Relaxation based PTV with Delaunay triangulation

To improve the independence and matching efficiency of NRX (New Relaxation based Particle Tracking Algorithm), instead of settled thresholds, DT (Delaunay Triangulation) unstructured grid was introduced to determine the matching candidate particles set and reference particle set in which the selected particles are close to and quasi parallel with the target particle. The validity of introduced DT was thoroughly tested by simulated motion of monopolar vortices in a strain flow. It indicates that DT can determine the reference particle set effectively, while DT fails to determine the candidate particle set because the nearby-selected property of DT is inconsistent with the physical property of particles termed as being neighboring of candidate particles. Finally, on the basis of NRX, a new algorithm DT-NRX was proposed by using DT to determine the reference particle set. Compared to the conventional NRX, DT-NRX behaves more independently by abandoning one parameter and more effectively in high-density cases.