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Numerical study of transient elastohydrodynamic lubrication subjected to sinusoidal dynamic loads for rough contact surfaces

Abd-Alsamieh Mohamed F.

Acta Mechanica et Automatica

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2022

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Vol. 16, no. 2

162--168

EN

The purpose of this paper is to study the behaviour of transient elastohydrodynamic contacts subjected to forced harmonic vibrations, including the effect of surface waviness for concentrated counterformal point contact under isothermal conditions. Profiles of pressure and film thickness are studied to reveal the combined effects of sinusoidal external load and surface roughness on the lubrication problem. The time-dependent Reynolds' equation is solved using Newton–Raphson technique. The film thickness and pressure distribution are obtained at different snap shots of time by simultaneous solution of the Reynolds’ equation and film thickness equation including elastic deformation and surface waviness. It is concluded that the coupling effects of the transient sinusoidal external load and wavy surface would result in increase in modulations of the pressure and film thickness profile in comparison to the case where the smooth contact surfaces are subjected to sinusoidal external load.

2

Non-Darcy mixed convection heat and mass transfer from a vertical wavy surface in porous media

Mohamed R. A., Mahdy A.

International Journal of Applied Mechanics and Engineering

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2009

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Vol. 14, no 3

813-827

EN

This paper reports a study of mixed convection heat and mass transfer from a vertical wavy surface embedded in a homogeneous fluid-saturated porous medium using the Forchheimer flow model. The buoyancy effect is due to the variation of temperature and concentration across the boundary layer. We consider the boundary-layer regime where the Péclet number is very lager, […]. Appropriate transformations are employed to transform the governing partial differential equations into the boundary layer equations. The transformed equations have been solved numerically employing the Runge Kutta integration scheme with the shooting technique. Extensive computations are presented for a wide range of wave amplitudes the mixed convection parameter inertial parameter […] the Lewis number and the buoyancy ratio The numerical results illustrating the effects of all previously involved parameters on the velocity profiles[…] temperature […] mass […] the local Nusselt number […] and the local Sherwood number […] are presented and discussed in detail.

3

Non-Darcy natural convection flow along a vertical wavy plate embedded in a Non-Newtonian fluid saturated porous medium

Hady F. M., Mohamed R. A., Mahdy A.

International Journal of Applied Mechanics and Engineering

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2008

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Vol. 13, no 1

91-100

EN

The present analysis investigates the non-Darcian free convection of a non-Newtonian fluid from a vertical sinusoidal wavy plate embedded in a homogenous porous medium with constant wall temperature. After a suitable coordinate transformation to reduce the complexity of the goveming boundary-layer equations, the resulting nonlinear, coupled differential equations were solved with the Runge-Kutta integration scheme. The Darcy-Rayleigh number is considered to be very large. The power-law model is used for non-Newtonian fluids with exponent n < 1 for pseudoplastic fluids; n= 1 for Newtonian fluids and n > 1 for dilatant fluids. The effects of the Grashof number Gr * , the wavy geometry, and the non-Newtonian nature of the fluids on the local and global rates of heat transfer are discussed. An increase in the power-law index leads to a greater fluctuation of the local Nusselt number and increasses the global rate of heat transfer. An increase in the Grashof num ber leads to a smaller fluctuation of the local heat transfer and increasing the boundary layer thickness, hence decreasing the global rate ofheat transfer.