Effect of Warp on the Multiple Equilibria of a Hydrodynamically Coupled Flexible Disk

2006 ◽  
Author(s):  
Nikhit N. Nair ◽  
Grant M. Warner
Keyword(s):  
Manufacturing Process ◽  
Shooting Method ◽  
Multiple Equilibria ◽  
Rotation Speed ◽  
Coupled System ◽  
Instability Phenomenon ◽  
Disk Rotation ◽  
Hybrid Formulation ◽  
Flexible Disk ◽  
Disk Rotation Speed

In this paper, a hydrodynamically coupled flexible disk rotating in a thin housing is mathematically modeled and an attempt is made to explain the jump instability phenomenon that occurs when the disk rotation speed is varied slightly. The disk is assumed to have an initial warped profile due to slight imperfections in the manufacturing process. After non-dimensionalization of the participating variables, a hybrid formulation is carried out. Radial flows above and below the disk are taken into consideration. The deflection and pressure equations form a coupled system, and a solution is attempted using the shooting method. The deflections obtained are plotted to obtain the deflected disk profile and appropriate conclusions are drawn.

On the Instability Mechanisms of a Disk Rotating Close to a Rigid Surface

1995 ◽  
Vol 62 (3) ◽  
pp. 764-771 ◽  
Author(s):  
F. Y. Huang ◽  
C. D. Mote
Keyword(s):  
Rotation Speed ◽  
Maximum Speed ◽  
Film System ◽  
Rigid Surface ◽  
Flow Component ◽  
Flutter Speed ◽  
Disk Rotation ◽  
Viscous Shear ◽  
Air Film ◽  
Disk Rotation Speed

The instability mechanisms of a rotating disk, coupled to a rigid surface through a viscous fluid film at the interface, are investigated analytically. The fluid in the film is driven circumferentially by the viscous shear, and it flows outwards radially under centrifugal forces. The circumferential flow component creates an equivalent viscous damping rotating at one half the disk rotation speed. This film damping dissipates all backward traveling waves where the undamped wave speeds are greater than one half the disk rotation speed. The radial flow component creates a nonsymmetric stiffness in the disk-film system that energizes any wave mode at rotation speeds above its flutter speed. Instabilities in the disk-film system are of two types. A rotating damping instability is caused by the rotating film damping at rotation speeds above a critical value that is less than the flutter speed. A combination instability is caused by the combined effect of the film stiffness and damping at rotation speeds above a threshold that is greater than the flutter speed. The maximum rotation speed of stable disk vibration is bounded above by the lowest onset speed of rotating damping instability. This speed limit is predicted for two wall enclosure designs. The maximum stable rotation speed of a 5.25-inch diameter flexible, memory disk, separated from a rigid surface by a viscous air film, is shown to be more than 15 times greater than the maximum speed of the disk without the air film.

scholarly journals Design and study of seeding devices for small selection seeding machines

2019 ◽  
Vol 126 ◽  
pp. 00008
Author(s):  
Vladimir Nemtinov ◽  
Nikolai Kryuchin ◽  
Alexandr Kryuchin ◽  
Yulia Nemtinova
Keyword(s):  
Linear Dependence ◽  
Rotation Speed ◽  
Rotation Frequency ◽  
Field Studies ◽  
Disk Rotation ◽  
Seed Supply ◽  
Computer Technologies ◽  
Laboratory Results ◽  
Agricultural Plants ◽  
Disk Rotation Speed

In this paper, it is proposed to use a self-propelled pneumatic mini-seeder with replaceable mechanical sowing devices designed and manufactured using computer technologies, advanced software and threedimensional printing for seeds selection. As a result of the research, hightech operating devices for a grain-drill feed with screw and disk-pin continuous seed metering are designed and manufactured. Grain-drill feeds allow sowing of free-flowing and non-free-flowing seeds, when used as seed meters on self-propelled pneumatic mini-seeders for selection sowing of grass seeds. Analysis of laboratory results of and field studies of the proposed grain-drill feeds allowed to determine the qualitative indicators of their performance: at a disk rotation speed of up to 15 rpm a linear dependence of the seed supply on the rotation frequency is provided; in the field studies, the instability of bluegrass seeding did not exceed 8%. The highest performance of the screw is obtained at the angle of choke inclination of 30...35 degrees with the seeding instability indicator of 2.5...3.5%. The developed grain-drill feed will significantly reduce the range of seeders and expand the set of sown seeds of various agricultural plants with one brand of a grain-drill feed.

scholarly journals Results of laboratory and bench-scale studies of seed dispensers with an electric drive of working tools

2021 ◽  
Vol 34 (06) ◽  
pp. 1761-1767
Author(s):  
Anatoly Ivanovich Zavrazhnov ◽  
Aleksandr Vladimirovich Balashov ◽  
Sergey Petrovich Strygin ◽  
Nikita Yurievich Pustovarov ◽  
Andrey Anatolyevich Zavrazhnov
Keyword(s):  
Control System ◽  
Electric Drive ◽  
Rotation Speed ◽  
Soybean Seeds ◽  
Seeding Rate ◽  
Linear Speed ◽  
Bench Scale ◽  
Disk Rotation ◽  
Trajectory Length ◽  
Disk Rotation Speed

Mechanical and pneumatic seed drills of both domestic and foreign production are used in Russian farms. They are equipped with a mechanical drive of working tools and an electronic seeding control system. Due to the slipping of the wheels or the breakage of the chains, the sowing of seeds in individual seed dispensers interrupts. According to the results of laboratory and bench-scale studies in respect to soybean seeds, the required power for the electric drive of one seed dispenser was determined, which, depending on the disk rotation speed from 10 to 60 rpm, ranged from 30 to 120 W. By calculation, using the analytical expression, the power, required for the fan drive of a 12-row seed drill, was determined, which, depending on the disk rotation speed, ranged from 1.6 to 2.47 kW. A condition is formulated, which will eliminate the probability of shifting and rolling seeds along the furrow after their fall out of the sowing disc rotating in the opposite direction to the movement of the seeder unit, provided correspondence of the linear speed of the sowing disc and the speed of the seeder unit (the effect of zero overlaps). In this case, the trajectory length of the seeds falling to the furrow should be consistent with the speed of the seeder unit and the seeding rate according to the proposed expression.

Multiple Equilibria of a Hydrodynamically Coupled Flexible Disk Rotating Inside a Thin Housing

2003 ◽  
Vol 70 (1) ◽  
pp. 142-147
Author(s):  
G. M. Warner and ◽  
A. A. Renshaw
Keyword(s):  
Simple Model ◽  
Multiple Equilibria ◽  
Radial Flow ◽  
Rotation Speed ◽  
Experimental Results ◽  
Jump Phenomenon ◽  
Abrupt Jump ◽  
Sensitive Function ◽  
Small Change ◽  
Flexible Disk

Experimental results are reported and a simple model proposed to explain a phenomenon in which the equilibrium deflection of a flexible disk rotating inside a narrow housing undergoes an abrupt jump when the rotation speed is varied slightly. Discontinuous jumps are observed in a small fraction (25%) of Zip disks rotating between 3000 rpm and 4500 rpm. For those disks exhibiting jumps, the jumps are repeatable for both increases and decreases in rotation speed during a test; no hysteresis is observed. A disk that initially exhibits the jump phenomenon may fail to exhibit jumps several days or weeks later and vice versa. Numerical results for a rotating membrane hydrodynamically coupled to the surrounding flow show that the number of possible equilibria is a sensitive function of the radial flows above and below the disk. In particular, a small change in radial flow from a radially inward flow to a radially outward flow can abruptly change the number of possible equilibria from two to one. The characteristics of this transition are compatible with the experimental observations.

scholarly journals MAGNETIC PROPERTIES AND MAGNETIC STRIP DOMAINS IN MICRO STRIPES PrDyFeCoB

2021 ◽  
pp. 86-93
Author(s):  
D.V. Korolev ◽  
◽  
Yu.V. Stolyankov ◽  
V.P. Piskorsky ◽  
R.A. Valeev ◽  
...  
Keyword(s):  
Hysteresis Loop ◽  
Coercive Field ◽  
Rotation Speed ◽  
Magnetic Phase ◽  
Hysteresis Loops ◽  
Zero Field ◽  
Phase 2 ◽  
Soft Magnetic ◽  
Disk Rotation ◽  
Disk Rotation Speed

The article provides the analysis of PrDyFeCoB magnetic microstripes prepared by extracting material from a melt on a rotating cooling disk. The phases 2-14-1, 1-4-1 and 1-2, α-FeСо were verified in the samples. The division of a hysteresis loop into two strands shows that the coercive field of the α-FeСо phase (500–700 Oe) determines the width of the hysteresis loop near the zero field, while the coercive field of the 2-14-1 phase (10 kOe) corresponds to lateral hysteresis loops. The saturation magnetization increases by 25% with an increase in the disk rotation speed by 3 times together with correspondent acceleration of the cooling rate. This is due to the increase in the proportion of the soft magnetic phase α-FeCo and the increase in the proportion of the amorphous phase with a decrease in the proportion of the main magnetic phase 2-14-1. Strip domains and their dynamics during magnetization were detected using Kerr magneto-optical microscopy.

scholarly journals Characterization of the Transverse Distribution of Fertilizer in Coffee Plantations

Agronomy ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 601
Author(s):  
Alan Delon Andrade ◽  
Gabriel Araújo e Silva Ferraz ◽  
Murilo Machado de Barros ◽  
Rafael De Oliveira Faria ◽  
Fábio Moreira da Silva ◽  
...  
Keyword(s):  
Rotation Speed ◽  
Fertilizer Application ◽  
Production Costs ◽  
Distribution Profile ◽  
Transverse Distribution ◽  
Operating Modes ◽  
Disk Rotation ◽  
Coffee Plants ◽  
The Impact ◽  
Disk Rotation Speed

Considering the impact of fertilizers on coffee production costs, the search for greater efficiency in the use of these inputs has an important role. Accordingly, the aim of the present study is to evaluate the transverse distribution of fertilizer by a centrifugal spreader in a coffee plantation and to compare two operating modes: fertilizer application on one side (FA1), or both sides (FA2) of the coffee plants. In addition, three doses (200, 300 and 400 kg ha−1) of monoammonium phosphate and three spreading disk rotation speeds (240, 375 and 750 rpm) were tested. To characterize fertilizer distribution profiles, collectors were placed under the canopy of coffee plants, and the collected fertilizer was weighed. From the data obtained, distribution profile histograms were constructed, and coefficients of variation were calculated for each treatment. Distribution profiles with higher uniformity were related to the morphologic characteristics of the coffee plants. Regarding the operating modes evaluated, FA1 presented better results with a disk rotation speed of 750 rpm (FA1-W3); FA2 produced the best results with a disk rotation speed of 240 rpm. By relating these results with information on root morphology, FA1-W3 was found to be the most appropriate application method.

Influence of Peripheral on Central Stereopsis: An Induced Depth Tilt Effect

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 276-276
Author(s):  
S Müller ◽  
E R Wist
Keyword(s):  
Opposite Direction ◽  
Rotation Speed ◽  
Neutral Density ◽  
Neutral Density Filter ◽  
Disk Rotation ◽  
Optimal Rotation ◽  
Density Filter ◽  
Pulfrich Effect ◽  
Variable Errors ◽  
Tilted Disk

A large rotating black/white sectored disk (58 deg diameter) viewed with a neutral density filter over one eye is perceived as tilted in depth according to the Pulfrich phenomenon. But with fixation on a centrally located vertical bar (7 deg in length), the disk is perceived as vertical while the central bar is perceived as tilted in the opposite direction. This effect remains even if the central 38 deg portion of the disk is occluded leaving a peripheral annulus 10 deg in width. At an optimal rotation speed of 45° s−1 and a filter of 2 log units, the inter-individual perceived tilt of the bar ranges between 5° and 10° as measured by nulling out the illusory tilt by adjustment with a joystick. Variable errors were extremely small and corresponded well with central stereoscopic resolution. The amount of illusory tilt depends on the speed of disk rotation and filter density, and its direction on the relation between the direction of motion and the filter-covered eye. The effect is not limited to Pulfrich-induced stereotilt: When the disk was stationary but physically tilted in depth, the induced tilt on the central bar corresponded to about 50% of the physical tilt. This effect, in turn, could be cancelled or enhanced by rotating the tilted disk and inducing an appropriate Pulfrich effect. With monocular viewing no induced depth tilt occurs. The results are interpreted in terms of a stereoscopic induced effect operating beyond the known peripheral limits of stereopsis.

Two Way Coupled Analysis of Fluid Force in the Annular Plain Seal and Vibration of the Rotor System Using Shooting Method

2019 ◽  
Author(s):  
Yudai Kunori ◽  
Tsuyoshi Inoue ◽  
Kenjiro Miyake
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Shooting Method ◽  
Coupled System ◽  
Coupled Analysis ◽  
Fluid Element ◽  
Fluid Force ◽  
Precise Prediction ◽  
Shaft Vibration ◽  
Rotor Dynamic

Abstract In turbomachinery, the rotor dynamic (RD) fluid force generated in a fluid element is one of the causes of shaft vibration. RD fluid force is caused by the interaction between shaft vibration and fluid force, and its precise prediction for various rotor’s orbit is difficult. This study performs a two-way coupled analysis of the fluid flow in the annular plain seal and shaft vibration using the shooting method. The frequency response is obtained and compared with that obtained from a direct numerical simulation of the coupled system, and the validity of the analysis is confirmed. The onset speed of instability is effectively and accurately obtained using the two-way coupled analysis with the shooting method, and the effects of the parameters on it are investigated.

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