Simultaneous 3D measurement of the translation and rotation of finite-size particles and the flow field in a fully developed turbulent water flow

Abstract

We report a novel experimental technique that measures simultaneously in three dimensions the trajectories, the translation and the rotation of finite-size inertial particles together with the turbulent flow. The flow field is analyzed by tracking the temporal evolution of small fluorescent tracer particles. The inertial particles consist of a super-absorbent polymer that renders them index and density matched with water and thus invisible. The particles are marked by inserting at various locations tracer particles into the polymer. Translation and rotation, as well as the flow field around the particle are recovered dynamically from the analysis of the marker and tracer particle trajectories. We apply this technique to study the dynamics of inertial particles much larger in size (Rp/η ≈ 100) than the Kolmogorov length scale η in a von Kármán swirling water flow (Rλ ≈ 400). We show, using the mixed (particle/fluid) Eulerian second-order velocity structure function, that the interaction zone between the particle and the flow develops in a spherical shell of width 2Rp around the particle of radius Rp. This we interpret as an indication of a wake induced by the particle. This measurement technique has many additional advantages that will make it useful to address other problems such as particle collisions, dynamics of non-spherical solid objects, or even of wet granular matter.

Large sphere motion in a nonhomogeneous turbulent flow

“…We consider in particular the influence of the large-scale (inhomogeneous) flow structure and its impact on the particle's dynamics. This complements recent studies [11,12] which have focused on the local flow surrounding the particles, but ignoring the influence of anisotropy and inhomogeneity of the flow at large scales. Our motivation stems from the possibility that particles with sizes close to the integral scale may be sensitive to the kinetic energy injection details and hence the largescale structure of the flow.…”

“…Very few studies have been carried out for particles with size comparable to the integral length scale [10][11][12], despite their potential importance for applied situations [13,14]. It has recently been shown that such particles show a very intermittent dynamics of both translation and rotation.…”

Translational and rotational dynamics of a large buoyant sphere in turbulence

“…Many physical experiments rely on image analysis to obtain these parameters from experimental data (Bovik 2010;Meyer et al 2013). Most of these systems capture translation and retrieve orientation from relative motion of translating nodes (Klein et al 2013). In the more elementary forms, the translation of nodes could be used to determine the velocities of the particles.…”

Buoyant finite-size particles in turbulent duct flow

“…However, they are often difficult to scale-up due to issues related to long-time properties of the suspending solution, thermal stability, handling and cost. Super-absorbent hydrogel particles in water, used in this study, can be advantageously used for performing RIM-PIV as previously shown in Klein et al [13], Byron and Variano [14] and Harshani et al [15]. The mechanical properties of commercially available spherical hydrogel particles are discussed in Dijksman et al [16].…”