Influence Of Inertia Forces Research Articles

The influence of inertia forces on steady-state rolling contact

The influence of inertia forces on steady-state rolling contact between two elastic cylinders is investigated. It is assumed that the cylinders consist of the same material. The contact problem is dealt with analytically based on the two-dimensional constitutive relations which are derived by considering dynamic effects of moving loads on the surface of a half-space. Dynamic effects are found to be negligible for contact problems concerning practical engineering applications.

The influence of fluid inertia on the operating characteristics of finite journal bearings

The extended Reynolds equation is solved numerically by using the finite difference method to determine the effects of the fluid film inertia forces on the performance of finite journal bearings. Data concerning the operating characteristics of finite journal bearings are provided as a function of length-to-diameter ratio, clearance ratio, reduced Reynolds' number and eccentricity ratio. The pressure distributions are also presented in graphical form. Numerical results reveal that the influence of inertia forces on loadcarrying capacity and attitude angle in finite journal bearings is small at moderate values of the reduced Reynolds number. The principal effect of inertia forces is a significant increase in the side flow rate.

Experimental investigation of hybrid journal bearings

Experimental pressure distribution measurements in hybrid journal bearings are presented and the influence of inertia forces in the recess outlets and pressure generation in the pockets for high rotating speeds are shown. These results are in good agreement with the theoretical results given by an established model.

Dynamic Elastic Buckling of Complete Spherical Shells with Initial Imperfections∗

ABSTRACT The dynamic elastic buckling behavior of a geometrically imperfect complete spherical shell that is subjected to a uniform external step pressure is examined using Sander's equilibrium and kinematic equations, appropriately modified to include the influence of inertia forces and initial stress-free imperfections in the radius. A finite-difference procedure with either the Houbolt or Park methods of time integration is used to predict the axisym-metric dynamic elastic buckling pressures and associated critical mode numbers. The dynamic buckling pressure is significantly smaller than the corresponding static value for small initial imperfections, but is less imperfection

Effects of inertia in forced corner flows

When viscous fluid is contained in the corner between two planes intersecting at an angle α, a flow may be ‘forced’ either by relative motion of the two planes keeping α constant (the ‘paint-scraper’ problem – Taylor 1960) or by relative rotation of the planes about their line of intersection (the hinged-plate problem – Moffatt 1964). In either case, a similarity solution is available describing the flow sufficiently near the corner, where inertia forces are negligible. In this paper, we investigate the effects of inertia forces, by constructing regular perturbation series for the stream function, of which the leading term is the known similarity solution. The first-order inertial effect is obtained analytically, and, for the Taylor problem with α = ½π, 25 terms of the perturbation series for the wall stress are generated numerically. Analysis of the coefficients suggests that the radius of convergence of the series is given by [rscr ] where r is distance from the corner, U is the relative speed of the planes, and v is the kinematic viscosity of the fluid. For the hinged-plate problem, discussed in § 5, the unsteadiness of the flow contributes to an inertial effect which is explicitly incorporated in the analysis. For both problems, streamline plots are presented which indicate the first influence of inertia forces at distances from the corner at which these become significant.

Influence of Inertia Forces in Film Rupture in Laminar and Turbulent Lubrication

A discussion is presented concerning the choice of boundary conditions to be used in converging-diverging lubrication films. It is concluded that, although no unique solution exists, under usual lubrication conditions (film rupture), the well-known condition dp/dx = 0 seems to hold indeed true, on the physical ground that this condition corresponds to a maximum accumulated mechanical energy from the moving surface via friction stresses. The calculation of pressure distributions and operating characteristics of infinitely long journal bearings, for laminar and turbulent flow, including the effects of inertia, is then presented in light of the discussion of boundary conditions. The effects of inertia forces in full journal bearings were found to be small, except for large Reynolds numbers. The effects are diminished as the eccentricity ratio is increased, and the principal effect is an increase in the attitude angle.

Influence of convective acceleration in the stokes equation on the pressure in a fluid

High rates of slip at points of friction, and also the use of water as a lubricant lead one to consider the problem of the influence of inertial forces on the development of the load capacity of a film of lubricant. A number of authors [1–6] have taken into account the convective terms in the Navier-Stokes equation in determining the pressure in a fluid film of lubricant in a bearing. An increase in the load capacity of the lubricant film by 20% at Re = 5000 was noted in [6]. In the present paper, we show that the convective inertia terms in the Navier-Stokes equation are equivalent to the square of the pressure, the tangential stresses, and the vorticity. The derived equation is used to determine in the first approximation the contribution of the inertial forces to the load capacity of the lubricant film of a high-speed bearing.

Method of outer and inner asymptotic expansions in the theory of Brownian motion of aerosol particles

We examine the Brownian motion of particles in a gaseous medium, complicated by the influence of inertial forces. The equation for the distribution function in phase space describing motion of this type was obtained in [1]. Also presented in [1] are the solutions of this equation for certain simple particular cases. The approximate equations of motion of aerosol particles in coordinate space were first obtained in [2] and solved for certain concrete problems in [3,4]. More exact equations of motion in coordinate space, and also the limits of applicability of the equations of [2], are presented in [5].

On the influence of inertia forces in turbulent and laminar self-acting films

On the influence of inertia forces in turbulent and laminar self-acting films

Closure to “Discussion of ‘On the Influence of Inertia Forces in Turbulent and Laminar Self-Acting Films’” (1970, ASME J. Lubr. Technol., 92, p. 480)

Closure to “Discussion of ‘On the Influence of Inertia Forces in Turbulent and Laminar Self-Acting Films’” (1970, ASME J. Lubr. Technol., 92, p. 480)

On the Influence of Inertia Forces in Turbulent and Laminar Self-Acting Films

A method is given for determining the motion in a fluid film including inertia forces. The method is developed for infinitely long bearings and can be used for both laminar and turbulent flows, as well as for incompressible and compressible lubricants. The obtained results show that for steady films, convective inertia forces lead basically to Bernoulli effects, while for unsteady films inertia forces may influence both damping and stiffness characteristics of the bearing. At the same time it is pointed out that when Bernoulli effects are important, similar effects may occur in the inlet region of the film. A generalization of the method for bearings of finite dimensions is also given.

On Gas Lubrication in Turbulent Regime

This paper analyzes first the transient conditions from laminar to turbulent regime for gas lubricated bearings. Then the pressure equation is deduced for self-acting gas-lubricated bearing by using Prandtl’s mixing length theory. A simple method for determining the pressure and the operating characteristics for bearings operating at high numbers H is given, based on an analogy with the corresponding laminar case. The pressure equation is also given for thrust and journal gas bearings under variable forces and velocities. The last two sections examine the influence of turbulence in externally pressurized gas bearings and the influence of inertia forces, respectively. The results obtained show that the turbulence does not alter qualitatively the operation conditions of gas-lubricated bearings. Moreover, the influence of turbulence in self-acting gas bearings is less important than in the case of liquid-film lubrication and even negligible when the bearing operates at high numbers H.