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In this paper, we investigate small amplitude oscillations of a thin shape-morphing plate submerged in a quiescent, Newtonian, incompressible, viscous fluid in the vicinity of a solid wall. The plate undergoes prescribed, time-varying shape-morphing deformation in phase with the transverse oscillation, consisting of periodic curvature to an arc of a circle. As the presence of the solid wall in close proximity of the oscillating plate is known to significantly increase hydrodynamic damping on the structure due to squeeze film effects, shape-morphing is considered as a potential strategy to modulate and control hydrodynamic forces, as well as power dissipation. Via a rigorous formulation based on unsteady Stokes equations and the boundary element method, we show that the shape-morphing strategy is effective in reducing hydrodynamic forces on the structure as well as hydrodynamic power dissipation due to viscous effects. Additionally, such a reduction is enhanced as the gap between the oscillating plate and the solid wall is reduced. We present a comprehensive parametric study which investigates the effect of oscillation frequency, gap size, and imposed curvature on the hydrodynamic performance of the system and support our findings with asymptotics from inviscid flow theory and lubrication theory. These findings are of direct interest and applicability in several cantilever-based sensing and actuation systems, such as atomic force microscopy and microelectromechanical systems in liquids. [ABSTRACT FROM AUTHOR]

A novel contact resonance atomic force microscopy (CR-AFM) method utilizing a two-dimensional Kirchhoff-Love plate framework is presented. Theoretical formulations are discussed, and the classic CR-AFM problem is re-cast into an easily implementable generalized eigenvalue problem. An analysis is performed to determine the optimal placement of the sensing tip for plates of different aspect ratios. Finally, an experiment is conducted using the finite element method to numerically verify the proposed technique. By using a plate geometry for CR-AFM and optimizing the sensor tip location, we achieve a higher measurement sensitivity and modal density when compared with standard AFM cantilever geometries. A higher modal density allows CR-AFM measurement to be conducted using more information extracting eigenmodes in a given frequency bandwidth. [ABSTRACT FROM AUTHOR]

Nanostructured bimetallic reactive multilayers can be conveniently produced by ball milling of elemental powders. This research explores the non-equilibrium microscale conductive thermal transport in ball-milled particulate fractal structures during fabrication, arising from heat dissipation by bulk plastic deformation and surface friction. Upon impactor collisions, temperature increments are determined at interface joints and domain volumes using Green's functions, mirrored by source images with respect to warped ellipsoid domain boundaries. Heat source efficiency is calibrated via laboratory data to compensate for thermal expansion and impactor inelasticity, and the thermal analysis is coupled to a dynamic mechanics model of the particulate fracture. This thermomechanical model shows good agreement with the fractal dimensions of the observed microstructure from ball milling experiments. The model is intended to provide a comprehensive physical understanding of the fundamental process mechanism. In addition, the model could serve as a realtime thermal observer for closed-loop process control, as well as for interfacial diffusion and reaction analysis during ball milling. [ABSTRACT FROM AUTHOR]

This paper investigates and compares four commonly used flow transport equation-based cavitation models and their applicability to predict the cavitation performance of an industrial centrifugal pump with a helical inducer. The main purpose of this study is to identify, for this specific application, the most appropriate cavitation model and the associated empirical constants. Each cavitation model is reviewed in detail and the uniqueness of each model is outlined. Each cavitation model is incorporated in a computational fluid dynamics code to study the vaporization and condensation transport rate of the fluid. Experimental tests are conducted on a pump system to determine the true cavitation performance in terms of net positive suction head (NPSH). Experimental results are compared to simulation results for different cavitation models to validate cavitation performance predictions, along with the empirical constants. Lastly, bubble formation, cavitation inception, and bubble growth predicted by each cavitation model are compared with the experimental results. A sensitivity analysis is conducted in order to determine the impact of each set of empirical constants to the condensation and the vaporization rate in the centrifugal pump. Results show that two of the cavitation models exhibit high dependency on the empirical constants in terms of change in vaporization rate. Modifications to empirical constants for two of the four cavitation models are suggested to obtain agreement with the experimentally observed cavitation behavior and better predict NPSH performance for the industrial pump studied. [ABSTRACT FROM AUTHOR]

In this paper, the effect of the inducer tip clearance is studied to understand its impact on the cavitating and noncavitating performance of centrifugal pumps. Helical inducers with constant pitch and with variable (progressive) pitch are considered. Computational fluid dynamics (CFD) simulations of a single stage pump are conducted on each inducer type to determine the cavitating (two-phase) and noncavitating (single-phase) performance for varying inducer tip clearance. The Rayleigh-Plesset cavitation model is used to understand the bubble dynamics under the assumptions of single fluid undergoing no thermal energy transfer between each phase. Experimental tests are conducted on a pump with the variable pitch inducer to determine the true performance in cavitating and noncavitating operating conditions. Experimental results are compared to the simulations to validate the accuracy of the proposed numerical modeling. Net positive suction head (NPSH) with 3% differential head drop is used as a criterion to identify the true cavitation performance of each inducer configuration. It is found that, as the inducer tip clearance increases, excessive back leakage and larger vortex recirculation occur at the tip location. This results in pressure loss within the inducer and, consequently, degrades the cavitation performance. In addition, the change in cavitation performance with the tip clearance is much more evident for variable pitch inducer geometries as compared to the constant pitch case. Furthermore, the impact on the noncavitating performance of inducer tip clearance is found to be minimal. [ABSTRACT FROM AUTHOR]