An Analysis of the Squeeze Film Between Rough Porous Rectangular Plates With Arbitrary Porous Wall Thickness

1984 ◽  
Vol 106 (2) ◽  
pp. 218-222 ◽  
Author(s):  
J. Prakash ◽  
K. Tiwari
Keyword(s):  
Wall Thickness ◽  
Hydrodynamic Lubrication ◽  
Stochastic Theory ◽  
Porous Wall ◽  
Squeeze Film ◽  
Rectangular Plates ◽  
Approximate Analysis ◽  
Bearing Material ◽  
Porous Walls ◽  
Influencing Parameters

The Christensen’s stochastic theory of hydrodynamic lubrication of rough surfaces is used to study the effects of surface roughness on the response of the squeeze film between rectangular plates when one plate has a porous facing. An exact solution, valid for arbitrary wall thickness, is obtained for the film pressure and pressure in the bearing material. A comparison is made with an earlier approximate analysis, applicable to thin porous walls to determine the range of influencing parameters for which the approximate solution is acceptable.

Roughness Effects in Porous Circular Squeeze-Plates With Arbitrary Wall Thickness

1983 ◽  
Vol 105 (1) ◽  
pp. 90-95 ◽  
Author(s):  
J. Prakash ◽  
K. Tiwari
Keyword(s):  
Wall Thickness ◽  
Hydrodynamic Lubrication ◽  
Stochastic Theory ◽  
Squeeze Film ◽  
Approximate Analysis ◽  
Tabular Form ◽  
Circular Plates ◽  
Roughness Effects ◽  
Influencing Parameters ◽  
Effect Of Surface

The stochastic theory of hydrodynamic lubrication of rough surfaces is used to study the effect of surface roughness on the response of a squeeze film between two circular plates when one plate has a porous facing. An exact solution is given for the film pressure and pressure in the bearing matrix, valid for arbitrary wall thickness. The results are presented in tabular form and a comparison is made with an earlier approximate analysis to determine the range of influencing parameters for which the approximate solution is acceptable.

scholarly journals Squeeze Film Lubrication between Rough Poroelastic Rectangular Plates with Micropolar Fluid: A Special Reference to the Study of Synovial Joint Lubrication

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
N. B. Naduvinamani ◽  
G. K. Savitramma
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Micropolar Fluid ◽  
Stochastic Theory ◽  
Squeeze Film ◽  
Rectangular Plates ◽  
Synovial Joint ◽  
Synovial Joints ◽  
Joint Lubrication ◽  
Load Carrying

The effects of surface roughness and poroelasticity on the micropolar squeeze film behavior between rectangular plates in general and that of synovial joints in particular are presented in this paper. The modified Reynolds equation, which incorporates the randomized surface roughness structure as well as elastic nature of articular cartilage with micropolar fluid as lubricant, is derived. The load-carrying capacity and time of approach as functions of film thickness during normal articulation of joints are obtained by using Christensen stochastic theory for rough surfaces with the assumption that the roughness asperity heights are to be small compared to the film thickness. It is observed that the effect of surface roughness has considerable effects on lubrication mechanism of synovial joints.

scholarly journals Turbulent channel flow over an anisotropic porous wall – drag increase and reduction

2018 ◽  
Vol 842 ◽  
pp. 381-394 ◽  
Author(s):  
Marco E. Rosti ◽  
Luca Brandt ◽  
Alfredo Pinelli
Keyword(s):  
Drag Reduction ◽  
Channel Flow ◽  
High Speed ◽  
Vertical Direction ◽  
Porous Wall ◽  
Turbulent Channel Flow ◽  
Spanwise Direction ◽  
Normal Velocity ◽  
Porous Walls ◽  
The One

The effect of the variations of the permeability tensor on the close-to-the-wall behaviour of a turbulent channel flow bounded by porous walls is explored using a set of direct numerical simulations. It is found that the total drag can be either reduced or increased by more than 20 % by adjusting the permeability directional properties. Drag reduction is achieved for the case of materials with permeability in the vertical direction lower than the one in the wall-parallel planes. This configuration limits the wall-normal velocity at the interface while promoting an increase of the tangential slip velocity leading to an almost ‘one-component’ turbulence where the low- and high-speed streak coherence is strongly enhanced. On the other hand, strong drag increase is found when high wall-normal and low wall-parallel permeabilities are prescribed. In this condition, the enhancement of the wall-normal fluctuations due to the reduced wall-blocking effect triggers the onset of structures which are strongly correlated in the spanwise direction, a phenomenon observed by other authors in flows over isotropic porous layers or over ribletted walls with large protrusion heights. The use of anisotropic porous walls for drag reduction is particularly attractive since equal gains can be achieved at different Reynolds numbers by rescaling the magnitude of the permeability only.

On the theory of two-dimensional wind tunnels with porous walls

1955 ◽  
Vol 233 (1192) ◽  
pp. 74-90 ◽  
Keyword(s):  
Mach Number ◽  
Pressure Gradient ◽  
Solid Wall ◽  
Porous Wall ◽  
Effective Length ◽  
Wind Tunnels ◽  
Special Cases ◽  
Porous Surfaces ◽  
Independent Variable ◽  
Porous Walls

A mathematical theory is developed enabling wind tunnels with porous walls to be designed to give zero tunnel blockage in subsonic compressible flow. The tunnel walls are taken to be porous over only a finite range R , and solid elsewhere, and a sealed jacket is placed over the porous section so that the pressure on the outside of the porous wall can be controlled. The porous wall is assumed to have the characteristic that the component of velocity normal to it is proportional to the pressure drop across it, the constant of proportionality, λ, being termed the ‘porosity’ of the wail. Infinite porosity and zero porosity correspond to free streamline and solid wall boundaries respectively, which are thus included in the theory as special cases. The problem solved in this paper is to determine the relation between λ, R , the tunnel height H , and the Mach number M , so that the ‘blockage’, or velocity increment at the model caused by the tunnel walls, vanishes. It is found that for a given value of the porosity the length of the porous wall, R , must be reduced with increasing Mach number to keep the blockage zero. Thus the tunnel needs to be fitted with adjustable sections of solid wall which can be moved across the porous surfaces to reduce their effective length (see figure 1). Both ‘solid ’ and ‘wake’ blockage are considered in the paper. The effects of wake blockage, which are particularly important at high subsonic speeds due to the rapid increase in drag, cannot be completely eliminated by varying R alone. This is because wake blockage, unlike solid blockage, causes a pressure gradient in the tunnel. This gradient and the blockage can be eliminated simultaneously only by introducing a further independent variable. A very convenient one for this purpose can be created by pumping air at a certain rate from the jacket and exhausting it outside the tunnel. The rate of removal of the air from the jacket can be adjusted to eliminate the induced pressure gradient completely.

Dynamic Behavior of Pure Squeeze Films in Narrow Porous Bearings

1974 ◽  
Vol 96 (3) ◽  
pp. 361-364 ◽  
Author(s):  
P. R. K. Murti
Keyword(s):  
Dynamic Behavior ◽  
Cyclic Load ◽  
Journal Bearing ◽  
Load Capacity ◽  
Squeeze Film ◽  
Closed Form Expression ◽  
Cyclic Loads ◽  
Eccentricity Ratio ◽  
Form Expression ◽  
Bearing Material

The dynamic behavior of squeeze film in a narrow porous journal bearing under a cyclic load is analyzed. A thin-walled bearing with a nonrotating journal is considered and a closed form expression for the pressure distribution is derived. The locus of the journal center is found by numerical methods and it is established with an example that actual contact between the journal and bearing can be avoided by appropriate design of the bearing. Consequently, it is proved that pure squeeze films have a load capacity only under cyclic loads. The analysis also reveals that the permeability of the bearing material and the wall thickness of the bearing influence significantly the operating eccentricity ratio.

An Investigation Into the Influence of Fluid Viscoelasticity in a Squeeze Film Bearing

1978 ◽  
Vol 100 (1) ◽  
pp. 56-64 ◽  
Author(s):  
John A. Tichy ◽  
Ward O. Winer
Keyword(s):  
Molecular Weight ◽  
Film Thickness ◽  
High Molecular Weight ◽  
Hydrodynamic Lubrication ◽  
Load Capacity ◽  
Surface Film ◽  
Free Fall ◽  
Squeeze Film ◽  
Delayed Response ◽  
High Molecular Weight Polymers

This investigation concerns a prediction of the behavior of viscoelastic fluids in a parallel circular squeeze film with a constant approach velocity, and a comparison to experimental results. The squeeze film geometry has direct application to unsteady hydrodynamic lubrication. The analysis predicts that load capacity of a viscoelastic fluid may be increased due to normal stress effects or decreased due to a delayed response of shear stress to a change in shear rate. Ten tested fluids include Newtonian control fluids, silicone fluids, high molecular weight polymers in petroleum oils, and extremely high molecular weight polymers in water and glycerin. The experimental squeezing is accomplished by the free fall of a cylindrical steel rod along its axis toward a stationary opposing surface. Film thickness, velocity of approach and load are measured. The velocity of approach is essentially constant in the range of film thickness considered. The water-glycerin-polymer solutions exhibited load capacity increases up to 33 percent, while the petroleum-polymer and silicone fluids showed decreases to 23 percent. It appears that viscoelastic effects cannot account for the reported improved bearing performance of polymer-additive lubricants.

Couple-stress squeeze films between porous rectangular plates

2003 ◽  
Vol 217 (3) ◽  
pp. 229-234 ◽  
Author(s):  
N. B. Naduvinamani ◽  
Syeda Tasneem Fathima ◽  
P. S. Hiremath
Keyword(s):  
Couple Stress ◽  
Reynolds Equation ◽  
Velocity Slip ◽  
Squeeze Film ◽  
Rectangular Plates ◽  
Couple Stresses ◽  
Load Carrying ◽  
Porous Interface ◽  
Couple Stress Fluids ◽  
Film Lubrication

In this paper, the squeeze-film lubrication theory between two isotropic porous rectangular plates has been advanced to analyse the effects of couple stresses arising due to the presence of microstructure additives in the lubricant, using the Stokes theory of couple-stress fluids. The most general form of the modified Reynolds equation is derived for the squeeze-film lubrication of the porous rectangular plates by taking into account of the velocity slip at the porous interface. An eigentype of expression is obtained for the squeeze-film pressure. The effects of the isotropic permeability, the couple stresses and the velocity slip parameters on the characteristics of the squeeze-film lubrication are discussed. A significant increase in the load-carrying capacity and the delayed squeeze-film time are observed for the couple-stress fluids in comparison with Newtonian fluids.

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