Experimental Observation of Cavitating Squeeze-Film Dampers

1987 ◽  
Vol 109 (2) ◽  
pp. 290-294 ◽  
Author(s):  
J. F. Walton ◽  
J. A. Walowit ◽  
E. S. Zorzi ◽  
J. Schrand
Keyword(s):  
High Speed ◽  
Axial Flow ◽  
Squeeze Film ◽  
Test Results ◽  
Film Rupture ◽  
Video Recordings ◽  
Order Of Magnitude ◽  
Circumferential Extent ◽  
The Right ◽  
Right Order

This paper presents the results of an experimental investigation intended to observe cavitation in squeeze-film bearing dampers representative of those commonly found in aircraft gas turbine engines. Two different squeeze-film damper geometries were tested with both high-speed motion pictures and stroboscopic video recordings acquired at speeds up to 20,000 r/min. The results presented are limited to 8000 r/min due to the increased clarity of the photos acquired at the lower speeds and the similarity of trends at the higher speeds. Comparisons are also made with analysis formulated to handle the dynamics of the film rupture for the “short” damper case. The test results confirmed several of the commonly held “short” bearing assumptions (i.e., predominant axial flow and the effect of supply pressure and eccentricity on the cavitation zone). However, the test results demonstrated that significant flow reversals and film rupture were experienced in the feed/drain grooves in contradiction to the assumed boundary conditions. While agreement between analysis and test is of the right order of magnitude in predicting the cavitation zone shape and circumferential extent, current analyses do not adequately account for the observed variations in the boundaries and change in shape of the cavitation zone.

scholarly journals Berechnung der Oberfläche von Kernmaterie mit Hilfe spezieller Einteilchen-Wellenfunktionen

1962 ◽  
Vol 17 (8) ◽  
pp. 640-649
Author(s):  
Franz Lanzl
Keyword(s):  
Surface Energy ◽  
Plane Waves ◽  
Yukawa Interaction ◽  
Range Interaction ◽  
Zero Range ◽  
Volume Energy ◽  
Order Of Magnitude ◽  
The Right ◽  
Right Order ◽  
Surface Thickness

Using a YUKAWA interaction between the nucleons the volume energy per particle and the specific surface energy are calculated. These expressions assume a very simple form for a zero range interaction. The space parts of the applied orthogonal single particle wave functions are products of plane waves and a momentum independent function which brings about the decrease in density within the surface layer. First the volume energy per particle as a function of the density in the interior of nuclear matter is minimized. The interaction parameters are so selected that the values of the volume energy per particle and the density at the minimum agree with the experimental data. Then the surface energy as a function of the surface thickness is minimized. The values of the surface energy and the surface thickness in the minimum are compared with the empirical data. They are found to be of the right order of magnitude

Nucleon-Nucleon Scattering Calculations in a Pole Regularized Spinor Theory

1974 ◽  
Vol 29 (7) ◽  
pp. 981-990
Author(s):  
K. Dammeier
Keyword(s):  
Quantum Theory ◽  
Cross Section ◽  
Test Object ◽  
Nucleon Nucleon ◽  
Coupling Constant ◽  
Nonlinear Spinor ◽  
Spinor Theory ◽  
Order Of Magnitude ◽  
The Right ◽  
Right Order

A pole regularized nonlinear spinor theory may be a suitable test object to compare scattering calculations of Stumpf's functional quantum theory with LSZ-results. To apply the LSZ-technique in this theory, a dressing of the occurring massless Green's function is necessary. It is shown which special approximations allow for this dressing. The renormalized nucleon-nucleon coupling constant yields the right order of magnitude for the elastic nucleon cross section.

scholarly journals Generation of Coronal Currents by the Solar Convection Zone

2001 ◽  
Vol 18 (4) ◽  
pp. 329-335 ◽  
Author(s):  
D. J. Galloway ◽  
Y. Uchida ◽  
N. O. Weiss
Keyword(s):  
Convection Zone ◽  
Energy State ◽  
Minimum Energy ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Poynting Flux ◽  
Available Energy ◽  
Order Of Magnitude ◽  
The Right ◽  
Right Order

AbstractSolar flares are thought to be caused by reconnection of magnetic fields and their associated electric currents in the solar corona. The currents have to be there to provide available energy over and above the current-free minimum energy state, but what generates them has been little discussed. This paper investigates the idea that twisting motions in the turbulent convection zone below may provide a natural source for the currents and explain some of their properties. The twists generate upward-propagating Alfvén waves with a Poynting flux of the right order of magnitude to power a flare. Depending on the depth it takes place, the twisting event that initiates a particular flare may occur hours, days or even months before the flare itself.

Flow Visualization and Forces From a Squeeze Film Damper Operating With Natural Air Entrainment

2003 ◽  
Vol 125 (2) ◽  
pp. 325-333 ◽  
Author(s):  
Luis San Andre´s ◽  
Sergio E. Diaz
Keyword(s):  
High Speed ◽  
Air Entrainment ◽  
Squeeze Film ◽  
Natural Phenomenon ◽  
Squeeze Film Damper ◽  
Feed Pressure ◽  
Video Recordings ◽  
Free Air ◽  
Through Flow ◽  
Discharge Operation

Measurements of dynamic film pressures and high-speed photographs of the flow field in an open-ended Squeeze Film Damper (SFD) operating with natural free air entrainment are presented for increasing whirl frequencies (8.33–50 Hz), and a range of feed pressures to 250 kPa (37 psig). The flow conditions range from lubricant starvation (air ingestion) to a fully flooded discharge operation. The test dynamic pressures and video recordings show that air entrainment leads to large and irregular gas fingering and striation patterns. This is a natural phenomenon in SFDs operating with low levels of external pressurization (reduced lubricant through flow rates). Air ingestion and entrapment becomes more prevalent as the whirl frequency raises, and increasing the feed pressure aids little to ameliorate the loss in dynamic forced performance. As a result of the severity of air entrainment, experimentally estimated damping forces decrease steadily as the whirl frequency (operating speed) increases.

The Transonic Flow Through a Plane Turbine Cascade as Measured in Four European Wind Tunnels

1986 ◽  
Vol 108 (2) ◽  
pp. 277-284 ◽  
Author(s):  
R. Kiock ◽  
F. Lehthaus ◽  
N. C. Baines ◽  
C. H. Sieverding
Keyword(s):  
Transonic Flow ◽  
High Speed ◽  
Turbine Rotor ◽  
Wind Tunnels ◽  
Test Results ◽  
Turbine Rotor Blade ◽  
Pressure Distributions ◽  
Order Of Magnitude ◽  
Blade Section ◽  
Flow Through

Reliable cascade data are esssential to the development of high-speed turbomachinery, but it has long been suspected that the tunnel environment influences the test results. This has now been investigated by testing one plane gas turbine rotor blade section in four European wind tunnels of different test sections and instrumentation. The Reynolds number of the transonic flow tests was Re2 = 8 × 105 based on exit flow conditions. The turbulence was not increased artificially. A comparison of results from blade pressure distributions and wake traverse measurements reveals the order of magnitude of tunnel effects.

Dielectric relaxation of dihalobenzenes. I. Ortho and meta Cl2, Br2, and I2 in benzene solution

1968 ◽  
Vol 46 (24) ◽  
pp. 2745-2748 ◽  
Author(s):  
Abhai Mansingh ◽  
David B. McLay
Keyword(s):  
Benzene Solution ◽  
Relaxation Times ◽  
Dielectric Constants ◽  
Cole Plot ◽  
Molecular Reorientation ◽  
Dielectric Data ◽  
Distribution Parameters ◽  
Order Of Magnitude ◽  
The Right ◽  
Right Order

Dielectric data have been measured for the dilute solutions in benzene at 20.0 °C of the ortho- and meta-isomers of dichlorobenzene, dibromobenzene, and diiodobenzene. The "static" dielectric constants have been measured at 100 kHz, the dielectric constants and losses have been measured at both 9.06 and 21.00 GHz, and the refractive indices have been measured at optical wavelengths. Cole–Cole plots can be fitted to the data to yield mean relaxation times τ0 and distribution parameters α. The values of the relaxation times in the ortho-isomers are 11.8, 14.9, and 20.6 ps for dichlorobenzene, dibromobenzene, and diiodobenzene respectively. The corresponding values for the meta-isomers are 8.6, 10.7, and 13.5 ps respectively, values which increase in the same direction with halogen substituent but which are significantly smaller than the relaxation times for the other isomers. All of these times are of the right order of magnitude for molecular reorientation and there is no evidence for dipole–dipole interactions. Although the nonzero values of the distribution parameters will allow mathematical descriptions in terms of two relaxation times τ1 and τ2, the values derived from two such descriptions yield two unrealistic relaxation times for each molecule. It is concluded that the analysis based on the Cole–Cole plot gives the most meaningful results.

scholarly journals POTENTIAL, IMPEDANCE, AND RECTIFICATION IN MEMBRANES

1943 ◽  
Vol 27 (1) ◽  
pp. 37-60 ◽  
Author(s):  
David E. Goldman
Keyword(s):  
Membrane Potential ◽  
Constant Electric Field ◽  
Kinetic Equations ◽  
Giant Axon ◽  
Membrane Structures ◽  
Ion Motion ◽  
Order Of Magnitude ◽  
The Right ◽  
Right Order ◽  
Good Agreement

Impedance and potential measurements have been made on a number of artificial membranes. Impedance changes were determined as functions of current and of the composition of the environmental solutions. It was shown that rectification is present in asymmetrical systems and that it increases with the membrane potential. The behavior in pairs of solutions of the same salt at different concentrations has formed the basis for the studies although a few experiments with different salts at the same concentrations gave results consistent with the conclusions drawn. A theoretical picture has been presented based on the use of the general kinetic equations for ion motion under the influence of diffusion and electrical forces and on a consideration of possible membrane structures. The equations have been solved for two very simple cases; one based on the assumption of microscopic electroneutrality, and the other on the assumption of a constant electric field. The latter was found to give better results than the former in interpreting the data on potentials and rectification, showing agreement, however, of the right order of magnitude only. Although the indications are that a careful treatment of boundary conditions may result in better agreement with experiment, no attempt has been made to carry this through since the data now available are not sufficiently complete or reproducible. Applications of the second theoretical case to the squid giant axon have been made showing qualitative agreement with the rectification properties and very good agreement with the membrane potential data.

Blast-Resistant Window Concepts

2003 ◽  
Author(s):  
W. S. Strickland ◽  
Mark Anderson ◽  
Dov Dover
Keyword(s):  
High Speed ◽  
Building Design ◽  
Design Concepts ◽  
Terror Attacks ◽  
Video Recordings ◽  
Protective Films ◽  
Order Of Magnitude ◽  
Key Issues ◽  
Response Modes ◽  
Air Force Research Laboratory

Terrorist bombs threaten American civilians and military personnel both at home and abroad. Analysis of data from previous terror attacks indicates the largest number of injuries result from projected glass shards from shattered windows and facades. Three key issues have led to increased interest in new window materials, as well as changes in building design codes: (1) actual terror attacks; (2) the threat of future terror attacks; and (3) monetary losses due to hurricanes. New protective products include a wide variation of films and laminated glasses for retrofit / replacement. Air Force Research Laboratory (AFRL) research has shown that these protective films will reduce the fragmentation of the enclosed glass. However, protective films that are not anchored will not provide retention of the film/glass system under the severe blast loadings expected from terror bombs. The paper introduces the Flex window, a patent-pending blast-resistant window developed at AFRL, along with key design concepts. In addition, the paper presents results from actual blast tests of the Flex window. Tabular data and photo-documentation is used to illustrate the ability of the Flex window to handle blast pressures a full order of magnitude greater than the typical commercial “blast proof” window. New AFRL methods for modeling both exterior and interior loading functions are presented. In addition, possible response modes are discussed, based on observations of high-speed video recordings.

The Coastal Sea Breeze in Relation to Diurnal Temperature Changes in the Lower Atmosphere (Southern California)

1947 ◽  
Vol 28 (8) ◽  
pp. 371-380
Author(s):  
Luna B. Leopold ◽  
Charles G. P. Beer
Keyword(s):  
Los Angeles ◽  
Vertical Motion ◽  
Sea Breeze ◽  
Lower Atmosphere ◽  
Los Angeles Basin ◽  
Temperature Changes ◽  
Coastal Sea ◽  
Order Of Magnitude ◽  
The Right ◽  
Right Order

A diurnal variation of temperature at constant levels in the lower atmosphere was observed at all stations in the Los Angeles basin area. The amplitude of the variation increases with height. This variation has been studied as a diurnal oscillation in the height of isentropic surfaces. The rise and fall of isentropic surfaces may indicate an appreciable diurnal change of vertical motion, but in the higher levels, are at least partly explained by errors in measurement of temperatures by radiosondes. In levels below 4,000 feet msl vertical motion of the right order of magnitude could be caused by the diurnal accumulation and depletion of air as a result of the sea-breeze regime.

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