From observations of swimming of the shell-less pteropod mollusc Clione antarctica we compare swimming velocities achieved by the organism using ciliated surfaces alone with velocities achieved by the same organism using a pair of flapping wings. Flapping dominates locomotion above a swimming Reynolds number Re in the range 5–20. We test the hypothesis that Re≈ 5–20 marks the onset of ‘flapping...

We review wall-bounded turbulent flows, particularly high–Reynolds number, zero–pressure gradient boundary layers, and fully developed pipe and channel flows. It is apparent that the approach to an asymptotically high– Reynolds number state is slow, but at a sufficiently high Reynolds number the log law remains a fundamental part of the mean flow description. With regard to the coherent motions...

A physical model of gabion overflow dams was studied to determine the velocity profile and Reynolds shear stress. Physical tests were done under two different conditions of dam crest, overflow dams with impermeable and with permeable crests. Instantaneous velocity components over dam crest were measured by an ADV (Acoustic Doppler Velocimeter) instrument. This instrument is capable of measuring...

Abstract   An empirical investigation was carried out to study convective heat transfer of nanofluid flow inside an inclined copper tube under uniform heat flux condition. Required data are acquired for laminar and hydrodynamically fully developed flow inside round tube. The stable CuO-base oil nanofluid with different nanoparticle weight fractions of 0.5%, 1% and 2% was produced by means of ul...

Laminar two dimensional forced convective heat transfer of Al2O3 –water nanofluid in a horizontal microchannel has been studied numerically, considering axial conduction, viscous dissipation and variable properties effects. The existing criteria in the literature for considering viscous dissipation in energy equation are compared for different cases and the most proper one is applied for the re...

his disclosures, adding government and private funding sources, and indicating “a misunderstanding of the requirements for reporting of conflicts of interest.” However, a check of other online published COI statements shows that Reynolds failed to disclose additional pharmaceutical conflicts from the 36-month period prior to the submission of the work, which are required disclosures according t...

We use silicon strip detectors (originally developed for the CLEO III high energy particle physics experiment) to measure fluid particle trajectories in turbulence with temporal resolution of up to 70,000 frames per second. This high frame rate allows the Kolmogorov time scale of a turbulent water flow to be fully resolved for 140 ≥ Rλ ≥ 970. Particle trajectories exhibiting accelerations up to...

Roughness effects on lubricant flows are investigated via 2D lattice Boltzmann simulations. At a Reynolds numbers of order 1000 a transition from laminar to unsteady flow is observed by an increase of the roughness height from about 10% to about 25% of the channel width. At lower Reynolds numbers (where the flow is laminar in both channels), the transition is observed when increasing the wall r...

As technological advances allow us to fabricate smaller autonomous self-propelled devices, it is clear that at some point directed propulsion could not come from pre-specified deterministic periodic deformation of the swimmer's body and we need to develop strategies for extracting a net directed motion from a series of random transitions in the conformation space of the swimmer. We present a th...

A novel constrained formulation for the dynamic subgrid-scale model for large eddy simulation (LES) is proposed. It is employed as a dynamic wall model when the constraint is imposed in the near-wall region of wall-bounded flows. An externally prescribed Reynolds stress is used as the constraint. However, unlike conventional zonal approaches, Reynolds stress is not imposed as the solution, but ...