scholarly journals Partial integration of ADM1 into CFD: understanding the impact of diffusion on anaerobic digestion mixing

2020 ◽  
Vol 81 (8) ◽  
pp. 1658-1667 ◽  
Author(s):  
Yohannis Mitiku Tobo ◽  
Usman Rehman ◽  
Jan Bartacek ◽  
Ingmar Nopens
Keyword(s):  
Anaerobic Digestion ◽  
Homogeneous Distribution ◽  
Cfd Model ◽  
Homogeneity Analysis ◽  
Cfd Models ◽  
Mode Of Operation ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
Proper Performance ◽  
Partial Integration

Abstract Sufficient mixing is crucial for the proper performance of anaerobic digestion (AD), creating a homogeneous distribution of soluble substrates, biomass, pH, and temperature. The opaqueness of the sludge and mode of operation make it challenging to study AD mixing experimentally. Therefore, hydrodynamics modelling employing computational fluid dynamics (CFD) is often used to investigate this mixing. However, CFD models mostly do not include biochemical reactions and, hence, ignore the effect of diffusion-induced transport on AD heterogeneity. The novelty of this work is the partial integration of Anaerobic Digestion Model no. 1 (ADM1) into the CFD model. The aim is to better understand the effect of advection–diffusion transport on the homogenization of soluble substrates and biomass. Furthermore, AD homogeneity analysis in terms of concentration distribution is proposed rather than the traditional velocity distributions. The computed results indicate that including diffusion-induced transport affects the homogeneity of AD.

Impact of Heat Transfer on Contaminant Dispersion in a Public Building

2006 ◽  
Author(s):  
Sue Ellen Haupt ◽  
Robert F. Kunz ◽  
L. Joel Peltier ◽  
James J. Dreyer ◽  
Howard J. Gibeling
Keyword(s):  
Thermal Effects ◽  
Building Materials ◽  
Time Of Day ◽  
Thermal Coupling ◽  
Cfd Model ◽  
Thermal Heating ◽  
Contaminant Dispersion ◽  
Cfd Models ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

Computational fluid dynamics (CFD) models are effective at predicting dispersion of contaminants in or near a building. It is well known that thermal effects impact the flow around and within structures. This study assesses the importance of time of day, building materials, sky cover, etc. on the local thermal heating of a building. All these features affect the buoyancy, and thus, the resulting flow and dispersion about and inside a building. This study examines that impact through including full thermal coupling with flow calculations for an environmentally friendly building, including thermal radiation, conduction, and convection effects with a CFD model for both the interior and exterior of a building. The emphasis here is on simulating the impact of heating on contaminant dispersion.

scholarly journals A Study on Microscale Wind Simulations with a Coupled WRF–CFD Model in the Chongli Mountain Region of Hebei Province, China

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 731
Author(s):  
Shaohui Li ◽  
Xuejin Sun ◽  
Shan Zhang ◽  
Shijun Zhao ◽  
Riwei Zhang
Keyword(s):  
Wind Field ◽  
Complex Terrain ◽  
Wrf Model ◽  
Mountain Region ◽  
Weather Research And Forecasting ◽  
Cfd Model ◽  
Improved Method ◽  
Comprehensive Understanding ◽  
Cfd Models ◽  
Computational Fluid Dynamics Cfd

To ensure successful hosting of the 2022 Olympic Winter Games, a comprehensive understanding of the wind field characteristics in the Chongli Mountain region is essential. The purpose of this research was to accurately simulate the microscale wind in the Chongli Mountain region. Coupling the Weather Research and Forecasting (WRF) model with a computational fluid dynamics (CFD) model is a method for simulating the microscale wind field over complex terrain. The performance of the WRF-CFD model in the Chongli Mountain region was enhanced from two aspects. First, as WRF offers multiple physical schemes, a sensitivity analysis was performed to evaluate which scheme provided the best boundary condition for CFD. Second, to solve the problem of terrain differences between the WRF and CFD models, an improved method capable of coupling these two models is proposed. The results show that these improvements can enhance the performance of the WRF-CFD model and produce a more accurate microscale simulation of the wind field in the Chongli Mountain region.

3-D periodic CFD model of the heating system in a coke oven battery

2014 ◽  
Vol 24 (4) ◽  
pp. 891-906 ◽  
Author(s):  
Jacek Smolka ◽  
Adam Fic ◽  
Andrzej J. Nowak ◽  
Ludwik Kosyrczyk
Keyword(s):  
Coke Oven ◽  
Heating System ◽  
Cfd Model ◽  
Gas Combustion ◽  
Content Type ◽  
Cfd Models ◽  
Steady State Operation ◽  
Proposed Model ◽  
Computational Fluid Dynamics Cfd ◽  
Periodic Heat

Purpose – The purpose of this paper is to develop a 3-D fully transient numerical model of the heat and fluid flow associated with the chemical reactions that occur in the heating system of the coke oven battery. As a result, the model can be used to provide data for the control system of the battery to reduce energy consumption and emissions and to obtain a product of the desired quality. Design/methodology/approach – In the proposed model, an accurate representation of the heating flue geometry, the volumetric heat sources as a result of the coke oven gas combustion, the temperature- and mole fraction-dependent properties of the gases were taken into account. The most important part of the model was the unsteady boundary condition definition that allowed the modeling of the periodic heat delivery to the two oven heating walls, both in the coking and the reversion cycles. Findings – The temperatures obtained using the computational fluid dynamics (CFD) model showed the same pattern of temperature variations as that observed in the experiments. It was also found that the quality of the temperature variation predictions was highly dependent on the radiation model settings. Originality\value – The CFD models available in the literature describe the steady or pseudo-steady state operation of the heating system of the coke oven battery. The model developed in this work fully reflects the unsteady character of this heating system. Moreover, the proposed model is prepared for coupling with a model of the coking process that occurs in the two neighboring coke oven chambers.

scholarly journals Computational modeling of fire safety in metro-stations

2021 ◽  
Author(s):  
Philip McKeen
Keyword(s):  
Fire Safety ◽  
Performance Based Design ◽  
Cfd Model ◽  
Fire Dynamics ◽  
Evacuation Modeling ◽  
Fire Dynamics Simulator ◽  
Cfd Models ◽  
Smoke Spread ◽  
Modeling Software ◽  
Computational Fluid Dynamics Cfd

This research investigates and attempts to quantify the hazards associated with fire in metrostations. The use of numerical simulations for the analysis of fire safety within metro-stations allows for the prediction and analysis of hazards within the built environment. Such approaches form the growing basis of performance based design (PBD), which can optimize design solutions. The simulations utilize Fire Dynamics Simulator (FDS), a Computational Fluid Dynamics (CFD) model and Pathfinder, an evacuation modeling software. The safety of underground metro-stations is analyzed through the simulation of smoke spread and egress modelling. CFD models of TTC’s Union Station and TransLink’s Yaletown Station are developed to allow for simulations of smoke spread scenarios. These models are evaluated in regards to the preservation of tenability and influence on the Available Safe Egress Time (ASET). The egress of metro-stations is modelled and analyzed to determine the Required Safe Egress Time (RSET).

scholarly journals An Investigation of the Flow Distribution Inside a Radial Sidestream Inlet of a Centrifugal Compressor

2000 ◽  
Author(s):  
Zheji Liu ◽  
D. Lee Hill ◽  
Gary Colby
Keyword(s):  
Test Data ◽  
Centrifugal Compressor ◽  
Flow Distribution ◽  
Production Test ◽  
Cfd Model ◽  
Cfd Models ◽  
Multi Stage ◽  
Final Design ◽  
Computational Fluid Dynamics Cfd ◽  
Return Channel

A radial sidestream inlet is commonly utilized in multi-stage centrifugal compressors to introduce additional gas into the mid-stage of the compressor. The flow distribution after the junction of the sidestream and the main return channel of the upstream stage can significantly affect the performance of the next stage. In this study, the mixing between the fluid from the sidestream component and the fluid from the main return channel was investigated numerically using Computational Fluid Dynamics (CFD). A variety of CFD models of different geometry, different boundary conditions, and different grid density were developed to analyze the uniformity of the flow entering the impeller of the next stage. The flow distribution difference between the sidestream CFD model and the CFD model with the sidestream coupled to the main return channel suggests that both the return channel and the sidestream have to be modeled together to get meaningful results. The results of this effort were used in conjunction with production test data to help resolve a performance shortfall of a multi-stage centrifugal compressor with sidestream injection. The test data from the final design is also provided to show the resulting improvement in head rise.

scholarly journals Measurements of Discharge through a Pump-Turbine in Both Flow Directions Using Volumetric Gauging and Pressure-Time Methods

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4706
Author(s):  
Adam Adamkowski ◽  
Waldemar Janicki ◽  
Mariusz Lewandowski
Keyword(s):  
Operation Mode ◽  
Detailed Comparison ◽  
Pump Operation ◽  
Special Procedure ◽  
Pressure Time ◽  
Mode Of Operation ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Directions ◽  
The Impact ◽  
Low Uncertainty

This article presents the original procedures for measuring the flow rate using the pressure-time and the volumetric gauging method in the case of performance tests of a reversible hydraulic machine in either turbine or pump modes of operation. Achieving the lowest possible measurement uncertainty was one of the basic conditions during implemented machine tests. It was met using appropriate measuring procedures and high-class measuring equipment. Estimation of the uncertainty for both methods was made on the basis of an analysis consistent with current requirements in this respect. The pressure-time method was supplemented by the computational fluid dynamics (CFD) analysis that allowed reducing the impact of the pipeline complex irregular geometry on the uncertainty of flow measurement. Appropriate modifications of the calculation procedure enabled accurate measurements of flow during the pump mode of operation of the tested machine as well. The volumetric gauging method, thanks to a special procedure used for accurate measurement of the water level in the upper reservoir of the power plant, allowed measuring the discharge through the tested reversible machine with very low uncertainty. The obtained results allowed for a detailed comparison and mutual verification of the methods used to measure the discharge of the tested reversible machine in both modes of its operation. The most possible causes of obtained results are discussed and summarized in the paper. The need for further research was pointed out to explain the differences obtained and their influence on the accuracy of discharge measurement using the pressure-time method in pump operation mode.

scholarly journals Computational modeling of fire safety in metro-stations

2021 ◽  
Author(s):  
Philip McKeen
Keyword(s):  
Fire Safety ◽  
Performance Based Design ◽  
Cfd Model ◽  
Fire Dynamics ◽  
Evacuation Modeling ◽  
Fire Dynamics Simulator ◽  
Cfd Models ◽  
Smoke Spread ◽  
Modeling Software ◽  
Computational Fluid Dynamics Cfd

This research investigates and attempts to quantify the hazards associated with fire in metrostations. The use of numerical simulations for the analysis of fire safety within metro-stations allows for the prediction and analysis of hazards within the built environment. Such approaches form the growing basis of performance based design (PBD), which can optimize design solutions. The simulations utilize Fire Dynamics Simulator (FDS), a Computational Fluid Dynamics (CFD) model and Pathfinder, an evacuation modeling software. The safety of underground metro-stations is analyzed through the simulation of smoke spread and egress modelling. CFD models of TTC’s Union Station and TransLink’s Yaletown Station are developed to allow for simulations of smoke spread scenarios. These models are evaluated in regards to the preservation of tenability and influence on the Available Safe Egress Time (ASET). The egress of metro-stations is modelled and analyzed to determine the Required Safe Egress Time (RSET).

scholarly journals Hydrodynamic impact and power production of tidal turbines in a storm surge barrier

2020 ◽  
Vol 3 (3) ◽  
pp. 127-136
Author(s):  
Thomas O'Mahoney ◽  
Anton De Fockert ◽  
Arnout C. Bijlsma ◽  
Pieter De Haas
Keyword(s):  
Storm Surge ◽  
Energy Production ◽  
Field Experiments ◽  
Turbine Blades ◽  
Cfd Model ◽  
Hydrodynamic Impact ◽  
Tidal Turbines ◽  
Gate Opening ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

To estimate the impact on energy production and environment of tidal turbines placed in the Eastern Scheldt Storm Surge Barrier a Computational Fluid Dynamics (CFD) study has been carried out on the additional head differences induced by the turbines. The CFD model focusses on a single gate opening of the Storm Surge Barrier and includes half of the adjoining gates on either side. In this 40 m wide Gate a 1.2 MW array existing of five Tocardo T2 tidal turbines has been installed as part of a demonstration project in 2015. Transient computations of the barrier with and without the turbine array were carried out for a range of quasi stationary tidal phases. The turbines are resolved in detail as rotating equipment: real-time rotation of the turbine blades (involving the displacement of the mesh nodes in an unsteady setting) is implemented, and torque and thrust for the prescribed speed of rotation is provided as output. The results for velocity, power and thrust are compared with field experiments to validate the model. Based on these computations an estimate of the effect of turbines on the discharge capacity of the storm surge barrier is given. This information will be used to parameterize the tidal turbines in the far-field hydrodynamic model of Eastern Scheldt estuary for the ultimate assessment of the effect of tidal turbines on energy production and on the environment.

Evaluation of flow hydrodynamics in a pilot-scale dissolved air flotation tank: a comparison between CFD and experimental measurements

2015 ◽  
Vol 72 (7) ◽  
pp. 1111-1118 ◽  
Author(s):  
B. Lakghomi ◽  
Y. Lawryshyn ◽  
R. Hofmann
Keyword(s):  
Pilot Scale ◽  
Solid Particles ◽  
Cfd Model ◽  
Two Phase ◽  
Dissolved Air Flotation ◽  
Cfd Models ◽  
Three Phase ◽  
Computational Fluid Dynamics Cfd ◽  
Air Flotation ◽  
Dissolved Air

Computational fluid dynamics (CFD) models of dissolved air flotation (DAF) have shown formation of stratified flow (back and forth horizontal flow layers at the top of the separation zone) and its impact on improved DAF efficiency. However, there has been a lack of experimental validation of CFD predictions, especially in the presence of solid particles. In this work, for the first time, both two-phase (air–water) and three-phase (air–water–solid particles) CFD models were evaluated at pilot scale using measurements of residence time distribution, bubble layer position and bubble–particle contact efficiency. The pilot-scale results confirmed the accuracy of the CFD model for both two-phase and three-phase flows, but showed that the accuracy of the three-phase CFD model would partly depend on the estimation of bubble–particle attachment efficiency.

Profiling and modelling of thermal changes in a large waste stabilisation pond

2005 ◽  
Vol 51 (12) ◽  
pp. 163-172 ◽  
Author(s):  
D.G. Sweeney ◽  
J.B. Nixon ◽  
N.J. Cromar ◽  
H.J. Fallowfield
Keyword(s):  
Wind Shear ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Prevailing Wind ◽  
Cfd Model ◽  
Thermal Changes ◽  
Thermal Profiling ◽  
Computational Fluid Dynamics Cfd ◽  
High Degree ◽  
The Impact

A thermal profiling study was undertaken at four depths at each of nine sites, and at the inlets and outlets of a large waste stabilisation pond (WSP). Results were collected simultaneously using a network of 42 thermistors and dataloggers. Profiles at each site were categorised as either “stratified” or “unstratified”, and persistence analysis was used to determine the frequency and persistence of stratification events at each of the nine sites. Stratification was found to persist most strongly at the site furthest upwind in the WSP, with respect to prevailing wind during the study, leading to the conclusion that stratification induced short-circuiting will be greatest in this region of the WSP. A computational fluid dynamics (CFD) model was constructed of the WSP, including an energy balance to predict the bulk stratification gradient in the pond. Environmental conditions and WSP inlet temperature during one day in June 2001 were used as boundary conditions. The pond thermal profiles measured during the profiling study, together with outlet temperature during the day, were used to validate the CFD model results. The model predicted mean pond temperature with a high degree of accuracy (r2=0.92). However it was evident that even modest winds (≥1.5 m/s) partially broke down stratification, leading to poor prediction of the gradient by the CFD model, which did not directly account for the impact of wind shear stress on mixing in the WSP.

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