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.

Streamlines 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?!

NEWPAN2D Interface

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.