Sharif Digital Repository

This paper deals with the dynamic analysis of a delaminated composite beam under the action of moving oscillatory mass. The beam is analyzed as four interconnected sub-beams using the delamination limits as their boundaries. The constrained model is used to model the delamination region. The continuity and equilibrium conditions are satisfied between the adjoining beams. The beam response variation due to the delamination with respect to the intact beam has been investigated. Furthermore, the possible separation of the moving oscillator from the beam during the course of the motion is investigated by monitoring the contact force between the oscillator and the beam. The effect of the... 

CFD simulation of cylindrical bubble column including air as dispersed phase and water as continuous phase operating in churn-turbulent flow regime with diameter of 0.49 m, height of 3.6 m and gas superficial velocity of 0.14 m/s have been conducted. All simulations have been carried out in a 2D axisymmetric, unsteady and Euler/Euler framework with the aid of commercial software FLUENT v. 14.5. Simulations were validated by our experimental results through residence time distribution (RTD) data. Effect of bubble size distribution at inlet on column hydrodynamic was investigated and results clearly showed that equilibrium bubble size distribution in most parts of column is independent of... 

A 2D numerical investigation is performed to better understand the transient thermo-fluid processes in a vortex tube for a cold mass fraction equal to0.44. The results along the Ranque-Hilsch vortex tube reveal a close agreement with past numerical and experimental data. The distribution of axial, radial, and tangential velocities as well as the stagnation pressure and temperature are examined at different positions for different time steps. The results indicate that the tangential velocity is the most significant velocity component and dominates the heat transfer and energy conversion processes. In addition, it is evident that the core of the cold end experiences the highest pressure... 

The dynamic response of a delaminated composite beam under the motion of an oscillatory mass moving with a constant velocity has been studied. The delaminated composite beam is modeled as four interconnected sub-beams using the delamination limits as their boundaries. The constrained model is used to model the delamination region. The continuity and equilibrium conditions are forced to be satisfied between the adjoining beams. A set of derived governing differential equations along with those obtained by imposing boundary conditions are simultaneously solved in a closed form manner. The results for the response of the delaminated beam were compared with those of the intact beam. Furthermore,... 

To determine the curvature of the exit profile in the extrusion process of non-symmetrical flat dies, the dead metal zone profile was predicted using the energy minimization method. The dead zone is a natural non-linear die for the process and it is pragmatic to use this non-linear die to estimate the value of the exit profile curvature and the required bearing length for reducing this deviation. The velocity field is calculated based on Hermite cubic spline and some additional assumptions. In non-symmetrical dies the entrance section of the deformation region is not flat. Considering this fact, axial velocity decreases with increasing the distance to die center line which is in agreement... 

The dynamics of the flexible robot arm subjected to tip mass during an actual deployment is studied. The Euler-Bernoulli beam theory and the real deployment are considered in the simulation. A new real axial velocity profile is developed. This new suggested profile simulates the actual deployment such that the arm movement starts from immovability and after attaining the final required length comes back again to the static state. Using Lagrange's equation, the equations of motion of the system are derived to study the system dynamics in this suggested deployment profile. A series approximation is used to represent the lateral elastic displacements. Using variables separation and also some... 

The boundary layer integral method is used to investigate the development of the turbulent swirling flow at the entrance region of a conical nozzle. The governing equations in the spherical coordinate system are simplified with the boundary layer assumptions and integrated through the boundary layer. The resulting sets of differential equations are then solved by the fourth-order Adams predictor-corrector method. The free vortex and uniform velocity profiles are applied for the tangential and axial velocities at the inlet region, respectively. Due to the lack of experimental data for swirling flows in converging nozzles, the developed model is validated against the numerical simulations. The...