CFD Investigation of Particle Deposition in a Horizontal Looped Turbulent Pipe Flow

This paper presents comprehensive 3D numerical investigations on depositions of particles flowing through a horizontal pipe loop consisting of four bends. The multiphase mixture model available in FLUENT 6.2 was used in this study. In this numerical simulation, five different particle sizes have been used as secondary phases to calculate real multiphase effect in which inter-particle interaction has been considered. The deposition of particles along the periphery of the pipe wall was investigated as a function of particle size and fluid velocity. The simulations showed that near the upstream of the bends, maximum particle concentration occurred at the bottom of the pipe. However, downstream the bends, the maximum particle concentration occurred at an angle of 60° from the bottom. The larger particles clearly showed deposition near the bottom wall except downstream. As expected, the smaller particles showed less tendency of deposition and lesser at higher velocity. This numerical investigation showed qualitative agreement with the experiments conducted by Commonwealth Scientific and Industrial Research Organisation, Melbourne team for similar conditions.     

Extended Analytical Turbulent Diffusion Model for Particle Dispersion and Deposition in a Horizontal Pipe: Comparison with CFD Simulation

A 2D analytical turbulent diffusion model for particle dispersion and deposition at different heights along the pipe flow and circumferential deposition has been developed. This liquid–solid turbulent diffusion model presented in this paper has emanated from an existing gas–liquid turbulent diffusion model. This model can be used as a handy tool for quick estimation one and two-dimensional deposition fluxes of particles in water distribution networks. A comprehensive 3D numerical investigation has been carried out using multiphase mixture model available in “Fluent 6.2” to verify the above analytical model. Different particles sizes and densities were used for 3D numerical investigations. The deposition was studied as a function of particle diameter, density, and fluid velocity. The deposition of particles, along the periphery of the pipe wall and at different depths, was investigated. Both the models findings matched with qualitative phenomena such as deposition of heavier particles at the bottom of the pipe wall were higher at lower velocities and lower at higher velocities. The lighter particles were found mostly suspended with homogeneous distribution. Smaller particles were also suspended with marginal higher concentration near the bottom of the pipe wall. This marginal higher concentration of the smaller particles was found to be slightly pronounced for lower velocity. These analogies of particles are well discussed with the ratio between free-flight velocity and the gravitational settling velocity. Extended analytical model results were compared with the 3D computational fluid dynamics simulation results. Discrepancies in the model results were discussed.     

Modelling the Effects of Inflow Parameters on Lake Water Quality

A one-dimensional lake water quality model which includes water temperature, phytoplankton, phosphorus as phosphate, nitrogen as ammonia, nitrogen as nitrate and dissolved oxygen concentrations, previously calibrated for Lake Calhoun (USA) is applied to Uokiri Lake (Japan) for the year 1994. The model simulated phytoplankton and nutrient concentrations in the lake from July to November. Most of the water quality parameters are found to be the same as for Lake Calhoun. To predict probable lake water quality deterioration from algal blooming due to increased nutrient influx from river inflow, the model was run for several inflow water conditions. Effects of inflow nutrient concentration, inflow volume, inflow water temperatures are presented separately. The effect of each factor is considered in isolation although in reality more than one factor can change simultaneously. From the results it is clear that inflow nutrient concentration, inflow volume and inflow water temperature show very regular and reasonable impacts on lake water quality.     

Select chemical and engineering properties of wastewater biosolids

The select chemical and engineering characteristics of biosolids produced at a wastewater treatment plant in Eastern Australia were investigated to assess its suitability as structural fill material in road embankments. Results of comprehensive set of geotechnical experimentation including compaction, consolidation, creep, hydraulic conductivity and shear strength tests implied that biosolids demonstrate behavior similar to highly organic clays with a higher potential for consolidation and settlement. Results of chemical study including heavy metals, dichloro diphenyl trichloroethane (and derivatives) and organochlorine pesticides, indicate that biosolids samples are within the acceptable limits which allows their usage under certain guidelines. Results of tests on pathogens (bacteria, viruses or parasites) also indicated that biosolids were within the safe acceptable limits. Technical and management suggestions have been provided to minimize the possible environmental risks of using biosolids in road embankment fills.     

Optimisation of rainwater tank design from large roofs: A case study in Melbourne, Australia

Rainwater tanks for larger roof areas need optimisation of tank size, which is often not carried out before installation of these tanks. This paper presents a case study of rainwater tank evaluation and design for large roof areas, located in Melbourne, Australia, based on observed daily rainfall data representing three different climatic regimes (i.e. dry average, and wet years). With the aim of developing a comprehensive Decision Support Tool for the performance analysis and design of rainwater tanks, a simple spreadsheet based daily water balance model is developed using daily rainfall data, contributing roof area, rainfall loss factor, available storage volume, tank overflow and irrigation water demand. In this case study, two (185 m³ and 110 m³) underground rainwater tanks are considered. Using the developed model, effectiveness of each tank under different climatic scenarios are assessed. The analysis shows that both the tanks are quite effective in wet and average years, however less effective in dry years. A payback period analysis of the tanks is preformed which reveals that the total construction cost of the tanks can be recovered within 15-21 years time depending on tank size, climatic conditions and future water price increase rates. For the tanks, a relationship between water price increase rates and payback periods is developed. The study highlights the need for detailed optimisation and financial analysis for large rainwater tanks to maximise the benefits.     

Addressing sustainability through waste management: a perspective from higher education institutions in Southeast Asia

Journal of Material Cycles and Waste Management - Waste management is vital for global sustainable development. Sustainable development goals of a country would not be achieved if the waste...