## 6 Results and Discussion  
The air flow field around the cubical geometry is presented in Figure 9 using normalized velocity profiles on the symmetry plane at different streamwise positions upstream, downstream, and at the middle of the roof of the cube (X/H = 5.5) for all three scenarios [44; 54; 61; 62; 63; 64; 65]. Comparisons are also made with [PERSON] and [PERSON]'s experimental data [60] for Scenario A. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Averaging Period (s)** & **Mean Value** & **Variance** & **Autocovariance** \\ \hline
200–400 & 0.2449 & 0.0186 & 0.9584 \\
400–600 & 0.2445 & 0.0198 & 0.9532 \\
600–800 & 0.2480 & 0.0193 & 0.9548 \\
800–1000 & 0.2463 & 0.0195 & 0.9524 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mean Value, Variance and Autocovariance for Specific Time Periods. Figure 8: Concentration of the pollutant for Scenarios A and C at the position with coordinates of X: 7.5 H, Y: 5.5 H and Z: 0.5 H for the time period of 200 to 1000 (s). Differences in the normalized velocity profile between Scenario C and Scenarios A and B are observed especially in the wake region of the cube, where the mixing layer for Scenario C has moved almost one cube height above the mixing layer of the other two scenarios. This is caused by the strong buoyant forces created in this case. Figure 10 shows the streamlines of the flow for Scenario A. A detachment of the flow at the top surface of the building and a recirculation of the flow on both the frontal and the rear surfaces of the building are observed. Different recirculation lengths \(\mathbf{X_{f}}\), \(\mathbf{X_{b}}\), and \(\mathbf{X_{r}}\) are defined for the frontal, rear, and roof recirculation of the building, respectively. Table 3 presents a comparison of the length of different recirculation zones in comparison with available experimental data. \begin{table}
\begin{tabular}{c c c c} \hline  & \(\mathbf{X_{f}}\) & \(\mathbf{X_{b}}\) & \(\mathbf{X_{r}}\) \\ \hline [PERSON] and [PERSON] [61] & 1.04 H & 1.61 H & - \\ [PERSON] [62] & 0.651 H & 2.182 H & 0.432 H \\ [PERSON], [PERSON] [63] & 0.75 H & 1.4 H & 0.57 H \\ [PERSON] and [PERSON] [64] & 0.9 H & 1.4 H & 0.9 H \\ [PERSON], [PERSON] [65] & - & 1.31 H & 0.94 H \\ Scenario A & 0.79 H & 1.56 H & 0.56 H \\ Scenario B & 0.56 H & 1.97 H & 0.64 H \\ Scenario C & 0.86 H & 2.15 H & 0.73 H \\ \hline \end{tabular}
\end{table} 
Table 3: Recirculation length of the recirculation zones. Figure 9: Normalized velocity profiles on the symmetry plane at positions X/H = 0, X/H = 2, X/H = 4, X/H = 5.5, X/H = 7, X/H = 7.5, X/H = 8 and X/H = 10 for Scenarios A–C [44, 60]. The recirculation zone \(\mathbf{X_{f}}\) in front of the upstream surface of the building for Scenario A is 41% higher than the corresponding for Scenario B and 8.14% lower than Scenario C. In addition, the recirculation zone on the roof \(\mathbf{X_{r}}\) for Scenario A is 20.81% lower than the recirculation zone of Scenario B and 27.44% lower than for Scenario C. The recirculation zone in the wake region \(\mathbf{X_{b}}\) of the building for Scenario A is 13% lower than the corresponding recirculation zone of Scenario B and 23.28% lower than the recirculation zone for Scenario C.  
Figure 11 shows the normalized vertical temperature profile for Scenario C at the position with coordinates of X = 7 H and Y = 5.5 H, on the symmetry plane and two heights behind the building. The present numerical results are in good agreement with the experimental data of [PERSON] and [PERSON] [41], who studied the stability of the atmospheric flow inside an urban street canyon placed normal to the wind direction. They found that inside the canyon exists a stable thermal stratification as shown above, which weakens the cavity eddy. Figure 12 shows the temperature distribution on the vertical and horizontal surfaces of the building for Scenario C, along the intersection lines with the transverse symmetry plane (path No. 3) and two other planes parallel to it at distances 0.25 H (path No. 2) and 0.45 H (path No. 1), respectively.