The velocity vector is given by $V=u\u2009x\u0302+vy\u0302+w\u2009z\u0302$, where $x\u0302$, $y\u0302$, and $z\u0302$ are the unit vectors along the coordinate axes (shown in Fig. 5). Since the top facet is located in the **X–Y** plane, and due to the symmetric structure of the cube, the nondimensionalized velocity gradient is expected to dominate along **Z** (velocity gradient∼O(10 deg)) and was found to be negligible across the **X**,**Y** direction (velocity gradient ∼ O(10^{−15})) as shown in Fig. 5. The gradient of the velocity along **Z** is attributed to the no-slip boundary condition at the top facet, which leads to the development of a transverse boundary layer. This transverse boundary layer and the resulting velocity gradient are the primary causes of the surface shear stress calculated on the facet. Since the incident flow is in the **X** direction, $\u2009|u|$ (magnitude of $u\u2009$) is greater than $\u2009|v|$, and therefore, the magnitude of $\u2202v/\u2202z$ is smaller by an order of magnitude compared to $\u2202u/\u2202z$, as also shown in Fig. 5. In addition, contribution of $\u2202v/\u2202z$ toward $(\tau \xafs)top$ can be ignored when averaged, given the symmetry involved in the structure. Similarly, the average of $\u2202w/\u2202z$ across the top facet was estimated to be zero (not shown) and therefore does not contribute toward the shear stress experienced by the top facet. From Fig. 5, $\u2202u/\u2202z$ exhibits the maximum magnitude compared to all other velocity gradients that contribute toward shear stress. The negligible magnitude of all other velocity gradients, $(\u2202v/\u2202x),\u2009(\u2202w/\u2202x),\u2009(\u2202u/\u2202y),(\u2202w/\u2202y)$ ∼ O(10^{−15}) as observed in Fig. 5 suggests that the variation of velocity $V$ in a direction normal to a particular facet predominantly influences the magnitude of shear stress at that facet. Therefore, the surface shear stress is largest along the edges of the facet (∼1.5 times larger than the average over the facet) and peaks near the corners of the facet (∼2.5 times larger than the average over the facet). Thus, one would hypothesize that structures having multiple edges and corners should experience higher overall shear stress, but as can be seen from Figs. 3 and 4, this is not the case. This discrepancy arises as the actual surface area of edges and corners is negligible compared to the overall facet area and therefore contributes minimally (<2%) to the overall average shear stress.