Vortex profile analysis under different diffuser size for inlet channel of gravitational water vortex power plant

Hydropower is a renewable technology to store the amount of electricity which is the least expensive. Gravitational Water Vortex Power Plant is an ultra-low head micro hydropower system working ranging from 0.7 m to 2m without having the needs of a large reservoir and installation area. Several researches have been conducted on its basin configuration, orifice diameter, blade configuration, the geometry of the basin shape but not onto the addition of the diffuser at the inlet channel. The function of the diffuser is to direct the water into the basin allowing the water vortex to travel towards the tangential direction where this phenomenon will increase the rate of speed flow through the turbine. The simulation results showed that the addition of the diffuser has significantly increased the tangential velocity and the kinetic energy of the vortices. The increase in the velocity of the flow increased the height of the vortex which also led to the increase in the strength of the vortex and affects the vortex uniformity.

Effect of Printing Process Parameters on the Shape Transformation Capability of 3D Printed Structures

The aim of our research was to investigate and optimise the main 3D printing process parameters that directly or indirectly affect the shape transformation capability and to determine the optimal transformation conditions to achieve predicted extent, and accurate and reproducible transformations of 3D printed, shape-changing two-material structures based on PLA and TPU. The shape-changing structures were printed using the FDM technology. The influence of each printing parameter that affects the final printability of shape-changing structures is presented and studied. After optimising the 3D printing process parameters, the extent, accuracy and reproducibility of the shape transformation performance for four-layer structures were analysed. The shape transformation was performed in hot water at different activation temperatures. Through a careful selection of 3D printing process parameters and transformation conditions, the predicted extent, accuracy and good reproducibility of shape transformation for 3D printed structures were achieved. The accurate deposition of filaments in the layers was achieved by adjusting the printing speed, flow rate and cooling conditions of extruded filaments. The shape transformation capability of 3D printed structures with a defined shape and defined active segment dimensions was influenced by the relaxation of compressive and tensile residual stresses in deposited filaments in the printed layers of the active material and different activation temperatures of the transformation.

Cavitation erosion behavior of hydraulic concrete under high-speed flow

Purpose Cavitation erosion has always been a common technical problem in a hydraulic discharging structure. This paper aims to investigate the cavitation erosion behavior of hydraulic concrete under high-speed flow. Design/methodology/approach A high-speed and high-pressure venturi cavitation erosion generator was used to simulate the strong cavitation. The characteristics of hydrodynamic loads of cavitation bubble collapse zone, the failure characteristics and the erosion development process of concrete were investigated. The main influencing factors of cavitation erosion were discussed. Findings The collapse of the cavitation bubble group produced a high frequency, continuous and unsteady pulse load on the wall of concrete, which was more likely to cause fatigue failure of concrete materials. The cavitation action position and the main frequency of impact load were greatly affected by the downstream pressure. A power exponential relationship between cavitation load, cavitation erosion and flow speed was observed. With the increase of concrete strength, the degree of damage of cavitation erosion was approximately linearly reduced. Originality/value After cavitation erosion, a skeleton structure was formed by the accumulation of granular particles, and the relatively independent bulk structure of the surface differed from the flake structure formed after abrasion.

Aerospace Flight Modeling and Experimental Testing

Validation processes for aerospace flight modeling require to articulate uncertainty quantification methods with the experimental approach. On this note, the specific strategies for the reproduction of re-entry flow conditions in ground-based facilities are reviewed. It shows how it combines high-speed flow physics with the hypersonic wind tunnel capabilities.