Post-critical flow over arrangements of multiple rough cylinders

In this study, a comprehensive set of wind-tunnel experiments was undertaken to gain insight into the variation of force coefficients (lift and drag) across different wind angles and spacings for equidistant cylinder arrangements (two, three, and four cylinders) in post-critical flows. The effect of both the cylinder spacing and wind incidence angle was examined for a roughness Reynolds number of approximately 770. The broad trends in the force coefficients previously observed for cylinders in sub-critical flow are shown to persist in post-critical flow, although the magnitudes of the coefficients are different, particularly for the maximum lift coefficient. Additionally, several methods are examined for predicting the forces experienced by multiple cylinder combinations using data obtained from the two-cylinder case. In general, these methods provide good predictions for large cylinder spacings but are inconsistent when the cylinders are spaced closer together.