Low Kinematic Viscosity Research Articles

Turbulent pipe flow of He I and He II

Turbulent pipe flow of liquid 4He has been investigated for Reynolds numbers from Re=3×10 3 to Re=3×10 6 to examine He I and He II turbulence in the presence of shear. The extremely low kinematic viscosity of liquid helium allows us to achieve high Reynolds numbers in small laboratory apparatus. Our results agree with those using classical fluids, showing the utility of helium as a fluid for turbulence research.

Second-Generation Synthetic Drilling Fluids

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering. Summary At the start of the 1990's, three synthetic materials were introduced:esters, ethers, and polyalphaolefins (PAO's). Now heading toward the last half of this decade, a new generation of synthetics is gaining popularity - linearalpha oletins (LAO's), internal or isomerized olefins (IO's), and linearparaffins (LP's). While similar, they also have differences, both as base fluids and as formulated drilling muds. These second-generation synthetic-based fluids (SBF's) have benefits over their predecessors in that they have lowerkinematic viscosity and are less expensive. As drilling fluids, these technical advantages give rise to a more flexible fluid to meet greater drilling demands for high-temperature/high-pressure (HTHP) applications, extended-reach-drilling projects, and deepwater drilling. As with the first-generation materials, environmental issues are the drivers for the development and use of these second-generation synthetics. Introduction Drilling with synthetic-based muds (SBM's) or pseudo-oil-based muds (OBM's)has become commonplace in both the Gulf of Mexico and North Sea areas. Synthetics also are in use or their implementation is planned in numerous other regions, such as the Far East, Australia, Mexico, Continental Europe, South America, and Russia. Because of the evolving marketplace, the view is that the industry has moved to at least the second generation of synthetics or pseudos. The boundary that separates first- from second-generation SBM's is arguably arbitrary but generally is delineated by both the cost and kinematic viscosity of the base fluid. Typically, second-generation synthetics are cheaper and thinner. Even considering these factors, second-generation SBM's have not totally replaced first-generation ones, although the use of the former flourishes while the latter wanes in areas where they coexist. Therefore, the first-generation SBM's can be considered to be based on the ester, ether, and PAO, while in the subsequent generation, the LAO's, IO's, and LP's are the base materials. Table 1 gives a more complete listing of first- and second-generation synthetics.

Emerging issues in helium turbulence

It has been appreciated recently that because helium has the lowest viscosity of any known material, it can be used in reaching the very highest Reynolds numbers and Rayleigh numbers. Critical helium gas, helium I and helium II are all candidates for such uses. Helium gas and helium I are classical fluids and the advantage stems solely from their low kinematic viscosity. Helium II obeys two-fluid equations and their use in turbulence investigations is under study. This article provides a brief introduction and review of this topic, outlining some of the progress already made and questions which need to be resolved as this relatively new field of investigation evolves. A summary of instrumentation available is included.

A physicochemical evaluation of perfluorochemicals for oxygen transport applications

The history of perfluorochemicals as oxygen transport agents and a comparison of potentialsecond generation perfluorochemicals is outlined. 1-Bromoperfluorooctane (perflubron,perfluorooctyl bromide, PFOB), a linear aliphatic perfluorochemical, has unexpectedlipophilic properties relative to other perfluorochemicals. The enhanced lipophilicity leadsto the unique combination of excellent emulsion stability and an exceptionally shortorgan retention time. Other medically desirable properties of PFOB include: high purityand definition; excellent gas solubility; superior compatibility with egg yolk phospholipids;the ability to provide contrast; low vapor pressure; low kinematic viscosity; and a positivespreading coefficient on a saline solution.

Particle transport through a hollow canine airway cast by high-frequency oscillatory ventilation.

High-frequency oscillatory ventilation (HFV) of the mammalian respiratory tract can maintain good respiratory ventilation, even with tidal volumes less than half of the anatomic dead space. A steady bidirectional drift is established in airways when the frequency is greater than 2 Hz, resulting in quasi-steady axial streams in the airways. Convective transport from the trachea to peripheral airways takes place in the central core of the bifurcating network of the bronchial tree. It takes place in the opposite direction in the annular regions near the airway walls. In this study, aerosol particle transport was measured in a hollow cast of a canine tracheobronchial tree that extended from the trachea to terminal bronchioles. The 0.5 micron particles, placed in the upper trachea as a bolus, were transported rapidly to the terminal airways of the cast by HFV with tidal volumes of less than one third the volume of the cast. Carrier gases of different kinematic viscosity were used to investigate the fluid dynamics of the transport. Particle transport during HFV was fastest in a gas of high kinematic viscosity (helium), and slowest in a gas of low kinematic viscosity (sulfur hexafluoride). The results are consistent with the application of lubrication theory, improve our understanding of convective processes involved in HFV, and provide new insights into particle penetration in the airways and other aspects of respiratory ventilation.

Butyl methacrylate-styrene copolymers as V. I. improvers for ester oils

Ester oils exhibit low kinematic viscosity at 100~ (3-5 ~2/sec). Recently interest has been stimulated in oils with viscosities in the 7-8 mm2/sec range at 1000C. Thickening additives (V. I. improvers) are generally used to prepare these types of oils. Since special thickening additives (V. I. improvers) have not been developed for synthetic oils, the latter are often treated with V. I. improvers developed for petroleum-based oils, such as poly(alkyl methacrylates).

Numerical simulation of free and forced convection in the classical Czochralski method and in CACRT

We present the Czochralski bulk flow simulations of forced convection in a crucible filled with liquid copper performed by the procedure in our previous paper [11]. Moreover, we describe the extension of our programme for the numerical solution of the time-dependent Navier-Stokes equations with Boussinesq approximation and the convective heat conduction equation in the Czochralski crystal-growth arrangement. By means of several digital simulations with a low kinematic viscosity, typical for liquid metals, and characteristic rotational angular velocities of crystal and crucible, the influence of free buoyancy driven convection on the familiar forced convective flow patterns is studied with special emphasis on the occurrence of flow and temperature oscillations. Additionally, we show the combined free and forced convective flow patterns in the isorotational and the counterrotational Czochralski Accelerated Crucible (and Crystal) Rotation Technique arrangement (CACRT) for a fluid of the viscosity of liquid silicon.

A Theoretical Estimation of the Performance of Journal Bearings Operating in the Turbulent Lubrication Regime

The use of process fluids of low kinematic viscosity as lubricants and the ever increasing surface speeds which are being encountered in fluid-film bearings have meant an increase in the number of bearings which operate in the turbulent regime. This paper describes a theoretical evaluation of the performance of 360-degree journal bearings operating turbulently, presents generalized data and discusses the results with comments upon the assumptions made and practical realities.

A Bulk-Flow Theory for Turbulence in Lubricant Films

The purpose of this study on the turbulent lubricant film is: 1 To give a brief outline of a new theory called bulk-flow theory; 2 To investigate to what extent results of theories based on law of wall and mixing length concept agree with the newly developed theory; 3 To provide a theoretical basis for the design of bearings lubricated by fluids of low kinematic viscosity.