• Journal of computational fluids engineering
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• v.21 no.2
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• pp.70-80
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• 2016

The comparison of two commercial codes(FLUENT and STAR-CCM+) and an open-source code(OpenFOAM) are carried out for the aerodynamic analysis of flight vehicles at low speeds. Tailless blended-wing-body UCAV, main wing and propeller of HALE UAV(EAV-3) are chosen as geometries for the investigation. Using the same mesh, incompressible flow simulations are carried out and the results from three different codes are compared. In the linear region, the maximum difference of lift and drag coefficients of UCAV are found to be less than 2% and 5 counts, respectively and shows good agreement with wind tunnel test data. In a stall region, however, the reliability of RANS simulation is found to become poor and the uncertainty according to code also increases. The effect of turbulence models and meshes generated from different tools are also examined. The transition model yields better results in terms of drag which are much closer to the test data. The pitching moment is confirmed to be sensitive to the existence and the location of transition. For the case of EAV-3 wing, the difference of results with ${\kappa}-{\omega}$ SST model is increased when Reynolds number becomes low. The results for the propeller show good agreement within 1% difference of thrust. The reliability and uncertainty of three codes is found to be reasonable for the purpose of engineering use. However, the physical validity and reliability of results seem to be carefully examined when ${\kappa}-{\omega}$ SST model is used for aerodynamic simulation at low speeds or low Reynolds number conditions.

• Wind and Structures
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• v.11 no.4
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• pp.257-273
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• 2008

A number of passive aerodynamic drag reduction methods were applied separately and then in different combinations on an intercity bus model, through wind tunnel studies on a 1:20 scale model of a Mercedes Benz Tourismo 15 RHD intercity bus. Computational fluid dynamics (CFD) modelling was also conducted in parallel to assist with flow visualisation. The commercial CFD package $CFX^{TM}$ was used. It has been found that dramatic reductions in coefficient of drag ($C_D$) of up to 70% can be achieved on the model using tapered and rounded top and side leading edges, and a truncated rear boat-tail. The curved front section allows the airflow to adhere to the bus surfaces for the full length of the vehicle, while the boat-tails reduce the size of the low pressure region at the base of the bus and more importantly, additional pressure recovery occurs and the base pressures rise, reducing drag. It is found that the CFD results show remarkable agreement with experimental results, both in the magnitude of the force coefficients as well as in their trends. An analysis shows that such a reduction in aerodynamic drag could lead to a significant 28% reduction in fuel consumption for a typical bus on intercity or interstate operation. This could translate to a massive dollar savings as well as significant emissions reductions across a fleet. On road tests are recommended.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1724-1729
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• 2003

A new ground transportation system is often simulated by the wing in ground effect(WIG). Recently, several kinds of experimental and computational studies are being carried out to investigate the WIG aerodynamic characteristics which are of practical importance to develop the new ground transportation vehicle system. These works are mainly based on conventional wind tunnel tests, but many problems associated with the WIG aerodynamic characteristics can not be satisfactorily resolved. In order to develop the new ground transportation vehicle system the WIG should be further investigated. To do this, it is necessary to develop a s imulator appropriate to the WIG aerodynamics. The objective of the present study is to clarify the aerodynamic characteristics of the WIG and to develop a new experimental test rig for the investigation of the WIG aerodynamics. Some preliminary experiments are performed to investigate the usefulness of the WIG simulator.

• Wind and Structures
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• v.35 no.1
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• pp.67-81
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• 2022

While the aerodynamics of solid bluff bodies is reasonably well-understood and methodologies for their reliable numerical simulation are available, the aerodynamics of porous bluff bodies formed by assembling perforated plates has received less attention. The topic is nevertheless of great technical interest, due to their ubiquitous presence in applications (fences, windbreaks and double skin facades to name a few). This work follows previous investigations by the authors, aimed at verifying the consistency of numerical simulations based on the explicit modelling of the perforated plates geometry and their representation by means of pressure-jumps. In this work we further expand such investigations and, contextually, we provide insight into the flow arrangement and its sensitivity to important modelling and setup configurations. To this purpose, Unsteady Reynolds-Averaged Navier-Stokes (URANS) and Large-Eddy Simulations (LES) are performed for a 5:1 rectangular cylinder at null angle of attack. Then, using URANS, porosity and attack angle are simultaneously varied. To the authors' knowledge this is the first time in which LES are used to model a porous bluff body and compare results obtained using the explicit modelling approach to those obtained relying on pressure-jumps. Despite the flow organization often shows noticeable differences, good agreement is found between the two modelling strategies in terms of drag force.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.3
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• pp.393-404
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• 2017

Side jet effect on the aerodynamic characteristics of a missile was investigated using experimental and computational methods. A couple of side jets were injected toward outward downstream at mid point of missile body. Cold air jet was used in the wind tunnel test, and cold and hot jet were used in the computation. Wind tunnel test was carried out with jet and without jet, and calculation was performed for three cases ; no jet, cold air jet, and hot mixture gas jet. From the comparison of measured and calculated data for all cases, two points could be deduced. Firstly, side jet made static stability to be unstable by increasing body normal force near the side jet exit and by decreasing tail normal force. Secondly, hot mixture gas had more significant effect on the static stability of a missile-type body than cold air jet.

• Journal of Mechanical Science and Technology
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• v.20 no.4
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• pp.561-568
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• 2006

CFD simulation for one of tilt-rotor UAV configurations, TR-E2S1, was performed to investigate its aerodynamic characteristics. Control surfaces such as elevator and rudder were deflected and wing incidence angle was changed. Also aerodynamic stabilities were analyzed with the variation of pitch and yaw angles. The comparison of CFD with wind tunnel test results reveals the same trends in the aerodynamic characteristics and stabilities. However 12% scale wind tunnel test model is too small for accurate data collection and should build a high fidelity model for quantitative data comparison.

• Wind and Structures
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• v.7 no.1
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• pp.29-40
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• 2004

This study has focused on aerodynamics for a wind-resistance design about the single and tandem box girder sections to realize a super-long span bridge in the near future. Three-dimensional static analysis of flows around the fundamental single and tandem box girder sections with fairing is carried out by means of the IBTD/FS finite element technique with LES turbulence model. As the results of the analysis, computations have verified aerodynamic characteristics of both sections by the histories of aerodynamic forces, the separation and reattachment flow patterns and the surface pressure distributions. The relationship between the section shapes and the aerodynamic characteristics is also investigated in both sections. And the mechanism about the generation of fluctuating aerodynamic forces is discussed.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1939-1944
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• 2004

Recently, several kinds of experimental and computational studies are being carried out to investigate the WIG aerodynamic characteristics which are of practical importance to develop the new ground transportation vehicle system. These works are mainly based upon conventional wind tunnel tests, but many problems associated with the WIG aerodynamic characteristics cannot be satisfactorily resolved due to the wind tunnel blockage effects or string problems to support the test object. To do this, it is necessary to develop a novel simulator appropriate to the WIG aerodynamics. The objective of the present study is to clarify the aerodynamic characteristics of a new developed WIG simulator, which is able to imitate real WIG flow circumstances such as gradually decelerating and accelerating flows.

• Journal of Aerospace System Engineering
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• v.9 no.4
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• pp.62-66
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• 2015

During the conceptual design of turboprop aircraft, the power effect driven from rotating propeller is typically obtained from empirical data. In the present paper, propeller power effect was obtained by using unsteady three-dimensional Navier-Stokes solver with $k-{\omega}$ turbulence model for the accurate prediction of turboprop aircraft performance. In order to simulate the relative motion between propeller and fuselage, unsteady sliding mesh method was used. During simulation, three flow conditions such as climb, cruise and descending flight were selected considering the flight envelop of the real turboprop aircraft. For the correction of aerodynamic coefficients, the thrust effect of engine exhaust gas was included based on the engine manufacturer's data. Using the computational results, the correction table for the aerodynamic coefficient of turboprop aircraft was suggested for the performance analysis of turboprop aircraft.

• Wind and Structures
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• v.4 no.4
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• pp.315-332
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• 2001

Presented herein is a numerical study for evaluating the aerodynamic behaviour of equipped bridge deck sections. In the first part, the method adopted is described, in particular concerning turbulence models, meshing requirements and numerical approach. The validation of the procedure represents the aim of the second part of the paper: the results of the numerical simulation in case of two-dimensional, steady, incompressible, turbulent flow around a realistic bridge deck are compared to the data collected from wind-tunnel tests. In order to demonstrate the influence of the section details and of the partial streamlining of the deck geometry on its aerodynamic behaviour, in the third part of the paper the effect of the fairings and of each item of equipment of the section (such as central barriers, side railings and sidewalks) is evaluated. The study has been applied to the deck section of the Normandy cable-stayed bridge.