In this study, flow around a three dimensional wall-mounted square cylinder with aspect ratios (AR) of 2, 4, 6 and 8 has investigated experimentally using wind and smoke tunnels. Smoke tunnel has been used in order to visualize flow structure and vortex pattern around the cylinder at Re=2000. The visualization results showed that the wake width and separation angle increases with increasing the aspect ratio. In addition, it was found that Strouhal number obtained from visualization results increases as the aspect ratio increases which was 0.108, 0.119 and 0.123 for AR of 4, 6 and 8, respectively. Observation of flow pattern and structure of spanwise and tip vortices showed that the cylinder with AR=2 has different flow structure than those of AR=4, 6. Spanwise vortex shedding at AR=2 is so weak than those of the other aspect ratios. For AR=4, 6, the downwash flow separated from free-end leading edge, descends immediately behind the cylinder while for AR=2 this downwash flow moves downstream and descends gradually. Distribution of pressure coefficients on the cylinder have been measured using wind tunnel and pressure box. Based on the measured pressure coefficients, the pressure drag coefficient is determined. Results showed that the pressure drag coefficient increases as the aspect ratio increases from 2 to 8 due to increasing the size and strength of vortices behind the cylinder, both near the wall and near the free-end. Strouhal number, mean velocity profile and turbulence intensity for AR= 2, 4, 6 and 8 have been obtained based on the wind tunnel data using 1-D Hot-wire anemometry. One dominant vortex shedding frequency along the height of the cylinder is detected from results for all aspect ratios. In addition, the results showed that the aspect ratio of a cylinder highly affects the mean velocity profile and turbulence intensity. Simultaneous analysis of visualization and Hot-wire results showed that the downwash flow reaches to the wall at 7d behind the cylinder at AR=2, where d is cylinder side. For AR=4, 6 and 8, the downwash flow descends to mid-height of cylinder. It is found that the recirculation region grows for higher aspect ratios. This causes the streamwise velocity along the centerline at mid-span of the cylinder increases as the aspect ratio decreases. Strouhal number obtained from Hot-wire anemometry at Re=53000 was almost the same (about 0.105) for all aspect ratios employed. Keywords: Finite square cylinder, aspect ratio, wind tunnel, hot-wire anemometry, vortex structure, pressure coefficient, pressure drag coefficient, strouhal number
