Figure 3.

Illustration of three cases where interpolation one grid-point inwardly normal from the wall point k, for a two-dimensional problem, produces a stress representative of the interior fluid flow (a,c) and where the stress is unrepresentative (b). The shaded area is the interpolation box, which has center XC_k, it contains the evaluation point XE_k = X_k – hn_k of wall particle k, where h is the fluid grid spacing and n_k is the outward normal vector of the k’th particle. D_kr is the distance between the center of the interpolation box surrounding evaluation point XE_k and nearest wall particle r (shown only in b and c).