School of Mechanical Engineering Seminar
Wednesday, November 22, 2017 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

Methodology for estimating forces on Particles in Turbulence based on Lagrangian experiments

Yosef Meller

Tel Aviv University, under supervision of Prof. Alex Liberzon

Prediction of dynamics of particles in turbulent flows is a diverse problem, which involves both the problem of turbulence, which is not fully solved in itself, and the problem of how the flow interacts with a particle. Existing irrotational theory requires measurement of small turbulent scales not easily accessible to measurement or to direct simulation. To overcome that, we hypothesize that applying the equation within certain error bounds is possible in turbulence, with a resolution-dependent decrease in accuracy.

To test the hypothesis, we measured Lagrangian trajectories of fluid flow tracers and inertial particles simultaneously moving in turbulent flows, and compare the estimated force to theoretical predictions. The measurements are performed using the 3D-PTV method, which tracks particles in flow using volumetric photogrammetry techniques. The method requires several critical post-processing steps. We applied those to different temporal and spatial resolution data, as well as different turbulent flow conditions. We developed a method of modeling the under-resolved flow field in a way that gradually adds detail to the measurements.

The key results show that by the developed modeling methods we are able to achieve the monotonous improvement of the equation of motion with resolution. We also discuss the limitations of this approach.