Rheological modelling of fresh human faeces

2014 ◽  
Vol 4 (3) ◽  
pp. 484-489 ◽  
Author(s):  
S. M. Woolley ◽  
C. A. Buckley ◽  
J. Pocock ◽  
G. L. Foutch
Keyword(s):  
Fluid Dynamics ◽  
Reasonable Agreement ◽  
Model Parameters ◽  
Viscosity Data ◽  
Initial Screening ◽  
Human Faeces ◽  
Shear Thinning Fluids ◽  
Treatment Processes ◽  
Rheological Modelling ◽  
Generate Model

An analysis of viscosity data from sets of raw data on the shear rheological properties of fresh human faeces was performed to generate model constants that can be used for the design of faecal treatment processes. The models selected are standard choices in computational fluid dynamics software for shear-thinning fluids. Initial screening for model selection was based on a literature review of similarly viscous materials. Results showed reasonable agreement with Power Law (PL). PL model parameters were proposed for fresh human faeces and correlated against sample properties. A PL model for shear stress as a function of moisture content was proposed.

An Improved Computational Fluid Dynamics (CFD) Model for Erosion Prediction in Oil and Gas Industry Applications

2014 ◽  
Author(s):  
Deval Pandya ◽  
Brian Dennis ◽  
Ronnie Russell
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Surface Velocity ◽  
Particle Model ◽  
Model Parameters ◽  
Cfd Model ◽  
Erosion Model ◽  
Erosion Prediction ◽  
Erosion Models ◽  
Computational Fluid Dynamics Cfd

In recent years, the study of flow-induced erosion phenomena has gained interest as erosion has a direct influence on the life, reliability and safety of equipment. Particularly significant erosion can occur inside the drilling tool components caused by the low particle loading (<10%) in the drilling fluid. Due to the difficulty and cost of conducting experiments, significant efforts have been invested in numerical predictive tools to understand and mitigate erosion within drilling tools. Computational fluid dynamics (CFD) is becoming a powerful tool to predict complex flow-erosion and a cost-effective method to re-design drilling equipment for mitigating erosion. Existing CFD-based erosion models predict erosion regions fairly accurately, but these models have poor reliability when it comes to quantitative predictions. In many cases, the error can be greater than an order of magnitude. The present study focuses on development of an improved CFD-erosion model for predicting the qualitative as well as the quantitative aspects of erosion. A finite-volume based CFD-erosion model was developed using a commercially available CFD code. The CFD model involves fluid flow and turbulence modeling, particle tracking, and application of existing empirical erosion models. All parameters like surface velocity, particle concentration, particle volume fraction, etc., used in empirical erosion equations are obtained through CFD analysis. CFD modeling parameters like numerical schemes, turbulence models, near-wall treatments, grid strategy and discrete particle model parameters were investigated in detail to develop guidelines for erosion prediction. As part of this effort, the effect of computed results showed good qualitative and quantitative agreement for the benchmark case of flow through an elbow at different flow rates and particle sizes. This paper proposes a new/modified erosion model. The combination of an improved CFD methodology and a new erosion model provides a novel computational approach that accurately predicts the location and magnitude of erosion. Reliable predictive methodology can help improve designs of downhole equipment to mitigate erosion risk as well as provide guidance on repair and maintenance intervals. This will eventually lead to improvement in the reliability and safety of downhole tool operation.

scholarly journals Cluster-associated viscosity model and methods for determining its parameters

2020 ◽  
Vol 2 (313) ◽  
pp. 27-37
Author(s):  
A. M. Makasheva ◽  
Keyword(s):  
Viscous Flow ◽  
Hierarchical Cluster ◽  
Reference Points ◽  
Viscosity Model ◽  
Liquid Lithium ◽  
Model Parameters ◽  
Viscosity Data ◽  
Thermal Barriers ◽  
Degree Of Association ◽  
Processing Techniques

A detailed development of a hierarchical cluster-associate mathematical viscosity model is shown. The model is based on the equilibrium Boltzmann’s distribution and, therefore, is regarded as a chaosensitive property of a fluid inherent in it not only in motion but also at rest. In this model, the key characteristics are chaotic thermal barriers at the melting and boiling points, in connection with which the behavior of a liquid is determined by the action of three energy classes of particles – crystal-mobile, liquid-mobile, and vapor-mobile. An important single indicator in the new model depends on temperature and makes sense of the degree of association of clusters of crystal-mobile particles. The assignment of the activation energy of the viscous flow of melts determined by the Frenkel’s equation to the degree of cluster association gives a constant value commensurate with the binding energy of the van der Waals particle attractive forces. On this basis, the authors hypothesized that a viscous flow occurs due to the destruction of cluster associates while preserving the clusters themselves. To adapt the cluster-associate model to experimental data, certain data processing techniques have been developed to identify unknown model parameters. All calculations are illustrated on liquid lithium and have shown their high adequacy. Also added is a method for processing viscosity data using the entire set of viscosity data while maintaining two reference points and processing the rest to determine the degree of aggregation of associates.

scholarly journals Experimental and Computational Analysis of NOx Photocatalytic Abatement Using Carbon-Modified TiO2 Materials

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1366
Author(s):  
Tatiana Zhiltsova. ◽  
Nelson Martins ◽  
Mariana R. F. Silva ◽  
Carla F. Da Silva ◽  
Mirtha A. O. Lourenço ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Kinetic Model ◽  
Photocatalytic Oxidation ◽  
Cfd Simulation ◽  
Emission Spectra ◽  
Chemical Kinetic ◽  
Solar Light ◽  
Model Parameters ◽  
Chemical Kinetic Model ◽  
Simulated Solar Light

In the present study, two photocatalytic graphene oxide (GO) and carbon nanotubes (CNT) modified TiO2 materials thermally treated at 300 °C (T300_GO and T300_CNT, respectively) were tested and revealed their conversion efficiency of nitrogen oxides (NOx) under simulated solar light, showing slightly better results when compared with the commercial Degussa P25 material at the initial concentration of NOx of 200 ppb. A chemical kinetic model based on the Langmuir–Hinshelwood (L-H) mechanism was employed to simulate micropollutant abatement. Modeling of the fluid dynamics and photocatalytic oxidation (PCO) kinetics was accomplished with computational fluid dynamics (CFD) approach for modeling single-phase liquid fluid flow (air/NOx mixture) with an isothermal heterogeneous surface reaction. A tuning methodology based on an extensive CFD simulation procedure was applied to adjust the kinetic model parameters toward a better correspondence between simulated and experimentally obtained data. The kinetic simulations of heterogeneous photo-oxidation of NOx carried out with the optimized parameters demonstrated a high degree of matching with the experimentally obtained NOx conversion. T300_CNT is the most active photolytic material with a degradation rate of 62.1%, followed by P25-61.4% and T300_GO-60.4%, when irradiated, for 30 min, with emission spectra similar to solar light.

Hydraulic study and optimisation of water treatment processes using numerical simulation

2002 ◽  
Vol 2 (5-6) ◽  
pp. 135-142 ◽  
Author(s):  
K. Craig ◽  
C. De Traversay ◽  
B. Bowen ◽  
K. Essemiani ◽  
C. Levecq ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Water Treatment ◽  
Large Range ◽  
Physical Constraints ◽  
Treatment Processes ◽  
Water Treatment Plants ◽  
Hydraulic Behaviour ◽  
Computational Fluid Dynamics Cfd ◽  
Secondary Settling

Until recently, water treatment plants were frequently designed solely on the basis of the biological, chemical and physical constraints of processes. Nowadays, the use of Computational Fluid Dynamics (CFD) software enables the dimensioning of water treatment processes by taking into account the real hydraulic behaviour of processes. That has be done for the Coliban Water Aqua 2000 project, which consists of the construction of three water treatment plants. The disinfection performance of three ozone contactors were compared using the CFD software, Fluent. Moreover, the CFD application has been extended to a large range of water treatment processes in recent years. The paper presents several of these: flocculation tanks, UV reactors and secondary settling tanks.

Optimization of a Two-Fluid Hydrodynamic Model of Churn-Turbulent Flows

2009 ◽  
Author(s):  
Donna Post Guillen ◽  
Jonathan K. Shelley ◽  
Steven P. Antal ◽  
Elena A. Tselishcheva ◽  
Michael Z. Podowski ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Design Optimization ◽  
Turbulent Flows ◽  
Bubble Size ◽  
Hydrodynamic Model ◽  
Model Parameters ◽  
Interfacial Forces ◽  
Closure Models ◽  
Size Groups

A hydrodynamic model of two-phase, churn-turbulent flows is being developed using the computational multiphase fluid dynamics (CMFD) code, NPHASE-CMFD. The numerical solutions obtained by this model are compared with experimental data obtained at the TOPFLOW facility of the Institute of Safety Research at the Forschungszentrum Dresden-Rossendorf. The TOPFLOW data is a high quality experimental database of upward, co-current air-water flows in a vertical pipe suitable for validation of computational fluid dynamics (CFD) codes. A five-field CMFD model was developed for the continuous liquid phase and four bubble size groups using mechanistic closure models for the ensemble-averaged Navier-Stokes equations. Mechanistic models for the drag and non-drag interfacial forces are implemented to include the governing physics to describe the hydrodynamic forces controlling the gas distribution. The closure models provide the functional form of the interfacial forces, with user defined coefficients to adjust the force magnitude. An optimization strategy was devised for these coefficients using commercial design optimization software. This paper demonstrates an approach to optimizing CMFD model parameters using a design optimization approach. Computed radial void fraction profiles predicted by the NPHASE-CMFD code are compared to experimental data for four bubble size groups.

Effect of Swirl Number on Combustion Characteristics in a Natural Gas Diffusion Flame

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
İlker Yılmaz
Keyword(s):  
Fluid Dynamics ◽  
Natural Gas ◽  
Diffusion Flame ◽  
Recirculation Zone ◽  
Reaction Scheme ◽  
Gas Diffusion ◽  
Combustion Characteristics ◽  
Model Parameters ◽  
Swirl Number ◽  
Simulation Results

This paper presents the effect of swirl number on combustion characteristics such as temperature, velocity, gas concentrations in a natural gas diffusion flame. Numerial simulations carried out using the commercial computational fluid dynamics (CFD) code, Fluent by choosing appropriate model parameters. The combustion reaction scheme in the flame region was modeled using eddy dissipation model with one step global reaction scheme. A standard k-ε turbulence model for turbulent closure and P-I radiation model for flame radiation inside the combustor is used in the numerical simulations. In order to investigate the swirling effect on the combustion characteristics, seven different swirl numbers including 0; 0.1; 0.2; 0.3; 0.4; 0.5; and 0.6 are used in the study. Numerical results are validated and compared with the published experimental and simulation results. A good consistency is found between the present results and those published measurement and simulation results in the available literature. The results shown that the combustion characteristics such as the flame temperature, the gas concentrations including CO2, H2O, O2, and CH4 are strongly affected by the swirl number. Depending on the degree of swirl, the fluid dynamics behavior of natural gas diffusion flame including axial velocity distribution, central recirculation zone (CTRZ) and external recirculation zone (ETRZ) were also strongly affected.

Computational fluid dynamics modelling of the visible light photocatalytic oxidation process of toluene for indoor building materials with locally doped titanium dioxide

2019 ◽  
Vol 29 (2) ◽  
pp. 163-179 ◽  
Author(s):  
Koki Nakahara ◽  
Mahbubul Muttakin ◽  
Kiyoshi Yamamoto ◽  
Kazuhide Ito
Keyword(s):  
Fluid Dynamics ◽  
Mathematical Model ◽  
Computational Fluid Dynamics ◽  
Titanium Dioxide ◽  
Gas Phase ◽  
Photocatalytic Oxidation ◽  
Building Materials ◽  
Model Parameters ◽  
Surface Boundary ◽  
Cfd Analysis

Computational fluid dynamics (CFD) is one of the promising methods that can precisely predict non-uniform air flow and contaminant distribution in indoor environments. The overarching objective of this study was to develop a mathematical model for describing the photocatalytic oxidation (PCO) reaction mechanism of gas phase toluene with titanium dioxide (TiO2)-bound indoor building materials. This mathematical model was developed based on Langmuir-Hinshelwood type kinetics and for the integration with CFD simulations as a wall surface boundary condition. The effects of gas phase toluene concentration, illuminance and humidity on the toluene oxidation reaction were considered with locally TiO2-doped building materials. Especially, humidity dependence was explicitly integrated as a competitive adsorption model between toluene and water vapour. Moreover, surface compositions of TiO2 and the substrate (ceramic tile in this study), and the physical adsorption properties of those materials, were modelled and integrated into the mathematical model. A 0.02 m3 chamber experiment and adsorption isotherm measurements were conducted to identify the model parameters. CFD analysis was carried out according to experimental scenarios, and an optimization procedure for the model parameters was proposed for their application as the boundary conditions in the CFD analysis.

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