Abstract
Measurements of the surface velocity and surface texture of a freely propagating shear jamming front in a dense suspension are compared. The velocity fields are captured with particle image velocimetry (PIV), while the surface texture is captured in a separated experiment by observing a direct reflection on the suspension surface with high-speed cameras. A method for quantifying the surface features and their orientation is presented based on the fast Fourier transform of localized windows. The region that exhibits strong surface features corresponds to the the solid-like jammed region identified via the PIV measurements. Moreover, the surface features within the jammed region are predominantly oriented in the same direction as the eigenvectors of the strain tensor. Thus, from images of the free surface, our analysis is able to show that the surface texture contains information on the principle strain directions and the propagation of the jamming front.Graphic
Highlights
Suspensions of hard spheres in a Newtonian fluid are known to jam at a critical volume fraction (Krieger 1972)
We show that in certain regions of the flow, the direction of the texture and the eigenvectors of the strain tensor are predominantly oriented in the same direction
The surface texture is captured by high-speed images of the free surface looking into a direct reflection
Summary
Suspensions of hard spheres in a Newtonian fluid are known to jam at a critical volume fraction (Krieger 1972). Beyond a critical concentration of particles, flow ceases, and a finite yield stress is observed Brown and Jaeger (2014). For some suspensions, such as cornstarch and water, a jammed state is accessible for volume fractions lower than the critical volume fraction when stress is applied. 1 3 Vol.:(0123456789) 226 Page 2 of 13
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