Particle velocimetry in high-gradient/high-curvature flows

Particle-velocimetry techniques typically rely on the assumption that particle velocities match fluid velocities. However, this assumption may be invalid if external forces or inertia cause the particle motion to differ from that of the flow. In this paper, particle motion through premixed stagnation flames is modeled, including Stokes-drag and thermophoretic forces. The finite time interval employed in particle-tracking techniques can act as a low-pass filter in flow regions with large curvature in the velocity field. To account for this effect, the modeled-particle-tracking profile for a specified time interval is estimated from the predicted particle position in time and compared to measurements. The implementation presented here is applicable to other simulated flow fields and allows direct comparisons with particle-velocimetry measurements. Expressions are also derived that allow particle-tracking data to be corrected for these effects.