An Experimental Investigation of the Dissipation Mechanisms in the Suction Side Boundary Layer of a Turbine Blade

The present work is part of an extensive experimental activity carried out by the authors in recent years aimed at investigating the boundary layer transition phenomenon in turbine blades. The large scale of the cascade and the use of advanced LDV instrumentation and precision probe traversing mechanism resulted in high degree of spatial resolution and high accuracy of measurements. The main dissipation mechanism determining the profile losses in turbomachinery blades is the work of deformation of the mean motion within the boundary layer operated by both viscous and turbulent shear stresses. In the present paper, the local viscous and turbulent deformation works have been directly evaluated from the detailed measurements of boundary layer mean velocity and Reynolds shear stress. The results show the distributions and the relative importance of the viscous and turbulent contributions to the loss production, in relation with the boundary layer states occurring along the turbine profile.

Seismic design of low-rise steel building frames with self-centering hybrid damping connections

This paper develops a practice-oriented seismic design procedure for an emerging lateral force resisting system.The system combines the favorable re-centering feature with the attractive hybrid damping capacity.The system overcomes the detrimental frame expansion effect that occurs in conventional self-centering building frames without the cost of building space.Following the proposed design procedure,multiple designs with different parameters to achieve performance objectives were performed for a representative three-story building in which the considered lateral force resisting system is used to resist the seismic forces.Nonlinear response history analyses were performed for the designs to evaluate the applicability and adequacy of the proposed design approach.Based on the analyses conducted in this research,it was found that the considered system designed using the proposed approach can meet both transient and residual inter-story drift requirements specified for the selected performance objectives.While an initial design per the proposed design approach may be inadequate,the re-design strategy recommended can help transform the design to an acceptable one after only one round of modification.Moreover,the composition of hybrid damping may affect the maximum floor acceleration responses.In this study,the maximum floor acceleration can be reduced 12.75%at most by replacing hysteretic damping with viscous damping.This should be included in design consideration in the proposed approach through adjusting the hybrid damping composition.