International Journal of Applied Mechanics and Engineering
The present paper is a theoretical study of the motion of an inclined cavity of a paraboloid form filled with an ideal and incompressible fluid. The cavity is placed in the gravity field and its roto-translation motion is unknown. We look for determining the translation and rotation velocities of the cavity, the velocity potential of the fluid particles as well as the form of the fluid free surface...
Efforts have been made to study the effect of longitudinal surface roughness on the performance of a hydrodynamic squeeze-film between a non-rotating spherical surface and a hemispherical bearing under a steady load using the general stochastic analysis without using a specific probability distribution for describing random roughness, It is assumed that the bearing surface as well as the surface of...
The influence of the labyrinth seals on the dynamic behaviour of a flexible rotor in journal bearings is investigated. In particular a code which makes possible the determination of the stiffness and damping coefficients and the calculus of the stability threshold in the absence of unbalance is discussed. The pressure field in journal bearings and in the labyrinth seal is determined using Warner's...
This paper describes a theoretical analysis of transient motion of a viscous incompressible fluid in a vertical channel. The motion of the fluid is caused by the buoyancy force arising from the temperature gradient as a result of constant heat flux at one wall and an adiabatic condition on the other wall. Expressions for the velocity and temperature fields are derived with the help of the Laplace...
Electro-rheological and magneto-rheological fluids react to electric and magnetic fields respectively undergoing changes in their mechanical characteristics, viscosity and stiffness in particular. Their macroscopic behaviour is represented by the Bingham plastic model. In the last decade there has been an increasing attention toward the employment of ER and MR fluids in active bearings and active...
In this paper, we present a polar fluid model for electrorheological fluids using the methods of extended irreversible thermodynamics. In the first part of this paper, the fluid is described as a non-polar fluid. We show that certain well-known models emerge as special cases of our rate-type constitutive equations for the extra stress and the electric displacement. In the second part, we account for...
The paper presents a description of pine wood failure under compression. From among various failure criteria, the anisotropic failure Ascenazi criterion was used for description, assuming that wood is an orthotropic material. The experiments and description were carried out in one of the main orthotropy planes. An attempt to describe the dependence of compression strength on the density mass was made...
In this note, we construct a 3-D solution to the heat equation by means of the Fourier sine transform. If there exists no source of heat and the initial inner temperature of the body is zero our solution depends on x, y, z and t only by the similarity variables _ , _ and _ . Moreover, the corresponding 2-D and 1-D solutions appear as limiting cases for _ or _ and _ .
The effect of the Suction-Injection-Combination (SIC) on the onset of Rayleigh-Benard convection in suspensions is studied in a porous medium using the Rayleigh-Ritz technique. The critical eigenvalue is obtained for free-free, free-rigid and rigid-rigid boundary combinations with isothermal or adiabatic temperature condition. The microrotation of the suspended particles is assumed to vanish at the...
The distribution due to line source in a homogeneous isotropic thermoelastic half space has been investigated by applying a combination of the Laplace and Fourier transform technique in the context of generalised theories of thermoelasticity. The inverse transform integrals have been evaluated by using the Cagniard method to obtain the exact closed algebraic expressions for the displacement and temperature...
In the present work, a wear evaluation of the UHMWPE tibial insert of a total knee joint is attempted based on a simple wear model. A user subroutine has been written and integrated into a commercial finite element program to allow for a structural-kinematic model of the joint. The kinematic model simulates the relative angular velocity and linear movements between tibia and femur during walking....
Different failure mechanisms are possible in cyclic contact phenomena, from wear to surface or subsurface fatigue. The limit of the material elastic shakedown is a critical parameter, because an early failure has to be expected when it is exceeded. It depends on all the tribological quantities involved in the process, which determine the effective stress field in the bulk of contacting bodies. This...
A test rig for the experimental validation of the rotordynamic coefficients of annular and labyrinth seals using Active Magnetic Bearings (AMBs) exciters is presented. The rotordynamic coefficients for annular and labyrinth seals are obtained, with two computer programs using the Reynolds' gas lubrication equation and the bulk flow model with two volume control, respectively. The AMBs exciters allow...
This paper addresses the inversion threshold between equilibrium and self-sustained oscillations through an energy-balance approach quite suitable for moderately non-conservative mechanical systems with non-linear friction/speed characteristics. The analysis leads to the definition of an inversion surface in the coordinate space of the variables, emphasizing the influence of the friction curve shape...
The thermosolutal instability of Walters' (model B') elastico-viscous rotating fluid in a porous medium is considered in the presence of a uniform rotation, suspended particles and variable gravity field. the stable solute gradient, rotation, gravity field, suspended particles and viscoelasticity introduce oscillatory modes. For the stationary convection, the stable gradient and rotation have stabilizing...
A finite-difference solution to the unsteady free and forced convection flow of a dissipative fluid through a homogeneous porous medium past an infinite vertical isothermal plate is derived. Velocity and temperature profiles are shown graphically whereas the numerical values of the skin-friction and the rate of heat transfer are listed in a table. It is observed that the velocity decreases when the...
Computer simulations of the laminar flow past three-dimensional bluff bodies are presented. The focus is on the time-dependent wake flow behind linearly tapered circular cylinders and downstream of a circular cylinder with an abrupt change in diameter. In both cases the intricate vortex shedding phenomena observed in earlier laboratory experiments are convincingly reproduced by the computer experiments...
Bubble-driven flows, which belong to the large group of bubbly multiphase flows, are important in many industrial processes. Relevant examples are metal refining operations such as tapping of steel furnaces, gas-stirred lades, and aluminum electrolysis. Over the last 15 years, numerical solutions of mathematical models for bubble-driven flows have contributed to a better understanding of the governing...
Computational Fluid Dynamics (CFD) has increased in usage within many areas of industry. In a large number of cases CFD is seen as an extension of CAD or FEM modelling and a long term vision is the integration of CFD with CAD and FEM structural analysis. Because of this it is now commonplace to import CAD based solid models into CFD packages for the use of studies. This is in principle a very practical...
Multipath ultrasonic transit time flow meters (USM) represent an alternative to conventional meters for fiscal gas flow measurement. When the meter is installed close to bend(s), the flow profile can be quite complex, with asymmetric axial and transversal flow profiles. To investigate the accuracy of the measurement in such situations, computational fluid dynamic (CFD) simulations of 3D flow in various...