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Multiphysics Cavitation Model with Application to the Dynamic Behavior of Journal Bearings

Pierson, Kristopher C
http://orcid.org/0000-0002-3222-2586
http://rave.ohiolink.edu/etdc/view?acc_num=akron1555440702757939

Abstract Details

2019, Doctor of Philosophy, University of Akron, Mechanical Engineering.
A physics based, gaseous cavitation model is proposed to model cavitation in journal bearings. The model is developed using the Rayleigh-Plesset-Scriven (RPS) equation of bubble growth which includes surface dilatation. Surface dilatation is a dynamic surface tension term that arises from the resistance of a bubble’s surface to changing shape. This term is shown to be crucial in modeling liquid tension which sometimes occurs in the divergent region of a journal bearing. The RPS equation is first modified to disregard inertial terms which are shown to be negligible for the very small bubbles which occur from this type of cavitation. The equation is then manipulated to solve in terms of void fraction rather than bubble radius to allow the model to become grid independent, an important aspect for numerical simulations. The resulting cavitation model is then coupled with the Reynolds equation (RE) to run numerical simulations of journal bearing operation. The modified RPS (mRPS) equation is used to determine density and viscosity profiles of a two-phase homogenous mixture of air and oil. The properties are then input to the RE to determine the static load and attitude angle of the journal. A comparison to experimental pressure profiles to those computed using the coupled RE-mRPS model is presented to demonstrate the ability of the RE-mRPS model to simulate tension in the lubricating oil. There are three cavitation model settings which arise from the development of the mRPS model; a parametric study is performed to determine the effect of altering each of these cavitation model settings. The RE-mRPS model is then coupled to a heat equation to demonstrate the effect that heat generation has on the void fraction and pressure profiles of the journal bearing. The RE-mRPS cavitation model is then used in conjunction with a perturbed RE to determine linear dynamic coefficients of stiffness and damping of the oil. It is shown that the perturbed RE accurately determines dynamic coefficients for some methods of cavitation modeling; however, the perturbed RE does not provide acceptable results for the RE-mRPS model. An alternative method of direct numerical simulation is proposed to more accurately determine dynamic coefficients for the RE-mRPS model. After the proposed method is verified to accurately determine dynamic coefficients, the effect of tension in the lubricating oil on the stability of the journal bearing is evaluated. The effect of lubricating oil tension on the dynamic stability of journal bearings has not been investigated in previous research. Through determination of rotordynamic properties of the journal bearing using dynamic coefficients, it is shown that the presence of tension in the lubricating oil leads to a less stable operating condition.
Minel Braun, PhD (Advisor)
Alex Povitsky, PhD (Committee Member)
Nicholas Garafolo, PhD (Committee Member)
Robert Veillette, PhD (Committee Member)
Graham Kelly, PhD (Committee Member)
Scott Sawyer, PhD (Committee Member)
Kevin Kreider, PhD (Committee Member)
Hazel Marie, PhD (Committee Member)
277 p.
Mechanical Engineering
Cavitation; journal bearings; dynamics; vibrations; liquid tension; Rayleigh-Plesset

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Citations

  • Pierson, K. C. (2019). Multiphysics Cavitation Model with Application to the Dynamic Behavior of Journal Bearings [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555440702757939

    APA Style (7th edition)

  • Pierson, Kristopher. Multiphysics Cavitation Model with Application to the Dynamic Behavior of Journal Bearings. 2019. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1555440702757939.

    MLA Style (8th edition)

  • Pierson, Kristopher. "Multiphysics Cavitation Model with Application to the Dynamic Behavior of Journal Bearings." Doctoral dissertation, University of Akron, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555440702757939

    Chicago Manual of Style (17th edition)

akron1555440702757939
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This open access ETD is published by University of Akron and OhioLINK.