Wall effects in two-dimensional axisymmetric flow over a circular disk oriented normal to flow in a cylindrical tube

The effect of cylindrical walls on the drag of a neutrally buoyant disk (with zero inertia) oriented normal to the direction of flow has been investigated numerically. Using FLUENT, the field equations have been solved to obtain the values of the total, pressure and friction components of drag as a function of the Reynolds number and of the blockage ratio. The results presented herein encompass the following ranges of the conditions: Reynolds number: 1 to 100; and the blockage ratio (disk diameter/cylinder diameter): 0.02 to 0.5. As expected, the drag is found to be higher under the confined flow conditions than that in the unconfined flow conditions. However, the confining boundaries appear to exert only a weak influence on the formation and size of the wake region. The drag values are also weakly influenced by the thickness of the disk. However, this effect progressively disappears as the Reynolds number is gradually increased. The present numerical values corresponding to the unconfined flow conditions are in excellent agreement with the previous numerical and experimental results available in the literature.