Wake Flow Dynamic Characteristics of Triangular Prisms

Abstract

The influence of the Reynolds number (Re) and the aspect ratio of triangular prisms on the wake flow dynamic characteristics is investigated using hydrogen bubble flow visualization, computational flow simulation, and PIV (particle image velocimetry) experiments. The key flow information, including vorticity distributions, time-averaged flow fields, and Reynolds stresses, is obtained by means of processing the velocity fields; thus, the overall flow dynamics is studied. The simulation and experimental results show that the flow separation point can exist only at the upper or lower vertex of the bottom edge; the period time of vortex shedding decreases and the vortex shedding is intensified, as the Reynolds number increases with the same aspect ratio; the period time and the strength of the vortex shedding, as well as the wake flow dimensions, increase, as the aspect ratio increases under the same Reynolds number, which leads to a decrease in the Strouhal number (St) and more unsteady wake flow fields; an increase in the aspect ratio makes the velocity component Uy increase more rapidly, so it takes longer for the backflow generation and extends the single cycle time of vortex shedding; the backflow acceleration is greater than an increase in the velocity component Ux, so that the back-flow generation time decreases, as the Reynolds number increases; Etk1 and Etk4 are the main TKE (turbulent kinetic energy) producers, and the spanwise turbulivity of the 75° triangular prism is highest resulting in greatest wake flow resistance.