Digital Slot: A Tool for Optimization and Development of New Hydraulic Fracturing Technologies

We present the digital slot — a tool for the development of new hydraulic fracturing technologies via digitization of slurry flow in narrow channels. We consider slurry containing fluid, proppant, and fiber components. The flow is described by a continuum mathematical model based on the lubrication theory. The numerical algorithm utilizes Lagrangian approach with finite volume pressure solver. We present the results of laboratory validation and simulation examples showing the key effects affecting solids transport in hydraulic fracturing: settling, bridging, gravity slumping, materials degradation, viscosity contrast, and bank formation.

Computational Fluid Dynamics Simulation of Suspended Solids Transport in a Secondary Facultative Lagoon Used for Wastewater Treatment

The facultative lagoon hydrodynamics has been evaluated using computational fluid dynamics tools, however, little progress has been made in describing the transport of suspended solids within these systems, and their effects on fluid hydrodynamics. Traditionally, CFD models have been built using pure water. In this sense, the novelty in this study was to evaluate the influence of suspended solids transport on the hydrodynamics of an facultative lagoon. Two three-dimensional CFD models were developed, a single-phase model (pure water) and a two-phase model (water and suspended solids), for a conventional FL in Ginebra, Valle del Cauca, Colombia. Model results were compared with experimental tracer studies, displaying different tracer dispersion characteristics. Differences in the fluid velocity field were identified when suspended solids were added to the simulation. The fluid velocities in the single-phase model were greater than the fluid velocities obtained in the two-phase model, (0.127 m·s−1 and 0.115 m·s−1, respectively). Additionally, the dispersion number of each model showed that the single-phase model (0.478) exhibited a better behavior of complete mixing reactor than the two-phase model (0.403). These results can be attributed to the effect of the drag and slip forces of the solids on the velocity of the fluid. In conclusion, the fluid of FL in these models is better represented as a two-phase fluid in which the particle–fluid interactions are represented by drag and slip forces.

A Transient Solids Transport Model for Solids Removal Evaluation in Coiled-Tubing Drilling

Summary Poor hole cleaning is a major concern in coiled-tubing drilling (CTD), and it is often associated with long nonproductive time that contributes significantly to the operational cost. In this study, a transient solids transport model is developed based on transport equations of phases in the flow to predict the evolution of solids conveyed in the wellbore. The developed model is able to provide forecasts of the distribution of cuttings along the annulus, which can be important information for deciding to improve solids removal. Based on the concept of a two-layersteady-state model, a 1D time-dependent model is developed using two layers: a lower layer of solids bed and an upper layer of a solid-liquid mixture with the mechanisms of solids deposition and solids entrainment taken into account. The model is discretized by using a finite volume scheme and then solved by employing a semi-implicit numerical solution. The model’s hyperparameters, such as a deposition factor and an entrainment factor, are calibrated with experimental data conducted by the use of the large indoor flow loop (LIFL) to achieve a better match. The model is combined with a 2D cross-sectional model to handle the effect of pipe eccentricity and bed presence. Predictions from the model agree well with the experimental data acquired by using an oil-based mud for the majority of the cases.

Towards a Solid Particle Hydrodynamic (SPH)-Based Solids Transport Model Applied to Ultra-Low Water Usage Sanitation in Developing Countries

Distribution of toilet facilities and low-cost small-bore simplified sewerage systems (SS) in peri-urban areas provide opportunities to improve public health, provide safely managed sanitation, and protect the environment in low-to-middle income countries. Smoothed particle hydrodynamics (SPH) offers opportunities for optimisation of ultra-low water usage systems, but not without computational challenges. Results from SPH modelling of low cost, low water usage sanitary appliances were compared to a validated 1D finite difference model (DRAINET) for evaluation and calibration. An evaluation of system performance linked solid transport capabilities to physical geometries. The SPH model was developed for a pour-flush toilet pan connected to a 100 mm diameter pipe. The scheme utilized a free surface turbulent model to evaluate solid (faecal) transport efficacy. Performance was greatly influenced by the artificial viscosity factor, ViscoBoundFactor, within SPH, relating to the interaction of fluid and fluid particles and fluid and boundary particles. Results indicate that an increase in this factor leads to a reduction in fluid velocity with an attendant reduction in solid transportation distance, leading to inaccuracies. Other issues such as the use of density and mass in the definition of solid characteristics made it less predictable than the established 1D model for predicting solid transport. Overall, SPH was found to be useful for characterising the geometry of the pour flush pan but not for whole system assessment. A hybrid method is thus recommended whereby the design and performance characteristics for the input stage can be modelling in SPH but the whole system pipe network evaluation is better suited to the 1D DRAINET model.

A Novel Modeling Approach for Plastics Melting within a CFD-DEM Framework

Existing three-dimensional modeling approaches to single-screw extrusion can be classified according to the process sections. The discrete element method (DEM) allows describing solids transport in the feed section. The melt flow in the melt section can be calculated by means of computational fluid dynamics (CFD). However, the current state of the art only allows a separate consideration of the respective sections. A joint examination of the process sections still remains challenging. In this study, a novel modeling approach is presented, allowing a joint consideration of solids and melt transport and, beyond that, the formation of melt. For this purpose, the phase transition from the solid to liquid states is modeled for the first time within the framework CFDEMCoupling®, combining CFD and DEM by a novel melting model implemented in this study. In addition, a melting apparatus for the validation of the novel melting model is set up and put into operation. CFD-DEM simulations are carried out in order to calculate the melting rate and are compared to experimental results. A good agreement between the simulation and experimental results is found. From the findings, it can be assumed that the CFD-DEM simulation of single-screw extruder with a joint consideration of the feed and melt section is feasible.

Comparison of the MUSLE Model and Two Years of Solid Transport Measurement, in the Bouregreg Basin, and Impact on the Sedimentation in the Sidi Mohamed Ben Abdellah Reservoir, Morocco

The evaluation and quantification of solids transport in Morocco often uses the Universal Soil Loss Model (USLE) and the revised version RUSLE, which presents a calibration difficulty. In this study, we apply the MUSLE model to predict solid transport, for the first time on a large river basin in the Kingdom, calibrated by two years of solid transport measurements on four main gauging stations at the entrance of the Sidi Mohamed Ben Abdellah dam. The application of the MUSLE on the basin demonstrated relatively small differences between the measured values and those expected for the calibrated version, these differences are, for the non-calibrated version, +5% and +102% for the years 2016/2017 and 2017/2018 respectively, and between −33% and +34% for the calibrated version. Besides, the measured and modeled volumes that do not exceed 1.78 × 106 m3/year remain well below the dam’s siltation rate of 9.49 × 106 m3/year, which means that only 18% of the dam’s sediment comes from upstream. This seems very low because it is calculated from only two years. The main hypothesis that we can formulate is that the sediments of the dam most probably comes from the erosion of its banks.

A Stochastic Model to Predict Flow, Nutrient and Temperature Changes in a Sewer under Water Conservation Scenarios

Reducing water use could impact existing sewer systems but this is not currently well understood. This work describes a new flow and wastewater quality model developed to investigate this impact. SIMDEUM WW® was used to generate stochastic appliance-specific discharge profiles for wastewater flow and concentration, which were fed into InfoWorks® ICM to quantify the impacts within the sewer network. The model was validated using measured field data from a sewer system in Amsterdam serving 418 households. Wastewater concentrations of total suspended solids (TSS), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphorus (TPH) were sampled on an hourly basis, for one week. The results obtained showed that the InfoWorks® model predicted the mass flow of pollutants well (R-values 0.69, 0.72 and 0.75 for COD, TKN and TPH respectively) but, due to the current lack of a time-varying solids transport model within InfoWorks®, the prediction for wastewater concentration parameters was less reliable. Still, the model was deemed capable of analysing the effects of three water conservation strategies (greywater reuse, rainwater harvesting and water-saving appliances) on flow, nutrient concentrations, and temperature in sewer networks. Results show through a 62% reduction in sewer flow, COD, TKN and TPH concentrations increased by up to 111%, 84% and 75% respectively, offering more favourable conditions for nutrient recovery.