Forced vibration of delaminated Timoshenko beams subjected to a moving load

A composite beam with single delamination under the action of moving load has been modeled accounting for the Poisson’s effect, shear deformation, and rotary inertia. The existence of the delamination changes the stiffness of the structure, and this affects the dynamic response of the structure. We have used a constrained mode to simulate the behavior between the delaminated surfaces. Based on this mode, eigensolution technique is used to obtain the natural frequencies and their corresponding mode shapes for the delaminated beam. Then, the Ritz method is adopted to derive the dynamic response of the beam subjected to a moving load. The obtained results for the free and forced vibrations of beams are verified against reported similar results in the literature. Moreover, the maximum dynamic response of such beam is compared with an intact beam. The effects of different parameters such as the size, depth, and spanwise location of the delamination, the load velocity, the different ply configurations, and the Poisson’s effect on the dynamic response of the beam are studied.

Dynamic Analysis of a Delaminated Composite Beam due to a Moving Oscillatory Mass

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 parameters such as the oscillator axial velocity and the size, depth and spanwise location of the delamination on the dynamic response of the beam and on the oscillator separation from the delaminated beam has been studied. It is shown that the delamination has significant influence on the dynamic response of the beam and on the oscillator separation from the beam.

Radial Transport and Momentum Exchange in an Axial Compressor

The objective of this work was to examine radial transport in axial compressors from two perspectives. The first was to compare the mixing coefficient based on a secondary flow model (using measured radial velocities) with that based on a turbulent diffusion model. The second was to use measured airfoil pressure forces and momentum changes to assess the validity of the assumption of diffusive radial transport, which is common to both models. These examinations were carried out at both design and off-design conditions as well as for two rotor tip clearances. In general it was seen that radial mixing was strongest near the hub and that it increased dramatically at near-stall conditions. It was also seen that radial transport could cause large differences (≈ 100 percent) between the force on an airfoil and the change in momentum across the airfoil at the same spanwise location.

On the instability of flow in a streamwise corner

The linear stability of an incompressible laminar flow in the blending boundary layer between the boundary layer in a 90° streamwise corner and a Blasius boundary layer well away from the corner is examined using a locally parallel flow approximation. It is shown that the magnitude of the cross flow in the boundary layer is too small to be a significant factor in the observed early transition in the blending layer. However, the influence of the outer boundary conditions associated with oblique modes of disturbances which are anti-symmetric about the bisector plane are shown to have a profound effect on the stability of the flow. As a result, the square root of the critical streamwise Reynolds number R er , associated with a spanwise location is significantly reduced as the corner is approached, being R er = 54 approximately for spanwise distance of z * = 6 x * R -1 from the corner compared with R er = 322 approximately for z * = 20 x * R -1 , where x * measures downstream distance from the leading edges and R 2 is the streamwise Reynolds number. At R = 600, the growth rate of the most amplified mode of disturbance at the former location is over six times greater than that at the latter; the corresponding wave angle at the two locations is respectively 44° and 5°, approximately.

Radial Transport and Momentum Exchange in an Axial Compressor

The objective of this work was to examine radial transport in axial compressors from two perspectives. The first was to compare the mixing coefficient based on a secondary flow model (using measured radial velocities) with that based on a turbulent diffusion model. The second was to use measured airfoil pressure forces and momentum changes to assess the validity of the assumption of diffusive radial transport which is common to both models. These examinations were carried out at both design and off-design conditions as well as for two rotor tip clearances. In general it was seen that radial mixing was strongest near the hub and that it increased dramatically at near-stall conditions. It was also seen that radial transport could cause large differences (≈ 100%) between the force on an airfoil and the change in momentum across the airfoil at the same spanwise location.

The Relative Eddy in Axial Turbine Rotor Passages

It has been observed that strong radially outward flow can be present on the pressure surface of an axial turbine rotor blade. This paper demonstrates that the relative eddy plays a major role in producing this radial flow. An analysis of the relative eddy indicates that it can explain observed trends both with blade incidence as well as with spanwise location on the blade. Suggestions are offered as to how the turbine designer might exercise some control over this aerodynamic mechanism.