Volume I - Section IV - Experimental Work and Verification of CFD Methodology 
Page IV - 97 
The fill plot of the speed field at plane 1 for the CFD simulation is shown in figure 4.70. The plot 
does not show the same blocks of high speed that are shown in the equivalent experimental plot. 
Further, the plot also indicates the clear acceleration of air towards the exhaust located in the 
upper right comer of the plot, that is an expected feature at this plane. The fill plot of the speed 
field at plane 8 for the CFD simulation is shown in figure 4.71. The plot shows a more consistent 
flow field associated with the diffuser than the experimental data. In particular, although higher 
speed flow exists close to the diffuser itself, this flow is quickly slowed as air is entrained into 
the jets. There are no spots of higher velocity away from this region as there are in the 
experimental plot. 
Temperature Results 
The fill plot of the experimental temperature field at experimental plane 1 (i.e. the plane 0.15m 
(6”) from the north wall) is shown in figure 4.72. Note that the left-hand side of the plot indicates 
the east wall, and that the key range is between 21.1 to 25.0 °C (70.0 and 77.0 °F). The plot 
clearly shows the demarcation of the various experimental measurement zones. In particular, 
there are sections of the plot that show same color blocks that indicate regions of approximately 
the same temperature: others sections show different temperature regions. The reason for this is 
that the experimental data in the individual zones were taken with different wall surface 
conditions, as outlined in appendix I: section 4.3.1. This effect is even more marked on 
consideration of figure 4.73, that displays the fill plot of experimental temperature field at 
experimental plane 8 (i.e. the plane halfway through the room, 1.22m (48”) from the north wall). 
However, in the CFD simulation, the boundary walls were defined as being at an average surface 
temperature. As a result, the fill plots for the temperature fields do not exhibit the dominant 
effect of the wall surface temperature. Figure 4.74 displays the fill plot of the temperature field at 
plane 1 (i.e., the plane 0.15m (6”) from the north wall). As the flow field exhibits essentially well 
mixed, isothermal conditions here, the temperature field shows relatively little variation. At the 
center plane of the room, plane 8 (i.e., the plane 1.22m (48”) from the north wall), the shape of 
the incoming diffuser air is evident, as shown in figure 4.75. 
Despite the apparent differences in the two sets of data, the levels of difference between the data 
is reasonable, as demonstrated in tables 4.2.13 and table 4.2.14. In particular, the average 
difference at plane 1 is around 11.6 percent, while that at plane 8 is around 16.8 percent. These 
are well within normally accepted experimental uncertainty. 
Discussion and Conclusions 
The above comparison demonstrates that reasonable agreement was obtained with regards to the 
temperature field, while the experimental speed field displayed several features and values that 
were subject to doubt. 
The experimental temperature and speed fields highlight the difficulty of maintaining isothermal 
conditions in a test facility, despite the adherence to rigorous experimental protocol. This has a 
