The phenomenon of apparent slip in micro-channel flows is analyzed by means of a two-phase mesoscopic lattice Boltzmann model with non-ideal fluid–fluid and fluid–wall interactions. Analytical solutions of the weakly inhomogeneous hydrodynamic limit of this model are successfully compared with numerical simulations and show that the present mesoscopic approach is capable of filling the gap betw...

We describe a generalization of the tensorial slip boundary condition, originally justified for a thick (compared to texture period) channel, to any channel thickness. The eigenvalues of the effective slip-length tensor, however, in general case become dependent on the gap and cannot be viewed as a local property of the surface, being a global characteristic of the channel. To illustrate the us...

Superhydrophobic surfaces reduce drag by combining hydrophobicity and roughness to trap gas bubbles in a microscopic texture. Recent work has focused on specific cases, such as arrays of pillars or grooves, with limited theoretical guidance. Here, we consider the experimentally relevant limit of thin channels and obtain rigorous bounds on the effective slip length for any two-component (e.g., l...

The dynamics of the fluctuations of a liquid film on a heterogeneous substrate is analyzed. We consider the case of a viscous liquid in the Stokes limit, with small variations of substrate height and a small varying slip length. We discuss the possibility of extracting the topographic profile or the slip length profile at the liquid-solid interface from the measurement of the fluctuations of th...

Traditional analyses of slip at corners of contacts, based on linear elasticity and a Coulomb friction law, are very sensitive to the details of local geometries, owing to the effects of elastic singularities. Following the use of cohesive-zone models to address such issues in mode-II fracture, we present analyses of slip and wear at corners of contacts when a finite interfacial shear strength ...

[1] We find that slow seismic events have smaller fault slips compared to ordinary earthquakes with similar dimensions. For ordinary earthquakes, the ratio of slip to fault length is largely consistent, yet the physical controls on this ratio are unknown. Recently discovered slow slip or creep events in which faults move quasi-statically over periods of days to years shed new light on this old ...

We present dissipative particle (DPD) simulations of electrolyte flow in nanochannels for varying salt concentration and surface slip conditions. First, a method is presented by which the slip length δ Β at the channel boundaries can be tuned systematically from negative to infinity by introducing suitable wall-fluid friction forces. Using this method, we study electroosmotic flow (EOF) in nano...

[1] We model ruptures on faults that weaken in response to flash heating of microscopic asperity contacts (within a rate-and-state framework) and thermal pressurization of pore fluid. These are arguably the primary weakening mechanisms on mature faults at coseismic slip rates, at least prior to large slip accumulation. Ruptures on strongly rate-weakening faults take the form of slip pulses or c...

We examine gas flow adjacent to a molecularly smooth, solid, muscovite mica. The fluctuations in force acting on a glass sphere as a function of proximity to a mica plate were measured in air and were used to obtain the damping. The damping was interpreted as a lubrication force. The measured damping as a function of separation in the slip-flow regime corresponds to a slip length of 480 ± 70 nm...

A systematic study into the effect of solid roughness on the slip boundary condition during shear flow is presented. Atomic roughness is modeled by varying the size and spacing between solid atoms at constant packing fraction while the interaction parameters and the thermodynamic state of the fluid are kept constant. It is shown that the fluid structure as manifest in the amplitude of the densi...