Study of Two-Phase Nonlinear Advection Dispersion Model for Displacement Washing of Porous Particles Using OCFE with Lagrangian Basis

A numerical algorithm is developed for a detailed 3D simulation of the two-phase flow field in fluid-energy mills used for pulverization and drying of fossil fuels in large power plants. The gas phase equations are solved using finite differences and the control volume method, whereas a Lagrangian formulation with a stochastic particle dispersion model is adopted for the particulate phase. Fluid-particle interaction is taken into account to calculate the mass, momentum, and heat transfer between phases. Advanced numerical techniques for partially-blocked cells and local grid refinement have been utilized to achieve an accurate representation of the domain geometry and to enhance the accuracy of the results. Particle collisions, fragmentation mechanism, and moisture evaporation are simulated by corresponding models, whereas the special treatment employed for the rotating fan region provides the capability to solve the two-phase flow simultaneously in the entire rotating and nonrotating mill domain. The flow and the operation characteristics of a recently developed lignite mill are measured, and the numerical algorithm is used to predict the mill performance under various inlet profiles of the fuel mass flow rate. The predicted results are reasonable, and in agreement with the available measurements and observations, thus offering a deeper insight into the complex dynamic and thermal behavior of the two-phase flow in the mill.

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An urban large-eddy-based dispersion model for marginal grid resolutions: CAIRDIO v1.0

10.5194/gmd-2020-313 ◽

2020 ◽

Author(s):

Michael Weger ◽

Oswald Knoth ◽

Bernd Heinold

Keyword(s):

Dynamic Models ◽

Numerical Models ◽

Dispersion Model ◽

Fluid Dynamic ◽

Horizontal Resolution ◽

Two Phase ◽

Data Set ◽

Wide Range ◽

Large Eddy ◽

Diffusive Interface

Abstract. The capability for high spatial resolutions is an important feature of accurate numerical models dedicated to simulate the large spatial variability of urban air pollution. On the one hand, the well established mesoscale chemistry transport models have their obvious short-comings attributed to their extensive use of paramterizations. On the other hand, obstacle resolving computational fluid dynamic models, while accurate, still often demand too high computational costs, to be applied on a regular and holistic basis. The major reason for the inflated numerical costs is the required horizontal resolution to meaningfully apply the obstacle discretization, which is most often based on boundary-fitted grids, like e.g. the marker-and-cell method. Here we present a large-eddy-simulation approach that uses diffusive obstacle boundaries, which are derived from a simplified diffusive interface approach for moving obstacles. The diffusive interface approach is well established in two-phase modeling, but to the author’s knowledge has not been applied in urban boundary layer simulations so far. Our dispersion model is capable of representing buildings over a wide range of spatial resolutions, including marginally coarse resolutions inaccessible for standard methods. This opens up a very promising opportunity for application of accurate air quality simulations and forecasts on entire mid-sized city domains. Furthermore, our approach is capable of incorporating the influence of the land orography by the additional optional use of terrain-following coordinates. We validated the dynamic core against a set of numerical benchmarks and a standard high-quality wind-tunnel data set for dispersion-model evaluation.

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An urban large-eddy-simulation-based dispersion model for marginal grid resolutions: CAIRDIO v1.0

Geoscientific Model Development ◽

10.5194/gmd-14-1469-2021 ◽

2021 ◽

Vol 14 (3) ◽

pp. 1469-1492

Author(s):

Michael Weger ◽

Oswald Knoth ◽

Bernd Heinold

Keyword(s):

Air Pollution ◽

Numerical Models ◽

Dispersion Model ◽

Urban Air Pollution ◽

Horizontal Resolution ◽

Diffuse Interface ◽

Grid Spacing ◽

Two Phase ◽

Wide Range ◽

Large Eddy

Abstract. The ability to achieve high spatial resolutions is an important feature for numerical models to accurately represent the large spatial variability of urban air pollution. On the one hand, the well-established mesoscale chemistry transport models have their obvious shortcomings due to the extensive use of physical parameterizations. On the other hand, obstacle-resolving computational fluid dynamics (CFD) models, although accurate, are still often too computationally intensive to be applied regularly for entire cities. The major reason for the inflated computational costs is the required horizontal resolution to meaningfully apply obstacle discretization, which is mostly based on boundary-fitted grids, e.g., the marker-and-cell method. In this paper, we present the new City-scale AIR dispersion model with DIffuse Obstacles (CAIRDIO v1.0), in which the diffuse interface method, simplified for non-moving obstacles, is incorporated into the governing equations for incompressible large-eddy simulations. While the diffuse interface method is widely used in two-phase modeling, this method has not been used in urban boundary-layer modeling so far. It allows us to consistently represent buildings over a wide range of spatial resolutions, including grid spacings equal to or larger than typical building sizes. This way, the gray zone between obstacle-resolving microscale simulations and mesoscale simulations can be addressed. Orographic effects can be included by using terrain-following coordinates. The dynamic core is compared against a standard quality-assured wind-tunnel dataset for dispersion-model evaluation. It is shown that the model successfully reproduces dispersion patterns within a complex city morphology across a wide range of spatial resolutions tested. As a result of the diffuse obstacle approach, the accuracy test is also passed at a horizontal grid spacing of 40 m. Although individual flow features within individual street canyons are not resolved at the coarse-grid spacing, the building effect on the dispersion of the air pollution plume is preserved at a larger scale. Therefore, a very promising application of the CAIRDIO model lies in the realization of computationally feasible yet accurate air-quality simulations for entire cities.

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Seasonal Variation of Drainage System in the Lower Ablation Area of a Monsoonal Temperate Debris-Covered Glacier in Mt. Gongga, South-Eastern Tibet

Water ◽

10.3390/w10081050 ◽

2018 ◽

Vol 10 (8) ◽

pp. 1050 ◽

Cited By ~ 3

Author(s):

Qiao Liu ◽

Shiyin Liu ◽

Wulong Cao

Keyword(s):

Seasonal Variation ◽

Dispersion Model ◽

Drainage System ◽

Hydrodynamic Dispersion ◽

Ablation Area ◽

Advection Dispersion ◽

Dye Tracer ◽

Eastern Tibet ◽

Glacier Ice ◽

Subglacial Drainage

Seasonal evolution of the subglacial drainage system in the lower ablation area of the Hailuogou glacier ice tongue were revealed by repeated dye tracer (Rhodamine WT) experiments during the 2009 ablation season. Between April and October, 18 dye tracer experiments were conducted by injecting the tracer at one location of the lower ablation area of the Hailuogou Glacier to diagnose the seasonal variation of the subglacial drainage system of this section of glacier ice tongue. Using a simple advection-dispersion model (ADM), the flow velocity, hydrodynamic dispersion coefficient, and degree of tracer spreading were deduced. Tracer transit velocity through the tested subglacial channel varied from 0.148 to 0.555 m s−1 during the 2009 ablation season. Dispersivity showed a relatively high value than that found at other glaciers, which varied between 27.05 and 287.49 m2 s−1. Seasonal changes of these indexes indicated that the subglacial drainage system of the lower ablation area of the Hailougou Glacier is a relatively stable existing system in the case of its longitudinal shape, whereas its hydraulic efficiency is low in the early and late ablation seasons and high during the middle of summer due to subglacial channel expansion.

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Numerical Solution of a 3-D Advection-Dispersion Model for Dissolved Oxygen Distribution in Facultative Ponds

E3S Web of Conferences ◽

10.1051/e3sconf/20183103006 ◽

2018 ◽

Vol 31 ◽

pp. 03006 ◽

Cited By ~ 1

Author(s):

Sunarsih ◽

Dwi P. Sasongko ◽

Sutrisno

Keyword(s):

Dissolved Oxygen ◽

Oxygen Concentration ◽

Dispersion Model ◽

Oxygen Distribution ◽

Dissolved Oxygen Concentration ◽

3 Dimensional ◽

Advection Dispersion ◽

Advection Diffusion Equation ◽

Advection Diffusion ◽

The Finite Difference Method

This paper describes a mathematical model for the dissolved oxygen distribution in the plane of a facultative pond with a certain depth. The purpose of this paper is to determine the variation of dissolved oxygen concentration in facultative ponds. The 3-dimensional advection-diffusion equation is solved using the finite difference method Forward Time Central Space (FTCS). Numerical results show that the aerator greatly affects the occurrence of oxygen concentration variations in the facultative pond in the certain depth. The concentration of dissolved oxygen decreases as the depth of the pond increases.

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Unsteady solute dispersion in small blood vessels using a two-phase Casson model

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2017.0427 ◽

2017 ◽

Vol 473 (2204) ◽

pp. 20170427 ◽

Cited By ~ 7

Author(s):

Jyotirmoy Rana ◽

P. V. S. N. Murthy

Keyword(s):

Blood Flow ◽

Dispersion Model ◽

Fluid Model ◽

Two Phase ◽

Small Arteries ◽

Solute Dispersion ◽

Small Vessels ◽

Significant Difference ◽

Casson Fluid Model ◽

Mean Concentration

This study explores the transport of a solute in an unsteady blood flow in small arteries with and without absorption at the wall. The Casson fluid model is suitable for blood flow in small vessels. Owing to the aggregation of red cells in the central region of the small vessels, a two-phase model is considered in this investigation. Using the generalized dispersion model (Sankarasubramanian & Gill 1973 Proc. R. Soc. Lond. A 333 , 115–132. (doi:10.1098/rspa.1973.0051)), the convection, dispersion and mean concentration of the solute are analysed at all times in small arteries of different radii. The effects of the yield stress, wall absorption, the amplitude of the fluctuating pressure gradient component, the peripheral layer thickness, the Womersley frequency parameter, the Schmidt number and the Peclet number on the dispersion process are discussed. A comparative study of solute dispersion among single- and two-phase fluid models is presented. For small vessels, a significant difference between these models is observed during the solute dispersion; however, this difference becomes insignificant for large vessels. The mean concentration of solute reduces with increasing radius of the vessels. The present investigation is more realistic for understanding the transportation process of drugs in blood flow in small arteries using the non-Newtonian fluid model.

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