Inertia

About: Inertia is a research topic. Over the lifetime, 12006 publications have been published within this topic receiving 164291 citations.

Porous media characterization by the two-liquid method: effect of dynamic contact angle and inertia.

Abstract: The validity of using the Lucas-Washburn (LW) equation for porous media characterization by the two-liquid capillary penetration method was tested numerically and experimentally. A cylindrical capillary of known radius and contact angle was used as a model system for the tests. It was found that using the LW equation (i.e., ignoring inertia and dynamic contact angle effects) may lead to very erroneous assessment of the capillary radius and the equilibrium contact angle, for a relatively wide range of capillary radii and equilibrium contact angles. A correct assessment requires the application of a penetration kinetics equation that considers inertia and the dynamic contact angle.

Stability of the unison response for a rotating system with multiple tautochronic pendulum vibration absorbers

Abstract: Due to spatial and balancing considerations, the implementation of centrifugal pendulum absorbers (CPVA's) invariably requires that the total absorber inertia be divided into several absorber masses and stationed about the center of rotation. To achieve the designed-for performance, the CPVA's are expected to move in exact unison, since the selection of the total absorber mass is made by assuming an equivalent single absorber mass. In this paper, we determine the conditions under which the unison motion ofa system of several identical CPVA's is dynamically stable. This is done for the special case of tautochronic absorbers subjected to a purely harmonic torque. The stability criterion is obtained by an asymptotic method that exploits certain symmetries in the equations of motion and is based on the assumption that total moment of inertia of the absorbers is much smaller than that of the entire rotating system-an assumption that is almost always satisfied in practice. It is expressed in terms of a critical torque level that is proportional to the square root of the equivalent viscous damping of the individual absorbers. The result is verified by numerical simulations of the system near the critical parameter conditions. A future paper will consider the post-critical response of the system.

Numerical simulation of the dynamics of freely falling discs

Abstract: We present a comprehensive parametric study of the transition scenario of freely falling discs. The motion of the discs is investigated by a direct numerical simulation of the solid-fluid interaction. The discs are assumed to be homogeneous and infinitely thin. The problem is shown to depend on two independent parameters, the Galileo number expressing the ratio between effects of gravity and viscosity and the non-dimensionalized mass characterizing the inertia of the disc. The obtained results are in agreement with known experimental and numerical data and provide both detailed and comprehensive picture of the transition scenario in the two-parameter plane defined by the Galileo number and the non-dimensionalized mass.

Inertial range structure of turbulent velocity and scalar fields in a Lagrangian renormalized approximation

Abstract: The inertial range structure of turbulence is studied on the basis of an approximation derived by a systematic method of Lagrangian renormalized expansions. This method is also applied to the problem of a passive scalar field convected by turbulence, and some of its consequences are examined. Numerical values are obtained for various dimensionless constants in the inertial range including those in the k−5/3 spectrum law for the turbulent energy and the scalar field.

Dynamic calibration of a wheelchair dynamometer.

Abstract: The inertia and resistance of a wheelchair dynamometer must be determined in order to compare the results of one study to another, independent of the type of device used. The purpose of this study was to describe and implement a dynamic calibration test for characterizing the electro-mechanical properties of a dynamometer. The inertia, the viscous friction, the kinetic friction, the motor back-electromotive force constant, and the motor constant were calculated using three different methods. The methodology based on a dynamic calibration test along with a nonlinear regression analysis produced the best results. The coefficient of determination comparing the dynamometer model output to the measured angular velocity and torque was 0.999 for a ramp input and 0.989 for a sinusoidal input. The inertia and resistance were determined for the rollers and the wheelchair wheels. The calculation of the electro-mechanical parameters allows for the complete description of the propulsive torque produced by an individual, given only the angular velocity and acceleration. The measurement of the electro-mechanical properties of the dynamometer as well as the wheelchair/human system provides the information necessary to simulate real-world conditions.