Taut Wire Research Articles

AERODYNAMIC NOISE GENERATION BY A STATIONARY BODY IN A TURBULENT AIR STREAM

When a vortex street formed at the trailing edge of an upstream plate is arranged to impinge upon the leading edge of a small downstream block of similar thickness, a very powerful aerodynamic noise source of tonal quality is formed. Such an arrangement in which the down stream block is suspended on taut wires has been used to investigate Curle's prediction of the relation between the fluctuating lift force exerted by the block on the stream and the radiated sound power in the frequency domain for flow speeds ranging from 70 m/s to 190 m/s.The possible effect of additional stiff constraint to the motion of the clock in the direction of the fluctuating lift force on the radiated noise has also been investigated. The apparent effect of the additional constraint was to increase the magnitude of the fluctuating force on the radiating block but in either the case of constrained or unconstrained block the measured sound power data tends to agree with Curle's prediction at flow speeds above 140 m/s but gradually to diverge upward at lower flow speeds toward a prediction based upon a small vibrating sphere. In all cases the measured sound power levels tend to be bounded by Curle's prediction below and 9·5 dB above by a prediction based upon a small vibrating sphere.

Electro-mechanics of drift tube wires

The position and stability of the sense wires in very long drift tubes are affected by both gravitational and electrostatic forces, as well as by the wire tension. For a tube to be used as an element of a high-resolution detector all these forces and their effects must be understood in appropriately precise detail. In addition, the quality control procedures applied during manufacture and detector installation must be adequate to ensure that the internal wire positions remain within tolerances. It may be instructive to practitioners to review the simple theory of a taut wire in the presence of anisotropic gravitational and electrostatic fields to illustrate the conditions for stability, the equilibrium wire displacement from straightness, and the effect of the fields on the mechanical vibration frequencies. These last may be used to monitor the wire configuration externally. A number of practical formulae result and these are applied to illustrative examples.

Acetyl-l-carnitine 1: Effects on mortality, pathology and sensory-motor performance in aging rats

Three different test sites assessed the effects of acetyl-l-carnitine (AC) on age-related changes in general health, sensory-motor skills, learning, and memory. Two groups of rats began the experiments at 16 months of age. One group (OLD-AC) was given AC, 75 mg/kg/day, beginning at 16 months. The other group (OLD-CON) was treated identically except it was not given the drug. Beginning at 22 months of age, these rats and a group of young (3–4 months old) rats (YG-CON) were given a series of sensory-motor tasks. AC decreased mortality, and had no reliable effect on body weight, fluid intake, or the general health of the rats. These data indicate that a chronic dose of AC does not interfere with food and water intake, and may increase longevity. An age-related decline of performance occurred in most of the sensory-motor tasks; locomotor activity was reduced in a novel environment and in a runwheel, and the ability to prevent falling was reduced in tests on a taut wire, rotorod, inclined screen, and several types of elevated bridges. An age-related decline of performance did not occur in grooming, or in the latency to initiate several different behaviors. AC had no effect on performance in any sensory-motor task. These data indicate that the improvements produced by AC in some tests of spatial memory may be due to the effects of AC on cognitive abilities rather than on sensory-motor skills.

Three Dimensional Dynamic Analysis for Laying and Recovery of Optical Submarine Cables

The author has developed two types of cable laying simulation programs based on three dimensional dynamic analysis method in order to analyze dynamic behavior of cables, repeaters and branching unit during laying and recovery.One is a computer simulation program for laying and recovery of submarine cables with repeaters. This program has following two new functions is addition to conventional cable laying simulation.(1) Slack control laying function. The cable pay-out speed is automatically calculated by internal feed back loop so as to make bottom cable slacks be constant. Using this function, the optimum cable pay -out speed history can be obtained by giving the bottom profile and cable ship speed profile.(2) Tension control laying function. The cable pay-out speed is automatically calculated by internal feed back loop so as to make shipboard tension be constant. The speed error of cable ship measured by 'taut wire' is discussed using this program. This error is exactly analyzed using this tension control laying simulation.The other is a computer program for laying and recovery submarine cables with a cable branching unit. The cable branching unit (BU) is newly installed to the optical submarine cable systems. This newly developed program can analyze dynamic behavior of BU and cables around it, and help to study how to lay BU with sufficient cable slacks and recover it safety.The sea trial was carried out in order to measure hydrodynamic constant of the submarine cable and verify this computer simulation method at the depth of 6000m by attaching sensors to the submarine cable at some intervals. According to the sea trial, the normal drag coefficient Cd was measured to 2.5, andd the cable configuration measured by this experiment was in good agreement with the result of the computer simulation.

Wave modes in magnetic elements in a stratified atmosphere

view Abstract Citations (9) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Wave modes in magnetic elements in a stratified atmosphere. Wilson, P. R. Abstract The vibration modes of a magnetic flux element embedded in a compressible, gravitationally stratified atmosphere are considered. A local dispersion relation is first derived for a force-free field which decreases exponentially with height, and this is applied to a magnetic flux sheath lying within the local region. The sheath is embedded in an isothermal, gravitationally stratified plasma for which the standard dispersion relation applies globally. The velocity and pressure balance conditions across the interface restrict the possible vibration modes of the system. For the pulsation or varicose mode, a modified acoustic mode and a modified fast mode are obtained. The latter has a cutoff frequency which is greater than the acoustic cutoff and suggests that waves of shorter periods may occur in the presence of magnetic elements. For the sinuous or taut wire mode, complex solutions for the dispersion equation are obtained. For one of these the real part is large and negative, indicating that, within the limitations of a linear analysis, waves propagate with increasing amplitude. The possible significance of this is briefly discussed. Publication: The Astrophysical Journal Pub Date: November 1978 DOI: 10.1086/156573 Bibcode: 1978ApJ...225.1058W Keywords: Magnetohydrodynamic Waves; Plasma Waves; Stellar Magnetic Fields; Wave Propagation; Atmospheric Models; Boundary Value Problems; Perturbation Theory; Propagation Modes; Solar Magnetic Field; Geophysics; Alfven Waves:Solar Magnetic Fields; Hydromagnetics full text sources ADS |

A pocket calculator program for some simple vibration problems

An earlier buckling program [1] has been adapted to give the natural frequencies and mode shapes for free axial vibrations of bars, transverse vibrations of taut wires and torsional vibrations of shafts. The cross section of the bar, wire or shaft can vary at intervals along its length, and so can its distributed mass (or inertia for the shaft), which is allowed for in a classically exact way. Lumped masses (or rotors for shafts) and spring supports can be attached anywhere along the length, and the ends can be free or clamped. The program just fits on a Hewlett-Packard HP-25 pocket calculator, which can store only 49 program steps and 13 numbers.

Wave modes in a magnetic flux sheath

view Abstract Citations (15) References (1) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Wave modes in a magnetic flux sheath. Wilson, P. R. Abstract The symmetric wave modes of a two-dimensional magnetic flux sheath embedded in a compressible isothermal but nongravitational atmosphere are investigated under more general conditions than those considered earlier by Cram and Wilson. Both two-dimensional 'taut wire' and pulsation modes are considered, and explicit solutions are obtained when the thickness of the flux sheath is small compared with the transverse scale size of the perturbations. In particular, it is found that the taut wire or Alfven-type mode may be unstable if the density within the sheath is less than that outside. The solutions for the pulsation mode are compared with those obtained by Defouw under similar conditions. Agreement is obtained only in the limit as the sound speed in the nonmagnetic region tends to infinity. It is shown that Defouw's analysis, which neglects all transverse variations in the perturbations, is unsuitable to the problem and that the approximation which he makes eliminates the interaction between the magnetic and nonmagnetic plasmas. Publication: The Astrophysical Journal Pub Date: April 1978 DOI: 10.1086/156071 Bibcode: 1978ApJ...221..672W Keywords: Astrophysics; Magnetic Effects; Magnetic Flux; Magnetohydrodynamic Waves; Plasma Sheaths; Propagation Modes; Wave Propagation; Atmospheric Models; Magnetic Fields; Astrophysics; Hydromagnetics full text sources ADS |

The design and testing of a vertical-axis wind turbine using sails

A vertical-axis wind turbine using sails rather than solid blades has been designed and tested at large model scale in a 15 ft diameter wind tunnel. The turbine has a relatively high solidity, three blades and an operating range of tip speed ratios from zero to about 2.5. Two types of sail have been tested—a double sail consisting of two layers of cloth wrapped round a circular leading edge dowel, and a jib sail consisting of a single layer of cloth with the leading edge held by a taut wire. The measured power outputs are about half those of a turbine with solid aerofoil blades running at tip speed ratios of 5 or 6. However, the cost and skill required for manufacture of the sail turbines are less and it is concluded that the present designs, which can be self starting if the trailing edge tension is appropriately set, may have application for 1 kW machines in developing countries.

The one-dimensional diatomic lattice

Describes a student exercise in which a one-dimensional lattice of atoms is simulated by a row of lead weights on a taut wire. Atoms of two kinds are represented by different masses. The model enables all the normal modes of the system to be excited and studied. The omega -K diagram can be plotted, the acoustical and optical modes distinguished and a reasonable theoretical fit obtained by using the dispersion relationships for the infinite one-dimensional diatomic lattice.

Planktonic Foraminifera: Selective solution and the lysocline

Pacific Ocean waters appear to be undersaturated with calcium carbonate at all depths except in the uppermost few hundred meters. This leads to continuous destruction of almost all calcareous sediment exposed on the Pacific Ocean floor. Samples derived from sediment and from plankton were exposed for four months on a taut wire buoy in the central Pacific, in order to assess the effects of solution on foraminiferal death assemblages. The rate of destruction varied for different species and for different variants within species. Sediment assemblages therefore should tend to become enriched with resistant (non-spinose) species and with opaque (usually thick-shelled), zero and negative forms, i.e., specimens with small terminal chambers. Results obtained by laboratory experiments compare well with those obtained from the solution experiments in the field. The distribution of resistant forms in surface sediment samples from the East Pacific Rise shows that there exists a level of rapid solution increase (lysocline) in this area. The surface of the lysocline is at approximately 4,000 m depth in the tropics on the western side of the East Pacific Rise. The lysocline surface slopes upward toward Antarctica and toward South America and apparently becomes less well defined in high latitudes and near the continent. The calcium carbonate compensation depth results from a balance of rates of solution and of rates of supply of calcareous matter and usually lies well below the lysocline. The existence of a lysocline implies an associated oxygen minimum roof, and is bound to both active bottom water production and excess calcite supply by planktonic organisms.

Radiolarian Skeletons: Solution at Depths

Radiolarian skeletons were placed at several depths on the taut mooring wire of a buoy in the central Pacific for 4 months. Recent radiolarian sediment dissolved at appreciable rates at depths shallower than 2000 meters; solution was greatest near the surface and decreased with depth. This pattern correlates with bathymetric distributions of dissolved silicon and of temperature. Siliceous Radiolaria from planktonic samples appeared to dissolve about eight times faster than those from sediment. Tripyleans seemed to be less resistant than polycystins. Acantharia dissolved completely at all depths.

Foraminiferal Ooze: Solution at Depths

Samples of foraminiferal ooze were exposed to ocean water at various depths for 4 months, attached to the taut wire of a buoy in the central Pacific. Appreciable solution took place below 1000 meters and increased rapidly below 3000 meters and below 5000 meters. The fact that samples from different locations appear to dissolve at different rates suggests that the previous history of a sample determines its solubility. Solution is selective; it changes species composition, size distribution, content of damaged shells, and average particle weight of an assemblage.

Aeolian Tones Associated with Resonant Vibration

Experiments were conducted on taut wires stretched normally across an open jet test section of a low turbulence wind tunnel at various subsonic wind velocities. Measurements were taken of radiated sound-pressure level, lateral spatial correlation of wake velocity fluctuation, end-support acceleration, wire damping, and oscillatory lift on the wire for various ratios of vortex shedding frequency to wire resonant frequency for the first four wire-resonant frequencies. The radiated sound was essentially dipole at the Strouhal frequency of vortex shedding. Its intensity increased as U20 as the Strouhal frequency approached a wire resonant frequency from below. This is markedly in excess of the U6 dependence predicted by Phillips [J. Fluid Mech. 1, Pt. 6 (1956)] for rigid cylinders. The difference results from the influence of resonant vibration upon the root-mean-square sectional lift coefficient and the correlation length of vortex shedding. [Work carried out under General Hydromechanics Research Program administered by the David Taylor Model Basin, U. S. Navy.]

Dynamic Behavior of Massive Guy Cables

The dynamic behavior of massive guy cables under the action of an harmonic guy-top excitation and viscous damping is studied. Theoretical expressions for the complex stiffness modulus and vibration amplitudes are derived, based on the parabolic approximation of the cable form. The complex guy stiffness is expressed as two functions, corresponding to the horizontal guy reaction in phase and in quadrature with the deflection. The stiffnesses are expressed nondimensionally in terms of the soil called taut wire stiffness as functions of the initial cable strain, the ratio of cable weight to tension, the critical damping ratio, and a dimensional frequency ratio based on the taut wire frequency. Experiments on dynamic model guy cables confirm that the results are accurate for small amplitude motions. The study showed that a potentially dangerous situation arises at certain characteristic frequencies of the guy when the modulus becomes negative and the guy then tends to pull the mast over.

A robust torsion balance which can detect a force of 2 10-8dyn

A relatively robust torsion balance which will withstand baking in vacuo at 450°C, has a period of 6 seconds and can detect a force of about 2 × 10-8 dyn is described. It consists of a light metal vane mounted on a taut tungsten wire 10 μm in diameter. The rotation of the vane is measured by using a mirror and a light-beam amplifier of the type developed by Jones and Richards. The smallest torque detectable produces a rotation about equal to the r.m.s. Brownian deflection.

Remote Reading Bottom-Hole Pressure Gauges- An Evaluation of Installation Techniques And Practical Applications

Abstract Since 1959, 50 field installations of remote reading bottom-hole pressure gauges have been made on the Cedar Creek anticline in Eastern Montana. The installations were made in wells 9,000 ft deep with bottom-hole temperatures as high as 200F, and included both taut wire and bourdon tube bottom-hole pressure transducers. The initial installations had short periods of operational life because of cable and instrument failures. Continued investigation of installation techniques and types of cable have resulted in operational periods in excess of one year with an expected life of two years or more. Eleven types of cables were tested with various types of insulation and protective sheaths, various outside diameters, and solid and stranded conductors. Several methods of splicing were evaluated for mechanical strength and insulating qualities; a new cable clamp had to be designed; dawn-hole and surface conductor pack-offs were revised; and surface handling techniques had to be developed. Several case histories of practical applications are cited, which include bottom-hale pressure build-up surveys, water flood observation well surveillance and performances of producing wells. The installation cost figures included demonstrate that, although the use of remote bottom-hole pressure gauges cannot be justified in every producing well of this depth, installation in most key observation wells can be justified, depending upon the volume and importance of the data required. Practical installations of remote reading bottom-hole pressure gauges can now be made and have resulted in another valuable tool available to the petroleum engineer. Introduction Accurate and current down-hole pressure data are desirable to produce oil and gas wells at their optimum rate and by the most economical means. A permanently installed bottom-hole pressure gauge is an instrument which can provide such data for production personnel and engineers. The installation of remote reading bottom-hole pressure gauges in every producing well would be ideal from the standpoint of determining producing and static pressures and for detecting subtle equipment malfunctions. However, limited life expectancy and the existence of other indirect methods for determining bottom-hole pressure data have previously limited these installations to specialized cases. The development of the German-produced bottom-hole pressure transmitting system and its widespread use in the Schoonebeek and other fields in Europe prompted the investigation of practical applications in various Shell areas in the United States in 1958. Initial installations in the Pacific Coast, Texas and Rocky Mountain areas resulted in varying degrees of success. Fairly successful installations were made in relatively shallow wells, but the results were disappointing in wells ranging in depth from 6,000 to 9,000 ft. Short operational life and consequent expense were experienced in these wells. In view of the potential application of a direct reading and permanently installed pressure gauge, the development of practical installation techniques was classified as a General Development and Evaluation Project by Shell Oil and a sum of money was granted to the Rocky Mountain area for investigation and development of installation procedures and equipment evaluation. From these investigations, installation techniques have been refined and operating expenses have been reduced, permitting greater utilization and justification for these instruments. The remote reading bottom-hole pressure gauge has become an operational and a practical tool for wells producing highly aromatic hydrocarbons at depths to 9,000 ft, temperatures to 220F (104C) and pressures to 3,500 psi. Presently installed instruments have operated for an average duration of one year or more, and two year runs have been quite common. Installations in wells having less severe conditions should operate for significantly longer periods. This paper presents the experience obtained to date with these gauges and includes recommended installation and operating practices and materials. Theory of Operation of Existing Instruments To date two operational gauges are available for measuring bottomhole pressures on a remote reading basis. They are the German-produced taut wire gauge and the United States- produced bourdon tube-type gauge. The taut wire gauge was developed in 1948 and tested in German oil fields during 1950. JPT P. 1303^

Measurements on a Vibrating Conductor in a Magnetic Field

A taut wire, vibrating freely in a magnetic field, generates an emf. If current is allowed to flow as a result, it damps the vibratory motion. On the other hand, vibration can be caused by an applied ac current. Then, large changes in the imaginary component of the complex impedance are noted when the frequency approaches an odd harmonic of the wife's mechanical resonance. These effects have been measured and found in agreement with a recently proposed theory.

Measurements of the Pacific Equatorial Countercurrent

As part of Doldrums, the third of three International Geophysical Year oceanographical expeditions of the Scripps Institution of Oceanography, direct current measurements were made in the centre of the equatorial countercurrent, 7° 52′ N., 107° 30′ W. The techniques were similar to those used three months previously, when measurements were made of the Cromwell current at the equator, 140° W.1. In the top 300 m. observations were made by suspending a propeller-type current meter (a modified Roberts meter) from a drifting ship and measuring the apparent velocity at different depths from the flow of water past the meter while at the same time observing by radar the drift of the ship from a fixed reference point—a taut wire buoy anchored in 2,200 fathoms. Below 300 m. measurements were made by following the drift of Swallow current floats2.

An Automatic Bat-Collecting Device

Previous methods of collecting bats are satisfactory in many situations, but each has inherent limitations in usefulness. Shooting requires considerable experience and produces damaged or dead specimens. Nets of the insect-catching variety (Lyman, 1926) and modifications of the same produce only one bat per thrust in most situations and are usually effective only in close quarters. Gill (Jackson, 1926) are useful in some instances, but Japanese mist nets (Dalquest, 1954) are particularly effective. However, the latter require constant attention, for captured bats quickly become entangled, requiring considerable time to extract them, and if unattended, the net is soon damaged by bats that attempt to and frequently succeed in escaping by chewing their way to freedom, producing gaping holes in the net. My experience has shown that, if large numbers of bats are captured at one time, the bats and net become a hopelessly entangled mass. Griffin (1940) described the use of tunnel nets and metal or celluloid cylinders for capturing bats as they leave small openings in buildings, and he introduced the use of smooth-sided trap receptacles for housing captured bats, eliminating the necessity of cage doors. Similarly, the author has used glass or plastic sheets, placed in a vertical position at building roost exits, such as Spanish tile roofing openings; bats strike the obstruction and slide into a smooth-sided container below. Borrell (1937) captured bats by tripping them with taut wires, arranged horizontally just above the water surface of open water tanks, from which flying bats drink by scooping mouthfuls of water. This remarkable method requires constant attention, or the bats will escape or drown. Bats may be extracted from roosts with long forceps, a hooked wire, or by hand. Numerous modifications of the above procedures, as well as less satisfacto y techniques, have been employed. T ese methods, each being desirable under certain circumstances, lack ad ptability to all situations, and none fully satisfie the need arising when thousands of flying bats must be captured unharmed in pen space or in such places as large cave entrances. Furthermore, most of these techniqu s require considerable experience in the field and the presence of an operator. The discovery of bat rabies in the United Stat s (Venters, et al., 1954) and subsequent developments in this field stimulated the author to devise an automatic

Magneto-Striction Noise from Telephone Wires

WHEN magnetic material is subjected to a mechanical force, its magnetization is changed; and conversely, if its magnetization is changed, the material expands or contracts. There is thus a relationship between the stress and magnetization of magnetic materials which is called magnetostriction. According to an article by M. T. Dow (Bell Lab. Rec., 22, No. 10; June 1944), noise encountered some eight years ago on certain telephone lines was found to be caused by vibrations set up by wind in a long river-crossing consisting of steel conductors, and experiments indicated clearly that the noise was due to magneto-striction. The alternating stresses in the taut wires vibrating under the influence of wind, resulted in corresponding changes in the magnetization of the steel wires, and these magnetic fluctuations induced voltages in the wires that appeared as noise at the ends of the line.