is so natural, and so powerful, you must try it!
The "3D Slicer" is available to take one or more planar cuts through
a model, evaluate the values of the surface variables along the
intersection, and display these values as graph lines with a
labelled axis in the 3D Graph Viewer. In addition, the position
of the cutting plane can be "swept" through the model interactively,
giving very powerful visualisation of the variations over the surface.
By providing automatic integration of sectional pressures at a
number of stations (e.g. across the span of a wing, or down the
keel of a boat) we are able to compute and display "Spanwise Loadings".
During aerodynamic design this is a critically important property
to visualise and to tailor. Loadings per-component, totals, and
comparisons between models and runs are all supported.
If we select a complete grid component for display in the 3D
Graph Viewer, we are able to visualise the "contours" of the
variable mapped over the 3D surface, from any viewing direction.
Think of this as a much improved version of carpet plotting.
Comparing the results from one model with those of another is a fundamental
requirement for a post-processor, yet have you noticed how poorly supported
this is by many? Consider for example two aerodynamic models where we have
redesigned/repositioned the wing. In VIEWPAN we are able to:
- visualise the models in 3D side-by-side, from synchronised viewing
directions, using auxiliary viewers with slaved viewpoints;
- examine sectional results, e.g. pressure distributions, and align these results between models to overlay them for direct comparison. The Graph Viewer allows
us to specify the application of the 2D-3D mapping, making it trivial to
align the various sections such that features like their leading
or trailing edges are overlayed.
Another powerful capability is visualisation of on- and off- surface
streamlines. Given the availability of surface velocity vectors
(available at every grid node after a NEWPAN run), VIEWPAN provides
"point and click" interactive streamline seeding from any point on
the body - both downstream, and upstream to a stagnation point.
Alternatively, dozens or hundreds of streamlines may be "painted"
over the surface of the model from regularly spaced seeding points,
providing a rapid picture of the surface flow patterns.
In addition to evaluation of the streamline path, a "2.5D" integral
boundary layer calculation is automatically performed along each
streamline. Allowance is made for the convergence/divergence of
adjacent streamlines. If the adjacent
streamlines diverge this acts to thin the boundary layer - conversely if
they converge this thickens the boundary layer and makes separation
more likely. The calculation procedure takes full account of runs
of laminar flow, transition by various mechanisms including modelling
of laminar separation bubbles, and fully turbulent flow.
The boundary layer evaluation down streamlines provides rapid and
reliable estimates for areas of separation and the location of
transition. The state of the boundary layer may be represented according
to a simple colour convention - this gives a very clear visual
summary of the degree of flow attachment over the surface of the model.
Useful characteristics such as skin friction, b/l thickness and
shape factor may also be plotted.
Off-surface streamlines may also be visualised using VIEWPAN. These can
be computed after a NEWPAN run - there is no need to work out where you
wish to seed them before running the solver. The OFFBODY streamline
generator features an advanced induced velocity evaluation, ensuring
accurate results and finer resolution as a streamline gets closer and
closer to part of the model surface. How many times have you seen
presentations featuring streamlines that pass erroneously straight through
the surface of the model?!
Thus far we have demonstrated some of the visualisation possibilities
provided by VIEWPAN. But equally significant is the launch pad it
provides to sectional redesign, thanks to the tight coupling to NEWPAN2D.
This is achieved using a specialised version of the standard Graph Viewer already described. Sections of components from the 3D model may be imported and
analysed by NEWPAN2D, and their geometry and results displayed in the
Graph Viewer. This facility is most applicable to wing or foil-like shapes
which may be composed of one or several elements. Sections from the 3D
model are sat in their model's three dimensional flowfield, as computed
by NEWPAN. By this means, we can exploit the powerful features of
NEWPAN2D, such as strong viscous coupling and inverse aerofoil redesign,
on a sectional basis applied to the 3D model.
A description of NEWPAN2D is provided here.
Following a NEWPAN2D redesign, the new geometry and results appear
alongside their original counterparts in the VIEWPAN database. They
may also be transferred directly to the GEMS pre-processor for their
integration into a new 3D model.