Using deioned water as a working fluid, the influence of the microscale effects on liquid flow resistance in microtubes with inner diameters of 19.6 and 44.2 lm, respectively, is experimentally studied. The temperature rise resulted from the microscale effects, such as viscous dissipation, electric double layer, wall rough on the wall surface, etc., is obtained by an IR camera with a special ma...

The scaling of the kinematic boundary layer thickness λu and the friction factor Cf at the topand bottom-wall of Rayleigh-Bénard convection is studied by Direct Numerical Simulation (DNS). By a detailed analysis of the friction factor, a new parameterisation for Cf and λu is proposed. The simulations were made of an L/H = 4 aspect-ratio domain with periodic lateral boundary conditions at Ra = {...

Nowadays, the Colebrook equation is used as a mostly accepted relation for the calculation of fluid flow friction factor. However, the Colebrook equation is implicit with respect to the friction factor (λ). In the present study, a noniterative approach using Artificial Neural Network (ANN) was developed to calculate the friction factor. To configure the ANN model, the input parameters of the Re...

The dynamic interplay between static and sliding friction is fundamental to many animal movements. One interesting example of stick-slip friction is found in the sound-producing apparatus of many spiny lobster species (Palinuridae). The acoustic movements of the spiny lobster's plectrum over the file are generated by stick-slip friction between the two surfaces. We examined the microscopic anat...

An earthquake source mechanism is described from the standpoint that the dynamic characteristics of friction play a more important role in the dislocation motion than the boundary condition does. By considering an earthquake dislocation as a slip motion in a mechanical system involving friction, which depends upon velocity during slip, a displacement time function G(t)=1-exp(-t/τ)(1+t/τ) which ...

Atomic force microscopy (AFM) experiments and molecular dynamics (MD) simulations were conducted to examine single-asperity friction as a function of load, surface orientation, and sliding direction on individual crystalline grains of diamond in the wearless regime. Experimental and simulation conditions were designed to correspond as closely as state-of-the-art techniques allow. Both hydrogen-...

In this paper, we study the stability of an initially straight elastic fibril clamped at one end, while the other end is subjected to a constant normal compressive force and a prescribed shear displacement. We found the buckling load of a sheared fibril to be always less than the Euler buckling load. Furthermore, if the end of the fibril loses adhesion, then the buckling load can be considerabl...

After falls, skiers or snowboarders often slide on the slope and may collide with obstacles. Thus, the skier’s friction on snow is an important factor to reduce incidence and severity of impact injuries. The purpose of this study was to measure snow friction of different fabrics of ski garments with respect to roughness, speed, and contact pressure. Three types of fabrics were investigated: a c...