Investigation of Air Entrainment: A Numerical Approach

2003 ◽  
Author(s):  
J. T. Kshirsagar ◽  
S. G. Joshi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Vortex Formation ◽  
Flow Analysis ◽  
Air Entrainment ◽  
Numerical Approach ◽  
Test Cases ◽  
Two Phase ◽  
Root Cause ◽  
Model Study

The air entrainment in sumps (Pump Intake) is a commonly observed phenomenon at low water level and high Froude number corresponding to flow rates higher than the rated flow. The air entrainment initiates with the formation of small vortex like structure on the surface with its position varying in the vicinity of Pump intake portion. Normally it calls for two-phase flow analysis (and possibly transient also) to correctly predict the air entrainment phenomenon using computational fluid dynamics approach. We at CRED, Kirloskar Brothers Limited could predict the root cause for air entrainment by studying the vortex formation well within the flow. A single-phase steady state flow was analyzed. Two test cases were studied. IOWA University had published a sump case with results from computational fluid dynamics studies. The other case was the actual sump model study carried out using experimental setup wherein the air entrainment was observed. The paper presents the comparison of the predictions with results from these two test cases.

Features of Automotive Gas Tank Filler Pipe Two-Phase Flow: Experiments and Computational Fluid Dynamics Simulations

2002 ◽  
Vol 124 (2) ◽  
pp. 412-420 ◽  
Author(s):  
R. Banerjee ◽  
K. M. Isaac ◽  
L. Oliver ◽  
W. Breig
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Air Entrainment ◽  
Imaging Features ◽  
Two Phase ◽  
Progressive Development ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Extensive Flow ◽  
Dynamics Simulations

Extensive flow visualization in an automotive fuel filler pipe made visible by introducing dyes and smoke in water and air, respectively, were conducted for nominal flow rates of 4–18 liters per minute. Video and still cameras were used for imaging. Features of the flow such as laminar-to-turbulent transition, progressive development of strong swirl along filler pipe axis, air entrainment, and mixing with the liquid were observed in the experiments. The experimental observations were supported by computational fluid dynamics (CFD) simulations of the flow which also showed features such as swirl and air entrainment.

scholarly journals Numerical Simulation and Analysis on Spray Drift Movement of Multirotor Plant Protection Unmanned Aerial Vehicle

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2399 ◽  
Author(s):  
Fengbo Yang ◽  
Xinyu Xue ◽  
Chen Cai ◽  
Zhu Sun ◽  
Qingqing Zhou
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Droplet Size ◽  
Wind Field ◽  
Flow Model ◽  
Two Phase Flow ◽  
Plant Protection ◽  
Three Dimensional ◽  
Phase Flow ◽  
Two Phase

In recent years, multirotor unmanned aerial vehicles (UAVs) have become more and more important in the field of plant protection in China. Multirotor unmanned plant protection UAVs have been widely used in vast plains, hills, mountains, and other regions, and become an integral part of China’s agricultural mechanization and modernization. The easy takeoff and landing performances of UAVs are urgently required for timely and effective spraying, especially in dispersed plots and hilly mountains. However, the unclearness of wind field distribution leads to more serious droplet drift problems. The drift and distribution of droplets, which depend on airflow distribution characteristics of UAVs and the droplet size of the nozzle, are directly related to the control effect of pesticide and crop growth in different growth periods. This paper proposes an approach to research the influence of the downwash and windward airflow on the motion distribution of droplet group for the SLK-5 six-rotor plant protection UAV. At first, based on the Navier-Stokes (N-S) equation and SST k–ε turbulence model, the three-dimensional wind field numerical model is established for a six-rotor plant protection UAV under 3 kg load condition. Droplet discrete phase is added to N-S equation, the momentum and energy equations are also corrected for continuous phase to establish a two-phase flow model, and a three-dimensional two-phase flow model is finally established for the six-rotor plant protection UAV. By comparing with the experiment, this paper verifies the feasibility and accuracy of a computational fluid dynamics (CFD) method in the calculation of wind field and spraying two-phase flow field. Analyses are carried out through the combination of computational fluid dynamics and radial basis neural network, and this paper, finally, discusses the influence of windward airflow and droplet size on the movement of droplet groups.

Comparison of four types of membrane bioreactor systems in terms of shear stress over the membrane surface using computational fluid dynamics

2013 ◽  
Vol 68 (12) ◽  
pp. 2534-2544 ◽  
Author(s):  
N. Ratkovich ◽  
T. R. Bentzen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Membrane Fouling ◽  
Two Phase Flow ◽  
Membrane Surface ◽  
Cross Flow ◽  
Membrane Bioreactors ◽  
Phase Flow ◽  
Two Phase ◽  
Computational Fluid Dynamics Cfd

Membrane bioreactors (MBRs) have been used successfully in biological wastewater treatment to solve the perennial problem of effective solids–liquid separation. A common problem with MBR systems is clogging of the modules and fouling of the membrane, resulting in frequent cleaning and replacement, which makes the system less appealing for full-scale applications. It has been widely demonstrated that the filtration performances in MBRs can be greatly improved with a two-phase flow (sludge–air) or higher liquid cross-flow velocities. However, the optimization process of these systems is complex and requires knowledge of the membrane fouling, hydrodynamics and biokinetics. Modern tools such as computational fluid dynamics (CFD) can be used to diagnose and understand the two-phase flow in an MBR. Four cases of different MBR configurations are presented in this work, using CFD as a tool to develop and optimize these systems.

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