scholarly journals Computational fluid dynamics simulation and parametric study of an open channel ultra-violet wastewater disinfection reactor

2014 ◽  
Vol 50 (1) ◽  
pp. 58-71 ◽  
Author(s):  
Rajib Kumar Saha ◽  
Madhumita Ray ◽  
Chao Zhang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Parametric Study ◽  
Open Channel ◽  
Ultra Violet ◽  
Dynamics Simulation ◽  
Inactivation Kinetics ◽  
Cfd Model ◽  
Particle Tracking Method ◽  
Numerical Predictions

The disinfection characteristics of an open channel ultra-violet (UV) disinfection reactor is investigated numerically. The computational fluid dynamics (CFD) model used in this study is based on the volume of fluid (VOF) method to capture the water–air interface. The Lagrangian particle tracking method is used to calculate the microbial particle trajectory and the discrete ordinate (DO) model is used to calculate the UV intensity field inside the reactor. A commercial CFD software package ANSYS FLUENT is used to solve the governing equations. Custom user defined functions (UDFs) are developed to calculate the UV doses. A post-processor is developed in MATLAB to implement the inactivation kinetics of the microbes. The post-processor provides the probabilistic dose distribution and reduction equivalent dose (RED) values achievable in the reactor. The numerical predictions are compared with available experimental data to validate the CFD model. A parametric study is performed to understand the effects of different parameters on disinfection performance of the reactor. The low/high dosed particle trajectories, which can provide an insight for hydraulic and optical characteristics of the reactor for possible design improvements, are identified.

Microscale Computational Fluid Dynamics Simulation for Wind Mapping Over Complex Topographic Terrains

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Ashkan Rasouli ◽  
Horia Hangan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Spatial Resolution ◽  
Three Dimensional ◽  
Dynamics Simulation ◽  
Scale Model ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Wide Range ◽  
Wind Mapping

Wind mapping is of utmost importance in various wind energy and wind engineering applications. The available wind atlases usually provide wind data with low spatial resolution relative to the wind turbine height and usually neglect the effect of topographic features with relatively large or sudden changes in elevation. Two benchmark cases are studied for computational fluid dynamics (CFD) model evaluation on smooth two-dimensional (2D) and three-dimensional (3D) hills. Thereafter, a procedure is introduced to build CFD model of a complex terrain with high terrain roughness heights (dense urban area with skyscrapers) starting from existing topography maps in order to properly extend the wind atlas data over complex terrains. CFD simulations are carried out on a 1:3000 scale model of complex topographic area using Reynolds averaged Navier–Stokes (RANS) equations along with shear stress transport (SST) k-ω turbulence model and the results are compared with the wind tunnel measurements on the same model. The study shows that CFD simulations can be successfully used in qualifying and quantifying the flow over complex topography consisting of a wide range of roughness heights, enabling to map the flow structure with very high spatial resolution.

Computational Fluid Dynamics Simulation of Syngas Nozzle of Gas Turbine for Syngas

2019 ◽  
Author(s):  
Bo Zhang ◽  
Ye Qin ◽  
Shaoping Shi ◽  
Shu Yan ◽  
Yanfei Mu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Natural Gas ◽  
Gas Turbine ◽  
Coal Gasification ◽  
Flame Stabilization ◽  
Combined Cycle ◽  
Dynamics Simulation ◽  
Cfd Model ◽  
Heating Value

Abstract Integrated Gasification Combined Cycle (IGCC) is a technology that integrates the coal gasification and combined cycle to produce electricity efficiently. Due to the fact that the heating value of syngas from coal gasification process is typically lower than that of the natural gas, the conventional gas turbine will have to be adapted for syngas. The nozzle adjustment is the key to the successful transformation since the ignition properties are different between syngas and natural gas which have totally different compositions. The nozzles suitable for natural gas have been prone to partially melting around the flame stabilization holes on sidewalls of the nozzle in real operation. Thus a computational fluid dynamics (CFD) model was constructed for the syngas nozzles as well as combustion chamber of the gas turbine for low heating value syngas to study the thermostability of the nozzle. The detailed structure of the syngas nozzle, the combustion characteristics of syngas, as well as the actual operation condition of the gas turbine were all employed in the CFD model to improve the simulation accuracy. The reason of partially melting of the nozzles suitable for natural gas can be attributed to that the syngas leaked from the flame stabilization holes into the mainstream air can quickly mix with air, adhere to the sidewalls of the nozzles and then ignite around the holes which result in temperatures high enough to melt the material of the nozzle around the holes through CFD simulation. Finally, a new structure of the syngas nozzle was proposed and validated by CFD simulations. The simulation result shows that the flames caused by the syngas leaked from the flame stabilization holes are no longer adhering to the nozzle sidewalls and local high temperature can be lowered by about 30% which will not be able to melt the nozzle material.

Computational Fluid Dynamics Simulation of the Transient Behavior of Liquid Loading in Gas Wells

2020 ◽  
Author(s):  
Mohamed Khaled ◽  
Mohammad Azizur Rahman ◽  
Ibrahim Hassan ◽  
Rasel A. Sultan ◽  
Rashid Hasan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Transient Behavior ◽  
Dynamics Simulation ◽  
Computational Time ◽  
Test Accuracy ◽  
Cfd Model ◽  
Hexahedral Mesh ◽  
Gas Wells ◽  
Liquid Loading

Abstract Liquid loading is one of the major flow assurance challenges in gas wells, causing production problems and reducing the ultimate recovery. Liquid loading is defined as the inability of a well to carry all the co-produced liquid up the tubing. This leads to liquid accumulation in the well resulting in increased bottomhole pressure and decline of gas flow rate. Although many studies have been performed on liquid loading phenomena, available models generally lack the ability to capture transient behavior of liquid loading in gas wells. We have developed a computational fluid dynamics (CFD) model using Ansys Fluent 19.1 R3 version to model the transient features of liquid loading. In this study, the CFD model is developed and validated with data from 42 meter long vertical pipe lab at Texas A&M University. The Eulerian multiphase approach combined with volume of fluid approach (VOF) - Multi-fluid VOF model with realizable k-Є turbulence closure is used to study the flow behavior. In addition, hexahedral mesh is utilized and compared to tetrahedron mesh to test accuracy and computational time. The developed CFD model has unique parameters combinations that shows an acceptable agreement with the experimental work. Model accuracy and computational time is improved by using hexahedral mesh. Liquid film flow reversal mechanism is expected to be the root cause of liquid loading in gas wells rather than droplet fall back mechanism. The CFD model captures the transition from one phase to another that is crucial for determining well end life. Model novelty is based on the ability to be a reliable predictive tool that can help in the remediation of liquid loading and give a precise representation of liquid loading transient behavior in gas wells.

Computational Fluid Dynamics Simulation of Steel Bars Cooling by Free Convection and Thermal Radiation

2015 ◽  
Vol 798 ◽  
pp. 170-174
Author(s):  
Paulo Henrique Terenzi Seixas ◽  
Paul Campos Santana Silva ◽  
Rudolf Huebner
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Thermal Radiation ◽  
Cfd Simulation ◽  
Dynamics Simulation ◽  
Cfd Model ◽  
Computational Fluid Dynamics Simulation ◽  
Slow Cooling ◽  
Steel Bars ◽  
Computational Fluid Dynamics Cfd

In this article, the pilling process of hot steel bars is analyzed. During the loading three bars are placed over a wood surface, after those other three are placed over the previous for two times with 5 minutes intervals between them.They are all subject to a slow cooling by thermal radiation and free convection.A Computational Fluid Dynamics (CFD) model to predict the temperature profile of them is developed. Comparison between the CFD simulation results and experimental data yielded an average difference in the bars temperature between -0.3oC and 3.5oC.

Numerical prediction of the performance of marine propellers using computational fluid dynamics simulation with transition-sensitive turbulence model

2018 ◽  
Vol 233 (2) ◽  
pp. 515-527 ◽  
Author(s):  
Mohamed M Helal ◽  
Tamer M Ahmed ◽  
Adel A Banawan ◽  
Mohamed A Kotb
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Turbulence Model ◽  
Numerical Models ◽  
Dynamics Simulation ◽  
Flow Transition ◽  
Transition Flow ◽  
Computational Fluid Dynamics Simulation ◽  
Marine Propellers ◽  
Numerical Predictions

Determining and understanding the performance characteristics of marine propellers by experiments is quite a complex and costly task. Numerical predictions using computational fluid dynamics simulations could be a valuable alternative provided that the laminar-to-turbulent transition flow effects are fundamentally understood with the suitable numerical models developed. Experience suggests that the use of classical turbulent flow models may lead to high discrepancies especially at low rotational speeds where the effects of fluid flow transition from the laminar to the turbulent state may influence the predicted propeller’s performance. This article proposes a complete and detailed procedure for the computational fluid dynamics simulation of non-cavitating flow over marine propellers using the “ k–kl–ω” transition-sensitive turbulence model. Results are evaluated by “ANSYS FLUENT 16” for the “INSEAN E779A” propeller. Comparisons against the fully turbulent standard “ k–ε” model and against experiments show improved agreement in way of flow transition zones at lower rotational speeds, that is, at low Reynolds numbers.

scholarly journals Computational Fluid Dynamics Simulation of Oxygen Seepage in Coal Mine Goaf with Gas Drainage

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Guo-Qing Shi ◽  
Mao-xi Liu ◽  
Yan-Ming Wang ◽  
Wen-Zheng Wang ◽  
De-Ming Wang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Spontaneous Combustion ◽  
Cfd Simulation ◽  
Economic Loss ◽  
Dynamics Simulation ◽  
Cfd Model ◽  
Public Attention ◽  
Gas Drainage ◽  
Mine Fires

Mine fires mainly arise from spontaneous combustion of coal seams and are a global issue that has attracted increasing public attention. Particularly in china, the closure of coal workfaces because of spontaneous combustion has contributed to substantial economic loss. To reduce the occurrence of mine fires, the spontaneous coal combustion underground needs to be studied. In this paper, a computational fluid dynamics (CFD) model was developed for coal spontaneous combustion under goaf gas drainage conditions. The CFD model was used to simulate the distribution of oxygen in the goaf at the workface in a fully mechanized cave mine. The goaf was treated as an anisotropic medium, and the effects of methane drainage and oxygen consumption on spontaneous combustion were considered. The simulation results matched observational data from a field study, which indicates CFD simulation is suitable for research on the distribution of oxygen in coalmines. The results also indicated that near the workface spontaneous combustion was more likely to take place in the upper part of the goaf than near the bottom, while further from workface the risk of spontaneous combustion was greater in the lower part of the goaf. These results can be used to develop firefighting approaches for coalmines.

Reaction Kinetics of Pressurized Entrained Flow Coal Gasification: Computational Fluid Dynamics Simulation of a 5 MW Siemens Test Gasifier

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Stefan Halama ◽  
Hartmut Spliethoff
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reaction Kinetics ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Dynamics Simulation ◽  
Cfd Model ◽  
Entrained Flow ◽  
Conversion Rates ◽  
Entrained Flow Gasifiers

Modeling pressurized entrained flow gasification of solid fuels plays an important role in the development of integrated gasification combined cycle (IGCC) power plants and other gasification applications. A better understanding of the underlying reaction kinetics is essential for the design and optimization of entrained flow gasifiers—in particular at operating conditions relevant to large-scale industrial gasifiers. The presented computational fluid dynamics (CFD) simulations aim to predict conversion rates as well as product gas compositions in entrained flow gasifiers. The simulations are based on the software ansys fluent 15.0 and include several detailed submodels in user defined functions (UDF). In a previous publication, the developed CFD model has been validated for a Rhenish lignite against experimental data, obtained from a pilot-scale entrained flow gasifier operated at the Technische Universität München. In the presented work, the validated CFD model is applied to a Siemens test gasifier geometry. Simulation results and characteristic parameters, with focus on char gasification reactions, are analyzed in detail and provide new insights into the gasification process.

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