A lateral suspension, suitable for a microseismometer application, has been fabricated using deep reactive-ion etching. The critical dynamic parameters of the suspension, namely the normal modes along the compliant axis and the damping, have been determined from slow-scan imaging in an environmental scanning electron microscope. The results show the presence of an unwanted spurious mode which c...

We introduce a simplified model for thin layer flows of granular materials with yield. The model is derived from a Drucker–Prager rheology, and describes the dynamics of the velocity profile and of the transition between static and flowing material. We compare the analytical solution in the inviscid case, and the numerical solution in the viscous case, to experimental data. Although the model d...

We develop a loosely coupled fluid-structure interaction finite element solver based on the Lie operator splitting scheme. The scheme is applied to the interaction between an incompressible, viscous, Newtonian fluid, and a multilayered structure, which consists of a thin elastic layer and a thick poroelastic material. The thin layer is modeled using the linearly elastic Koiter membrane model, w...

The local statistical and geometric structure of three-dimensional turbulent flow can be described by the properties of the velocity gradient tensor. A stochastic model is developed for the Lagrangian time evolution of this tensor, in which the exact nonlinear self-stretching term accounts for the development of well-known non-Gaussian statistics and geometric alignment trends. The nonlocal pre...

Shear induced drainage of a foamy yield-stress fluid is investigated using MRI techniques. Whereas the yield stress of the interstitial fluid stabilizes the system at rest, a fast drainage is observed when a horizontal shear is imposed. It is shown that the sheared interstitial material behaves as a viscous fluid in the direction of gravity, the effective viscosity of which is controlled by she...

Also described as low viscous or low viscosity dextran, dextran 40 is prepared by acid hydrolysis and differential fractionation of a crude macromolecular polysaccharide produced from the fermentation of sucrose by the bacterium, Leuconostoc mesenteroides (strain B-512). The crude material is composed of linked glucose units. In the fraction represented by dextran 40, 80% of the molecules have ...

We propose a dynamical mechanism leading to the fluidization by external mechanical fluctuations of soft-glassy amorphous material driven below the yield stress. The model is based on the combination of memory effect and nonlinearity, leading to an accumulation of tiny effects over a long term. We test this scenario on a granular packing driven mechanically below the Coulomb threshold. We provi...

The transition from frictional to lubricated flows of a dense suspension of non-Brownian particles is studied. The pertinent parameter characterizing this transition is the Leighton number Le=eta(s)gamma / sigma, the ratio of lubrication to frictional forces. Le defines a critical shear rate below which no steady flow without localization exists. In the frictional regime the shear flow is local...

We describe a new approach to understanding the progressive transition from linear to nonlinear rheological response in complex fluids and soft solids. Large amplitude oscillatory shear (LAOS) tests are carried out over a wide range of frequencies and strain amplitudes. The resulting material response to an oscillatory input can be represented in terms of Lissajous figures and can also be decom...

Diverse material classes exhibit qualitatively similar behavior when made viscous upon cooling toward the glass transition, suggesting a common theoretical basis. We used seven different measurement methods to determine the mechanical relaxation kinetics of a prototype molecular glass former over a temporal range of 13 decades and over a temperature range spanning liquid to glassy states. The d...