Channels, Fall 2020

Channels • 2 020 • Volume 5 • Number 1 Page 8 The two-dimensional CFD study of circular cylinders showed a trend of drag reduction using various groove configurations along the surface. To conduct the study, Song’s [1] cases were followed by duplicating their cylinder diameter and groove parameters such as depth, width, and α. Using a Reynolds number of 6 * 10 4 and a windspeed of 35 m/s, we found similar drag reduction as shown in Table IV. Fig. 8 compares the wake regions behind the cylinder of the smooth model, Model A, and Model B. In Fig. 8, a reduction in the area of the velocity wake region can be observed that correlates with the lower drag coefficients found in Table IV. TABLE IV N UMERICAL D RAG C OEFFICIENTS FOR CIRCULAR CYLINDERS Model Numerical 2D Song [1] C d Smooth 1.393 1.21 Model A 0.746 0.83 Model B 0.724 0.785 Fig. 8 Velocity (m/s) wake region behind 2D circular (a) smooth cylinder (b) Model A and (c) Model B A closer look at the surface of the different models shows that, as the grooves are added to the surface, the wake detaches at a lower angle from the cylinder. This difference can be seen in Fig. 9 as the angle of detachment of the flow decreases from the smooth when compare to the other models. Fig. 9 also shows a more gradual velocity transition in the wake region in Models A and B versus the stark contrast between high and low velocity in the smooth cylinder wake. Table IV supports the hypothesis that reduced wake region and detachment angle of flow correlate to the reduction of drag around a body.