High-speed film-thickness measurements between a collapsing cavitation bubble and a solid surface with total internal reflection shadowmetry

2019 ◽  
Vol 31 (9) ◽  
pp. 097108 ◽  
Author(s):  
Fabian Reuter ◽  
Sebastian A. Kaiser
Keyword(s):  
Film Thickness ◽  
Solid Surface ◽  
Cavitation Bubble ◽  
Total Internal Reflection ◽  
High Speed ◽  
Internal Reflection ◽  
High Speed Film ◽  
Thickness Measurements

Some Limitations in Applying Classical EHD Film Thickness Formulas to a High-Speed Bearing

1981 ◽  
Vol 103 (2) ◽  
pp. 295-301 ◽  
Author(s):  
J. J. Coy ◽  
E. V. Zaretsky
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Heating Effects ◽  
Theoretical Predictions ◽  
Traction Fluid ◽  
Shear Heating ◽  
Thickness Measurements ◽  
Inner Race ◽  
Maximum Stresses ◽  
Good Agreement

Elastohydrodynamic film thickness was measured for a 20-mm ball bearing using the capacitance technique. The bearing was thrust loaded to 90, 448, and 778 N (20, 100, and 175 lb). The corresponding maximum stresses on the inner race were 1.28, 2.09, and 2.45 GPa (185,000, 303,000, and 356,000 psi). Test speeds ranged from 400 to 14,000 rpm. Film thickness measurements were taken with four different lubricants: (a) synthetic paraffinic, (b) synthetic paraffinic with additives, (c) neopentylpolyol (tetra) ester meeting MIL-L-23699A specifications, and (d) synthetic cycloaliphatic hydrocarbon traction fluid. The test bearing was mist lubricated. Test temperatures were 300, 338, and 393 K. The measured results were compared to theoretical predictions using the formulae of Grubin, Archard and Cowking, Dowson and Higginson, and Hamrock and Dowson. There was good agreement with theory at low dimensionless speed, but the film was much smaller than theory predicts at higher speeds. This was due to kinematic starvation and inlet shear heating effects. Comparisons with Chiu’s theory on starvation and Cheng’s theory on inlet shear heating were made.

Film Thickness and Heat Transfer Measurements in a Spray Cooling System With R134a

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
Eduardo Martínez-Galván ◽  
Juan Carlos Ramos ◽  
Raúl Antón ◽  
Rahmatollah Khodabandeh
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Film Thickness ◽  
High Speed ◽  
Average Nusselt Number ◽  
Cooling System ◽  
Spray Cooling ◽  
Heat Fluxes ◽  
Long Distance ◽  
Thickness Measurements

Experimental measurements in a spray cooling test rig have been carried out for several heat fluxes in the heater and different spray volumetric fluxes with the dielectric refrigerant R134a. Results of the heat transfer and the sprayed refrigerant film thickness measurements are presented. The film thickness measurements have been made with a high speed camera equipped with a long distance microscope. It has been found that there is a relation between the variation in the average Nusselt number and the film thickness along the spray cooling boiling curve. The heat transfer regimes along that curve are related not only with a variation in the average Nusselt number but also with changes in the film thickness. The qualitative analysis of those variations has served to understand better the heat transfer mechanisms occurring during the spray cooling.

A New OpenFOAM Solver Capable of Modelling Oil Jet-Breakup and Subsequent Film Formation for Bearing Chamber Applications

2019 ◽  
Author(s):  
Andrew Nicoli ◽  
Richard Jefferson-Loveday ◽  
Kathy Simmons
Keyword(s):  
Experimental Data ◽  
Film Thickness ◽  
High Speed ◽  
Surface Film ◽  
Thin Liquid Film ◽  
Research Centre ◽  
Source Terms ◽  
Thickness Measurements ◽  
Edge Separation ◽  
Fully Coupled

Abstract To create an adequate computational model of oil behaviour in an aeroengine bearing chamber previous work at the Gas Turbine and Transmissions Research Centre (G2TRC) suggests it is necessary to be able to model oil shedding from bearings, breaking up into droplets/ligaments and forming thin and thick films driven by gravity and shear. Our previously published work using Fluent successfully coupled volume of fluid with the Eulerian thin film model (ETFM) and identified the challenges coupling the ETFM with the discrete phase modelling (DPM). For this latter work comparison was made to published experimental and modelling data in which a jet is injected into a duct breaking up into droplets before forming a wall film. In this paper the use of the open-source CFD code OpenFOAM is investigated for this application recognising that such an approach eliminates some of the restrictions in a commercial product. A transient solver for spray particle cloud modelling and thin liquid film transport (sprayParcelFilmFoam) has been developed and incorporated within OpenFOAM. Fully coupled DPM-ETFM is presented, capable of modelling both primary atomization and secondary breakup. In addition two new film sub-models have been implemented for film stripping and edge separation. In order to achieve accurate statistical representation of droplets, modifications to the DPM particle injector code were implemented. CFD results are validated against published high speed imaging and phase Doppler experimental data and in addition there is a comparison to computational results obtained using ANSYS Fluent. The fidelity of both the solver and the novel surface film sub-models are evaluated against average film thickness measurements along the duct centreline. With the inclusion of both film stripping and edge separation, a normalized root mean squared deviation of 5.1 % was achieved when compared to film thickness measurements, improving significantly on the results obtained with Fluent. A comparison with experimental data of particle diameters and velocities downstream of the expansion edge gives good qualitative agreement. Future work is recommended to provide a better formulation for the edge-separated droplet diameters. Analysis of film momentum source terms highlights the necessity for including both the gas and hydrostatic pressure source terms within the film momentum transport equation. This CFD investigation has successfully established a fully coupled two-way DPM-ETFM approach. This work illustrates an advance in bearing chamber modelling capability and has established a necessary foundation for future aeroengine bearing chamber film modelling.

Application of Laser Interferometry for Transient Film Thickness Measurements

Volume 1 ◽  
2004 ◽  
Author(s):  
Peter Kelly-Zion ◽  
William Collins ◽  
Diana Glawe
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Silicone Oil ◽  
Laser Interferometry ◽  
Bottom Surface ◽  
Glass Slides ◽  
Helium Neon Laser ◽  
Thickness Measurements ◽  
Helium Neon ◽  
Transient Measurements

A laser interferometry technique for making transient measurements of film thickness of the order of 10 to more than 1000 μm is described. The basis for these measurements was reported previously [1] but the technique was applied to solid glass slides and a slowly thinning silicone oil film. The current work describes an adaptation of the technique for the measurement of rapidly changing film thickness, as occurs with evaporating films. A beam from a helium-neon laser is focused on the film at an oblique angle. Some of the laser light is reflected off of the top surface of the film and some is reflected off of the bottom surface. The light reflected from the two surfaces forms a concentric interference fringe pattern which is projected onto a screen and recorded by a high-speed camera. The film thickness is directly related to the spacing of the fringes. To demonstrate the technique, measurements of the time-varying thickness of three evaporating films are presented and experimental considerations are discussed.

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