scholarly journals EXPERIMENTAL AND CFD- SIMULATION OF POLLUTANT TRANSPORT IN POROUS MEDIA

2021 ◽  
Vol 25 (4) ◽  
pp. 23-39
Author(s):  
Nebras Q. Hussein ◽  
◽  
Sadiq S. Muhsun ◽  
Zainab T. Al-Sharify ◽  
Huda T. Hamed ◽  
...  
Keyword(s):  
Porous Media ◽  
Physical Model ◽  
Initial Velocity ◽  
Cfd Simulation ◽  
Pollutant Transport ◽  
Pollutant Concentration ◽  
Initial Porosity ◽  
Noticeable Effect ◽  
Inlet Velocity ◽  
Simulated Model

Efforts were made in this search to design a physical and computer model using the CFD techniques to simulate the problem of transporting pollutants through a porous media in unsteady state case. A physical model was built to measure the transmission of a copper nitrate pollutant at an initial concentration of 25 mg/l in a medium consists of (sand + gravel) and study the movement of the pollutant through. Then the results of the pollutant transport through used in the physical model were entered as entry data to the CFD simulated model using COMSOL 5.4. Software. The results of the CFD simulated model showed that the change in the inlet velocity to more than 20% of the initial velocity increases the pollutant concentration and reduces the time wanted to reach the highest value of the pollutant, while reducing the inlet velocity to less than 20% of the initial velocity, cause to decrease the concentration and increase the time to reach the highest pollutant value. When changing the porosity by (30%, -15%) of the initial porosity, it was noticed that increasing the porosity value reduces the pollutant concentration and increases the time required to reach the highest value of the pollutant. while when the porosity decreases to 15% of the initial porosity, the concentration increases the time decreases to reach the highest value of the pollutant at all control points. The adsorption factor has a noticeable effect on the emergence of the pollutant, while the temperature change was almost imperceptible for all degrees. However, the results of laboratory work were compared with the results of the CFD simulated model, which showed a good match between them.

scholarly journals Numerical Investigation for the Resin Filling Behavior during Ultraviolet Nanoimprint Lithography of Subwavelength Moth-Eye Nanostructure

Coatings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 799
Author(s):  
Yuanchi Cui ◽  
Xuewen Wang ◽  
Chengpeng Zhang ◽  
Jilai Wang ◽  
Zhenyu Shi
Keyword(s):  
Simulation Model ◽  
Nanoimprint Lithography ◽  
Cfd Simulation ◽  
Boundary Slip ◽  
Accurate Analysis ◽  
Inlet Velocity ◽  
Filling Height ◽  
Proposed Model ◽  
Good Consistency ◽  
Computational Fluid Dynamics Cfd

Accurate analysis of the resin filling process into the mold cavity is necessary for the high-precision fabrication of moth-eye nanostructure using the ultraviolet nanoimprint lithography (UV-NIL) technique. In this research, a computational fluid dynamics (CFD) simulation model was proposed to reveal resin filling behavior, in which the effect of boundary slip was considered. By comparison with the experimental results, a good consistency was found, indicating that the simulation model could be used to analyze the resin filling behavior. Based on the proposed model, the effects of process parameters on resin filling behavior were analyzed, including resin viscosity, inlet velocity and resin thickness. It was found that the inlet velocity showed a more significant effect on filling height than the resin viscosity and thickness. Besides, the effects of boundary conditions on resin filling behavior were investigated, and it was found the boundary slip had a significant influence on resin filling behavior, and excellent filling results were obtained with a larger slip velocity on the mold side. This research could provide guidance for a more comprehensive understanding of the resin filling behavior during UV-NIL of subwavelength moth-eye nanostructure.

scholarly journals CFD Simulation of Pollutant Emission in a Natural Draft Dry Cooling Tower with Flue Gas Injection: Comparison between LES and RANS

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3630
Author(s):  
Guangjun Yang ◽  
Xiaoxiao Li ◽  
Li Ding ◽  
Fahua Zhu ◽  
Zhigang Wang ◽  
...  
Keyword(s):  
Flow Field ◽  
Flue Gas ◽  
Cooling Tower ◽  
Cfd Simulation ◽  
Concentration Field ◽  
Pollutant Concentration ◽  
Pollutant Emission ◽  
Navier Stokes ◽  
Dry Cooling Tower ◽  
Reynolds Average

Accurate prediction of pollutant dispersion is vital to the energy industry. This study investigated the Computational Fluid Dynamics (CFD) simulation of pollutant emission in a natural draft dry cooling tower (NDDCT) with flue gas injection. In order to predict the diffusion and distribution characteristics of the pollutant more accurately, Large Eddy Simulation (LES) was applied to predict the flow field and pollutant concentration field and compared with Reynolds Average Navier-Stokes (RANS) and Unsteady Reynolds Average Navier-Stokes (URANS). The relationship between pollutant concentration pulsation and velocity pulsation is emphatically analyzed. The results show that the flow field and concentration field simulated by RANS and URANS are very close, and the maximum value of LES is about 43 times that of RANS and URANS for the prediction of pollutant concentration in the inner shell of cooling tower. Pollutant concentration is closely related to local flow field velocity. RANS and URANS differ greatly from LES in flow field prediction, especially at the outlet and downwind of cooling tower. Compared with URANS, LES can simulate flow field pulsation with a smaller scale and higher frequency.

Physical model analysis of foam–TCE displacement in porous media

AIChE Journal ◽  
2003 ◽  
Vol 49 (3) ◽  
pp. 782-788 ◽  
Author(s):  
Seung-Woo Jeong ◽  
M. Yavuz Corapcioglu
Keyword(s):  
Porous Media ◽  
Physical Model ◽  
Model Analysis

Simulation of Combustion in Porous Media With a Two-Energy Equation Model

2011 ◽  
Author(s):  
Marcelo J. S. deLemos ◽  
Jose´ E. A. Coutinho
Keyword(s):  
Porous Media ◽  
Flame Front ◽  
Control Volume ◽  
Numerical Technique ◽  
Simple Algorithm ◽  
Equation Model ◽  
Gas Temperature ◽  
Inlet Velocity ◽  
Excess Air ◽  
Porous Burner

This work presents numerical results for two-dimensional combustion of an air/methane mixture in inert porous media using turbulence and radiation models. Distinct energy equations are considered for the porous burner and for the fuel in it. Inlet velocity and excess air-to-fuel ratio are varied in order to analyze their effects on temperature and flame front location. The macroscopic equations for mass, momentum and energy are obtained based on the volume average concept. The numerical technique employed for discretizing the governing equations was the control volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was used to handle the pressure-velocity coupling. Results indicate that for high excess air values, the gas temperature peaks are reduced. Also, for the same conditions the flame front moves towards the exit of the burner. Results also indicate that the same flame front behavior occurs as the inlet velocity increases.

Investigation of Numerical Stability of Pipe-Flow Simulation under Strong Oscillation of Inlet Velocity

2012 ◽  
Vol 591-593 ◽  
pp. 801-805
Author(s):  
Xiao Gang Yi ◽  
Chao Luo ◽  
Dong Li ◽  
Zuo Liang Zhang
Keyword(s):  
Cfd Simulation ◽  
Fuel Injection ◽  
Flow Simulation ◽  
Numerical Instability ◽  
Cavitation Model ◽  
Significant Information ◽  
Inlet Velocity ◽  
Cyclic Oscillation ◽  
Volume Method ◽  
Pipe Vibration

Pressure distribution inside a fluid-conveying pipe is significant information for reasonable pipe design or mitigation of pipe vibration caused by fluid impact. Generally, a steady solution of pressure information can be obtained based on traditional CFD simulation if the inlet velocity of pipe is time independent. Unfortunately, strong oscillation of inlet velocity often happens in real engineering operations such as fuel injection or pumping process. This paper focuses on the simulation of the transient phenomenon of fluid flow inside a pipe based on the time-dependant inlet velocity. A 2D numerical pipe with an elbow is built based on Eulerian scheme and structured mesh. It is found that numerical instability occurs and convergence becomes difficult if inlet velocity presents obvious cyclic oscillation with big amplitude. Numerical oscillation increases especially when inlet velocity decreases from a big value to zero. Traditional finite volume method and cavitation model are tried and numerical results show that the convergence can be improved evidently based on cavitation model although numerical instability can not be overcome completely.

Refilling and Rewetting of a Hot Horizontal Tube: Part I—Experiments

1981 ◽  
Vol 103 (2) ◽  
pp. 281-286 ◽  
Author(s):  
A. M. C. Chan ◽  
S. Banerjee
Keyword(s):  
Initial Velocity ◽  
Time Lag ◽  
Horizontal Tube ◽  
Film Boiling ◽  
Flow Rates ◽  
Gravitational Effects ◽  
Inlet Velocity ◽  
Horizontal Tubes ◽  
Model Average ◽  
Stratification Effect

Experiments on refilling and rewetting of hot horizontal tubes indicate that gravitational effects are important and lead to flow stratification. The tube is quenched at a given location upwards from the bottom and there is a significant time lag before the top is quenched. The rewetting front is preceded by a liquid layer that is supported by film boiling and forms a “liquid tongue”. Significant pre-cooling is observed at the bottom due to the presence of this tongue. No well defined rewetting temperature exists. The channel quenches at temperatures which can vary considerably between the top and bottom of the tube, and along the tube. The results cannot be explained by a conduction controlled rewetting model. Average rewetting velocities decrease with increases in initial wall temperature, and increase with increases in inlet flow rates and subcooling. These trends are consistent with other investigations in vertical reflood. For low inlet flows and low initial wall temperatures rewetting velocities can be higher than the constant inlet liquid flow velocity. This is due to the flow stratification effect that allows the front of the liquid tongue to move with a higher initial velocity than the inlet velocity.

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