Fiber Tracking Velocimetry for Two-Point Statistics of Turbulence

We propose and validate a novel experimental technique to measure two-point statistics of turbulent flows. It consists in spreading rigid fibers the flow tracking their position orientation time therefore been named ``Fiber Tracking Velocimetry'' (FTV). By choosing different fiber lengths, i.e. within inertial or dissipative range scales, turbulence fluctuations at selected lengthscale can be probed accurately by simply measuring velocity its two ends, projecting it along transverse-to-the-fiber direction. means fully-resolved direct numerical simulations experiments, we show that these fiber-based transverse increments are statistically equivalent (unperturbed) increments. Moreover, energy dissipation rate measured exploiting sufficiently short fibers. The has tested against standard Particle Velocimetry (PTV) tracers with excellent agreement. Our overcomes well-known problem PTV probe reliably because fast relative diffusion prevents mutual distance between particles remain constant interest. This problem, making difficult obtain converged for fixed separation distance, is even more dramatic natural flows open domains. A prominent example oceanic currents, where drifters (i.e.~the tracer-particle counterpart used field measurements) disperse quickly, but same number limited save costs. Inspired our laboratory pairs connected as viable option solve issue.