-2/3rds slope. -6 slope Primary range of interest. Typical range at model scale Typical full scale

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Francis Sutton
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3 -2/3rds slope ns u2-6 slope Primary range of interest Typical range at model scale Typical full scale n x Lu U Figure 1: Non-dimensional power spectrum of longitudinal turbulence at model and full scale Figure 2: Curved Shanghai Center Tower, 1:500 model Figure 3: High Reynolds number tests on Shanghai Center, 1:85 model

For the Shanghai Center testing pressure measurements were measured at a series of levels in smooth and turbulent flow at the two scales and comparisons made of the mean, RMS and peak pressure

4 For the Shanghai Center testing pressure measurements were measured at a series of levels in smooth and turbulent flow at the two scales and comparisons made of the mean, RMS and peak pressure coefficients. Figure 4 shows an example of these comparisons in very low turbulence intensity. Figure 4: Mean and peak pressure coefficients at high and low Reynolds number in low turbulence The higher Reynolds number results in Figure 4 show increased suctions at the two upwind corners. However, it was found that in turbulent flow this trend disappeared and was even reversed at very high turbulence intensity. Surface roughness also can have a major impact on Reynolds number effects. In the course of wind tunnel testing of a super tall tower with a slotted circular cross-section, and with protruding columns, sectional tests were done at low Reynolds number in RWDI s Guelph wind

5 tunnels and at high Reynolds number, Figure 5, in the National Research Council of Canada s 9 m 9 m wind tunnel in Ottawa. The high Reynolds number model was 1 m in diameter, aspect ratio 4.5:1, and was tested at speeds up to 50 m/s. As reference cases it was also decided to obtain high Reynolds number data without the slots (i.e. on a pure circular cylinder) with and without the protruding columns. The wind direction shown in Figure 5 exhibited the highest cross-wind excitation due to vortex shedding. The results for mean drag coefficient, fluctuating lift coefficient and Strouhal number for this direction are illustrated in Figure 6(a) for the cylinder with and without rib-columns in low turbulence. It can be seen that the rib-columns, which protruded 1.5% of the diameter from the cylinder surface, had a dramatic effect on the drag coefficient, lift coefficient and Strouhal number compared with a nominally smooth cylinder at high Reynolds number. The columns also reduced sensitivity of the slotted tower cross-section to Reynolds number, compared with a smooth cylinder, as illustrated in Figure 6(b). The cylinder results in Figure 6(a) are generally consistent with the trends indicated by ESDU [1] for circular cylinders at high Reynolds number, although the roughness of the ribcolumns is somewhat higher than the range covered by ESDU. On the tower model with slots and columns, drag and lift coefficients were reduce by about 20% in going from low to high Reynolds number (i.e. from Re = 8x104 to Re = 2x106) and Strouhal number was reduced by about 5%. It was noteworthy that the strength of vortex shedding on the model of the full tower was reduced by about a factor of two compared with the two-dimensional section model data, indicating how important three dimensional end effects are on tall towers. WORST WIND DIRECTION 30o Slots closed off for circular cylinder configuration Figure 5: Sectional high Reynolds number tests at 1:100 scale on slotted cylindrical tower in NRC 9m x 9m wind tunnel These results suggest an area where knowledge is still somewhat hazy: namely the interaction of Reynolds number effects with turbulence, surface roughness and aspect ratio for cylindrical bodies with curved faces or rounded corners of various radii. It does appear that turbulence and roughness tend to suppress the Reynolds number effects seen in smooth flow around smooth bodies but how much one can count on this has not been well quantified other than in isolated examples such as the one just described. There is the potential for reduced crosswind excitation at full scale Reynolds numbers on rounded towers with smooth exterior surfaces, which would allow significant cost reductions to be obtained in the structural system, but this will depend heavily on how much turbulence is present and on details of the surface

FLow pattern around cable and its aerodynamic characteristics in critical Reynolds number range

The 22 World Congress on Advances in Civil, Environmental, and Materials Research (ACEM 2) Seoul, Korea, August 26-3, 22 FLow pattern around cable and its aerodynamic characteristics in critical Reynolds