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This paper studies the dynamic deployment of cylindrical thin-shell structures with open cross section, attached to a rigid base. The structures are elastically folded and then released. Previous experiments have shown that the total energy decreases while a fold moves back and forth along the structure, which was explained in terms of energy losses related to the fold "bouncing" against the boundary. This paper uses a rigorous numerical simulation, based on an in-house isogeometric shell finite element code that simultaneously eliminates shear locking and hourglassing without any intrinsic energy dissipation, to show that the total energy of the system is conserved during deployment. The discrepancy with the previous results is explained by showing that energy transfers from low-frequency, "rigid body" modes, to higher frequency modes. [ABSTRACT FROM AUTHOR]

An in-depth understanding of stall behavior is essential to improve the safe and stable operation of the pump turbine. In this research, the detached eddy simulation (DES) is used to investigate the various characteristics and propagation mechanism of the rotating stall of the hump instability region. The frequency characteristics and spatial intensity distribution of the stall cells are studied by adopting the proper orthogonal decomposition (POD) method. The results indicate that the energy loss at 0.80QDES and 0.75QDES are induced by the rotating stall with three cells that occur in the diffuser flow channel, and the corresponding high amplitude frequencies are St0.0074 and St0.0111, respectively. The effect of the stall cells is particularly severe near the hub. When the flow rate is further reduced to 0.68QDES, the three rotating stall cells develop into two symmetrically distributed stable stall cells with no definite characteristic frequencies, and the blocking phenomenon is concentrated near the shroud. With the stall cells losing their rotational characteristics, they have less impact on the flow field and contribute less energy. This paper also reveals that the energy loss in the diffuser contributes significantly to the hump formation on the performance curve. [ABSTRACT FROM AUTHOR]

This paper has revisited the roof deformation and collapse of stamps with isolated grooves based on a contact mechanics approach, with emphasis on establishing the nonadhesive and adhesive contact solutions for surfaces containing a shallow rectangular groove with the effects of applied load and interfacial adhesion taken into account. By solving singular integral equations and using the energy release rate approach, closed-form solutions are derived analytically for the deformed groove shapes, interfacial stress distributions, and equilibrium relations between load and contact size, which reduce to the previously proposed solutions without adhesion or without applied load. Finite element (FE) analysis is performed to validate the nonadhesion solutions, while experiment results of stamp collapse reported in the literature are adopted to examine the adhesion solutions. By introducing the Johnson parameter a to represent a competition between surface energy and elastic strain energy of the groove, four kinds of contact behaviors of the groove roof can be characterized appropriately: nonadhesion, weak adhesion, intermediate adhesion, and strong adhesion. Hysteresis loop and energy loss due to distinct load/unloading paths are revealed in the cases of intermediate and strong adhesion. We have also provided the critical applied pressure to achieve roof collapse and the corresponding equilibrium contact size for full range of a. [ABSTRACT FROM AUTHOR]

In this paper, we consider the interlayer slidable friction structures on soft-substrate as the hardcover book-like-laminated-plates with internal friction on the Winkler foundation. For a quasi-static problem, a detailed analysis of the bending response and energy dissipation is carried out for a three-point-supported layered plate on the Winker foundation. Our numerical investigations show that the hardcover, friction, and substrate have a great influence on bending response, and in particular, the friction can cause a considerable amount of energy dissipation within per loading-unloading cycle. The study is not only to predict the mechanical interactions behavior in-between of geometry, friction, elasticity, and substrate but also as a representative case to help finding some clue on the universal behaviors of interlayer slidable friction structures on soft-substrate. [ABSTRACT FROM AUTHOR]