• 한국항공운항학회지
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• 제17권4호
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• pp.32-41
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• 2009

This paper presents the work being carried out in order to reduce the ground turbulence by the fence in the vicinity of airport runway. In preliminary study, we knows that cross-wind effect in the vicinity of runway is highly dependent on the shape of the buildings and have predicted results confirmed reduction of wind-effect by doing that set up the building with a fence, terraced shape or gap. This study is to figure out effect of ground turbulence by the building with fence, which is changing fence height, in using two-dimensional computational fluid dynamics analysis.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1132-1135
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• 2008

In this study, a circular and indoor soil tank foundation was manufactured to study the improvement according to the degree of turbulence arising from PBD penetration, using the existing plate-type shoe and improved V-type shoe to change the degree of turbulence. Furthermore, to study the foundation improvement effect, the strength, settlement speed in the turbulence area were compared according to the shoe penetration. The results of the study showed that the V-type shoe reduced the strength coefficient decrease effect, and the foundation improvement effect according to the degree of turbulence was identified.

• 한국공간구조학회논문집
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• 제21권1호
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• pp.51-59
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• 2021

In this paper, the effect of the turbulence intensity in across-wind direction on the wind load in CFD(Computational fluid dynamics) simulation was analyzed. 'Ansys fluent' software was used for CFD simulation. And the fluctuating wind speed applied to the simulation was generated according to Korean Design Standard and Von Karman wind turbulence model. The turbulence intensity in across-wind direction for simulation was applied from 0 to 100% of the turbulence intensity in along-wind direction. The analysis results showed that the turbulence intensity in across-wind direction had a particularly great effect on the wind load in across-wind direction.

• 대한기계학회논문집
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• 제14권2호
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• pp.440-452
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• 1990

Comprehensive numberical computations have been made for four turbulent swirling jets with and without recirculation to critically evaluate the accuracy and universality of several exising turbulence models as well as of the modified k-.epsilon. model proposed in the present study. A numerical scheme based on the full Navier-Stoke equations ha been developed and used for this purpose. Inlet conditions are given by experiments, whenever possible, to minimize the error due to incorrect initial conditions. The standard k-.epsilon. model performs well for the strongly swirling jets with recirculation while it underpredicts the influence of swirl for weakly swirling jets. Rodi's swirl correction and algebraic stress model do not exhibit universality for the swirling jets. The present modified k-.epsilon. model derived from algebraic stress model accounts for anisotropy and streamline curvature effect on turbulence. This model performs consistently better than others for all cases. It may be because these flows have a strong dependence of stresses on the local strain of the mean flow. The predictions of truculence intensities indicate that this model successfully reflect the curvature effect in swirling jets, i.e. the stabilizing and destabilizing effects of swirl on turbulence transport.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 추계 학술대회논문집
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• pp.51-57
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• 2001

The eddy viscosity turbulence models were applied to predict the flows through a cascade, and the prediction performances of turbulence models were assessed by comparing with the experimental results for a controlled diffusion(CD) compressor blade. The original $\kappa-\omega$ turbulence model and $\kappa-\omega$ shear stress transport(SST) turbulence model were used as two-equation turbulence model which were enhanced for a low Reynolds number flow and the Baldwin-Lomax turbulence model was used as algebraic turbulence model. Farve averaged Wavier-Stokes equations in a two-dimensional, curvilinear coordinate system were solved by an implicit, cell-centered finite-volume computer code. The turbulence quantities are obtained by lagging when the men flow equations have been updated. The numerical analysis was made to the flows of CD compressor blade in a cascade at three different incidence angles (40. 43.4. 46 degrees). We found the reversion in the prediction performance of original $\kappa-\omega$ turbulence model and $\kappa-\omega$ SST turbulence model when the incidence angie increased. And the algebraic Baldwin-Lomax turbulence model showed inferiority to two-equation turbulence models.

• Wind and Structures
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• 제18권6호
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• pp.599-618
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• 2014

In this study, a square rectangular tall building is considered to investigate the effects of turbulence integral length scale and turbulence intensity on the along-wind responses, across-wind responses and torsional responses of the tall building by Large Eddy Simulation (LES). A recently proposed inflow turbulence generator called the discretizing and synthesizing random flow generation (DSRFG) approach is applied to simulate turbulent flow fields. It has been proved that the approach is able to generate a fluctuating turbulent flow field satisfying any given spectrum, desired turbulence intensity and wind speed profiles. Five profiles of turbulence integral length scale and turbulence intensity are respectively generated for the inflow fields by the DSRFG approach for investigating the effects of turbulence integral length scale and turbulence intensity on the wind-induced responses of the tall building. The computational results indicate that turbulence integral length scale does not have significant effect on the along-wind (displacement, velocity and acceleration) responses, across-wind displacement and velocity responses, while the across-wind acceleration and torsional responses vary without a clear rule with the parameter. On the other hand, the along-wind, across-wind and torsional responses increase with the growth of turbulence intensity.

• 대한기계학회논문집
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• 제19권9호
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• pp.2328-2341
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• 1995

An experimental study on the flow over the axisymmetric backward-facing step was carried out. The purposes of the present study are to investigate the effect of the free stream turbulence intensity on the reattachment length and to understand the turbulence structure of the recirculating flows. Local mean and fluctuating velocity components were measured in the separated and reattaching axisymmetric turbulent boundary layer over the wall of convex cylinder placed in a water tunnel by using 2-color 4-beam fiber optics laser Doppler velocimetry. As the free stream turbulence intensity increased, the reattachment length became shorter due to the enhanced mixing in the separated shear layer. It was also observed that the reverse flow velocity and turbulent kinetic energy increase with increasing free stream turbulence intensity. Spectral data and flow visualization showed that low-frequency motions occur in the separated flow behind a backward-facing step. These motions have a significant effect on the time-averaged turbulence data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.746-751
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• 2001

We used a cylindrical model which simulates turbine blade leading edge to investigate the effects of free-stream turbulence intensity and blowing ratio on film cooling of turbine blade leading edge. Tests are carried out in a low-speed wind tunnel on a cylindrical model with three rows of injection holes. Mainstream Reynolds number based on the cylinder diameter was $7.1\times10^4$. Two types of turbulence grid are used to increase a free-stream turbulence intensity. The effect of coolant blowing ratio was studied for various blowing ratios. For each blowing ratios, wall temperatures around the surface of the test model are measured by thermocouples installed inside the model. Results show that blowing ratios have small effect on spanwise-averaged film effectiveness at high free-stream turbulence intensity. However, an increase in free-stream turbulence intensity enhances significantly spanwise-averaged film effectiveness at low blowing ratio.

• 대한기계학회논문집B
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• 제20권10호
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• pp.3282-3292
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• 1996

Flow velocity was measured using a hot wire anemometer. Turbulence intensity was in proportion to mean flow velocity regardless of swirl velocity. And integral length scale has proportional relation with swirl velocity regardless of measurement position. Flame speed calculated by radius of visualized flame was increased and then decreased according to lapse of time from spark. Maximum flame speed was increased according to increase of turbulence intensity. Burning speed and flame transport effect increased with increase of swirl velocity, but ratio of burning speed to flame speed decreased with increased of swirl velocity. Mass fraction burned versus volume fraction burned was increased in proportion to the increase of turbulence intensity, caused by increase of combustion promotion effect according to increase of turbulence intensity and scale.

• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.259-267
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• 2001

The flow field in a cylinder of a 4-valve pentroof engine is studied using the KIVA-3V code. Turbulence is generated from the jet flow through valves and broken down to the small scale eddies in the compression process. It is known that the tumble effectively keeps turbulence during the compression process. In the combustion process, turbulence is known to enhance flame speed by increasing mass, momentum and heat transfer rates. The effects of the intake port angles on the flow and combustion characteristics are studied in this study. To study the effect of turbulence on the combustion process, Cantore combustion model is applied in this study.