Experimental investigation of flow field behind triangular prisms at intermediate Reynolds number with different apex angles

• Study of flow around triangular prism with effect of apex angle is reported.
• PIV, hotwire and flow visualization are used to characterize the flow field.
• A linear relationship between vortex shedding frequency and apex angle is found.
• Minimum in drag coefficient and maximum Strouhal number is found for apex angle 30.

An experimental study of flow around triangular prism with effect of apex angle is reported. The focus of the study is towards understanding the effect of apex angle on flow structure and related forces occurring. Four triangular prisms with apex angle 30°, 45°, 60° and 90° respectively are reported at Reynolds number of 520 (based on cylinder diameter). The Particle image velocimetry (PIV), hotwire anemometry and flow visualization techniques are used to characterize the complete flow field. Results obtained in the present work are Strouhal number, drag coefficient, time averaged as well as instantaneous velocity field, statistical quantities like rms velocity, turbulence intensity, and shear stress. A linear relationship between vortex shedding frequency and apex angle is being observed. A minimum in drag coefficient and maximum in Strouhal number is seen for apex angle 30°. Corresponding small wake width is seen from flow visualization images. The power spectra shows additional peak other than dominant frequency peak due to non linear interaction between the Karman vortices.