The Effect of Bench Arrangements on the Natural Ventilation of a Multispan Greenhouse

2013 ◽  
Author(s):  
Sunita Kruger ◽  
Leon Pretorius
Keyword(s):  
Fluid Dynamics ◽  
Natural Ventilation ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Low Velocity ◽  
Lower Velocity ◽  
Cfd Models ◽  
Temperature Distributions ◽  
Computational Fluid Dynamics Cfd ◽  
Plant Level

In this paper, the influence of various bench arrangements on the microclimate inside a two-span greenhouse is numerically investigated using three-dimensional Computational Fluid Dynamics (CFD) models. Longitudinal and peninsular arrangements are investigated for both leeward and windward opened roof ventilators. The velocity and temperature distributions at plant level (1m) were of particular interest. The research in this paper is an extension of two-dimensional work conducted previously [1]. Results indicate that bench layouts inside the greenhouse have a significant effect on the microclimate at plant level. It was found that vent opening direction (leeward or windward) influences the velocity and temperature distributions at plant level noticeably. Results also indicated that in general, the leeward facing greenhouses containing either type of bench arrangement exhibit a lower velocity distribution at plant level compared to windward facing greenhouses. The latter type of greenhouses has regions with relatively high velocities at plant level which could cause some concern. The scalar plots indicate that more stagnant areas of low velocity appear for the leeward facing greenhouses. The windward facing greenhouses also display more heterogeneity at plant level as far as temperature is concerned.

The Effect of Time-Varying Wind Direction on the Indoor Climate of a Naturally Ventilated Greenhouse

2010 ◽  
Author(s):  
Sunita Kruger ◽  
Leon Pretorius
Keyword(s):  
Fluid Dynamics ◽  
Wind Direction ◽  
Three Dimensional ◽  
Time Varying ◽  
Two Dimensional ◽  
Indoor Climate ◽  
Transient Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Plant Level ◽  
Transient Wind

This paper presents a numerical investigation into the indoor climate of a four span naturally ventilated, four span greenhouse subject to a time-varying wind direction. The effect of transient wind conditions on the temperature and velocity distribution inside the greenhouse is numerically determined using Computational Fluid Dynamics (CFD). The research in this paper is an extension of work previously conducted on two-dimensional models of greenhouses. Current work concentrates on the three-dimensional effect of external winds. Results indicate that for a wind direction of 22.5 degrees, the microclimate at plant level varies throughout the length of the greenhouse. It was also found from transient simulations that even a slight change in wind direction have a pronounced effect on the indoor climate at plant level.

The Effect of Raised Benches Containing Crops on the Indoor Environment in Greenhouses

2015 ◽  
Author(s):  
Sunita Kruger ◽  
Leon Pretorius
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Velocity Distribution ◽  
Crop Production ◽  
Indoor Environment ◽  
Three Dimensional ◽  
Cfd Models ◽  
Computational Fluid Dynamics Cfd ◽  
Plant Level

The purpose of this paper is to investigate the influence of peninsular arranged perforated benches containing plants on the indoor environment of a naturally ventilated greenhouse. The results are compared to a greenhouse containing peninsular arranged solid benches with no plants. The investigation will be conducted numerically using three-dimensional Computational Fluid Dynamics (CFD) models. The overall temperature and velocity distribution were investigated at different sections of the greenhouse. The temperature and velocity distributions at plant level were of particular interest. Results indicated that the greenhouse containing the perforated benches were in general cooler, but also exhibited higher velocities throughout. The velocities observed were higher than those recommended by ASHRAE [1]. It was concluded that care should be taken when placing plants on the perforated benches especially in the regions adjacent to the walls, as this can lead to non-uniform crop production.

Uptake of Soluble Gases in the Entire Respiratory Systems of Rats and Humans Using Transient CFD/PBPK Models

2013 ◽  
Author(s):  
S. Kabilan ◽  
A. Kuprat ◽  
D. Einstein ◽  
J. Carson ◽  
R. Jacob ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Hydrogen Sulfide ◽  
Three Dimensional ◽  
Aerosol Deposition ◽  
Water Soluble ◽  
Computational Techniques ◽  
Nasal Airways ◽  
Cfd Models ◽  
Pbpk Models ◽  
Computational Fluid Dynamics Cfd

With the advancement of experimental and computational techniques, three-dimensional (3D) computational fluid dynamics (CFD) airflow models of the respiratory system have increasingly been used to evaluate aerosol deposition, gas exchange and airflow characteristics under various physiological and/or disease conditions. One specific application that is emerging in the field of toxicology is assessing the risk for exposure to highly reactive, water-soluble gases and vapors including formaldehyde, acetaldehyde, hydrogen sulfide, and acrolein by coupling CFD models of nasal airways of rats and humans to physiological based pharmacokinetic (PBPK) models.

Modeling of an Integrated Wind Energy Building

2007 ◽  
Author(s):  
William E. Pedersen ◽  
Daniel N. Pope
Keyword(s):  
Fluid Dynamics ◽  
Numerical Modeling ◽  
Wind Energy ◽  
Three Dimensional ◽  
Building Structure ◽  
Two Dimensional ◽  
Free Standing ◽  
Pressure Area ◽  
Computational Fluid Dynamics Cfd ◽  
Geographic Regions

This study presents the design and modeling of an integrated wind energy building. It is proposed that a building be constructed with an integral wind turbine that takes advantage of the funneling of wind from the building structure and the low pressure area above or leeward of the building. Computational Fluid Dynamics (CFD) was used to evaluate different building geometries and wind potentials. Preliminary investigations using two dimensional numerical modeling in both the horizontal and vertical planes are presented. Three dimensional analyses are also presented of promising geometries from the two dimensional preliminary results. While additional modeling efforts will be necessary to optimize this system, results indicate a significant improvement in performance over free standing turbines, allowing for utilization of wind power in geographic regions that have traditionally not been feasible.

The Use of Three-Dimensional Computational Fluid Dynamics in the Design of Extrusion Dies

1997 ◽  
Vol 16 (7) ◽  
pp. 661-674 ◽  
Author(s):  
W. A. Gifford
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Personal Computer ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Extrusion Dies ◽  
Depth Analysis ◽  
Computational Fluid Dynamics Cfd

With the proper use of three-dimensional computational fluid dynamics (CFD), the design of extrusion dies can be taken from that of an art to a science. Although replacing simpler traditional one- and two-dimensional approaches with fully three-dimensional ones requires a much more in depth analysis and a large amount of computations, the design of most dies can be performed on a personal computer. This paper demonstrates how these techniques are being used to obtain optimized designs of extrusion dies.

Direct Coupling of a Two-Dimensional Fan Model in a Turbofan Engine Performance Simulation

2016 ◽  
Author(s):  
Ioannis Templalexis ◽  
Alexios Alexiou ◽  
Vassilios Pachidis ◽  
Ioannis Roumeliotis ◽  
Nikolaos Aretakis
Keyword(s):  
Three Dimensional ◽  
Engine Performance ◽  
System Level ◽  
Design Parameters ◽  
High Fidelity ◽  
Two Dimensional ◽  
Performance Simulation ◽  
Cfd Models ◽  
Component Design ◽  
Complex Phenomena

Coupling of high fidelity component calculations with overall engine performance simulations (zooming) can provide more accurate physics and geometry based estimates of component performance. Such a simulation strategy offers the ability to study complex phenomena and their effects on engine performance and enables component design changes to be studied at engine system level. Additionally, component interaction effects can be better captured. Overall, this approach can reduce the need for testing and the engine development time and cost. Different coupling methods and tools have been proposed and developed over the years ranging from integrating the results of the high fidelity code through conventional performance component maps to fully-integrated three-dimensional CFD models. The present paper deals with the direct integration of an in-house two-dimensional (through flow) streamline curvature code (SOCRATES) in a commercial engine performance simulation environment (PROOSIS) with the aim to establish the necessary coupling methodology that will allow future advanced studies to be performed (e.g. engine condition diagnosis, design optimization, mission analysis, distorted flow). A notional two-shaft turbofan model typical for light business jets and trainer aircraft is initially created using components with conventional map-defined performance. Next, a derivative model is produced where the fan component is replaced with one that integrates the high fidelity code. For both cases, an operating line is simulated at sea-level static take-off conditions and their performances are compared. Finally, the versatility of the approach is further demonstrated through a parametric study of various fan design parameters for a better thermodynamic matching with the driving turbine at design point operation.

scholarly journals Modelling of working processes of non-contact oil free vacuum pumps by computational fluid dynamics (CFD) methods

2021 ◽  
Vol 2059 (1) ◽  
pp. 012003
Author(s):  
A Burmistrov ◽  
A Raykov ◽  
S Salikeev ◽  
E Kapustin
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Mathematical Models ◽  
Cfd Models ◽  
Ansys Cfx ◽  
Sst Turbulence Model ◽  
Computational Fluid Dynamics Cfd ◽  
Dynamic Meshing ◽  
Comparison With Experimental Data

Abstract Numerical mathematical models of non-contact oil free scroll, Roots and screw vacuum pumps are developed. Modelling was carried out with the help of software CFD ANSYS-CFX and program TwinMesh for dynamic meshing. Pumping characteristics of non-contact pumps in viscous flow with the help of SST-turbulence model were calculated for varying rotors profiles, clearances, and rotating speeds. Comparison with experimental data verified adequacy of developed CFD models.

Computational Fluid Dynamics Techniques for Flows in Lapple Cyclone Separator

2005 ◽  
Vol 498-499 ◽  
pp. 179-185
Author(s):  
A.F. Lacerda ◽  
Luiz Gustavo Martins Vieira ◽  
A.M. Nascimento ◽  
S.D. Nascimento ◽  
João Jorge Ribeiro Damasceno ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Turbulent Flow ◽  
Reynolds Stress ◽  
Cyclone Separator ◽  
Two Dimensional ◽  
Stress Components ◽  
Computational Fluid Dynamics Cfd

A two-dimensional fluidynamics model for turbulent flow of gas in cyclones is used to evaluate the importance of the anisotropic of the Reynolds stress components. This study presents consisted in to simulate through computational fluid dynamics (CFD) package the operation of the Lapple cyclone. Yields of velocity obtained starting from a model anisotropic of the Reynolds stress are compared with experimental data of the literature, as form of validating the results obtained through the use of the Computational fluid dynamics (Fluent). The experimental data of the axial and swirl velocities validate numeric results obtained by the model.

Direct Design of Ducts

2003 ◽  
Vol 125 (1) ◽  
pp. 158-165 ◽  
Author(s):  
A. Ashrafizadeh ◽  
G. D. Raithby ◽  
G. D. Stubley
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Distribution ◽  
Design Method ◽  
Three Dimensional ◽  
Viscous Flows ◽  
Simple Extension ◽  
Two Dimensional ◽  
Direct Design ◽  
Dependent Variables

This paper describes a method for calculating the shape of duct that leads to a prescribed pressure distribution on the duct walls. The proposed design method is computationally inexpensive, robust, and a simple extension of existing computational fluid dynamics methods; it permits the duct shape to be directly calculated by including the coordinates that define the shape of the duct wall as dependent variables in the formulation. This “direct design method” is presented by application to two-dimensional ideal flow in ducts. The same method applies to many problems in thermofluids, including the design of boundary shapes for three-dimensional internal and external viscous flows.

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