• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.5
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• pp.86-96
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• 1998

A numerical study has been carried out of three-dimensional turbulent flows around a MIRA reference vehicle model both with and without wheels in computation. Two convective difference schemes with two k-$\varepsilon$ turbulence models are evaluated for the performance such as drag coefficient, velocity and pressure fields. Pressure coefficients along the surfaces of the model are compared with experimental data. The drag coefficient, the velocity and pressure fields are found to change considerably with the adopted finite difference schemes. Drag forces computed in the various regions of the model indicate that design change decisions should not rely just on the total drag and that local flow structures are important. The results also indicate that the RNG model with the QUICK scheme predicts fairly well the tendency of velocity and pressure fields and gives more reliable drag coefficient rather than the other cases.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.10
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• pp.1309-1316
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• 2000

A surface flow visualization of a MIRA notchback reference car was conducted using a 1/4 -scale model in the POSTECH wind tunnel. The flow separation and reattachment phenomen a around A-pillar, C-pillar, backlight, and trunk were discussed with the help of the distributions of singular points such as nodes, saddles, and spiral foci. The locations of the singular points on the trunk and the backlight from experimental results are compared with those of CFD results using the turbulence modeling of RNG k -${\varepsilon}$ and RSM.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.120-126
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• 2006

Vehicle dynamic simulation has been carried out using the coherence of road roughness between left and right wheels. The generated twin tracks with the coherence of road roughness between left and right wheels are in good agreements with the measured coherence relation of left and right wheels. And these tracks reflect well on the roughness characteristics of real roads. Using the generated roads and multibody dynamic simulation program, vehicle dynamic simulation is performed. The vertical and roll motion analysis of a vehicle are carried out using the realistic road profiles with the coherence between left and right wheels and the results are in good agreements with the dynamic characteristics of a vehicle.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.31-39
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• 1996

The effect of rear-spoiler attached at rear end of automobile trunk on the aerodynamic characteristics of a MIRA reference car model was experimentally investigated. For different shapes and positions(G/H) of the rear-spoiler, the aerodynamic forces on the automobile were measured at various flow speed(ReL). The effect of rear-spoiler on the wake structure behind the automobile was also investigated using flow visualization and hot-wire anemometer. The rear-spoiler modifies the near wake structure and decreases aerodynamic drag and increases driving stability compared with those of the conventional automobile without rear-spoiler. From the experimental results, rear-spoiler of airfoil shape installed at the position of G/H=0.084 shows the best aerodynamic performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.1
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• pp.136-145
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• 1997

To analyzed ride quality and to predict durability in vehicle dynamics, it is essential to describe a road surface profile precisely. This paper presents a technique to generate road surface profiles in a spatial domain by using a power spectral density function. A single track power spectral density function is proposed to describe a road surface profile, which is also applicable for multi-track vehicle response analysis, The derived road surfaces are compared to ISO(International Organization for Standardization) standards and classifications, proposed by the MIRA(Motor Industry Research Association). The methodology in this paper is also proposed to generate road roughness description with a limited external data. A small amount of external curve data is combined with an internal PSD function to generate road surface roughness in a spatial domain.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.115-120
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• 2006

A Korean Road Roughness Classification(KRC) method is proposed. Using a dynamic road profiling device equipped with the Accelerometer Established Inertial Profiling Reference(AEIPR) method, road profile measurement is performed on various types of public paved roads in Korea. The road profiling data are processed to classify the characteristics of Korean road roughness. The resultant Korean road roughness classification(KRC) is shown different characteristics compared to the road classification proposed by ISO, MIRA, and Wong. The proposed KRC is composed of 8 classes(A-H, very good-poor) based on the power spectral density and is in good agreements with the characteristics of Korean paved road roughness and can be used well in vehicle ride comfort simulation using domestic road profile.