Drag coefficient

Table 1 presents a comparison of time-averaged drag coefficient of a square cylinder for zero angle of incidence; experiments as well as numerical simulation are compared. For three dimensional numerical simulation, the drag coefficient is a value averaged over the entire span of the cylinder. The experimental value is that of the cylinder mid-plane, obtained by a wake survey method. The drag coefficient from all studies are in the range of 1.95 to 2.32 and are comparable to each other.

Figure 3.44 shows the comparison of drag coefficient () with cylinder orientation from present experiments and two dimensional numerical simulation of Sohankar et al. (1998). The drag coefficient is based on the cylinder dimension rather than the projected area. The match is not good when we compare the mid-plane value with that of Sohankar (1998), possibly because of the dimensionality of the numerical simulation. The match improves when the 3-plane averaged value is compared with the cylinder average of three dimensional simulation. The minimum in the drag coefficient at is to be seen in both the mid-plane value as well as the average data. Sohankar et al. (1999) conducted a 3D numerical simulation of flow past a square cylinder at a low aspect ratio and found substantial variation in drag coefficient along the span-wise direction.