Mean wind velocity and intensity of turbulence profiles
were investigated for different roughness and we
obtained information on type and quality of the
boundary layer. The special devices like grids or foil and
2D barriers (Fig. 11) were inserted along wind tunnels
according 1.
The results of the experimental measurements in
BLWT STU for different barriers (height B=150-200
mm) and comparison with EN 1991-1-4 2 are shown
in Fig. 12.
The boundary layer simulation was developed and is
uniform in the area of test section used for
experiments on models. The mean velocity profiles in
the ABL simulations proved to be in good agreement
with logarithmic law. The best results gave us barrier
with height 150 -170 mm.
The detailed measurements of the wind action,
especially near the ground, help us to prepare
boundary layer in BLWT STU according to EN 1991-1-4.
We can classify ABL simulation and terrain roughness
in STU wind tunnel between the III and IV terrain
category, which corresponds to the roughness of
terrain in Bratislava and cities in Slovakia. Experimental
measurements in BLWT STU so far have ensured
height of boundary layer about 1.05 m and scale
factor - SF 366 - 390.
Figure 11: Arrangement of Boundary layer - plastic FASTRADE 20,
barrier 100-250
The roughness length for area with regular cover of
buildings or vegetation - terrain category III z 0 = 0.3 m,
our ABL simulation with value z 0 = 0.7 – 0.77 m is
closer to the terrain category IV, where z 0 = 1 m (area
with at least 15 % of the surface is covered with
buildings their height exceeds 15 m).
Figure 12: The profile of mean wind velocity compared with EN 1991-1-4
3/2017