Diffusion of ellipsoids in laboratory two-dimensional turbulent flow

Abstract

We report on the transport properties and orientational dynamics of ellipsoidal objects advected by laboratory two-dimensional turbulence. It is found that ellipsoids of different sizes have preferential direction of transport, either along their major axes or minor axes. The two components of the ellipsoid diffusion coefficient depend on the ratio of the length of the ellipsoids along major axes aa to the turbulence forcing scale L f. Large ellipsoids (aa > L f) diffuse faster in the direction parallel to their major axes. In contrast, small ellipsoids diffuse faster in the direction transverse to their major axes. We study this transition vs the ratio aa/L f and relate it to the coupling between translational and rotational motion of anisotropic objects. The features of the turbulent transport of ellipsoids can be understood by considering the interaction of these anisotropic objects with the underlying structure of two dimensional turbulent flows made of meandering coherent bundles.

Ultrasound‐assisted swelling of bacterial cellulose

“…The wavedriven turbulence provides an opportunity to study the BC development under well-controlled conditions since the statistical characteristics of such flows can be accurately characterised by a few key parameters: turbulence forcing scale, and the turbulence kinetic energy which is proportional to the supercriticality α (see above) 31,33 . These parameters control the diffusive motion of fluid particles at the liquid surface [37][38][39] . In addition to displacement of particles in turbulence from their initial position in a random-walk fashion, turbulent flows also lead to random rotation of finite size objects due to the generation of turbulent torque 40 .…”

Long non-axisymmetric fibres in turbulent channel flow

“…2013; Abbasi Hoseini, Lundell & Andersson 2015; Yang et al. 2019). In this context, Capone, Miozzi & Romano (2017) studied the dynamics of rigid, rod-like particles in turbulent channel flow.…”

“…rod-and disk-like particles. From table 1, it clearly emerges that a major proportion of the experimental studies in this field is limited to two-dimensional visualisation, and such studies focused mainly on orientation and concentration analysis (Bernstein & Shapiro 1994;Parsheh, Brown & Aidun 2005;Dearing et al 2012;Håkansson et al 2013;Abbasi Hoseini, Lundell & Andersson 2015;Yang et al 2019). In this context, Capone, Miozzi & Romano (2017) studied the dynamics of rigid, rod-like particles in turbulent channel flow.…”

Anisotropic Diffusion of Elongated Particles in Active Coherent Flows

“…This anisotropic nature results in the dynamic behaviors of particles that are markedly distinct from those of spherical particles, including directional variations and intricate coupling between translational and rotational motion. The behavior of anisotropic particles in passive fluids has been extensively studied theoretically and experimentally [49][50][51][52][53][54][55]. One year after the development of spherical particle theory, Albert Einstein extended Brownian dynamics to include rotational freedom, leading to the exploration of ellipsoidal particle diffusion.…”