Safety committees: Their role in preventing employee accidents in hotels and resorts

Employee accidents have a powerful and negative affect on the bottom line and profitability of a hotel or resort. In this professional paper, a literature review will be used to analyze the frequency and severity of injuries in hotels and resorts. Then, a guideline for a hotel safety committee will be established in an effort to help hotels and resorts decrease the amount, severity, and ultimately the cost associated with employee accidents. This professional paper aims to establish and implement guidelines for hotel and/or resort safety committees in order to increase the percentage of safe work practices on and off the job

Kolmogorov equation in fully developed turbulence

The Kolmogorov equation with a forcing term is compared to experimental measurements, in low temperature helium gas, in a range of microscale Reynolds numbers $R_{\lambda}$ between 120 and 1200. We show that the relation is accurately verified by the experiment (i.e. within +/- 3 % relative error, over ranges of scales extending up to three decades). Two scales are extracted from the analysis, and revealed experimentally, one characterizing the external forcing, and the other, varying as $R_{\lambda}^{-3/5}$, defining the position of the maximum of the function $- S_{3}(r)/r$, and for which a physical interpretation is offered.Comment: 4 pages, 4 figures, RevTe

Knudsen Diffusion in Silicon Nanochannels

Measurements on helium and argon gas flow through an array of parallel, linear channels of 12 nm diameter and 200 micrometer length in a single crystalline silicon membrane reveal a Knudsen diffusion type transport from 10^2 to 10^7 in Knudsen number Kn. The classic scaling prediction for the transport diffusion coefficient on temperature and mass of diffusing species,D_He ~ sqrt(T), is confirmed over a T range from 40 K to 300 K for He and for the ratio of D_He/D_Ar ~ sqrt(m_Ar/m_He). Deviations of the channels from a cylindrical form, resolved with transmission electron microscopy down to subnanometer scales, quantitatively account for a reduced diffusivity as compared to Knudsen diffusion in ideal tubular channels. The membrane permeation experiments are described over 10 orders of magnitude in Kn, encompassing the transition flow regime, by the unified flow model of Beskok and Karniadakis.Comment: 4 pages, 3 figure

Passive scalar intermittency in low temperature helium flows

We report new measurements of turbulent mixing of temperature fluctuations in a low temperature helium gas experiment, spanning a range of microscale Reynolds number, $R_{\lambda}$, from 100 to 650. The exponents $\xi_{n}$ of the temperature structure functions $\sim r^{\xi_{n}}$ are shown to saturate to $\xi_{\infty} \simeq 1.45 \pm 0.1$ for the highest orders, $n \sim 10$. This saturation is a signature of statistics dominated by front-like structures, the cliffs. Statistics of the cliff characteristics are performed, particularly their width are shown to scale as the Kolmogorov length scale.Comment: 4 pages, with 4 figure

Lagrangian Investigation of Two-Dimensional Decaying Turbulence

We present a numerical investigation of two-dimensional decaying turbulence in the Lagrangian framework. Focusing on single particle statistics, we investigate Lagrangian trajectories in a freely evolving turbulent velocity field. The dynamical evolution of the tracer particles is strongly dominated by the emergence and evolution of coherent structures. For a statistical analysis we focus on the Lagrangian acceleration as a central quantity. For more geometrical aspects we investigate the curvature along the trajectories. We find strong signatures for self-similar universal behavior

Contact angle determination in multicomponent lattice Boltzmann simulations

Droplets on hydrophobic surfaces are ubiquitous in microfluidic applications and there exists a number of commonly used multicomponent and multiphase lattice Boltzmann schemes to study such systems. In this paper we focus on a popular implementation of a multicomponent model as introduced by Shan and Chen. Here, interactions between different components are implemented as repulsive forces whose strength is determined by model parameters. In this paper we present simulations of a droplet on a hydrophobic surface. We investigate the dependence of the contact angle on the simulation parameters and quantitatively compare different approaches to determine it. Results show that the method is capable of modelling the whole range of contact angles. We find that the a priori determination of the contact angle is depending on the simulation parameters with an uncertainty of 10 to 20%.Comment: 14 pages, 7 figure

Comment on ``Large Slip of Aqueous Liquid Flow over a Nanoengineered Superhydrophobic Surface'' by C-H Choi and C Kim

In a recent Letter (Phys. Rev. Lett. vol 96, 066001 (2006), ref [1]), Choi and Kim reported slip lengths of a few tens of microns for water on nanoengineered superhydrophobic surfaces, on the basis of rheometry (cone-and-plate) measurements. We show that the experimental uncertainty in the experiment of Ref. [1], expressed in term of slip lengths, lies in the range 20 - 100 micrometers, which is precisely the order of magnitude of the reported slip lengths. Moreover we point out a systematic bias expected on the superhydrophobic surfaces. We thus infer that it is not possible to draw out any conclusion concerning the existence of huge slip lengths in the system studied by Choi and Kim.Comment: to appear in Physical Review Letter

Fluctuations in viscous fingering

Our experiments on viscous (Saffman-Taylor) fingering in Hele-Shaw channels reveal finger width fluctuations that were not observed in previous experiments, which had lower aspect ratios and higher capillary numbers Ca. These fluctuations intermittently narrow the finger from its expected width. The magnitude of these fluctuations is described by a power law, Ca^{-0.64}, which holds for all aspect ratios studied up to the onset of tip instabilities. Further, for large aspect ratios, the mean finger width exhibits a maximum as Ca is decreased instead of the predicted monotonic increase.Comment: Revised introduction, smoothed transitions in paper body, and added a few additional minor results. (Figures unchanged.) 4 pages, 3 figures. Submitted to PRE Rapi