scholarly journals Computational Fluid Dynamics Simulation of Gas–Solid Hydrodynamics in a Bubbling Fluidized-Bed Reactor: Effects of Air Distributor, Viscous and Drag Models

Processes ◽  
2019 ◽  
Vol 7 (8) ◽  
pp. 524 ◽  
Author(s):  
Khezri ◽  
Ghani ◽  
Masoudi Soltani ◽  
Biak ◽  
RobiahYunus ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Drop ◽  
Turbulence Models ◽  
Solid Particles ◽  
Dynamics Simulation ◽  
Actual Process ◽  
Momentum Exchange ◽  
Pressure Drops ◽  
Drag Models

In this work, we employed a computational fluid dynamics (CFD)-based model with a Eulerian multiphase approach to simulate the fluidization hydrodynamics in biomass gasification processes. Air was used as the gasifying/fluidizing agent and entered the gasifier at the bottom which subsequently fluidized the solid particles inside the reactor column. The momentum exchange related to the gas-phase was simulated by considering various viscous models (i.e., laminar and turbulence models of the re-normalisation group (RNG), k-ε and k-ω). The pressure drop gradient obtained by employing each viscous model was plotted for different superficial velocities and compared with the experimental data for validation. The turbulent model of RNG k-Ɛ was found to best represent the actual process. We also studied the effect of air distributor plates with different pore diameters (2, 3 and 5 mm) on the momentum of the fluidizing fluid. The plate with 3-mm pores showed larger turbulent viscosities above the surface. The effects of drag models (Syamlal–O’Brien, Gidaspow and energy minimum multi-scale method (EMMS) on the bed’s pressure drop as well as on the volume fractions of the solid particles were investigated. The Syamlal–O’Brien model was found to forecast bed pressure drops most consistently, with the pressure drops recorded throughout the experimental process. The formation of bubbles and their motion along the gasifier height in the presence of the turbulent flow was seen to follow a different pattern from with the laminar flow.

scholarly journals Computational fluid dynamics simulation of the turbulence models in the tested section on wind tunnel

2020 ◽  
Vol 11 (4) ◽  
pp. 1201-1209
Author(s):  
Ismail ◽  
Johanis John ◽  
Erlanda A. Pane ◽  
Budhi M. Suyitno ◽  
Gama H.N.N. Rahayu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Turbulence Models ◽  
Dynamics Simulation ◽  
Computational Fluid Dynamics Simulation

Computational Fluid Dynamics Simulation of Airflow Alteration in the Trachea Before and After Vascular Ring Surgery

2013 ◽  
Author(s):  
Tzu-Ching Shih ◽  
Tzyy-Leng Horng ◽  
Fong-Lin Chen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Vascular Ring ◽  
Dynamics Simulation ◽  
Positive Pressure ◽  
Local Pressure ◽  
Pressure Drops ◽  
Vascular Rings ◽  
Before And After ◽  
Key Factor

Vascular rings, congenital intracardic anomalies of the aortic arch and the vessels emerging from the heart, completely encircle the trachea and esophagus [1]. The vascular ring results in narrowing and obstruction of the trachea and the esophagus. Due to the existence of a complete or partial vascular ring compressing either the trachea or esophagus, symptoms of a vascular ring in children include cough, stridor, chronic cough, dysphagia, persistent wheeze, and noisy breathing [2]. Some studies reported that the vascular ring surgery provides an excellent chance to improve the patient respiration conditions, especially for relief of symptoms [1–3]. Al-Bassam et al. reported that the thoracoscopic division of vascular rings in infants and children is a safe and effective surgery rather than an open thoracotomy[4]. Even after the treatment of a surgical division of the vascular ring, however, the fixed obstruction is relieved but the patient continues to have dynamic collapse because the compressed trachea segment is always malacic. Airway resistance to flow in the airway, thus, is a key factor for not only clinical diagnosis severity assessment but also therapeutic decision in tracheal stenosis. Furthermore, Malvè et al. (2011) utilized the finite element-based commercial software code (ADINA R&D Inc.) to model the fluid structure interaction of a human trachea under different ventilation conditions [5]. They also found that the positive pressure in the trachea does not result in the airway collapse during the time period of mechanical breathing. Therefore, the purpose of this study is to use the computational fluid dynamics (CFD) technique to calculate the local pressure drops in the tracheal segment for different inspiratory and expiratory flow rates due to preoperative and preoperative vascular ring surgery.

Numerical Investigation of Dusts Removal from Tramway Surface by Street Vacuum Sweeper

2011 ◽  
Vol 236-238 ◽  
pp. 1619-1622 ◽  
Author(s):  
Bo Fu Wu ◽  
Jin Lai Men ◽  
Jie Chen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Model ◽  
Pressure Drop ◽  
Removal Efficiency ◽  
Pressure Drops ◽  
Operational Safety ◽  
Airflow Field ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method

In order to enhance the operational safety of tram vehicle and reduce the wear of guide wheels mounted on the vehicle, it is necessary to remove particles such as dusts and silts from tramway surface. The aim of this paper is to evaluate the effectiveness of street vacuum sweeper for sucking up dusts from tramway surface. A numerical model was developed based on dusts removal process. Under different pressure drops across the pickup head of the street vacuum sweeper, the flow field and dusts removal efficiency were analyzed with computational fluid dynamics (CFD) method. The numerical results show that a higher pressure drop can improve the airflow field in the pickup head and results in higher dusts removal efficiency, but higher pressure drop definitely need more energy. Therefore, a balance should be taken into consideration.

scholarly journals A Hybrid RANS-LES Computational Fluid Dynamics Simulation of an FDA Medical device benchmark

Mechanika ◽  
2019 ◽  
Vol 25 (4) ◽  
pp. 291-298
Author(s):  
Primož Drešar ◽  
Jožef Duhovnik
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Turbulence Models ◽  
The United States ◽  
Dynamics Simulation ◽  
Sudden Expansion ◽  
Detached Eddy Simulation ◽  
Cfd Validation ◽  
Eddy Simulation ◽  
Advection Schemes

Computational fluid dynamics (CFD) is a valuable tool that complements experimental data in the development of medical devices. The reliability of CFD still presents an issue and for that reason, no standardized approaches are currently available. The United States Food and Drug Administration (FDA) has initiated the development of a program for CFD validation, and has presented an idealized nozzle benchmark model. In this study, a nozzle flow with sudden expansion has been simulated using advanced RANS-LES turbulence models. Such models partially resolve the flow and are cheaper in computer resources and time in comparison to the Large Eddy Simulation (LES). Furthermore, they are more accurate than standard Reynolds-averaged Navier-Stokes (RANS) models. A collection of hybrid turbulence models has been investigated: Detached Eddy Simulation (DES), Stress Blended Eddy Simulation (SBES), and Scale Adaptive Simulation (SAS), and compared to a standard RANS Shear Stress Transport (SST) model. Subsequently, all models were validated by experimental results already published by different research groups. Particle Image Velociometry (PIV) experiments were performed by inter-laboratory study, and the results are available online for numerical validation.  The flow conditions in this study are only restricted to a turbulence flow at a Reynolds number of Re =6500. Complementing the turbulence models investigation, two advection schemes were tested: high resolution (HR) and bounded central difference scheme (BCD). Among all advanced models the SBES model with BCD scheme has the best agreement with the experimental values.

CFD MODELING OF BINARY MIXTURE HYDRODYNAMICS IN GAS-SOLID PARTICLE FLUIDIZED BED REACTOR SYSTEM

2016 ◽  
Vol 78 (6-5) ◽  
Author(s):  
Thanatepon Tangpattanatana ◽  
Veeraya Jiradilok ◽  
Pornpote Piumsomboon ◽  
Benjapon Chalermsinsuwan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Binary Mixture ◽  
Fluidized Bed ◽  
Dispersion Coefficient ◽  
Turbulent Dispersion ◽  
Dynamics Simulation ◽  
Cfd Modeling ◽  
Micron Size ◽  
Drag Models

The objective of this research was to compare the effect of a binary mixture between coal, including 500, 700 and 1000-micron size, and sand, 180-micron size, on the mixing behavior in a fluidized bed system. In addition, suitable computational fluid dynamics drag models were explored, including an EMMS model, Gidaspow model and Wen & Yu model. The simulation results were compared for correctness with real plant information. The EMMS model matched well with the obtained data, This is because the employed model considers the particle cluster effect. The EMMS drag model was then used for further computational fluid dynamics simulation. The levels of mixing between sand and coal were predicted by turbulent dispersion coefficient. These coefficients of coal particle were exhibited in axial and radial direction. The highest turbulent dispersion coefficients were found in the mixture with 500 and 1000 micron coal size for radial and axial directions, respectively. The low axial turbulent dispersion coefficient and high radial turbulent dispersion coefficient were preferred for good hydrodynamics behavior.

Computational Fluid Dynamics-Based Numerical Analysis of Acoustic Attenuation and Flow Resistance Characteristics of Perforated Tube Silencers

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Chen Liu ◽  
Zhenlin Ji
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Drop ◽  
Time Domain ◽  
Transmission Loss ◽  
Air Flow ◽  
Acoustic Attenuation ◽  
Pressure Drops ◽  
Wave Range ◽  
Perforated Tube

The 3D time-domain computational fluid dynamics (CFD) approach is used to calculate the acoustic attenuation performance of perforated tube silencers without and with flow. For the crossflow perforated tube silencer and straight-through perforated tube silencers, the transmission loss predictions agree well with the experimental measurements available in the literature. Then, the 3D time-domain CFD approach is employed to investigate the effects of flow velocity and temperature on the acoustic attenuation performance of perforated tube silencers. The numerical results demonstrated that the transmission loss is increased at most frequencies for the crossflow perforated tube silencer as the air flow increases, while the air flow has little influence on the acoustic attenuation in the plane wave range and increases the acoustic attenuation at higher frequencies for the straight-through perforated tube silencers. Increasing the air temperature shifts the transmission loss curve to higher frequency and lowers the resonance peaks somewhat. The pressure drops of perforated tube silencers are predicted by performing the 3D steady flow computation using CFD. The pressure drop of the crossflow perforated tube silencer is much higher than those of the straight-through perforated tube silencer at the same flow conditions, and the pressure drop of the straight-through perforated tube silencer increases gradually as the porosity increases.

scholarly journals A simple method for high-precision evaluation of valve flow coefficient by computational fluid dynamics simulation

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401771370 ◽  
Author(s):  
Xiao-Ming Zhou ◽  
Zhi-Kun Wang ◽  
Yi-Fang Zhang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Drop ◽  
Adaptation Strategy ◽  
Flow Coefficient ◽  
Dynamics Simulation ◽  
Accurate Estimation ◽  
Simple Method ◽  
Pressure Losses ◽  
The Difference

Flow coefficient is an important performance index associated with the energy efficiency of a valve, and an effective method to evaluate valve flow coefficient is necessary for valve industry. However, theoretical estimation often results in poor accuracy, while experimental measurements involve significant costs in time and equipment. In this article, a computational fluid dynamics method is proposed to achieve simple and accurate evaluation of valve flow coefficient. For each valve, a computational fluid dynamics model is established containing a valve section, an upstream section, and a downstream section. A grid-adaptation strategy is then applied to improve the accuracy of simulation. To calculate flow coefficient, the most important issue is to determine the net pressure loss induced by valve (Δ Pv). Herein, the overall pressure drop (Δ Po) is obtained first, and the pipe-induced pressure drop (Δ Pp) is estimated by linear fitting. Then, Δ Pv is calculated as the difference between Δ Po and Δ Pp. To ensure accurate estimation of the pressure losses, a length of 26 times of pipe diameter is preferred for the upstream section. The experiments demonstrated that the presented method can accurately predict flow coefficient for various types of valves and thus has great potential to be widely used in the valve industry.

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