Dynamic Analysis of Rupture in Thin Fluid Films. I—A Noninertial Theory

1983 ◽  
Vol 105 (1) ◽  
pp. 96-104 ◽  
Author(s):  
C. H. T. Pan
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Dynamic Analysis ◽  
Squeeze Film ◽  
Transient Condition ◽  
Film Rupture ◽  
Fluid Films ◽  
Film Pressure ◽  
Sliding Surfaces ◽  
Thin Fluid

A noninertial theoretical model for the dynamics of film rupture has been formulated. Under the transient condition, movement of the rupture boundary is governed by the condition of flow continuity between the film flux and adhered film transport in the cavitation domain. The traditional Swift-Stieber condition for film breakup is shown to be valid upon reaching steady-state. Generalization is extended to allow consideration of two sliding surfaces and the pure squeeze-film. The possibility of subcavitation film pressure is shown to result in dry regions in the cavitation domain.

Squeeze Film Dynamics of Two-Phase Seals

1992 ◽  
Vol 114 (2) ◽  
pp. 236-246 ◽  
Author(s):  
J. A. Yasuna ◽  
W. F. Hughes
Keyword(s):  
Steady State ◽  
Dynamic Analysis ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Transient Responses ◽  
Two Phase ◽  
Thermal Transients ◽  
Face Seals

A dynamic analysis of two-phase face seals including squeeze film effects and thermal transients is presented. Axial responses to perturbations from equilibrium for various sets of typical seal operating conditions are examined, and the sensitivity of these responses to certain parameters is discussed. Sample calculations indicate damped transient responses which often decay as steady state is approached asymptotically. In some cases, however, stable and unstable oscillations are observed.

The Significance of Tread Element Flexibility to Thin Film Wet Traction

1975 ◽  
Vol 3 (4) ◽  
pp. 215-234 ◽  
Author(s):  
A. L. Browne ◽  
D. Whicker ◽  
S. M. Rohde
Keyword(s):  
Thin Film ◽  
Time Dependent ◽  
Lateral Expansion ◽  
Wheel Slip ◽  
Fluid Films ◽  
Thin Fluid

Abstract An analysis is presented for the action of individual tire tread elements on polished sections of pavement covered by thin fluid films. Tread element flexibility, wheel slip, and time-dependent loading are incorporated. The effect of the lateral expansion of tread elements on groove closure is also studied.

A Theoretical Analysis of Floating Bush Journal Bearing With Axial Oil Film Rupture Being Considered

2002 ◽  
Vol 124 (3) ◽  
pp. 494-505 ◽  
Author(s):  
Kiyoshi Hatakenaka ◽  
Masato Tanaka ◽  
Kenji Suzuki
Keyword(s):  
Steady State ◽  
Reynolds Equation ◽  
Speed Ratio ◽  
Shaft Speed ◽  
Film Rupture ◽  
State Behavior ◽  
Oil Film ◽  
Rotordynamic Coefficients ◽  
The Stability ◽  
Very High

A new modified Reynolds equation is derived with centrifugal force acting on the hydrodynamic oil film being considered. This equation, together with a cavitation model, is used to obtain the steady-state equilibrium and calculate the rotordynamic coefficients of lightly loaded floating bush journal bearings operating at very high shaft speeds. The bush-to-shaft speed ratio and the linear cross-coupling spring coefficients of the inner oil film is found to decrease with the increase in shaft speed as the axial oil film rupture develops in the inner oil film. The present model can give reasonable explanation to the steady-state behavior and the stability behavior of the bearing observed in actual machines.

scholarly journals Modelling the light-ion densities in the ionosphere

1996 ◽  
Vol 39 (6) ◽  
Author(s):  
S. M. Stankov
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Satellite Measurements ◽  
Middle Latitudes ◽  
Analytical Functions ◽  
Density Ratios ◽  
Upper Ionosphere ◽  
Existing Data

A steady-state theoretical model is used to obtain variations of the H+/O+ and He+/O+ density ratios in the upper ionosphere at middle latitudes. The model results are compared with the existing data from satellite measurements. Analytical functions are constructed approximating the latitude and altitude variations of these ratios.

scholarly journals Dynamic analysis of firing mechanism of underwater pistol

2017 ◽  
Vol 20 (K2) ◽  
pp. 61-65
Author(s):  
Dung Thai Nguyen ◽  
Hung Van Nguyen
Keyword(s):  
Theoretical Model ◽  
Dynamic Analysis

The important problem of designing underwater pistol was analysed and calculated the dynamics of firing mechanism. On the basis of analyzing the performance of the underwater pistol, the paper presents a theoretical model for analysing the dynamics of firing mechanism of underwater pistol with the with the resistance of water acting on firing pin and slide. The result of this research can be applied to design the underwater pistol and underwater firearm.

Strain Enhanced Corrosion in the Iron-Caustic System

CORROSION ◽  
1976 ◽  
Vol 32 (9) ◽  
pp. 353-357 ◽  
Author(s):  
RONALD B. DIEGLE ◽  
DAVID A. VERMILYEA
Keyword(s):  
Steady State ◽  
Corrosion Rate ◽  
Strain Rate ◽  
Electrolyte Concentration ◽  
Applied Strain ◽  
Crack Advance ◽  
Film Rupture ◽  
Applied Strain Rate ◽  
Corrosion Of Iron ◽  
Kinetics Of

Abstract Straining electrode experiments were performed to investigate the nature of strain enhanced corrosion of iron in caustic electrolyte. The strain enhanced corrosion rate was generally linearly dependent on applied strain rate, and its potential dependence paralleled that of steady-state polarization behavior on non-straining electrodes. Data was presented as ratios, in which is the corrosion rate in cm/s and is the corresponding strain rate. This ratio, which was shown in a previously published theory to be numerically equal to the crack advance per film rupture event during film rupture SCC, depended on electrochemical variables such as electrolyte concentration and temperature in a manner similar to the kinetics of caustic cracking. Conditions which are known to be marginal in producing caustic cracking resulted in values for of about 10−7 cm, in excellent agreement with a previously developed theory. It was concluded that strain enhanced corrosion in this system results from repetitive film rupture and repair during straining.

Analytical approach for transient photoconductivity in undoped a-Si:H

1995 ◽  
Vol 377 ◽  
Author(s):  
M. Goerlitzer ◽  
P. Pipoz ◽  
H. Beck ◽  
N. Wyrsch ◽  
A. V. Shah
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Analytical Approach ◽  
Room Temperature ◽  
Free Electrons ◽  
Recombination Time ◽  
Sample Quality ◽  
Transient Photoconductivity ◽  
Light Intensities ◽  
Good Agreement

ABSTRACTTransient photoconductive response of undoped a-Si:H has been studied; the changes were analysed between two slightly different steady-state illumination conditions, at room temperature. A theoretical model is developed to describe transient photoconductivity; it yields good agreement with the measured curves for a whole range of light intensities. Numerical evaluations allows one to extract the recombination time of electrons. Comparison with steady-state photoconductivity yields a band mobility of free electrons between 0.1 and 6 cm2V−1s−1, depending upon sample quality.

scholarly journals The Damping Capacity of a Sealed Squeeze Film Bearing

1985 ◽  
Vol 107 (3) ◽  
pp. 411-418 ◽  
Author(s):  
M. M. Dede ◽  
M. Dogan ◽  
R. Holmes
Keyword(s):  
Theoretical Model ◽  
Gas Turbine ◽  
Squeeze Film ◽  
Damping Capacity ◽  
Test Rig ◽  
Squeeze Film Damper ◽  
Aero Engine

The purpose of this paper is to establish a theoretical model to represent a sealed squeeze-film damper bearing and to assess it against results from a test rig, simulating the essential features of a medium-sized gas turbine aero engine.

Steady-State Performance of Squeeze Film Damper Supported Flexible Rotors

1977 ◽  
Vol 99 (4) ◽  
pp. 552-558 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Steady State ◽  
Critical Speed ◽  
Rolling Element Bearing ◽  
Squeeze Film ◽  
Response Curves ◽  
Flexible Rotors ◽  
Steady State Operation ◽  
Bearing Life ◽  
Rolling Element ◽  
Single Mass

The synchronous steady-state operation of a centrally preloaded single mass flexible rotor supported in squeeze film bearing dampers is examined theoretically. Assuming the short bearing approximation and symmetric motions, frequency response curves are presented exhibiting the effect of relevant system parameters on rotor excursion amplitudes and unbalance transmissibilities for both pressurized and unpressurized lubricant supply. Hence, the influence of rotor flexibility, rotor mass distribution, rotor speed, bearing dimensions, lubricant viscosity, support flexibility can be readily determined, allowing for optimal rotor bearing system design. It is shown that with pressurized bearing mounts, the possibility of undesirable operation modes is eliminated and a smooth passage through the first pin-pin critical speed of the rotor is feasible, while absence of pressurization significantly limits the maximum safe unbalance in the vicinity of this critical speed. Significant decrease in transmissibility and rotor excursion amplitudes over those obtainable with rigid mounts are shown to be a practical possibility, with consequent decrease in the vibration level of the rotor mounts and prolongation of rolling element bearing life, while maintaining acceptable rotor vibration amplitudes. A design example is included to illustrate the use of the data.

Dynamic Analysis of a Coupled Dual-Rotor With Squeeze Film Damper Considering Sudden Unbalance

2021 ◽  
Author(s):  
Ying Cui ◽  
Yuxi Huang ◽  
Guogang Yang ◽  
Yongliang Wang ◽  
Han Zhang
Keyword(s):  
Steady State ◽  
Transient Response ◽  
Rotor System ◽  
Lubricating Oil ◽  
Squeeze Film ◽  
Radial Clearance ◽  
Oil Viscosity ◽  
Squeeze Film Damper ◽  
Damping Effect ◽  
Bistable State

Abstract A nonlinear multi-degree-of-freedom dynamic model of a coupled dual-rotor system with an intershaft bearing and uncentralized squeeze film damper is established by using finite element method. Based on the model, the critical speed characteristic diagram and vibration modes of the system were calculated. The steady-state unbalance response is obtained by using Newmark-β algorithm. The numerical results show the effect of SFD position in the dual-rotor system on response amplitude. It is found that with the decrease of radial clearance and the increase of length-diameter ratio and lubricating oil viscosity, the damping effect of SFD is enhanced and the bistable state phenomenon can be suppressed. The transient response of the system in case of sudden unbalance occurring at the fan was simulated by applying a step function. It is demonstrated that the SFD can effectively reduce the duration and maximum amplitude of the transient process, but at certain speeds, the SFD will increase the amplitude after the system returns to steady state, the damping effect on the transient response is also enhanced with the increase of length-diameter and the decrease of radial clearance, and with the increase of the sudden unbalance value, the response is more likely to stabilized at the high amplitude state of the bistable state.

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