We present a simple theoretical framework to describe the thermal noise of a microscopic mechanical beam in a viscous fluid: we use the Sader approach to describe the effect of the surrounding fluid (added mass and viscous drag), and the fluctuation dissipation theorem for each flexural modes of the system to derive a general expression for the power spectrum density of fluctuations. This predi...

BACKGROUND AND PURPOSE Hemodynamics are thought to play an important role in the mechanisms of aneurysm pathogenesis, progression, and rupture. The purpose of this study was to define quantitative measures related to qualitative flow characteristics previously analyzed and to investigate their relationship to aneurysm rupture. MATERIALS AND METHODS The hemodynamic environments in 210 cerebral...

This work aims at understanding the viscous effects of the outer potential flow on Prandtl’s boundary layer. For a body moving with a constant velocity in an otherwise quiescent liquid, the non-zero viscous dissipation of the outer potential flow gives rise to an additional drag, increasing the drag calculated from the boundary layer alone. The drag is considered in three cases here, on a two-d...

Recent observations suggest that neutron stars in low-mass X-ray binaries rotate within a narrow range of spin frequencies clustered around 300Hz. A proposed explanation for this remarkable fact is that gravitational radiation from a steady-state r-mode oscillation in the neutron star’s core halts the spin-up due to accretion. For the neutron star transients, balancing the time-averaged accreti...

In last decades many strategies for seismic vulnerability mitigation of structures have been studied and experimented; in particular energy dissipation by external devices assumes a great importance for the relative simplicity and efficacy. Among all possible approaches the use of fluid viscous dampers are very interesting, because of their velocity-dependent behaviour and relatively low costs....

Nanomechanical resonators enable a range of precision measurements in air or vacuum, but strong viscous damping makes applications in liquid challenging. Recent experiments have shown that fluid damping is greatly reduced in fluidic embedded-channel microcantilevers. Here we report the discovery of nonmonotonic energy dissipation due to the fluid in such devices, which leads to the intriguing p...

We describe a dissipation principle/variational principle which may be useful in modeling motion in small viscous systems and provide brief illustrations to brownian motor or molecular rachet situations which are found in intracellular transport. Monge-Kantorovich mass transport and Wasserstein metric play an interesting role in these developments. Some properties of the system that ensure the ...

For partial wetting, motion of the triple liquid-gas-solid contact line is influenced by heterogeneities of the solid surface. This influence can be strong in the case of inertial (e.g. oscillation) flows where the line can be pinned or move intermittently. A model that takes into account both surface defects and fluid inertia is proposed. The viscous dissipation in the bulk of the fluid is ass...

To model nonlinear viscous dissipative motions in solids, acoustical physicists usually add terms linear in Ė, the material time derivative of the Lagrangian strain tensor E, to the elastic stress tensor σ derived from the expansion to the third (sometimes fourth) order of the strain energy density E=E(tr E,tr E(2),tr E(3)). Here it is shown that this practice, which has been widely used in the...

For subduction to occur, plates must bend and slide past overriding plates along fault zones. This deformation is associated with significant energy dissipation, which changes the energy balance of mantle convection and influences the thermal history of the Earth. To parameterize these effects, a subduction zone was included in a small region of a finite element model for the mantle, which also...