Impact of a rigid sphere on a highly compressible porous layer imbibed with a Newtonian liquid

Abstract

The process of liquid flow takes place inside a highly compressible porous layer (HCPL) many times. In these cases, elastic forces of the HCPL solid phase are negligible, compared with hydrodynamic (HD) forces. Such processes were named ex-poro-HD (XPHD). A study of the impact process under XPHD conditions for circular and rectangular aligned plates was recently performed and presented by the authors. The impact of a rigid sphere on an HCPL, imbibed with a Newtonian liquid, under XPHD conditions, is analysed in the present paper. The Kozeny—Carman equation was used to compute the permeability variation as a function of compacticity/porosity. The Bowden and Tabor model for squeeze under impact was extended for XPHD conditions. The obtained model gives the impact pressure and force variations as the layer thickness decreases, so the damping capacity of the HCPL was evaluated. The maximum value of the absorbed energy, given by the optimal compacticity/porosity of the HCPL, is established. A comparison with the impact of a rigid sphere on a Newtonian liquid film under HD conditions is also done, keeping the same geometry and same kinematic and dynamic parameters, inherited from the XPHD model. The damping capacity of an HCPL is several orders of magnitude greater than that of the Newtonian liquid layer. The theoretical model was validated by two experiments, in which the HCPL is impacted by free falling ball tests.

Squeeze Flow of Bingham Fluids through Reticulated, Compressed Foams

“…This squeeze mechanism of liquids imbibed in highly deformable porous layers (named ex-poro-hydrodynamic lubrication-XPHD) was intensively studied by Pascovici and co-workers. They developed several theoretical models based on Darcy law (neglecting viscous and inertia effects) and made experiments for various types of contacts: Disc on plane [2], cylinder on plane [3], sphere on plane [4], cylinder on cylinder [5]. The results have proved the generation of high lift forces, greater than those typically obtained during pure fluid squeeze.…”

“…Their models were developed for Newtonian fluids, and based on three assumptions: (i) the porous material is highly deformable and the forces generated by the elastic structure are negligible compared to the fluid pressure forces; (ii) the permeability varies with porosity (which in turn is variable with the level of compression) and permeability-porosity correlation is given by Kozeny-Carman law; and (iii) the porous structure does not inflate during compression and correspondingly, the area normal to the direction of compression remains constant. Applications were imagined for squeeze dampers [6,7] and shock absorbers [4].…”

Non-Newtonian Effects on the Squeeze Film Characteristics between a Sphere and a Flat Plate: Rabinowitsch Model

“…The mechanical action (squeezing, shearing, etc.) leading to the generation of high pressure at the contacts [1][2][3][4] changes the rheology of the lubricants such as viscosity and density which account for the performance characteristics of machine elements. Dowson [5], Wada and Hayashi [6], and Yadav and Kapur [7] emphasized the variation of viscosity and density with temperature and pressure and reported significant changes in bearing characteristics.…”

Squeeze processes in a narrow circular damper with highly compressible porous layer imbibed with liquids

“…The studies of squeeze processes (normal motion) considered both constant velocity motion and variable velocity motion by loading the mobile part with a constant force or by impact. Recent studies concerning the squeeze process under impact conditions in XPHD regime were performed theoretically and experimentally for the aligned plates geometries [2] and sphere-to-plane contact [10].…”