• Journal of computational fluids engineering
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• v.17 no.2
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• pp.21-27
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• 2012

Reynolds-averaged Navier-Stokes equations solver based on a pressure-based cell-centered finite volume method was developed using OpenFOAM libraries, which was an open source and providing computational continuum mechanics libraries. For the reasonable development of the turbulent boundary layer on the bow of the ship, specified library was developed. Grid sensitivities, such as skewness and aspect ratio of a cell, were tested for the solution convergence. Pressure, turbulent kinetic energy, turbulent dissipation rate contours on the ship surface computed by the developed CFD code were compared with those computed by the commercial CFD code, Fluent.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.78-84
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• 2013

The objective of this paper is to develop 360 W class wind turbine tree using a helical type wind turbine. The performance of 100 W class helical wind turbine which finished the conceptual design has been forecast through the CFD analysis. After performed the analysis of one wind turbine performance, four wind turbine have been installed at the structure of a tree type and then the change of a output data has been verified through the CFD analysis. In this study, the CFD results of a helical wind turbine tree have been shown by a velocity and pressure distribution. The result could obtain more than rated power 360 W through the CFD analysis.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.1
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• pp.78-84
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• 2001

A CFD simulation of airflow and temperature field in a heated room has been described in this paper. The thermal wall jet created by a radiator greatly influences the airflow pattern, temperature distribution. The area close La a heat source has a higher risk of air-borne contamination and imposes a harmful effect on occupants in that area. The predicted flow field, temperature results show good agreement with the measured data. As the results were compared with experimental data, the applicability of CFD was satisfactorily verified. Also, the CFD simulation can capture the natural convective flow features. If a CFD simulation is applied ventilation design with a heat source, An effective design will be attained. Further study is required to improve the accuracy of CFD simulation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.10
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• pp.1341-1347
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• 2002

In order to improve efficiency of a system with three-dimensional flow characteristics, this paper presents a new method that overcomes three-dimensional effects by using two-dimensional CFD and neural network. The method was applied to shape optimization of cut-off in a multi-blade fan/scroll system. As the entrance conditions of two-dimensional CFD, the experimental values at the positions out of the inactive zone were used. The distributions of velocity and pressure obtained by two-dimensional CFD were compared with those of three-dimensional CFD and experimental results. It was found that the distributions of velocity and pressure have qualitative similarity. The results of two-dimensional CFD were used for teaming as target values of neural network. The optimal angle and radius of cut-off were determined as 71$^{\circ}$and 0.092 times the outer diameter of impeller, respectively. It is quantified in the previous report that the optimal angle and radius of cut-off are approximately 72$^{\circ}$and 0.08 times the outer diameter of impeller, respectively.

• Wind and Structures
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• v.13 no.4
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• pp.309-326
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• 2010

CFD techniques try to find their way in the bridge engineering realm nowadays. However, there are certain fields where they offer superior performance such as conceptual bridge design and bidding design. The CFD studies carried out for the conceptual design of a 425 m length cable-stayed bridge are presented. A CFD commercial package has been employed to obtain for a set of cross-sections the aerodynamic coefficients considering 2D steady state. Additionally, for those cross-sections which showed adequate force coefficients, unsteady 2D simulations were carried out to detect the risk of vortex shedding. Based upon these computations the effect on the aerodynamic behavior of the deck cross-section caused by a number of modifications has been evaluated. As a consequence, a new more feasible cross-section design has been proposed. Nevertheless, if the design process proceeds to a more detailed step a comprehensive set of studies, comprising extensive wind tunnel tests, are required to better find out the aerodynamic bridge behavior.

• Wind and Structures
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• v.23 no.6
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• pp.523-542
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• 2016

Snowdrift formation on roofs should be considered in snowy and windy areas to ensure the safety of buildings. Presently, the prediction of snowdrifts on roofs relies heavily on field measurements, wind tunnel tests and numerical simulations. In this paper, a new snowdrift modeling method by using CFD (Computational Fluid Dynamics) coupled with DEM (Discrete Element Method) is presented, including material parameters and particle size, collision parameters, particle numbers and input modes, boundary conditions of CFD, simulation time and inlet velocity, and coupling calculation process. Not only is the two-way coupling between wind and snow particles which includes the transient changes in snow surface topography, but also the cohesion and collision between snow particles are taken into account. The numerical method is applied to simulate the snowdrift on a typical stepped flat roof. The feasibility of using coupled CFD with DEM to study snowdrift is verified by comparing the simulation results with field measurement results on the snow depth distribution of the lower roof.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.3
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• pp.27-36
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• 2018

Effective pesticide applications are needed to assure the quality and economic competitiveness of fruit production and lower the risk of spray drift. Experimental studies have shown that better spray coverage and less driftability require an understanding of the transport of spray droplets within turbulent airflows in the orchard and the interaction between droplet dynamics and tree canopies. This study developed a computational fluid dynamics (CFD) model to predict pesticide flows in the orchard and spray drift discharged from an air-assisted orchard sprayer. The model represented the transport of spray droplets as well as droplets captured by tree canopies, which were modeled as a conical porous model and branched tree model. Validation of the CFD model was accomplished by comparing the CFD results with field measurements. Spray depositions inside tree canopies and at off-target locations were in good agreement with the measurements. The resulting data presented that 38.6%~42.3% of the sprayed droplets were delivered to the tree canopies while 13.6%~20.1% were drifted out of the orchard, part of them reached farther than 200 m from the orchard. The study demonstrates that CFD model can be used to evaluate spray application performance and spray drift potential.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.4
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• pp.85-92
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• 2006

A design program has been developed to predict film cooling performance of a liquid rocket engine. A thermal protecting effect of low mixture ratio gas layer has been analysed by CFD. A one-dimensional film cooling model based on the CFD results has been implemented to the previously developed design program of regenerative cooling. Satisfactory agreement has been achieved by comparing the predicted maximum heat flux at the throat of a subscale chamber and the average measured value, and the predicted nozzle average heat flux and the measured value for a full scale chamber with film cooling. It is ascertained that the film cooling is effective to reduce the throat heat flux in rocket engine chamber.

• Wind and Structures
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• v.13 no.2
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• pp.169-189
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• 2010

This paper describes the use of coupled Computational Fluid Dynamics (CFD) and Rigid Body Dynamics (RBD) in modelling the aerodynamic behaviour of wind-borne plate type objects. Unsteady 2D and 3D Reynolds Averaged Navier-Stokes (RANS) CFD models are used to simulate the unsteady and non-uniform flow field surrounding static, forced rotating, auto-rotating and free-flying plates. The auto-rotation phenomenon itself is strongly influenced by vortex shedding, and the realisable k-epsilon turbulence modelling approach is used, with a second order implicit time advancement scheme and equal or higher order advection schemes for the flow variables. Sequentially coupling the CFD code with a RBD solver allows a more detailed modelling of the Fluid-Structure Interaction (FSI) behaviour of the plate and how this influences plate motion. The results are compared against wind tunnel experiments on auto-rotating plates and an existing 3D analytical model.

• Wind and Structures
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• v.30 no.1
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• pp.99-117
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• 2020

This paper focuses on the processes of wind flow in atmospheric boundary layer, to produce realistic full scale pressures for design of low-rise buildings. CFD with LES turbulence closure is implemented on a scale 1:1 prototype building. A proximity study was executed computationally in CFD with LES that suggests new recommendations on the computational domain size, in front of a building model, apart from common RANS-based guidelines (e.g., COST and AIJ). Our findings suggest a location of the test building, different from existing guidelines, and the inflow boundary proximity influences pressure correlation and reproduction of peak loads. The CFD LES results are compared to corresponding pressures from open jet, full scale, wind tunnel, and the ASCE 7-10 standard for roof Component & Cladding design. The CFD LES shows its adequacy to produce peak pressures/loads on buildings, in agreement with field pressures, due to its capabilities of reproducing the spectral contents of the inflow at 1:1 scale.