Linear Oscillation Viscometer

1969 ◽  
Vol 40 (2) ◽  
pp. 339-345 ◽  
Author(s):  
M. S. White ◽  
C. Solomons
Keyword(s):  
Linear Oscillation ◽  
Oscillation Viscometer

Non-Linear Effects of Vibration in Gas Turbine Engines With Two or Three Rotors

2002 ◽  
Author(s):  
J. Pismenny ◽  
Y. Levy
Keyword(s):  
Complex System ◽  
Gas Turbine ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Practical Application ◽  
Turbine Engine ◽  
Non Linear ◽  
Linear Elements ◽  
Linear Effects ◽  
Linear Oscillation

The dependence of the vibration characteristics of gas turbine engines on the rotor speeds becomes highly complicated in engines with two and three rotors, both because of the simultaneous dynamic action of the multiple rotors and the ambiguous relationships between their speeds. In this paper, the gas turbine engine is analyzed in the context of the theory of non-linear oscillation — as a complex system comprising a large number of non-linear elements and multiple periodical forces of different frequencies (defined by the rotor speeds). This paper presents results, which indicate that the level of vibration can obtain critical values at certain relationships between the rotor speeds. As a practical application of this phenomena it is shown that the number of three-spool engines returns from the aircraft to the engine manufacturer, due to different kinds of malfunctions, for example due to activation of the “intensified vibration” alarm, may be approximately three times that of returns of analogous two-rotor engines.

Vertical linear self-motion perception during visual and inertial motion: More than weighted summation of sensory inputs

2005 ◽  
Vol 15 (4) ◽  
pp. 185-195 ◽  
Author(s):  
W.G. Wright ◽  
P. DiZio ◽  
J.R. Lackner
Keyword(s):  
Motion Perception ◽  
Visual Motion ◽  
Test Chamber ◽  
Vestibular Stimulation ◽  
Visual Scene ◽  
Inertial Motion ◽  
Physical Test ◽  
Head Mounted Display ◽  
Linear Oscillation ◽  
Self Motion

We evaluated visual and vestibular contributions to vertical self motion perception by exposing subjects to various combinations of 0.2 Hz vertical linear oscillation and visual scene motion. The visual stimuli presented via a head-mounted display consisted of video recordings of the test chamber from the perspective of the subject seated in the oscillator. In the dark, subjects accurately reported the amplitude of vertical linear oscillation with only a slight tendency to underestimate it. In the absence of inertial motion, even low amplitude oscillatory visual motion induced the perception of vertical self-oscillation. When visual and vestibular stimulation were combined, self-motion perception persisted in the presence of large visual-vestibular discordances. A dynamic visual input with magnitude discrepancies tended to dominate the resulting apparent self-motion, but vestibular effects were also evident. With visual and vestibular stimulation either spatially or temporally out-of-phase with one another, the input that dominated depended on their amplitudes. High amplitude visual scene motion was almost completely dominant for the levels tested. These findings are inconsistent with self-motion perception being determined by simple weighted summation of visual and vestibular inputs and constitute evidence against sensory conflict models. They indicate that when the presented visual scene is an accurate representation of the physical test environment, it dominates over vestibular inputs in determining apparent spatial position relative to external space.

scholarly journals Generalized Theory of Shell Flash and Accreting White Dwarfs

1981 ◽  
Vol 93 ◽  
pp. 191-206
Author(s):  
Daiichiro Sugimoto ◽  
Shigeki Miyaji
Keyword(s):  
White Dwarfs ◽  
Dissipative System ◽  
Finite Amplitude ◽  
Recurrence Time ◽  
Near Surface ◽  
Giant Stars ◽  
Deep Interior ◽  
Non Linear ◽  
Red Giant ◽  
Linear Oscillation

Shell flashes take place both in deep interior of red giant stars and near surface of accreting white dwarfs. Theories of shell flashes have been thus far presented piece by piece in different papers. It is the purpose of the present review to construct and generalize them in order to reach better understanding. A non-linear yet almost analytical theory is presented which treats the development of the shell flash in finite amplitude. Recurrence of the shell flashes is also shown to be well understood as a non-linear oscillation in dissipative system which tends to be its limit cycle. As a result strength of the peak energy-generation and recurrence time of the shell flashes are related with mass of the accreting white dwarfs, accretion rate, etc.

scholarly journals Angular-Momemtum Transfer by Nonradial Oscillations in Massive Main-Sequence Stars

1993 ◽  
Vol 137 ◽  
pp. 287-289
Author(s):  
Umin Lee ◽  
Hideyuki Saio
Keyword(s):  
Angular Momentum ◽  
Reynolds Stress ◽  
Main Sequence ◽  
Rotation Velocity ◽  
Main Sequence Stars ◽  
Oscillation Analysis ◽  
Oscillation Velocity ◽  
Time Average ◽  
Linear Oscillation ◽  
Nonradial Oscillations

Angular mementum distribution is one of the most important factors for stellar structutre and evolution. Among other mechanisms, angular momentum is transfered by non-axisymmetric oscillations (nonradial oscillations). In this mechanism the angular momentum is carried mainly by the Reynolds stress, which is proportional to the product between radial and azimuthal components of oscillation velocity; i.e., (Φ direction is the direction of rotation velocity). In the linear oscillation analysis, the phase difference between and is with A finite value of δ, which arises from excitation or damping of the oscillation, makes the time average of finite. Positive angular momentum is transfered from the driving zone to the damping zone by a prograde mode (Osaki 1986).

High-Speed X-Ray Imaging of Diesel Injector Needle Motion

2009 ◽  
Author(s):  
A. L. Kastengren ◽  
C. F. Powell ◽  
Z. Liu ◽  
K. Fezzaa ◽  
J. Wang
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Linear Increase ◽  
Nozzle Geometry ◽  
X Ray ◽  
Needle Position ◽  
X Ray Imaging ◽  
Linear Oscillation ◽  
Degree Of Convergence

Phase-enhanced x-ray imaging has been used to examine the geometry and dynamics of four diesel injector nozzles. The technique uses a high-speed camera, which allows the dynamics of individual injection events to be observed in real time and compared. Moreover, data has been obtained for the nozzles from two different viewing angles, allowing for the full three-dimensional motions of the needle to be examined. This technique allows the needle motion to be determined in situ at the needle seat and requires no modifications to the injector hardware, unlike conventional techniques. Measurements of the nozzle geometry have allowed the average nozzle diameter, degree of convergence or divergence, and the degree of rounding at the nozzle inlet to be examined. Measurements of the needle lift have shown that the lift behavior of all four nozzles consists of a linear increase in needle lift with respect to time until the needle reaches full lift and a linear decrease as the needle closes. For all four nozzles, the needle position oscillates at full lift with a period of 170–180 μs. The full-lift position of the needle changes as the rail pressure increases, perhaps reflecting compression of the injector components. Significant lateral motions were seen in the two single-hole nozzles, with the needle motion perpendicular to the injector axis resembling a circular motion for one nozzle and linear oscillation for the other nozzle. The two VCO multihole nozzles show much less lateral motion, with no strong oscillations visible.

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