Large eddy simulation of flow around an inclined finite square cylinder: Fid-Bau Portal

Large eddy simulation of flow around an inclined finite square cylinder

Hu, Gang / Tse, K.T. / Kwok, K.C.S. / Zhang, Yu

Abstract The flow field around a rigid finite square cylinder inclined away from the vertical direction was numerically investigated via large eddy simulations. The cylinder under investigation had a height-to-width ratio of 18 and the inclination angle, defined as the angle between the cylinder orientation and the vertical direction, varied from forward inclination to backward inclination. Pressure measurements and flow visualizations were taken in a wind tunnel to validate the numerical simulations. The forward inclination is found to enhance the downwash, which is initially observed behind the free end of the vertical cylinder, and amplify it to a downward axial flow. Conversely, the backward inclination promotes upwash, which originates behind the base of the vertical cylinder, to be an upward axial flow. On the other hand, the vertical cylinder produces two pairs of counter-rotating streamwise vortices (quadrupole wake) in its wake, but only one pair of vortices (dipole wake) is observed to form behind both the forward and backward inclined cylinders. Moreover, only a free-end vortex pair is exhibited behind the forward inclined cylinder whereas a base vortex pair exists behind the backward inclined cylinder. They are considered to generate the downward and upward axial flow respectively. It is anticipated that the presence of the axial flow significantly influence both the pedestrian-level wind conditions and the aerodynamic characteristics of the cylinder.

Highlights • Forward inclination enhances a downwash behind the top to a downward axial flow. • Backward inclination amplifies an upwash behind the bottom to an upward axial flow. • Both forward and backward inclinations change the quadrupole wake to a dipole one. • The dipole wakes are responsible for the downward and upward axial flow.