A Study of Fluid Squeeze-Film Damping

1966 ◽  
Vol 88 (2) ◽  
pp. 451-456 ◽  
Author(s):  
W. S. Griffin ◽  
H. H. Richardson ◽  
S. Yamanami
Keyword(s):  
Wide Frequency Range ◽  
Squeeze Film ◽  
Experimental Program ◽  
Working Fluid ◽  
Viscous Damping ◽  
Extreme Temperatures ◽  
Frequency Range ◽  
Approximate Design ◽  
Squeeze Film Damping ◽  
Intense Radiation

The fluid squeeze-film produced by relative axial or tilting motion of two closely spaced plates provides viscous damping action over certain ranges of operation. When gas is the working fluid, a damper can be realized which is operable over a wide frequency range in the presence of extreme temperatures and intense radiation. A linearized analysis and approximate design equations, verified by a limited experimental program, are presented for several useful damper configurations.

A simple expression for fluid inertia force acting on micro-plates undergoing squeeze film damping

2010 ◽  
Vol 467 (2126) ◽  
pp. 522-536 ◽  
Author(s):  
Shujuan Huang ◽  
Diana-Andra Borca-Tasciuc ◽  
John A. Tichy
Keyword(s):  
Separation Distance ◽  
Simple Expression ◽  
Squeeze Film ◽  
Inertia Force ◽  
Viscous Damping ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Viscous Forces ◽  
Squeeze Film Damping ◽  
Micro Plates

Squeeze film damping in systems employing micro-plates parallel to a substrate and undergoing small normal vibrations is theoretically investigated. In high-density fluids, inertia forces may play a significant role affecting the dynamic response of such systems. Previous models of squeeze film damping taking inertia into account do not clearly isolate this effect from viscous damping. Therefore, currently, there is no simple way to distinguish between these two hydrodynamic effects. This paper presents a simple solution for the hydrodynamic force acting on a plate vibrating in an incompressible fluid, with distinctive terms describing inertia and viscous damping. Similar to the damping constant describing viscous losses, an inertia constant, given by ρL 3 W / h (where ρ is fluid density, L and W are plate length and width, respectively, and h is separation distance), may be used to accurately calculate fluid inertia for small oscillation Reynolds numbers. In contrast with viscous forces that suppress the amplitude of the oscillation, it is found that fluid inertia acts as an added mass, shifting the natural frequency of the system to a lower range while having little effect on the amplitude. Dimensionless parameters describing the relative importance of viscous and inertia effects also emerge from the analysis.

scholarly journals Steady-State Unbalance Response of a Three-Disk Flexible Rotor on Flexible, Damped Supports

1978 ◽  
Vol 100 (3) ◽  
pp. 563-573 ◽  
Author(s):  
R. E. Cunningham
Keyword(s):  
Ball Bearing ◽  
Squeeze Film ◽  
Flexible Rotor ◽  
Frequency Range ◽  
Lateral Bending ◽  
Damping Coefficients ◽  
The Third ◽  
Unbalance Response ◽  
Squeeze Film Damping ◽  
Squeeze Film Dampers

Experimental data are presented for the unbalance response of a flexible, ball bearing supported rotor to speeds above the third lateral bending critical. Values of squeeze film damping coefficients obtained from measured data are compared to theoretical values obtained from short bearing approximation over a frequency range from 5000 to 31,000 cycles/min. Experimental response for an undamped rotor is compared to that of one having oil squeeze film dampers at the bearings. Unbalances applied varied from 0.62 to 15.1 gm-cm.

Damping of Heat Exchanger Tubes in Liquids: Review and Design Guidelines

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
M. J. Pettigrew ◽  
R. J. Rogers ◽  
F. Axisa
Keyword(s):  
Experimental Data ◽  
Heat Exchanger ◽  
Energy Dissipation ◽  
Design Guidelines ◽  
Squeeze Film ◽  
Viscous Damping ◽  
Shell Side ◽  
Squeeze Film Damping ◽  
Dissipation Mechanism ◽  
Semi Empirical

This paper addresses the question of damping of multispan heat exchanger tubes with liquids (mostly water) on the shell side. The different energy dissipation mechanisms that contribute to damping are investigated. The available experimental data from the literature and from our own measurements are reviewed and analyzed. Three important energy dissipation mechanisms emerge. These are viscous damping between the tube and liquid, squeeze-film damping in the clearance between the tube, and support and friction damping at the support. Viscous damping only accounts for approximately 25% of the total damping of a typical tube. Thus, about 75% of the damping energy is dissipated at the support. Squeeze-film damping appears to be the most important energy dissipation mechanism. Squeeze-film damping is related to the support width and is inversely proportional to the tube frequency. Damping is formulated in terms of tube and tube-support parameters. Semi-empirical formulations for damping of heat exchanger tubes in liquids are recommended for design purposes.

Vibration Damping in Multispan Heat Exchanger Tubes

1998 ◽  
Vol 120 (3) ◽  
pp. 283-289 ◽  
Author(s):  
C. E. Taylor ◽  
M. J. Pettigrew ◽  
T. J. Dickinson ◽  
I. G. Currie ◽  
P. Vidalou
Keyword(s):  
Heat Exchanger ◽  
Fretting Wear ◽  
Resonant Peak ◽  
Effect Of Temperature ◽  
Squeeze Film ◽  
Fluid Viscosity ◽  
Viscous Damping ◽  
Friction Damping ◽  
Flow Induced Vibration ◽  
Squeeze Film Damping

Heat exchanger tubes can be damaged or fail if subjected to excessive flow-induced vibration, either from fatigue or fretting-wear. Good heat exchanger design requires that the designer understands and accounts for the vibration mechanisms that might occur, such as vortex shedding, turbulent excitation or fluidelastic instability. To incorporate these phenomena into a flow-induced vibration analysis of a heat exchanger requires information about damping. Damping in multispan heat exchanger tubes largely consists of three components: viscous damping along the tube, and friction and squeeze-film damping at the supports. Unlike viscous damping, squeeze-film damping and friction damping are poorly understood and difficult to measure. In addition, the effect of temperature-dependent fluid viscosity on tube damping has not been verified. To investigate these problems, a single vertical heat exchanger tube with multiple spans was excited by random vibration. Tests were conducted in air and in water at three different temperatures (25, 60, and 90°C). At room temperature, tests were carried out at five different preloads. Frequency response spectra and resonant peak-fitted damping ratios were calculated for all tests. Energy dissipation rates at the supports and the rate of excitation energy input were also measured. Results indicate that damping does not change over the range of temperatures tested and friction damping is very dependent on preload.

A Magnetorheological Mount for Hydraulic Hybrid Vehicles

2009 ◽  
Author(s):  
The Nguyen ◽  
Mohammad Elahinia ◽  
Constantin Ciocanel
Keyword(s):  
Fuel Efficiency ◽  
Wide Frequency Range ◽  
Hybrid Vehicles ◽  
Working Fluid ◽  
Frequency Range ◽  
Isolation System ◽  
Power Sources ◽  
Hydraulic Hybrid ◽  
Operating Frequency Range ◽  
Stiffness And Damping

Advanced vehicular technologies have been increasingly popular since they improve fuel economy. Automobiles with variable cylinder management are capable of turning on/off the cylinders in order to optimize the fuel consumption. Hybrid vehicles such as hybrid electric vehicles (HEVs) or hydraulic hybrid vehicles (HHVs) allow the engines to operate in the most efficient region. Besides, the hybrid technology includes capturing the braking energy, otherwise wasted as heat, to aid the acceleration. However, the enhancement in fuel efficiency comes with unbalance, shock and wider range of frequency vibration. Noise and vibration is actually one of the main obstacles in commercializing the HHV technology. This study is to design a vibration isolator to work for HHVs effectively and economically. The vibration profile of HHVs is proven to include both shock load at the switches of power sources and wide frequency range of vibration. That the HHV’s engine is turned on/off frequently and the hydraulic pumps/motors operate between 0 and 2000RPM, corresponding to 0–300Hz, poses difficult challenges for the isolation system. Rubber mounts are cheap, but only good for static load support and suitable for low power engine. Passive hydraulic mounts are only effective for conventional engines with unvarying working schedules. On the other hand, the active mounts are responsive for any condition, but too costly for commercial vehicles. Semi-active mounts with magnetorheological fluid (MRF) have been researched and recognized as a highly potential solution for hydraulic hybrid vehicles. The semi-active MRF mount is constructed very similar to a conventional hydraulic mount. However, the working fluid is an MRF which can quickly change its characteristics when the magnetic field is present. The main features of the MRF mount include multiple controllable MR valves, utilizing the flow (valve) mode, to connect the top and bottom fluid chambers. In addition, the mount is also capable of employing the fluid in squeeze mode. The structure of the MRF mount allows the stiffness and damping to be controlled in real time. The controllability makes the mount tunable to particularly fit the requirements of the HHVs. In this study, a mathematical model was constructed to predict the performance of the mount. The parameters were tuned so that the mount is effective within the whole operating frequency range of the HHV’s vibration.

Response of MEMS Devices Under Shock Loads

2005 ◽  
Author(s):  
Mohammad I. Younis ◽  
Ronald Miles
Keyword(s):  
Rectangular Pulse ◽  
Squeeze Film ◽  
Viscous Damping ◽  
Mems Devices ◽  
Shock Loads ◽  
Modes Of Failure ◽  
Squeeze Film Damping ◽  
Model And Simulation ◽  
Electric Actuation ◽  
Conventional Models

There is strong experimental evidence for the existence of strange modes of failure of MEMS devices under shock. Such failures have not been explained with conventional models of MEMS. These failures are characterized by overlaps between moving microstructures and stationary electrodes, which cause electrical shorts. This work presents a model and simulation of MEMS devices under the combination of shock loads and electric actuation, which will shed the light on the influence of these forces on the pull-in instability. Our results indicate that the reported strange failures can be attributed to early dynamic pull-in instability. The results show that the combination of a shock load and an electric actuation makes the instability threshold much lower than the threshold predicted considering the effect of shock alone or electric actuation alone. Several results are presented showing the response of MEMS devices due to half-sine pulse, triangle pulse, and rectangular pulse shock loads of various durations and strengths. The effects of linear viscous damping and incompressible squeeze-film damping are also investigated.

Coupled effects of surface interaction and damping on electromechanical stability of functionally graded nanotubes reinforced torsional micromirror actuator

2021 ◽  
pp. 030932472110368
Author(s):  
Weidong Yang ◽  
Menglong Liu ◽  
Linwei Ying ◽  
Xi Wang
Keyword(s):  
Casimir Force ◽  
Volume Fraction ◽  
Nonlocal Parameter ◽  
Saddle Points ◽  
Functionally Graded ◽  
Heteroclinic Orbits ◽  
Phase Portraits ◽  
Squeeze Film ◽  
Squeeze Film Damping ◽  
Tilting Angle

This paper demonstrated the coupled surface effects of thermal Casimir force and squeeze film damping (SFD) on size-dependent electromechanical stability and bifurcation of torsion micromirror actuator. The governing equations of micromirror system are derived, and the pull-in voltage and critical tilting angle are obtained. Also, the twisting deformation of torsion nanobeam can be tuned by functionally graded carbon nanotubes reinforced composites (FG-CNTRC). A finite element analysis (FEA) model is established on the COMSOL Multiphysics platform, and the simulation of the effect of thermal Casimir force on pull-in instability is utilized to verify the present analytical model. The results indicate that the numerical results well agree with the theoretical results in this work and experimental data in the literature. Further, the influences of volume fraction and geometrical distribution of CNTs, thermal Casimir force, nonlocal parameter, and squeeze film damping on electrically actuated instability and free-standing behavior are detailedly discussed. Besides, the evolution of equilibrium states of micromirror system is investigated, and bifurcation diagrams and phase portraits including the periodic, homoclinic, and heteroclinic orbits are described as well. The results demonstrated that the amplitude of the tilting angle for FGX-CNTRC type micromirror attenuates slower than for FGO-CNTRC type, and the increment of CNTs volume ratio slows down the attenuation due to the stiffening effect. When considering squeeze film damping, the stable center point evolves into one focus point with homoclinic orbits, and the dynamic system maintains two unstable saddle points with the heteroclinic orbits due to the effect of thermal Casimir force.

Sign in / Sign up

Export Citation Format

Share Document