Three test cases were available for comparison; two using different materials for the forest canopy models and one case without a forest canopy model. The results are presented in Figure 5.13, and are divided into three graphs. Each graph represents one of the selected main wind directions: 315º, 202.5º and 157.5º, respectively.
Figure 5.13 shows that, even though the topography is shallow, it has an influence on the flow. This fact sets aside the concerns about the topography, but also emphasizes the importance of an adequate forest canopy model. By analyzing Figure 5.13a, for the 315º direction, the preliminary “90% canopy model” results (ε = 90% curve) are visibly different from the bare topography results (no forest curve); the “48% canopy model” results (ε = 48%
curve) follow approximately the same trend as the initial “90% canopy model” case. For this wind direction the forest upstream of the measurement location is non-homogeneous as it is dispersed into a large number of smaller forested patches. For this flow direction the boundary layer also does not recover over the available fetch, so the boundary layer is not in an “equilibrium” state and the flow most probably is transitioning. Unsteady transitional flows of this kind are usually highly dependent on the Reynolds number(s) involved. It is therefore probable that the small Reynolds number of the model compared to the full scale is an important factor for the discrepancies noticed between the wind tunnel modes (both porosity cases) an full scale. The analysis performed in this section will focus on the 202.5 º and 157.5º directions, where the forest upstream is less fragmented.
In the case the 202.5 º and 157.5º directions it is assumed that the material used for the 48% canopy model acts as a bluff body. This conclusion is drawn from Figure 5.13, where graphs (b) and (c) show that this case (ε = 48% curve) is offset from the trend of the “no forest” case (no forest curve). This implies an upward shift of the velocity profile by a distance noted in Section 5.5 as dtotal.
Section 5.5 analyzes the results presented in Figures 5.5 to 5.13 by exploring the effects caused by an abrupt roughness transition on the incoming flow. Boundary layer recovery distances are calculated and then compared to the measured distances from the coast to the investigated site for each of the considered wind directions.
85
(a) Comparison between wind tunnel data (topographic model with canopy model) and full sale data for the 315º direction. Full scale data was extracted for the month of January.
(b) Comparison between wind tunnel inlet profile and vertical profile measured at the met tower. Full scale data was extracted for
the month of January.
86 Wind tunnel result set description: - Direction 315º;
- “48% canopy model” case;
- Full scale data for March 2008;
(a) Comparison between wind tunnel data (topographic model with canopy model) and full sale data for the 315º direction. Full scale data was extracted for the month of March.
(b) Comparison between wind tunnel inlet profile and vertical profile measured at the met tower. Full scale data was extracted for
the month of March.
87 - “48% canopy model” case;
- Full scale data for September 2008;
(a) Comparison between wind tunnel data (topographic model with canopy model) and full sale data for the 315º direction. Full scale data was extracted for the month of September.
(b) Comparison between wind tunnel inlet profile and vertical profile measured at the met tower. Full scale data was extracted for
the month of September.
88 Wind tunnel result set description: - Direction 315º;
- “48% canopy model” case;
- Full scale data for October 2008;
(a) Comparison between wind tunnel data (topographic model with canopy model) and full sale data for the 315º direction. Full scale data was extracted for the month of October.
(b) Comparison between wind tunnel inlet profile and vertical profile measured at the met tower. Full scale data was extracted for
the month of October.
89 - “48% canopy model” case;
- Full scale data for December 2008;
(a) Comparison between wind tunnel data (topographic model with canopy model) and full sale data for the 315º direction. Full scale data was extracted for the month of December.
(b) Comparison between wind tunnel inlet profile and vertical profile measured at the met tower. Full scale data was extracted for
the month of December.
90 Result set description: - Direction 315º;
- “48% canopy moodel” case;
- Yearly full scale data;
Comparison between wind tunnel data (topographic model and canopy model) and full sale data for the 315º direction. Full scale data was plotted for each of the months which had valid
segments.
Comparison between wind tunnel inlet profile and vertical profile measured at the met tower. Figure 5.10: Summary plot of the comparison between the wind tunnel test and full scale data. “48% canopy model” case, direction: 315º, yearly data.
91 - “48% canopy model” case;
- Yearly full scale data;
Comparison between wind tunnel data (topographic model with canopy model) and full sale data for the 202.5º direction. Full scale data was plotted for each of the months which had valid
segments.
Comparison between wind tunnel inlet profile and vertical profile measured at the met
tower.
92 Result set description: - Direction 157.5º;
- “48% canopy model” case;
- Yearly full scale data;
Comparison between wind tunnel data (topographic model with canopy model) and full sale data for the 157.5º direction. Full scale data was plotted for each of the months which had valid
segments.
Comparison between wind tunnel inlet profile and vertical profile measured at the met
tower.
(a)
(b)
(c)