Channels, Fall 2020

Channels • 2 020 • Volume 5 • Number 1 Page 12 Fig. 16 Velocity distribution in boundary layer after complete separation (X = 0.005515m) Figs. 17 and 18 show that the detachment angle of the boundary layer decreases from the smooth cylinder to Model A, resulting in a smaller wake region and lower drag (Table V). The laminar model used could not reflect the turbulence in the grooves, but the velocity distribution of the boundary layer in the grooves showed that vortices formed in the grooves produced the “bearing” effect expected that leads to a smaller flow detachment and decreased wake region behind the cylinder. The effect found in these grooves reproduces the same trends that were found in the effect of turbulent vortices that resulted in drag reduction. TABLE V D RAG C OEFFICIENTS FOR E LLIPTICAL C YLINDERS Model Numerical Experimental Smooth 0.760 0.488 Model A 0.497 0.288 Fig. 17 Velocity (m/s) wake region behind 2D elliptical (a) smooth cylinder (b) Model A C. Numerical Wake Study In the three-dimensional studies, the cylinder used in CFD and in the wind tunnel was a 150 mm long circular cylinder with various groove parameters. Song’s work [1] used 3D simulations for circular cylinders but the cylinders occupied the entire transverse length of the computational domain which rendered the simulations essentially 2D. In order to show the effects of such