Showing papers on "Rotation published in 1975"

Sloping convection in a rotating fluid

Abstract: Laboratory experiments on thermal convection in a fluid which rotates about a vertical axis and is subject to a horizontal temperature gradient show that when the rotation rate Ω exceeds a certain critical value ΩR (which depends on the acceleration of gravity, the shape and dimensions of the apparatus, the physical properties of the fluid and the distribution and intensity of the applied differential heating) Coriolis forces inhibit overturning motion in meridian planes and promote a completely different type of flow which has been termed ‘sloping convection’ or ‘baroclinic waves’. The motion is then non-axisymmetric and largely confined to meandering ‘jet streams’, with trajectories of individual fluid elements inclined at only very small (though essentially non-zero) angles to the horizontal. The kinetic energy of the waves derives from the interaction of slight vertical motions with the potential energy field maintained by differential heating, and it is dissipated by friction arising largely...

The Rotation of the Earth: A Geophysical Discussion

Abstract: This book gives an account of certain observed irregularities on the rotation of the Earth, both in its rate of rotation (giving a variable length of day) and in the position of its axis. These irregularities are caused by events on and within the Earth and provide a means of studying a number of geophysical problems. Seasonal shifts in air masses and variable winds are causes of short-period fluctuations in the rotation. Climatic changes and their attendant sea levels are in part responsible for long-term fluctuations. Modern observations of the Moon and descriptions of ancient elipses both establish a secular increase in the length of day. The interpretation involves atmospheric, oceanic and bodily tides. The book provides a unified treatment of the rotation of the Earth, making this method of studying geophysical phenomena more readily accessible to geophysicists and others.

Experiments on turbulence in a rotating fluid

Abstract: Experiments have been carried out to investigate the effect of rotation of the whole system on decaying turbulence, generally similar to grid turbulence, generated in air in an annular container on a rotating table. Measurements to determine the structure of the turbulence were made during its decay, mean quantities being determined by a mixture of time and ensemble averaging. Quantities measured (as functions of time after the turbulence generation) were turbulence intensities perpendicular to and parallel to the rotation axis, spectra of these two components with respect to a wavenumber perpendicular to the rotation axis, and some correlation coefficients, selected to detect differences in length scales perpendicular and parallel to the rotation axis. The intensity measurements were made for a wide range of rotation rates; the other measurements were made at a single rotation rate (selected to give a Rossby number varying during the decay from about 1 to small values) and, for comparison, at zero rotation. Subsidiary experiments were carried out to measure the spin-up time of the system, and to determine whether the turbulence produced any mean flow relative to the container.A principal result is that increasing the rotation rate produces faster decay of the turbulence; the nature of the additional energy sink is an important part of the interpretation. Other features of the results are as follows: the measurements with-outrotation can be satisfactorily related to wind-tunnel measurements; even with rotation, the ratio of the intensities in the two directions remains substantially constant; the normalized spectra for the rotating and the non-rotating cases show surprising similarity but do contain slight systematic differences, consistent with the length scales indicated by the correlations; rotation produces a large increase in the length scale parallel to the rotation axis and a smaller increase in that perpendicular to it; the turbulence produces no measurable mean flow.A model for the interpretation of the results is developed in terms of the action of inertial waves in carrying energy to the boundaries of the enclosure, where it is dissipated in viscous boundary layers. The model provides satisfactory explanations of the overall decay of the turbulence and of the decay of individual spectral components. Transfer of energy between wavenumbers plays a much less significant role in the dynamics of decay than in a non-rotating fluid. The relationship of the model to the interpretation of the length-scale difference in terms of the Taylor-Proudman theorem is discussed.The model implies that the overall dimensions of the system enter in an important way into the dynamics. This imposes a serious limitation on the application of the results to the geophysical situations at which experiments of this type are aimed.The paper includes some discussion of the possibility of energy transfer from the turbulence to a mean motion (the ‘vorticity expulsion’ hypothesis). It is possible, on the basis of the observations, to exclude this process as the additional turbulence energy sink. But this does not provide any evidence either for or against the hypothesis in the conditions for which it has been postulated.

Low-Reynolds-number translation of a slender cylinder near a plane wall

Abstract: Low-Reynolds-number results are presented for the drag and induced torque on a slender circular cylinder translating near a single plane wall. Four representative situations are investigated, the principal feature of the analysis being that it is valid for all distances from the wall which are large compared with the radius of the cylinder. In particular, the results hold for distances from the wall of the same order of magnitude as the length of the cylinder. The direction and rate of rotation are given for those cases where it occurs.

Wind energy conversion device

Abstract: A wind energy conversion device for converting directional wind force to torque along on a vertical rotational axis. The device includes a plurality of flexible vanes mounted to a framework for rotation therewith about a vertical axis. The vanes are mounted to upright posts on the framework. Axial vane side edges extend to opposite radial sides of the posts and are connected in a specific manner to the frame in order to produce a positive effect on rotation of the device in a prescribed direction, in response to wind currents.

The Influence of Rotation on the Free Oscillations of the Earth

Abstract: We pursue an abstract investigation of the theory of the infinitesimal free elastic-gravitational oscillations of a fairly general rotating Earth model. By considering in some detail the transition to the non-rotating case, we are able to delineate certain of the intrinsic effects of rotation on the normal mode eigensolutions, and to show how profoundly rotation alters the fundamental mathematical and physical properties of these eigensolutions. In particular, we show that the displacement eigenfunctions of a rotating Earth model are not mutually orthogonal, and that the corresponding normal modes of oscillation cannot in general be represented by pure standing waves. We consider the excitation of the normal modes of oscillation of a rotating Earth model by a transient imposed body force distribution, and we show that the complex dynamical amplitude of each normal mode may, in many geophysical applications, be determined separately, in spite of the lack of orthogonality among the displacement eigenfunctions. The calculation of the associated static response after the decay of the normal modes of oscillation is, on the other hand, complicated considerably by the absence of orthogonality. We specifically examine the influence of rotation on the zero-frequency rigid body translational and rotational modes of any non-rotating Earth model, and show how to account for the corresponding rigid body modes of any rotating Earth model in excitation calculations.

Reorientation device for an object manipulator

Abstract: A reorientation device for use with a general purpose object manipulator is disclosed, comprised of an arrangement for rotating the object while in the grasp of the manipulator through predetermined detented angles, this reorientation thereby reducing the range of manipulation motions required to be executed by the manipulator device. The specific reorientation arrangement includes pneumatically operated rack and pinion devices adapted to rotate turnover plates through a 180° angle, each of the turnover plates being adapted to carry a respective one of a set of manipulator fingers. By means of a pneumatically operated interposer pin, the rotation of each turnover plate can be selectively arrested at a predetermined angle of rotation short of the full degree of rotation produced by the rack and pinion devices.

Endless conveyor with gripping elements

Abstract: A transport apparatus for printed products arriving in an imbricated formation, said transport apparatus comprising grippers or gripper elements anchored in spaced relationship from one another at a revolving traction element for engaging the leading edges of the printed products and for the transfer thereof for further conveying of such printed products. At a transfer zone the conveyor track of the imbricated product stream and a guide for the grippers extend in a direction towards one another. Each gripper comprises a guided upper clamping tongue or jaw and a lower clamping tongue or jaw which is mounted to be movable towards and away from the upper clamping jaw as well as being rotatably mounted. This lower clamping tongue or jaw, when assuming its open position, forms an angle together with the upper clamping jaw which is rearwardly directed and in its closed position the lower clamping jaw is held in a position which is in alignment with or underlies the upper clamping jaw by a holding device of the gripper. At the transfer zone there are provided means for positionally moving the lower clamping jaw into its closed position by rotation and displacement thereof, and along the path of movement of the grippers there are arranged further means in order to render the holding device ineffectual and to return the lower clamping jaw back into its open position.

On the extensional and flexural vibrations of rotating bars

Abstract: The non-linear equations of motion of a slender bar rotating at constant angular velocity about a transverse axis are formulated. Under the assumption that a small perturbed motion occurs about an initially stressed equilibrium configuration, linearized equations of motion for the longitudinal and flexural deformations of a rotating bar carrying a tip mass are derived. Numerical computations for the natural frequencies of the lowest three modes of free vibration reveal that the values of the extensional frequencies increase monotonically, contrary to previously published results, as the angular velocity of rotation increases.

Trailer tongue jack

Abstract: A jack for supporting and adjusting the elevation of a trailer tongue comprises a ground support post, having either a caster wheel or foot plate at its lower end, extending downwardly through a jack mechanism housing which is bolted to the trailer tongue. The post can be raised or lowered either by means of a rotatable crank extending from the housing or, alternately, after manual release of latching means in the housing and tilting of the crank, by manually sliding the post. The post has a toothed rack affixed along one side thereof. The mechanism in the housing comprises a pivotally movable support member on which a crank-driven worm and an intermeshing worm gear are rotatably mounted. The support member is spring biased and releasably latched into an upward position wherein the worm gear engages the rack (and functions as a pinion gear) and manual rotation of the crank is necessary to move the post up or down. Upon manual release of the latch, tilting of the crank moves the support member to a downward position wherein the worm gear is disengaged from the rack, whereupon the post is free to be slid manually to a desired position.

Reciprocating piston machine

Abstract: A reciprocating piston engine, pump or compressor including a crank-shaft having a crank-pin offset laterally from the axis of rotation of the crank-shaft, a connecting-rod pivotally-mounted on the crank-pin and pivotally-connected at the end thereof remote from the crank-pin to a piston, the axis of pivoting of the connecting-rod on the crank-pin being offset laterally from the longitudinal axis of the crank-pin, a non-rotatable gear mounted co-axially of the crank-shaft axis of rotation and a rotatable gear wheel mounted co-axially on the crank-pin for rotation thereon and in mesh with said non-rotatable gear, the connecting-rod being mounted on the rotatable gear for pivoting about an axis offset laterally from the longitudinal axis of the crank-pin, whereby the axis of pivoting of the connecting-rod on the crank-pin follows a predetermined locus as the crank-shaft is rotated.

Drive arrangement for rotary shredding apparatus

Abstract: A rotary shredder for waste materials has a pair of counterrotating cutting shafts, each of which mounts a series of spaced-apart disc-type cutters. The cutters on one shaft extend into the spaces between cutters on the other shaft so that the cutters on the two shafts coact to shred material fed therebetween. The two shafts are driven by a reversible radial piston hydraulic motor through a gear train arranged to rotate one cutter shaft at twice the speed of the other. The hydraulic motor is driven by an electric motor-driven fixed or variable displacement pump. A flow-reversing valve in the hydraulic motor control circuit controls the direction of fluid flow through the hydraulic motor. The reversing valve is electrically actuated automatically by a fluid pressure-operated switch to reverse flow and the direction of rotation of the cutters to prevent jamming whenever fluid pressure in the motor circuit rises to an abnormally high level. Upon detecting high pressure, the switch energizes a time delay relay which closes a relay contact to energize a solenoid which actuates the flow-reversing valve for a predetermined time period, after which the valve shifts to its normal position to operate the hydraulic motor in its normal directional mode to resume shredding.

The correction of great circular surface wave phase velocity measurements for the rotation and ellipticity of the Earth

Abstract: Normal mode perturbation theory is combined with a geometrical optics approximation in order to establish a procedure for correcting great circular Love and Rayleigh surface wave phase velocity measurements for the effects of the rotation and the hydrostatic ellipsoidal shape of the earth. The necessary correction can be made by utilizing in the measurement process an apparent path length Lapp(T, Θ) for great circular propagation of surface waves of period T around any path with a positive pole inclined at an angle Θ to the rotation axis of the earth. The apparent great circular path length Lapp(T, Θ) is given by Lapp(T, Θ) = 2πa[1 - χ1(T) cos Θ - χ2(T)(1 - 3 cos2 Θ)], where a is the mean radius of the earth and χ1(T) and χ2(T) can be expressed, respectively, in terms of the normal mode multiplet rotational and elliptical splitting parameters of the earth. For some models of the earth, especially those having sharp discontinuities or steep gradients in radial structure in the upper mantle, the apparent path length Lapp(T, Θ) appropriate to fundamental long-period Love and, especially, Rayleigh waves can differ from the actual path length by several tenths of a percent, in which case the need for correction becomes real.

Coacting wheels type football throwing device

Abstract: A football is projected with rotation on its longitudinal axis, in the manner of a forward pass, when it is fed into the space between, and thereby gripped frictionally by, the laterally spaced, confronting surfaces of a pair of driven wheels which confronting surfaces move in a forward, football throwing direction but in planes which extend forward angularly to opposite sides of the line on which the football is projected, the planes forming an included acute angle with each other. The speed and direction of football rotation may be varied by adjusting said angular relationship, and the speed of forward projection of the football may be varied by adjusting the rotational speed of the wheels. By adjusting said confronting surfaces to a common plane and feeding a football into the space therebetween such that said surfaces grip the football below its longitudinal centerline, the football is projected therefrom with rotation on its transverse axis, in the manner of an end-over-end kick-off.

Centrifugal support for workpieces

Abstract: A chuck for a workpiece, rotatable in spaced relation to and about an axis of rotation, and having a clamp jaw radially movable under centrifugal force to engage the workpiece against fixed mating clamp members. The structure can also have optional means enabling the chuck to tilt, with the workpiece, from a home position to a preselected angle under the rotation thereof about a pivot axis perpendicular to and spaced from the axis of rotation with return of the chuck to the home position under gravitational force when rotation thereof is stopped.

Well packer apparatus

Abstract: Disclosed is a retrievable, hydraulically set well packer which is locked in set position without need for tubing rotation and may be released from set position by shearing a retrieving link with either a straight pull on the production tubing or by the application of high pressure through the tubing. Dual, opposed cones are employed for retaining the packer slips anchored irrespective of the direction of the pressure differential acting on the packer and without need for an extra sleeve to transmit pressure induced forces to the cones. Compression seals are employed to hold the slips firmly anchored against longitudinal displacement in both directions without reliance on the presence of a pressure differential across the set packer. The seals are employed as two separate assemblies which are positioned above and below the slips to isolate a portion of the pressure induced forces from the retrieving link. A modified form of the invention employs the dual cone, dual seal design on a packer having multiple flow passages.

Rotation sensor for borehole telemetry

Abstract: A rotation sensor and output signal processing apparatus is presented. The rotation sensor is a ring core flux gate magnetometer whose output varies as a function of the earth's magnetic field. The phase angle of the second harmonic of the magnetometer output is sensed to provide an indication of the state of rotation of the magnetometer. When a state of no rotation is sensed, actuating signals are delivered to a control system to sense borehole parameters and telemeter the parameters to the top of the borehole.