Flow Properties Analysis and Identification of a Fly Ash-Waste Rock Mixed Backfilling Slurry

The use of waste rock as an aggregate in mining backfill is environmentally friendly and cost-saving. The backfill slurry flow property varies with the change in aggregate, binder content, solid concentration, and additives. The slurry flow in a pipeline is governed by its properties, which makes it crucial to study the flow properties and their effects. One example is a fly ash-waste rock mixed slurry in Jinchuan Nickel, China. Tests on the slump, slump flow, mortar consistency, layering degree, and bleeding rate are performed to reveal the effects of the slurry concentration, binder content, and fly ash addition on the flow properties. Those relations are analyzed, and two new indices are derived (F1 and F2) using the principal component analysis method. Finally, the application results show that F1 > 0 indicates a nonhomogeneous flow; F1 < 0 and F2 > 0 indicates a high-density slurry flow; F1 < 0 and F2 < 0 indicates a paste slurry flow.

Laminar Forced Convection of Nanofluids in a Circular Tube: A New Nonhomogeneous Flow Model

In this paper, the local and average heat transfer coefficient enhancement or deterioration, and rise in pumping power in steady, laminar alumina–water, titania–water, and carbon nanotube (CNT)–water nanofluids flow in a horizontal circular tube subjected to constant heat flux at the outer wall have been investigated numerically based on a new variable property nonhomogeneous flow model which takes into account agglomeration of nanoparticles. The results have been compared with the published experimental results of Utomo et al. (Utomo, A. T. et al., 2014, “The Effect of Nanoparticles on Laminar Heat Transfer in a Horizontal Tube,” Int. J. Heat Mass Transfer, 69, pp. 77–91.) using various property models of thermal conductivity and viscosity, and for equal Reynolds number, equal inlet velocity, equal mass flowrate, and equal pumping power of nanofluid and base fluid. Stream function–vorticity–temperature formulation and finite difference method have been used. Using the same Reynolds number of nanofluid and base fluid gives much higher enhancement in average heat transfer coefficient as compared to other modes of comparison. Interestingly, the criterion of equal pumping power gives negative percent enhancement in the case of CNT–water nanofluid. The pumping power is found to rise for all three nanofluids. It is found that consideration of agglomeration of nanoparticles has produced improved accuracy in the numerical solution.

Effects of Inlet Disturbances on Fan Stability

This paper investigates the effects of inlet disturbance caused by crosswind on a fan blade operation and addresses the possible aerodynamic instabilities, which can arise for such a fan-intake system. The work is carried out by using a three-dimensional unsteady computational fluid dynamics (CFD) model (AU3D), and for a modern low-speed fan rig for which extensive measured data is available. The computational domain includes the fan with outlet guide vanes for the bypass flow, engine-section stators for the core, and a symmetric intake upstream of the fan (a whole low-pressure domain). The unsteady full annulus simulations under crosswind are performed to analyze the effects of inlet disturbances on the operation of this blade. It was observed that, for sufficiently high amplitudes of crosswind, the intake lip separates, and results in a significant loss of stall margin. Moreover, even in the absence of lip separation, the blade can still stall prematurely due to nonhomogeneous flow caused by the two contra-rotating trailing vortices. In the second phase of this study, the effects of fan loading on the suppression of flow separation in the intake, and the consequent stall margin of the fan blade, were explored. The results indicated that, as the fan speed increases, it becomes more capable of reducing the inlet distortion levels, and consequently, the loss in stall margin decreases.