Impact of the Time Step in DEM Simulations on Granular Mixing Properties
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The document discusses how the time step in DEM (discrete element method) simulations affects granular mixing properties. It finds that the time step strongly influences velocity profiles and fluctuations, with larger time steps producing non-physical results. Even with time steps an order of magnitude below the critical value, there is still lack of convergence. The implications are that the critical time step should be used as a guide for ensuring solution consistency in DEM simulations of dynamical mixing systems.
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This document discusses challenges with scaling up processes from lab to production scale. It argues that problems are often approached as mixing issues when they may be more fundamentally problems of heat, mass, or momentum transfer. Two key observations are made. First, maintaining similar hydrodynamics is difficult at large scale, limiting transfer, and the solution is not always just improving mixing. Second, too much money and time is spent on computational fluid dynamics (CFD) models rather than doing appropriate experiments to determine practical operating parameters. Alternative approaches are proposed, such as using non-intrusive measurement techniques and extracting dynamic information from time-series data to characterize processes without relying solely on determining velocity fields.
Comparison of MOC and Lax FDE for simulating transients in Pipe Flows
This document compares the method of characteristics (MOC) and Lax finite difference explicit (Lax FDE) methods for simulating transients in pipe flows. It develops numerical models using both MOC and Lax FDE to discretize the governing equations of fluid flow through a pipe. The models are implemented using data from a previous study to simulate pressure and discharge changes after rapid valve closure. The results show that Lax FDE provides more damping of pressure and discharge fluctuations compared to MOC. Therefore, the document concludes that Lax FDE is a better numerical method for calculating hydraulic transients in pipes.
CacreFluidSolid.pptx
This document summarizes the key points in developing mathematical models for solid-liquid reaction kinetics:
1) Traditional models based on ideal particle geometries are often inadequate and a general shape factor approach can better account for real particle morphologies.
2) The reaction mechanism should be considered from chemical principles rather than just empirical rate expressions.
3) Particle size distributions must be accounted for to avoid drawing incorrect conclusions about reaction mechanisms.
4) Sensitivity analysis is important to determine how well model parameter values are defined by experimental data.
Ab experiments of fluid flow in polymer microchannel
1) The document discusses a computational fluid dynamics (CFD) study of droplet formation in a microfluidic cross-junction when the dispersed phase is a non-Newtonian fluid.
2) Simulations were performed using OpenFOAM to model droplet formation of xanthan gum solutions (shear thinning) in canola oil (Newtonian) across varying xanthan concentrations.
3) The results show that increasing the xanthan concentration leads to longer thread detachment times, wider thread widths at the junction entrance, and smaller dimensionless droplet diameters, demonstrating the impact of shear thinning behavior on droplet formation.
Unit 6 Dimensional Analysis.pdf Unit 5 Open Channel flow
Unit 5 Open Channel flowUnit 5 Open Channel flowUnit 5 Open Channel flowUnit 5 Open Channel flowUnit 5 Open Channel flowUnit 5 Open Channel flowUnit 5 Open Channel flowUnit 5 Open Channel flow
2018 - CFD simulation of fluid dynamic and biokinetic processes within activa...
This document describes a CFD simulation of fluid dynamics and biokinetic processes within an activated sludge reactor (ASR) operating under intermittent aeration. The CFD model considers fluid dynamics, oxygen transfer, and biological processes described by Activated Sludge Model No. 1 (ASM1). The model is used to evaluate two different aeration system configurations for an ASR in terms of their ability to satisfy effluent requirements with minimum energy consumption. Results show that modifying the air diffuser layout can improve energy consumption by 2.8%, and reducing the air flow rate per diffuser improves energy consumption by 14.5%. The model provides insight into aeration inefficiencies within ASRs.
Ppt HADJI.pptx
The document presents a thesis submitted by Hadji Mohammed Salah on optimizing the hydraulic performance of center pivot irrigation systems. It discusses conducting field experiments on existing center pivot systems in Algeria to evaluate their performance and optimize sprinkler spacing and sizing using a genetic algorithm model. The objectives are to identify configurations that improve irrigation uniformity, which increases crop productivity and quality. Results show the optimized configurations significantly improved the uniformity coefficient compared to traditional systems.
dimensional analysis
This document discusses dimensional analysis and its applications in fluid mechanics. Dimensional analysis uses dimensions and units to develop dimensionless parameters called Pi terms that relate variables in a system. The Buckingham Pi theorem states that any equation with k variables can be written in terms of k-r independent Pi terms, where r is the minimum number of fundamental dimensions needed to describe the variables. Examples show how to identify the relevant Pi terms for problems and how these terms allow experimental data with different scales to be correlated through a single relationship. Dimensional analysis and similitude are useful for modeling prototypes from scaled down models when the key dimensionless groups match between the two.
CFD Lecture (8/8): CFD in Chemical Systems
Above lecture can be downloaded from www.zeusnumerix.com
The presentation aims at explaining to the user the simulations that happen in the chemical industry. These simulations are characterized by the chemical reactions, mixing of fluids, particle flow etc. The standard NS equations requirement introduction of source terms and special methods for CFD simulations and these have been introduced.
Liquid chromatography still striving for high efficiency
The document discusses liquid chromatography and approaches to improve its efficiency. It provides an overview of the chromatographic process and factors that affect column efficiency such as mobile phase velocity, temperature, column length, particle size. Existing approaches to improve efficiency include high temperature liquid chromatography, monolithic stationary phases, fused-core particles, and sub-2-micron totally porous particles. Overall miniaturization shows potential for future efficiency gains in liquid chromatography.
A first order hyperbolic framework for large strain computational computation...
An explicit Total Lagrangian momentum-strains mixed formulation in the form of a system of first order hyperbolic conservation laws, has recently been published to overcome the shortcomings posed by the traditional second order displacement based formulation when using linear tetrahedral elements.
The formulation, where the linear momentum and the deformation gradient are treated as unknown variables, has been implemented within the cell centred finite volume environment in OpenFOAM. The numerical solutions have performed extremely well in bending dominated nearly incompressible scenarios without the appearance of any spurious pressure modes, yielding an equal order of convergence for velocities and stresses.
To have more insight into my research, please visit my website:
http://jibranhaider.weebly.com/
Natural Convection Heat Transfer of Viscoelastic Fluids in a Horizontal Annulus
a detailed discussion of the results in terms of the streamline profiles, isotherm contours, distribution of local Nusselt number, variation of velocity components, etc., is also presented. Finally, from an application standpoint, a simple correlation for the average Nusselt number is presented, which can be used for the interpolation of the present results for the intermediate values of the governing parameters in a new application.
Smooth Particle Hydrodynamics for Bird-Strike Analysis Using LS-DYNA
In this second of a three-paper sequence, we developed a standard work using the Smoothed Particle Hydrodynamic (SPH) approach in LS-DYNA and compared the results against those the Lagrangian model and available experimental results. First, the SPH model was validated against a one-dimensional beam centered impact’s analytical solution and the results are within 3% error. Bird-strike events were divided into three separate problems: frontal impact on rigid flat plate, 0 and 30 deg impact on deformable tapered plate. The bird model was modeled as a cylindrical fluid. We successfully identified the most influencing parameters when using SPH in LS-DYNA. The case for 0 deg tapered plate impact shows little bird-plate interaction because the bird is sliced in two parts and the results are within 5% difference from the test data available in the literature, which is an improvement over the Lagrangian model. Conclusion: The developed SPH approach is suitable for bird-strike events within 10% error.
Hmtc1300663
Natural convection in a differentially heated cavity plays a
major role in the understanding of flow physics and heat
transfer aspects of various applications. Parameters such as
Rayleigh number, Prandtl number, aspect ratio, inclination
angle and surface emissivity are considered to have either
individual or grouped effect on natural convection in an
enclosed cavity. In spite of this, simultaneous study of these
parameters over a wide range is rare. Development of
correlation which helps to investigate the effect of the large
number and wide range of parameters is challenging. The
number of simulations required to generate correlations for
even a small number of parameters is extremely large. Till
date there is no streamlined procedure to optimize the number
of simulations required for correlation development.
Therefore, the present study aims to optimize the number of
simulations by using Taguchi technique and later generate
correlations by employing multiple variable regression
analysis. It is observed that for a wide range of parameters,
the proposed CFD-Taguchi-Regression approach drastically
reduces the total number of simulations for correlation
generation.
Dynamic Process Modeling
The document provides an overview of general process modeling frameworks and approaches. It discusses theoretical, empirical and semi-empirical models. Theoretical models are derived from first principles like balances and property models, empirical models fit data to map inputs to outputs, and semi-empirical models use first principles and parameter fitting. It also describes types of process models like lumped vs distributed, steady state vs transient, and single vs multi-stage models. Key modeling concepts discussed include degrees of freedom, mass, energy and momentum balances, and modeling of flows, reactions and heat transfer.
Dynamic Process Modeling
The document provides an overview of general process modeling frameworks and approaches. It discusses theoretical, empirical and semi-empirical models. Theoretical models are derived from first principles like balances and property models, empirical models fit data to map inputs to outputs, and semi-empirical models use first principles and parameter fitting. It also describes types of process models like lumped vs distributed, steady state vs transient, and single vs multi-stage models. Key modeling concepts discussed include balances, degrees of freedom analysis, and modeling flows, reactions and heat transfer.
Paper id 36201531
This document compares the results of modeling toxic gas dispersion (hydrogen sulfide) using the CFD model PANACHE and the Gaussian plume model PHAST under different atmospheric conditions. The study found that PHAST consistently predicted higher concentrations than PANACHE due to not accounting for plant geometry and turbulence. Dispersion at stable conditions gave higher concentrations than neutral conditions. While PHAST is conservative, PANACHE more accurately models the plant scenario by considering geometry and turbulence. The maximum concentrations at 700m were below safety limits.
Aldo Fiori
This document summarizes lessons learned from physically-based hydrological models. It discusses how distributed hydrological models can be useful tools for understanding processes like streamflow generation, solute transport, and groundwater-surface water interactions through detailed numerical simulations. While complex models may not be suited for predictions, they can serve as virtual laboratories for testing hypotheses. 2D and 3D simulations discussed provide insights into mechanisms of streamflow generation, the old water contribution to streams, and the impact of heterogeneity on solute transport. Simpler models that are less realistic but more generalizable, like the Boussinesq model, can also provide useful understanding when calibrated against more complex simulations. The document evaluates the performance of lumped transport models representing
A Comprehensive Study of Multiphase Flow through Annular Pipe using CFD Approach
This study analyzes 3D fluid flow through the annular pipeline with multiphase fluids using CFD simulation. Eulerian Model with Reynolds Stress Model (RSM) turbulence closure is adopted to analyze multiphase fluid flow. The results are validated with existing experimental data and empirical correlations. A robust simulation model is developed that can be used further for different applied cases. Geometry and boundary conditions of flow are adopted from experimental works to validate the simulation. The sensitivity analysis is also conducted to observe the flow characteristics. Fluid inlet velocity of distinct phases, inner pipe rotation and eccentricity are used as input or independent parameters and pressure gradient and local concentration profile at different sections of geometry are the primary output parameter to analyze. The key results show that changing inner pipe rotation and eccentricity have a significant impact on output pressure and local particle distribution which eventually help to find a way out from particle blockage. This study would help the oil and gas industry in designing their pipelines.
Similar to Impact of the Time Step in DEM Simulations on Granular Mixing Properties (20)
Pore scale dynamics and the interpretation of flow processes - Martin Blunt, ...
Pore scale dynamics and the interpretation of flow processes - Martin Blunt, ...
Comparison of MOC and Lax FDE for simulating transients in Pipe Flows
Comparison of MOC and Lax FDE for simulating transients in Pipe Flows
Ab experiments of fluid flow in polymer microchannel
Ab experiments of fluid flow in polymer microchannel
Unit 6 Dimensional Analysis.pdf Unit 5 Open Channel flow
Unit 6 Dimensional Analysis.pdf Unit 5 Open Channel flow
2018 - CFD simulation of fluid dynamic and biokinetic processes within activa...
2018 - CFD simulation of fluid dynamic and biokinetic processes within activa...
Liquid chromatography still striving for high efficiency
Liquid chromatography still striving for high efficiency
A first order hyperbolic framework for large strain computational computation...
A first order hyperbolic framework for large strain computational computation...
Natural Convection Heat Transfer of Viscoelastic Fluids in a Horizontal Annulus
Natural Convection Heat Transfer of Viscoelastic Fluids in a Horizontal Annulus
Smooth Particle Hydrodynamics for Bird-Strike Analysis Using LS-DYNA
Smooth Particle Hydrodynamics for Bird-Strike Analysis Using LS-DYNA
A Comprehensive Study of Multiphase Flow through Annular Pipe using CFD Approach
A Comprehensive Study of Multiphase Flow through Annular Pipe using CFD Approach
Impact of the Time Step in DEM Simulations on Granular Mixing Properties
- 13. Mean velocity profiles H=5E-5s H=1E-5s H=2E-6s H=1E-6s
- 14. Fluctuating velocity field dt=5 E -5 dt=3.33 E -7