A Three-Dimensional Navier-Stokes–Based Numerical Model for Squeeze-Film Dampers. Part 1—Effects of Gaseous Cavitation on Pressure Distribution and Damping Coefficients without Consideration of Inertia

Rotor vibration attenuation is achieved with damping devices which work on different, often mutually coupled, physical principles. Squeeze film dampers are damping devices that have been widely used in rotordynamic applications. A new concept of a 5-segmented integral squeeze film damper, in which a flexure pivot tilting pad journal bearing is integrated, was investigated. The damper is studied for the eccentric position between the outer and inner ring of the squeeze film land. The ANSYS CFX software was used for solving the pressure and velocity distribution. The development of the complex three-dimensional computational fluid dynamics model of the squeeze film damper, learning more about the effect of the forces in the damper, and the knowledge about the behaviour of the flow are the principal contributions of this article.

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A numerical geotechnical model for computing soil slides at banks of water reservoirs

International Journal of Geo-Engineering ◽

10.1186/s40703-020-00129-w ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Nils Reidar B. Olsen ◽

Stefan Haun

Keyword(s):

Numerical Model ◽

Water Level ◽

Stokes Equations ◽

Limit Equilibrium ◽

Three Dimensional ◽

Field Measurements ◽

Navier Stokes ◽

Adaptive Grids ◽

Groundwater Levels ◽

Before And After

AbstractSoil slides can occur when the water level in a lake or a reservoir is lowered. This may take place in situations when a reservoir is flushed to remove sediments. The current study describes a three-dimensional numerical model used for the simulation of reservoir flushing that includes the slide movements. The geotechnical failure algorithms start with modelling the groundwater levels at the banks of the reservoir. A limit equilibrium approach is further used to find the location of the slides. The actual movement of the sediments is computed by assuming the soil to be a viscous liquid and by solving the Navier–Stokes equations. The resulting bed elevation changes from the slides are computed in adaptive grids that change as a function of water level, bed erosion and slide movements. The numerical model is tested on the Bodendorf reservoir in Austria, where field measurements are available of the bank elevations before and after a flushing operation. The results from the numerical simulations are compared with these observations. A parameter test shows that the results are very sensitive to the cohesion and less sensitive to the E and G modules of the soil.

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Numerical Modelling of Circulation in Lake Sperillen, Norway

Hydrology Research ◽

10.2166/nh.2000.0005 ◽

2000 ◽

Vol 31 (1) ◽

pp. 57-72 ◽

Cited By ~ 5

Author(s):

N. R. B. Olsen ◽

D. K. Lysne

Keyword(s):

Numerical Model ◽

Stokes Equations ◽

Three Dimensional ◽

Field Measurements ◽

Navier Stokes ◽

Water Current ◽

Simple Method ◽

Vertical Temperature Profile ◽

Navier Stokes Equations ◽

Good Agreement

A three-dimensional numerical model was used to model water circulation and spatial variation of temperature in Lake Sperillen in Norway. A winter situation was simulated, with thermal stratification and ice cover. The numerical model solved the Navier-Stokes equations on a 3D unstructured non-orthogonal grid with hexahedral cells. The SIMPLE method was used for the pressure coupling and the k-ε model was used to model turbulence, with a modification for density stratification due to the vertical temperature profile. The results were compared with field measurements of the temperature in the lake, indicating the location of the water current. Reasonably good agreement was found.

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Squeeze Film Dampers Executing Small Amplitude Circular-Centered Orbits in High-Speed Turbomachinery

International Journal of Aerospace Engineering ◽

10.1155/2016/5127096 ◽

2016 ◽

Vol 2016 ◽

pp. 1-16 ◽

Cited By ~ 4

Author(s):

Sina Hamzehlouia ◽

Kamran Behdinan

Keyword(s):

Pressure Distribution ◽

Small Amplitude ◽

High Speed ◽

Fluid Film ◽

Distribution Model ◽

Squeeze Film ◽

Fluid Inertia ◽

Inertia Effects ◽

Squeeze Film Dampers ◽

Reaction Forces

This work represents a pressure distribution model for finite length squeeze film dampers (SFDs) executing small amplitude circular-centered orbits (CCOs) with application in high-speed turbomachinery design. The proposed pressure distribution model only accounts for unsteady (temporal) inertia terms, since based on order of magnitude analysis, for small amplitude motions of the journal center, the effect of convective inertia is negligible relative to unsteady (temporal) inertia. In this work, the continuity equation and the momentum transport equations for incompressible lubricants are reduced by assuming that the shapes of the fluid velocity profiles are not strongly influenced by the inertia forces, obtaining an extended form of Reynolds equation for the hydrodynamic pressure distribution that accounts for fluid inertia effects. Furthermore, a numerical procedure is represented to discretize the model equations by applying finite difference approximation (FDA) and to numerically determine the pressure distribution and fluid film reaction forces in SFDs with significant accuracy. Finally, the proposed model is incorporated into a simulation model and the results are compared against existing SFD models. Based on the simulation results, the pressure distribution and fluid film reaction forces are significantly influenced by fluid inertia effects even at small and moderate Reynolds numbers.

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First Order Perturbation Technique for Squeeze Film Dampers Executing Small Amplitude Circular Centered Orbits With Aero-Engine Application

Volume 4B: Dynamics, Vibration, and Control ◽

10.1115/imece2016-65784 ◽

2016 ◽

Cited By ~ 1

Author(s):

Sina Hamzehlouia ◽

Kamran Behdinan

Keyword(s):

Pressure Distribution ◽

Small Amplitude ◽

Slenderness Ratio ◽

Order Perturbation ◽

Squeeze Film ◽

Zeroth Order ◽

Flow Equations ◽

First Order ◽

Squeeze Film Dampers ◽

First Order Perturbation

This work develops inertial expressions for the lubricant pressure distribution and fluid velocity components for squeeze film dampers (SFDs) executing small amplitude circular centered orbits (CCO), by applying a first order perturbation to the fluid equations. For small amplitude motions of the journal center, it is assumed that the fluid convective inertia terms are negligible relative to the unsteady (temporal) inertia terms. Firstly, a first order perturbation is applied to the pressure and velocity components in the flow equations. Subsequently, the flow equations are solved for the zeroth-order (i.e. non-inertial) velocities and the first-order (i.e. inertial) velocities. The velocity components are incorporated into the flow equations to develop separate expressions for the zeroth-order and the first order pressures. Furthermore, the pressure expressions are numerically solved by applying finite difference approximations to the equations. Finally, a simulation model is developed to determine the lubricant pressure distribution and fluid film reaction forces for different damper operating parameters, including Reynold’s number (i.e. inertia effect), journal eccentricity ratio, and bearing slenderness ratio.

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ISWFoam: A numerical model for internal solitary wave simulation in continuously stratified fluids

10.5194/gmd-2021-102 ◽

2021 ◽

Author(s):

Jingyuan Li ◽

Qinghe Zhang ◽

Tongqing Chen

Keyword(s):

Numerical Model ◽

Stokes Equation ◽

Nonlinear Models ◽

Three Dimensional ◽

Navier Stokes ◽

Discrete Equation ◽

Stratified Fluids ◽

Flat Bottom ◽

Navier Stokes Equation ◽

Laboratory Test Results

Abstract. A numerical model, ISWFoam, for simulating internal solitary waves (ISWs) in continuously stratified, incompressible, viscous fluids is developed based on a fully three-dimensional (3D) Navier-Stokes equation using the open source code OpenFOAM. This model combines the density transport equation with the Reynolds-averaged Navier-Stokes equation with the Coriolis force, and the model discrete equation adopts the finite volume method. The k-ω SST turbulence model has also been modified accordingly to the variable density field. ISWFoam provides two initial wave generation methods to generate an ISW in continuously stratified fluids, including solving the weakly nonlinear models of the extended Korteweg–de Vries (eKdV) equation and the fully nonlinear models of the Dubreil-Jacotin-Long (DJL) equation. Grid independence tests for ISWFoam are performed, considering the accuracy and computing efficiency, the appropriate grid size of the ISW simulation is recommended to be one-one hundred and fiftieth of the characteristic length and one-twenty fifth of the ISW amplitude. Model verifications are conducted through comparisons between the simulated and experimental data for ISW propagation examples over a flat bottom section, including laboratory scale and actual ocean scale, a submerged triangular ridge, a Gaussian ridge and slope. The laboratory test results, including the ISW profile, wave breaking location, ISW arrival time, and the spatial and temporal changes in the mixture region, are well reproduced by ISWFoam. The ISWFoam model with unstructured grids and local mesh refinement can accurately simulate the generation and evolution of ISWs, the ISW breaking phenomenon and the interaction between ISWs and complex structures and topography.

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Sealing Effect on the Performance of Squeeze Film Damper

Volume 3: Heat Transfer, Parts A and B ◽

10.1115/gt2009-60204 ◽

2009 ◽

Author(s):

Changhu Xing ◽

Minel J. Braun ◽

Hongmin Li

Keyword(s):

Pressure Distribution ◽

Finite Volume ◽

Piston Ring ◽

Hydrodynamic Forces ◽

Squeeze Film ◽

Squeeze Film Damper ◽

Damping Coefficients ◽

End Plate ◽

Inertia Coefficient ◽

Ring Seal

Seals used in the squeeze film damper restrict the side leakage of the lubricant, thus providing a measure of additional damping. In this paper, the serrated piston ring and end-plate seals are studied numerically using CFD-ACE+, a commercially available finite volume based algorithm. Research shows that the damping coefficients for the piston ring seal decrease in magnitude with the increase in the number of axial grooves in the circumferential direction until they reach a fairly constant value. However, the pressure distribution and hence the hydrodynamic forces are strongly affected by the number and geometry of the axial grooves. The damping coefficients for the end plate seal increase in magnitude rapidly with the decrease of the seal clearance below the clearance of the damper, but increase slowly when the seal clearance is larger than that of the damper. The direct inertia coefficient increases with the decrease in the seal clearance but the magnitude of cross-coupled inertia coefficients increases with the decrease in the seal clearance, and then falls down towards the values for the infinitely long bearing assumption. Both the damping and inertia coefficients increase with the increase in seal length.

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Numerical Modeling of Berm Breakwater Optimization With Varying Berm Geometry Using REEF3D

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4040508 ◽

2018 ◽

Vol 141 (1) ◽

Cited By ~ 3

Author(s):

Athul Sasikumar ◽

Arun Kamath ◽

Onno Musch ◽

Hans Bihs ◽

Øivind A. Arntsen

Keyword(s):

Numerical Model ◽

Three Dimensional ◽

Navier Stokes ◽

Flow Through Porous Media ◽

Cfd Model ◽

Production Chain ◽

Offshore Production ◽

Physical Model Tests ◽

Computational Fluid Dynamics Cfd ◽

Flow Through

Harbors are important infrastructures for an offshore production chain. These harbors are protected from the actions of sea by breakwaters to ensure safe loading, unloading of vessels and also to protect the infrastructure. In current literature, research regarding the design of these structures is majorly based on physical model tests. In this study a new tool, a three-dimensional (3D) numerical model is introduced. The open-source computational fluid dynamics (CFD) model REEF3D is used to study the design of berm breakwaters. The model uses the Volume-averaged Reynolds-averaged Navier-Stokes (VRANS) equations to solve the porous flows. At first, the VRANS approach in REEF3D is validated for flow through porous media. A dam break case is simulated and comparisons are made for the free surface both inside and outside the porous medium. The numerical model REEF3D is applied to show how to extend the database obtained with purely numerical results, simulating different structural alternatives for the berm in a berm breakwater. Different simulations are conducted with varying berm geometry. The influence of the berm geometry on the pore pressure and velocities are studied. The resulting optimal berm geometry is compared to the geometry according to empirical formulations.

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Feasibility of Applying Active Lubrication to Reduce Vibration in Industrial Compressors

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.1765123 ◽

2004 ◽

Vol 126 (4) ◽

pp. 848-854 ◽

Cited By ~ 23

Author(s):

Ilmar F. Santos ◽

Rodrigo Nicoletti ◽

Alexandre Scalabrin

Keyword(s):

Load Condition ◽

Squeeze Film ◽

Design Solution ◽

Maximum Speed ◽

Stability Margins ◽

Damping Coefficients ◽

Squeeze Film Dampers ◽

Tilting Pad ◽

Tilting Pad Bearings ◽

The Stability

In this paper the complete set of modified Reynolds’ equations for the active lubrication is presented. The solution of such a set of equations allows the determination of stiffness and damping coefficients of actively lubricated bearings. These coefficients are not just dependent on Sommerfeld number, as it would be the case of conventional hydrodynamic bearings, but they are also dependent on the excitation frequencies and gains of the control loop. Stiffness as well as damping coefficients can be strongly influenced by the choice of the control strategy, servo valve dynamics and geometry of the orifices distributed over the sliding surface. The dynamic coefficients of tilting-pad bearings with and without active lubrication and their influence on an industrial compressor of 391 Kg, which operates with a maximum speed of 10,200 rpm, are analyzed. In the original compressor design, the bearing housings are mounted on squeeze-film dampers in order to ensure reasonable stability margins during full load condition (high maximum continuous speed). Instead of having a combination of tilting-pad bearings and squeeze-film dampers, another design solution is proposed and theoretically investigated in the present paper, i.e., using actively lubricated bearings. By choosing a suitable set of control gains, it is possible not only to increase the stability of the rotor-bearing system, but also enlarge its operational frequency range.

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