scholarly journals Simulation of Natural Ventilation Inside Tunnel Greenhouse

2020 ◽  
Vol 38 (3) ◽  
pp. 752-757
Author(s):  
Cherine Lebbal ◽  
Saadi Bougoul ◽  
Samra Zeroual
Keyword(s):  
Turbulent Flows ◽  
Natural Ventilation ◽  
Three Dimensional ◽  
Vertical Gradient ◽  
Air Velocity ◽  
Hot Air ◽  
Heated Floor ◽  
Volume Method ◽  
Air Circulation ◽  
Three Dimensional Simulations

A study of the variation of the temperature and the speed under an open greenhouse with and without plant was developed and the effect of the wind speed on the internal climate under the greenhouse was analyzed by the use of the software Fluent-CFD based on the finite volume method. The airflow through the crop was introduced by using the porous medium approach. Three dimensional simulations which described turbulent flows in steady state were carried out and the turbulence was modeled by using the standard k-ε model. The air temperature variation shows a gradient from the sidewalls towards the center of the greenhouse due to the movement of the hot air rising towards the roof and another vertical gradient due to the air circulation above the surface of the heated floor. At the openings, the maximum air velocity was reached and the lowest values are observed in the middle of the greenhouse, at the crop level and at the corners. The variation of the climatic parameters affects greatly the growth of the plant. The results of the simulation given as airflows and temperature patterns are satisfactory while comparing them to those of the literature. These results can help to know the distribution of the internal climate inside the greenhouse, so they facilitate the openings design.

scholarly journals Optimizing air velocity for the underfloor forced ventilation to protect a refrigerated warehouse from frost heaving

2018 ◽  
Vol 38 (3) ◽  
pp. 321-327
Author(s):  
Jingfu Jia ◽  
Manjin Hao ◽  
Jianhua Zhao
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Frost Heave ◽  
Forced Ventilation ◽  
Air Velocity ◽  
Set Up

Forced or natural ventilation is the most common measure of frost heave protection for refrigerated warehouse floor. To optimize air velocity for the underfloor forced ventilation system of refrigerated warehouse, a steady state three-dimensional mathematical model of heat transfer is set up in this paper. The temperature fields of this system are simulated and calculated by CFD software PHOENICS under different air velocity, 1.5m/s, 2.5m/s or 3.5m/s. The results show that the optimized air velocity is 1.5m/s when the tube spacing is 1.5m.

Calculations of three-dimensional viscous flow in a multiblade centrifugal fan by modelling blade forces

2003 ◽  
Vol 217 (3) ◽  
pp. 287-297 ◽  
Author(s):  
S-J Seo ◽  
K-Y Kim ◽  
S-H Kang
Keyword(s):  
Mathematical Model ◽  
Turbulent Flows ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Centrifugal Fan ◽  
Complex Flows ◽  
Flow Through ◽  
Volume Method ◽  
The Mathematical Model

A numerical study is presented for Reynolds-averaged Navier-Stokes analysis of three-dimensional turbulent flows in a multiblade centrifugal fan. Present work aims at development of a relatively simple analysis method for these complex flows. A mathematical model of impeller forces is obtained from the integral analysis of the flow through the impeller. A finite volume method for discretization of governing equations and a standard k-ɛ model as turbulence closure are employed. For the validation of the mathematical model, the computational results for velocity components, static pressure, and flow angles at the exit of the impeller were compared with experimental data. The comparisons show generally good agreement, especially at higher flow coefficients.

Investigations on CFD Simulations for Predicting Windage Power Losses in Spur Gears

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Y. Marchesse ◽  
C. Changenet ◽  
F. Ville ◽  
P. Velex
Keyword(s):  
Three Dimensional ◽  
Volumetric Flow Rate ◽  
Spur Gears ◽  
Power Losses ◽  
Test Rig ◽  
Cfd Simulations ◽  
Specific Test ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method ◽  
Three Dimensional Simulations

In this paper, a computational fluid dynamics (CFD) code is applied to two- and three-dimensional simulations of windage power loss generated by spur gears rotating in air. Emphasis is placed on the various meshes associated with the finite volume method and on the choice of turbulence model. Comparing CFD predictions with the power losses measured on a specific test rig, it is shown that the fluid ejection in the radial direction must be included in order to reproduce the experimental evidence. The relative importance of the losses generated by the gear front and rear faces along with those due to the teeth is discussed. The volumetric flow rate expelled by the teeth is analyzed and the influence of flanges is highlighted.

scholarly journals Efficient investigation on fully developed flow in a mildly curved 180° open-channel

2014 ◽  
Vol 16 (6) ◽  
pp. 1250-1264 ◽  
Author(s):  
Yuchuan Bai ◽  
Xiaolong Song ◽  
Shuxian Gao
Keyword(s):  
Secondary Flow ◽  
Flow Pattern ◽  
Turbulent Flows ◽  
Three Dimensional ◽  
Engineering Application ◽  
Experimental Investigations ◽  
Shear Stresses ◽  
Fully Developed Flow ◽  
Wall Shear ◽  
Volume Method

Turbulent flow in meandering open channels is one of the most complicated and unpredictable turbulent flows as the interaction of various forces, such as pressure gradient, centrifugal force, and wall shear stresses severely affect the flow pattern. In order to improve significance in engineering application, understanding the overall flow characteristic is the focus. This paper presents the results of numerical and experimental investigations of flow in a 180° mild bend, which is close to criticality with curvature ratio R/B = 3. Considering the characteristic of various models, three-dimensional (3D) re-normalization group (RNG) k–ε model was adopted to simulate the flow efficiently. Governing equations of the flow were solved with a finite-volume method. The pressure-based coupled algorithm was used to compute the pressure. The flow velocities were measured experimentally with Micro acoustic Doppler velocimeter. Good agreement between the numerical results and measurements indicated that RNG k–ε model can successfully predict this flow phenomenon. The flow pattern in this bend is influenced widely by the secondary flow. The variations of velocity components, streamlines, secondary flow, and wall shear stresses are analysed in the study. Some newly discovered phenomenon in this special state are worth noting.

Research on the Reasonable Air Velocity of Blast Furnace Tuyere

2013 ◽  
Vol 680 ◽  
pp. 351-355 ◽  
Author(s):  
Xi Ping Guo ◽  
Wen Yue Han
Keyword(s):  
Blast Furnace ◽  
Gas Flow ◽  
Three Dimensional ◽  
Cooling Water ◽  
Air Velocity ◽  
Hot Gas ◽  
Hot Air ◽  
Blast Furnace Tuyere ◽  
Flow Rate Range ◽  
Velocity Interval

Researching on the influence of blast furnace tuyere under the condition of hot gas flow rate range of 60 ~240m / s by the method of using computational fluid dynamics. During the process of going through the tuyere, the tuyere cool the hot gas due to the cooling water inner it . At the same time, the more slow hot gas flow velocity is, the stronger cooling effect is, the greater energy is lost. Take this to hot air flow field of three dimensional numerical simulation, and discussed the reasonable air velocity interval, which can guarantee low thermal load and prevent a loss to larger energy .

scholarly journals Three dimensional simulations of Hall magnetohydrodynamics

2010 ◽  
Vol 6 (S274) ◽  
pp. 433-436 ◽  
Author(s):  
Daniel O. Gómez
Keyword(s):  
Magnetic Fields ◽  
Hall Effect ◽  
Turbulent Flows ◽  
Three Dimensional ◽  
Mhd Equations ◽  
Hall Parameter ◽  
Astrophysical Objects ◽  
Hall Mhd ◽  
Three Dimensional Simulations

AbstractTurbulent flows take place in a large variety of astrophysical objects, and often times are the source of dynamo generated magnetic fields. Much of the progress in our understanding of dynamo mechanisms, has been made within the theoretical framework of magnetohydrodynamics (MHD). However, for sufficiently diffuse media, the Hall effect eventually becomes non-negligible.We present results from simulations of the Hall-MHD equations. The simulations are performed with a pseudospectral code to achieve exponentially fast convergence. We study the role of the Hall effect in the dynamo efficiency for different values of the Hall parameter.

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