Figure 1. Concept of Virtual Ink Washout.

Illustration of the technique employed in this study to identify areas of stagnation. Two scenarios are illustrated, fluid flow through a straight cylinder (left) and through a deformed cylinder (right). At time point t0, fluid flow through the cylinders is changed from fluid with red ink to fluid without ink. Red fluid in the straight cylinder is washed out in accordance with a laminar flow profile. However, in the deformed cylinder, the red fluid is washed out more slowly, with stagnant areas still retaining red fluid by time point t₅ due to decreased localized flow.