scholarly journals Global Dynamics of Shaft Lines Rotating in Surrounding Fluids Application to Thin Fluid Films

2004 ◽  
Vol 10 (3) ◽  
pp. 213-220 ◽  
Author(s):  
David Lornage ◽  
Georges Jacquet-Richardet
Keyword(s):  
Fluid Film ◽  
Global Dynamics ◽  
Fluid Films ◽  
Structural Domains ◽  
Strongly Coupled ◽  
Hydrodynamic Bearing ◽  
Structural Deformations ◽  
Time Marching ◽  
Structural Parts ◽  
Realistic Structure

While often sufficiently accurate, approaches using rotor dynamics and bladed disc dynamics are not adapted to the study of certain important cases, i.e., when observing wheel/shaft coupling or when fluid elements are strongly coupled with local structural deformations. The approach proposed here is a step toward a global model of shaft lines. The whole flexible wheel/shaft assembly and the influence of specific fluid film elements are considered in a full threedimensional model. A modal projection associated with a grid located at the interface of the fluid and structural domains provides an efficient and adaptable coupling. The equations governing the whole system are solved within a time marching procedure which alternatively considers the equations of fluid and structure. The technique chosen is applied to two different test cases. The first is composed of a disc and a thin-walled shaft mounted on a hydrodynamic bearing. The second is intended for studying a more realistic structure composed of a shaft and a wheel coupled with a fluid film between the wheel and a casing. These applications make it possible to identify trends related to fluid effects and couplings between the flexible structural parts.

Effects of Wheel-Shaft-Fluid Coupling and Local Wheel Deformations on the Global Behavior of Shaft Lines

2002 ◽  
Vol 124 (4) ◽  
pp. 953-957 ◽  
Author(s):  
D. Lornage ◽  
E. Chatelet ◽  
G. Jacquet-Richardet
Keyword(s):  
Three Dimensional ◽  
Fluid Film ◽  
Global Behavior ◽  
Three Dimensional Model ◽  
Fluid Films ◽  
Strongly Coupled ◽  
Proposed Model ◽  
Structural Deformations ◽  
Time Marching ◽  
Fluid Coupling

Rotating parts of turbomachines are generally studied using different uncoupled approaches. For example, the dynamic behavior of shafts and wheels are considered independently and the influence of the surrounding fluid is often taken into account in an approximate way. These approaches, while often sufficiently accurate, are questionable when wheel-shaft coupling is observed or when fluid elements are strongly coupled with local structural deformations (leakage flow between wheel and casing, fluid bearings mounted on a thin-walled shaft, etc.). The approach proposed is a step toward a global model of shaft lines. The whole flexible wheel-shaft assembly and the influence of specific fluid film elements are considered in a fully three-dimensional model. In this paper, the proposed model is first presented and then applied to a simple disk-shaft assembly coupled with a fluid film clustered between the disk and a rigid casing. The finite element method is used together with a modal reduction for the structural analysis. As thin fluid films are considered, the Reynolds equation is solved using finite differences in order to obtain the pressure field. Data are transferred between structural and fluid meshes using a general method based on an interfacing grid concept. The equations governing the whole system are solved within a time-marching procedure. The results obtained show significant influence of specific three-dimensional features such as disk-shaft coupling and local disk deformations on global behavior.

Effects of Wheel-Shaft-Fluid Coupling and Local Wheel Deformations on the Global Behavior of Shaft Lines

2001 ◽  
Author(s):  
D. Lornage ◽  
E. Chatelet ◽  
G. Jacquet-Richardet
Keyword(s):  
Three Dimensional ◽  
Fluid Film ◽  
Global Behavior ◽  
Three Dimensional Model ◽  
Fluid Films ◽  
Strongly Coupled ◽  
Proposed Model ◽  
Structural Deformations ◽  
Time Marching ◽  
Fluid Coupling

Rotating parts of turbomachines are generally studied using different uncoupled approaches. For example, the dynamic behavior of shafts and wheels are considered independently and the influence of the surrounding fluid is often taken into account in an approximate way. These approaches, while often sufficiently accurate, are questionable when wheel-shaft coupling is observed or when fluid elements are strongly coupled with local structural deformations (leakage flow between wheel and casing, fluid bearings mounted on a thin-walled shaft, etc.). The approach proposed is a step toward a global model of shaft lines. The whole flexible wheel-shaft assembly and the influence of specific fluid film elements are considered in a fully three-dimensional model. In this paper, the proposed model is first presented and then applied to a simple disc-shaft assembly coupled with a fluid film clustered between the disc and a rigid casing. The finite element method is used together with a modal reduction for the structural analysis. As thin fluid films are considered, the Reynolds equation is solved using finite differences in order to obtain the pressure field. Data are transferred between structural and fluid meshes using a general method based on an interfacing grid concept. The equations governing the whole system are solved within a time marching procedure. The results obtained show significant influence of specific 3D features such as disc-shaft coupling and local disc deformations on global behavior.

Friction of composite cushion bearings for total knee joint replacements under adverse lubrication conditions

1997 ◽  
Vol 211 (6) ◽  
pp. 451-465 ◽  
Author(s):  
T Stewart ◽  
Z M Jin ◽  
J Fisher
Keyword(s):  
Cyclic Loading ◽  
Swing Phase ◽  
Mixed Lubrication ◽  
Fluid Film ◽  
Sliding Velocity ◽  
Normal Walking ◽  
Fluid Films ◽  
Stroke Length ◽  
Joint Replacements ◽  
Tissue Reactions

Conventional joint replacements consist of a polished metallic or ceramic component articulating against a layer of polyethylene. Although the friction in the contact between these articulating surfaces is low, polyethylene wear is produced as a result of a boundary/mixed lubrication regime. Wear debris is generated by direct asperity contact, abrasion, adhesion and fatigue, and has been shown to cause adverse tissue reactions which can lead to joint failure. The introduction of soft compliant materials, similar in stiffness to articular cartilage, has shown that with cyclic loading and relative motion between the articulating surfaces typical of normal walking, a fluid film can be maintained through combined entraining and squeeze-film actions, and hence wear can be minimized. For 95 per cent of the time, however, we are not walking but standing still or moving slowly. A pendulum simulator has been used in the present study to investigate the effect of adverse tribological conditions which may lead to fluid film breakdown, such as severe cyclic loading, particularly in the swing phase, reduced sliding velocity, reduced stroke length and start-up after a period of constant loading. Friction of a model composite cushion knee bearing, manufactured from a graded modulus (20–1000 MPa) layer of polyurethane, sliding against a polished metal cylinder has been measured for various lubricants and the results have been analysed using a Stribeck assessment. Severe cyclic loading, decreased sliding velocity and decreased stroke length have been found to limit the degree of fluid entrainment previously allowed during the swing phase of normal walking, thus allowing breakdown of fluid films and elevated levels of friction and surface damage. Soft layer joint replacements must therefore be designed to operate with thick elastohydrodynamic fluid films to provide some degree of protection when tribological conditions become severe, or alternatively incorporate alternative boundary or mixed lubrication mechanisms. This study quantifies a potential limitation of the cushion bearing concept.

scholarly journals Instability of inclined fluid-film flow with substrate filtration

2021 ◽  
Author(s):  
Hom N. Kandel
Keyword(s):  
Stokes Equations ◽  
Nonlinear Effects ◽  
Fluid Film ◽  
Navier Stokes ◽  
Neutral Stability ◽  
Fluid Films ◽  
Navier Stokes Equations ◽  
Gravity Driven ◽  
The Stability ◽  
Natural Settings

Gravity-driven flows of thin fluid films with a free surface along a porous substrate occur in many important circumstances found in industry and natural settings. In this thesis a model for such flows is derived by coupling the Navier-Stokes equations governing the clear flow in the fluid film with Darcy's law for the filtration of fluid through the porous medium. A linear stability analysis is conducted and the effect of various parameters on the state of neutral stability is investigated. A simplified model is developed by reducing the dimensionality of the problem, which is then employed in order to determine the nonlinear effects on the stability of the equilibrium flow.

Theoretical Studies of a Continuously Adjustable Hydrodynamic Fluid Film Bearing

2001 ◽  
Vol 124 (1) ◽  
pp. 203-211 ◽  
Author(s):  
J. K. Martin ◽  
D. W. Parkins
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Solution Procedure ◽  
Fluid Film ◽  
Theoretical Studies ◽  
Analysis Model ◽  
Operating Characteristics ◽  
Hydrodynamic Bearing ◽  
Wide Range ◽  
Fluid Film Thickness

Principles of a continuously adjustable hydrodynamic bearing are described together with an analysis model for studying its theoretical performance. The model included an expanded form of the governing Reynolds equation which took account of non-uniform variations in the fluid film thickness. A solution procedure was devised whereby for a given set of adjustment conditions, simultaneously converged fields of fluid film thickness, temperature, viscosity and pressure would result, together with oil film forces. A wide range of operating characteristics were studied with results predicting advantages and benefits over conventional hydrodynamic bearings.

Light Shutter Using ER Fluid Thin Films Dispersing ITO and ZnO Particles

1999 ◽  
Vol 13 (14n16) ◽  
pp. 2197-2204 ◽  
Author(s):  
Kunihiko Yamaguchi ◽  
Balachandran Jeyadevan ◽  
Toyohisa Fujita ◽  
Akira Nishihara
Keyword(s):  
Electric Field ◽  
Visible Light ◽  
Indium Tin Oxide ◽  
Near Infrared ◽  
Wavelength Region ◽  
Fluid Film ◽  
Fluid Films ◽  
Light Region ◽  
Infrared Rays ◽  
Zno Particles

We have studied optical properties of alkylnaphthalene suspensions dispersing semiconductor ultra fine ITO (Indium Tin Oxide) particles or insulator ZnO particles to apply them to light shutter. The suspensions behave like ER fluids which show an increase in viscosity under an electric field. When the ITO or ZnO dispersions are sandwiched between glass plates coated by a transparent conducting film, the fluid films transmit visible light. Application of the electric field in the direction of the light beam to the fluid film dispersing ITO particles shows an increase in the transmittance for near infrared rays, whereas the transmittance in visible light region decreases with the electric field. On the other hand, the transmittance through the fluid film dispersing ZnO particles decreases in the wavelength region from visible light to near infrared rays with the electric field. These phenomena depend on the cluster size under the electric field and the solid concentration of the suspensions. We can explain the results in terms of light scattering due to ITO or ZnO clusters formed in the electric field and optical absorption due to free carriers in ITO particles.

scholarly journals Nonsmooth Thermoelastic Simulations of Blade–Casing Contact Interactions

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Anders Thorin ◽  
Nicolas Guérin ◽  
Mathias Legrand ◽  
Fabrice Thouverez ◽  
Patricio Almeida
Keyword(s):  
Numerical Scheme ◽  
Frictional Contact ◽  
Unilateral Contact ◽  
Contact Dynamics ◽  
Nonsmooth Dynamics ◽  
Integration Scheme ◽  
Strongly Coupled ◽  
Measure Differential Inclusions ◽  
Time Marching ◽  
Stability Issues

In turbomachinery, it is well known that tighter operating clearances improve the efficiency. However, this leads to unwanted potential unilateral and frictional contact occurrences between the rotating (blades) and stationary components (casings) together with attendant thermal excitations. Unilateral contact induces discontinuities in the velocity at impact times, hence the terminology nonsmooth dynamics. Current modeling strategies of rotor–stator interactions are either based on regularizing penalty methods or on explicit time-marching methods derived from Carpenter's forward Lagrange multiplier method. Regularization introduces an artificial time scale in the formulation corresponding to numerical stiffness, which is not desirable. Carpenter's scheme has been successfully applied to turbomachinery industrial models in the sole mechanical framework, but faces serious stability issues when dealing with the additional heat equation. This work overcomes the above issues by using the Moreau–Jean nonsmooth integration scheme within an implicit θ-method. This numerical scheme is based on a mathematically sound description of the contact dynamics by means of measure differential inclusions and enjoys attractive features. The procedure is unconditionally stable opening doors to quick preliminary simulations with time-steps one hundred times larger than with previous algorithms. It can also deal with strongly coupled thermomechanical problems.

Linking Rigid and Flexible Multibody Systems via Thin Fluid Films Actively Controlled

2008 ◽  
Author(s):  
Edgar A. Estupinan ◽  
Ilmar F. Santos
Keyword(s):  
Film Thickness ◽  
Multibody Systems ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Fluid Film ◽  
Fluid Films ◽  
Thin Fluid ◽  
Dynamically Loaded ◽  
Reaction Forces ◽  
Fluid Film Thickness

This work describes in details the steps involved within the mathematical modelling of multibody systems (rigid and flexible) interconnected via controllable thin fluid films. The dynamics of the mechanical components are described with help of multibody dynamics and finite element method. In this paper, the methodology is applied to reciprocating machines such as hermetic reciprocating compressors and internal combustion engines. In previous studies [1], it has been shown that for a light duty vehicle, the friction losses may reach until 48% of the total energy consumption of an engine and from that, almost 30% are coming from bearings and crankshaft. Therefore, considering that the dynamics of the fluid films in the journal bearings can be actively controlled by means of different types of actuators, allowing significant reduction of wear and vibrations, one of the aims of this paper is to study the feasibility of applying active lubrication to the main journal bearings of reciprocating machines. In this framework the paper gives a theoretical contribution to the combined fields of fluid-structure interaction and active vibration control. The hydrodynamic pressure distribution for an active lubricated finite journal bearing dynamically loaded can be calculated by numerically solving the modified Reynold’s equation [2], by means of finite-difference method and integrated over the pressure area in order to obtain the dynamic reaction forces among components. These forces are strongly nonlinear and dependent on the relative kinematics of the system. From the point of view of active lubrication and specifically considered the case of a dynamically loaded journal bearing, the injection pressure should be controlled in the time domain. However, taking into account that the pressures and reaction forces in a reciprocating machine have a cyclic behaviour, the fluid film thickness of the main bearings may be modified by controlling the oil pressure injection, depending on the crank angle and the load bearing condition. It can be mentioned that the pressure and flow may be controlled by mechanical cam systems, piezoelectric nozzles [3] [4] or servovalves [5] [6], therefore, an adequate control strategy has to be defined. The fluid film forces are coupled to the set of nonlinear equations that describes the dynamics of the mechanical system. Such a set of equations is numerically solved giving some insights into the following parameters: a) maximum fluid film pressure, b) minimum fluid film thickness, c) maximum vibration levels and d) viscous frictional forces. The behaviour of such parameters is investigated when the system operate with conventional hydro-dynamic lubrication, passive hybrid lubrication and controlled hybrid lubrication.

Sign in / Sign up

Export Citation Format

Share Document