• Wind and Structures
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• v.18 no.2
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• pp.155-180
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• 2014

The safety of road vehicles on the ground in crosswind has been investigated for many years. One of the most important fundamentals in the safety analysis is aerodynamic characteristics of a vehicle in crosswind. The most common way to study the aerodynamic characteristics of a vehicle in crosswind is wind tunnel tests to measure the aerodynamic coefficients and/or pressure coefficients of the vehicle. Due to the complexity of wind tunnel test equipment and procedure, the features of flow field around the vehicle are seldom explored in a wind tunnel, particularly for the vehicle moving on the ground. As a complementary to wind tunnel tests, the numerical method using computational fluid dynamics (CFD) can be employed as an effective tool to explore the aerodynamic characteristics of as well as flow features around the vehicle. This study explores crosswind effects on a high-sided lorry on the ground with and without movement through CFD simulations together with wind tunnel tests. Firstly, the aerodynamic forces on a stationary lorry model are measured in a wind tunnel, and the results are compared with the previous measurement results. The CFD with unsteady RANS method is then employed to simulate wind flow around and wind pressures on the stationary lorry. The numerical aerodynamic forces are compared with the wind tunnel test results. Furthermore, the same CFD method is extended to investigate the moving vehicle on the ground in crosswind. The results show that the CFD results match with wind tunnel test results and the current way using aerodynamic coefficients from a stationary vehicle in crosswind is acceptable. The CFD simulation can provide more insights on flow field and pressure distribution which are difficult to be obtained by wind tunnel tests.

• Wind and Structures
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• v.24 no.1
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• pp.1-24
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• 2017

Wind environment in urban residential areas is an important index to consider when evaluating the living environment. However, due to the complexity of the flow field in residential areas, it is difficult to specify the correct inflow boundary conditions in the large eddy simulation (LES). In this paper, the weighted amplitude wave superposition (WAWS) is adopted to simulate the fluctuating velocity data, which satisfies the desired target wind field. The fluctuating velocity data are given to the inlet boundary of the LES by developing an UDF script, which is implemented into the FLUENT. Then, two numerical models - the empty numerical wind tunnel model and the numerical wind tunnel model with spires and roughness elements are established based on the wind tunnel experiment to verify the present method. Finally, the turbulence generation approach presented in this paper is used to carry out a numerical simulation on the wind environment in an urban residential area in Lisbon. The computational results are compared with the wind tunnel experimental data, showing that the numerical results in the LES have a good agreement with the experimental results, and the simulated flow field with the inlet fluctuations can generate a reasonable turbulent wind field. It also shows that strong wind velocities and turbulent kinetic energy occur at the passageways, which may affect the comfort of people in the residential neighborhood, and the small wind velocities and vortexes appear at the leeward corners of buildings, which may affect the spreading of the pollutants.

• Wind and Structures
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• v.31 no.3
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• pp.209-216
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• 2020

Aiming at the wind-resistant design of a sea-crossing arch bridge, the static aerodynamic coefficients of its girder (composed of stretches of π-shaped cross-section and box cross-section) were studied by using computational fluid dynamics (CFD) numerical simulation and wind tunnel test. Based on the comparison between numerical simulation, wind tunnel test and specification recommendation, a combined calculation method for the horizontal force coefficient of intermediate and small span bridges is proposed. The results show that the two-dimensional CFD numerical simulations of the individual cross sections are sufficient to meet the accuracy requirements of engineering practice.

• Journal of the Korean Society of Visualization
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• v.16 no.3
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• pp.59-64
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• 2018

Numerical simulations were carried out to analyze the flow characteristics of the wind tunnel. Flow field characteristics with velocity uniformity at the test sections are largely affected by inlet conditions of air flow rate and temperature. Axial average velocity of the flow field inside the test area was almost linearly decreased by 0.026% each 1m. The uniformity distributions of axial velocity showed the highest reduction rate of about 24% between nozzle outlets 1 ~ 2m. In addition, average velocity and the uniformity are increased with air temperature in the wind tunnel due to density variation. The results of this paper are expected to be useful for the basic design of wind tunnel and to be used for efficient design.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.138-141
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• 2008

The screen doors installed in the station of subway are subject to the train-wind pressure caused by the operation of trains. The train-wind pressure has to be correctly estimated for the design of safe structure of screen doors. As three-dimensional numerical flow analysis technology has been significantly developed, the analysis on the train-wind pressure with diverse variables such as train specifications, train speed, tunnel and station configurations, and blockage ratio can be effectively carried out with three-dimensional numerical method. In this study, computational analysis of train-induced wind in a subway tunnel employing the screen doors are carried out by using the three-dimensional numerical method with the model of the moving boundary for the run of trains. While the numerical analysis of train-wind pressure was applied on the one island-type station in the Seoul Subway Line 2, maximum pressure of 494 Pa was estimated on the screen door when two trains pass each other at the speed of 80km/h in the platform.

• Wind and Structures
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• v.38 no.3
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• pp.203-214
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• 2024

Large-span cantilevered roof represents a unique type of structure that is vulnerable to wind loads. Inspired by the need to maximumly reducing the rooftop wind loads, this study examined the feasibility of positioning vented slots on the leading edge, and the effectiveness of such aerodynamic mitigation measures are assessed via both physical and numerical simulations. The reliability of numerical simulation was evaluated via comparisons with the wind tunnel tests. The results indicated that, the variation of venting hole arrangement can cause significant change in the rooftop wind load characteristics. For the cases involved in this study, the maximum reduction of mean and peak wind suction coefficients are found to be 9% and 8% as compared to the original circular slot without venting holes. In addition, the effect of slot shape is also evident. It was shown that the triangular shaped slot tends to increase the wind suction near the leading edge, whereas the hexagonal and octagonal shaped slots are found to decrease the wind suction. In particular, with the installation of octagonal shaped slot, the maximum reduction of wind suction coefficients near the leading edge reaches up to 31% as compared to the circular shaped slot, while the maximum reduction of mean wind suction coefficients is about 30%.

• Wind and Structures
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• v.28 no.4
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• pp.239-253
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• 2019

Accurate numericalsimulation of wind field over complex terrain is an important prerequisite for wind resource assessment. In this study, numerical simulation of wind field over complex terrain was further carried out by taking the complex terrain around Siu Ho Wan station in Hong Kong as an example. By artificially expanding the original digital model data, Gambit and ICEM CFD software were used to create high-precision complex terrain model with high-quality meshing. The equilibrium atmospheric boundary layer simulation based on RANS turbulence model was carried out in a flat terrain domain, and the approximate inflow boundary conditions for the wind field simulation over complex terrain were established. Based on this, numerical simulations of wind field over complex terrain under different inflow wind directions were carried out. The numerical results were compared with the wind tunnel test and field measurement data for land and sea fetches. The results show that the numerical results are in good agreement with the wind tunnel data and the field measurement data which can verify the accuracy and reliability of the numerical simulation. The near ground wind field over complex terrain is complex and affected obviously by the terrain, and the wind field characteristics should be fully understood by numerical simulation when carrying out engineering application on it.

• Journal of Wind Energy
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• v.5 no.1
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• pp.33-42
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• 2014

The new aerofoil, KA2 was designed to apply to the wind turbine blade. For the aerofoil, numerical analysis was performed to review aerodynamic characteristics like lift and drag coefficient. And they are verified with test data using the digital wind tunnel and test samples from 3D printer. The digital wind tunnel was developed to test wing in the small laboratory, and verified with test of NACA0012 airfoil. KA2 aerofoil is asymmetric, and has the thickness ratio of 14%, and 12 degree of AOA at the maximum lift coefficient of 1.3. In this paper, aerodynamic characteristics from numerical and test approaches will be proposed with AOA in detail. Therefore, this aerofoil will be used for the design of wind turbine blade.

• Wind and Structures
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• v.7 no.1
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• pp.13-28
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• 2004

A method of numerical analysis without conducting 3D wind tunnel model tests was examined in our previous study for predicting vortex-induced oscillation of bridge girders with span-wise varying geometry. The aerodynamic damping forces measured for plural wind tunnel 2D models were used in the analysis. A further study was conducted to examine the precision of solution obtained by this method. First, the responses of vortex-induced oscillation of two rocking models and a taut-strip bridge girder model with span-wise varying geometry were measured. Next, the responses of these models were numerically analyzed by means of this method, and then a comparison was made between the obtained $Vr-A-{\delta}_a$ contour diagram of each 3D model in the wind tunnel test and the diagram in the numerical analysis. Since close correlations were observed between each two $Vr-A-{\delta}_a$diagrams obtained in the model test and in the analysis in cases where the 3D model did not have strong three-dimensionality, our findings revealed that the predicted solution proved to be reasonably accurate.

• Wind and Structures
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• v.28 no.1
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• pp.31-47
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• 2019

The accurate prediction of snow distributions under the wind action on roofs plays an important role in designing structures in civil engineering in regions with heavy snowfall. Affected by some factors such as building shapes, sizes and layouts, the snow drifting on roofs shows more three-dimensional characteristics. Thus, the research on three-dimensional snow distribution is needed. Firstly, four groups of stepped flat roofs are designed, of which the width-height ratio is 3, 4, 5 and 6. Silica sand with average radius of 0.1 mm is used to model the snow particles and then the wind tunnel test of snow drifting on stepped flat roofs is carried out. 3D scanning is used to obtain the snow distribution after the test is finished and the mean mass transport rate is calculated. Next, the wind velocity and duration is determined for numerical simulations based on similarity criteria. The adaptive-mesh method based on radial basis function (RBF) interpolation is used to simulate the dynamic change of snow phase boundary on lower roofs and then a time-marching analysis of steady snow drifting is conducted. The overall trend of numerical results are generally consistent with the wind tunnel tests and field measurements, which validate the accuracy of the numerical simulation. The combination between the wind tunnel test and CFD simulation for three-dimensional typical roofs can provide certain reference to the prediction of the distribution of snow loads on typical roofs.