The dynamic behavior of clamped-clamped straight pipes conveying gas-liquid two-phase flow is theoretically investigated, specifically the effect of the flow parameters on the frequency of the system. First, the equation of motion is derived based on the classic Païdoussis formulation. Assuming Euler-Bernoulli beam theory, small-deflection approximation and no-slip homogeneous model, a coupled fluid-structure fourth-order partial differential equation (PDE) is obtained. Then, the equation of motion is rendered dimensionless and discretized through Galerkin’s method. That method transforms the PDE into a set of Ordinary Differential Equations (ODEs). The system frequency is obtained by solving the system of ODEs by allowing the determinant to be equal to zero. System frequencies for different geometries, structural properties and flow conditions have been calculated. The results show t...

New manufacturing and rapid prototyping technologies have fueled the creation of affordable and easy to replicate upper-limb prostheses. In this matter, many types and designs of 3D-printed upper-limb prostheses have been created over the last years. However, there is no consensus in the testing methodology for these devices regarding their mechanical capabilities and the comparisons authors can make are limited to their own metrics, which could be considered as a subjective approach. In order to tackle this issue, this work revises the existing methods for testing both the mechanical resistance and the mechanical performance or efficiency of upper-limb prostheses; specifically, the ones that are relevant for 3D-printed body-powered prostheses. Then, the adaptations needed to apply these methods to 3D-printed prostheses are discussed. Finally, recommendations are given for prosthetists a...

The critical flow velocity for a horizontal clamped-clamped pipe conveying two-phase flow is investigated. The system is represented by a coupled fluid-structure fourth-order Partial Differential Equation (PDE). In the case of the multiphase flow, the no-slip homogeneous flow is adopted. The PDE is transformed to a set of first-order ODEs using both Galerkin and state-space methods. The final system of equations represents an eigenvalue problem, where the eigenvalues are the natural frequency of the system. Specialized software has been employed to solve it. Results of critical flow velocity of gas as a function of homogeneous void fraction (fraction of the transversal area occupied by the gas) are presented representing a velocity stability map. The later suggest that the critical flow velocity increases with increasing the homogeneous void fraction. © 2018 Begell House Inc.. All right...