Free-Stream Turbulence Effects on a Square Cylinder with a Forebody Screen at a Small Distance

This work shows that the presence of a forebody solid screen fixed at a relatively small distance can significantly influence the global aerodynamic behavior of a square cylinder, even for a flow perpendicular to the screen and in presence of free-stream turbulence. The present investigation represents an extension of previous two-dimensional experimental and numerical studies conducted by the same Authors on rectangular and square cylinders in smooth flow. Experiments in the wind tunnel were carried out by reproducing two different homogeneous isotropic turbulent flows and setting different distances between the screen and the front face of the prism. The pressure measurements revealed in turbulent flow qualitatively the same behaviour observed in smooth flow, though the effects of the screen are less pronounced. In particular, a pressure reduction immediately behind the front corners, a fast recover of it moving towards the back corners, and a strong variation of the lateral force coefficient in the direction of stability are the most apparent features.