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Advanced Building Simulation

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Shear<br />

Velocity<br />

Acceleration<br />

Curvature<br />

Rotation<br />

Figure 9.6 Tensor—local flow field visualization. (See Plate IX.)<br />

Immersive building simulation 225<br />

Reference<br />

Convergence<br />

Divergence<br />

Table 9.2 CFD data types, visualization techniques and spatial domain<br />

Order of data Spatial domain Visualization technique<br />

Scalar Volume Volume ray casting<br />

Scalar Surface Iso-surface<br />

Vector Point Arrow plot<br />

Vector Surface Stream surface<br />

Vector Point (space–time) Particle animation<br />

Tensor Line (space–time) Hyperstreamlines<br />

height maps and for the vector display are arrow plots and streamlines or particle<br />

paths. In addition, these data are classified further based on the spatial domain<br />

dimensionality of the visual objects (such as points, lines, surfaces and volumes) and<br />

their association with visualization techniques (Hesselink et al. 1994) (Table 9.2).<br />

In three-dimensional visualization of nonimmersive environments, the techniques<br />

known from the two-dimensional visualization of fluids are not applicable and can<br />

be misleading. However, in immersive environments, three-dimensional visualization<br />

of fluid data can be confusing. The use of iso-contours and pseudo-coloring provides<br />

a good way to visualize surfaces in the three-dimensional domain. This requires the<br />

application of some data reduction processes, such as the techniques described earlier<br />

in order to create surfaces in three-dimensional space for which two-dimensional<br />

visualization can be useful.<br />

Besides the data type, the structure of how the data is being organized plays an<br />

important role for visualization. In fluid visualization, data is organized using computational<br />

meshes. These meshes define certain ordering of the location in space and<br />

time where the governing partial differential equations of the problem are solved<br />

numerically. All flow data is stored at these discrete locations. The data may be stored<br />

at the node of the mesh or the center of the cell of the mesh. The quality of mesh and<br />

the choice of mesh arrangement impact the accuracy of the simulation. For example,

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