• Journal of computational fluids engineering
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• v.21 no.1
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• pp.30-35
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• 2016

In order to investigate effects of grid resolution on large-eddy simulation of flow over a heavy vehicle, large-eddy simulations over the vehicle with coarse grid and fine grid are conducted. In addition, comparison of drag coefficients with the experimental data obtained by a wind tunnel experiment is conducted. Both of the drag coefficients of coarse grid and fine grid large-eddy simulation show good agreement with the experimental data. Flow fields obtained by the coarse and the fine grid large-eddy simulation are compared in the vehicle frontal-face region, the vehicle rear wheel region, and the vehicle base region. Coarse grid large-eddy simulation shows good agreement with the fine grid large-eddy simulation in the vehicle front face region and the vehicle rear wheel region, since the flow over the present vehicle is dominated by flow separation which is geometrically pre-determined, not by the skin friction which is known to be sensitive to grid resolution.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1144-1150
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• 2009

Appropriate vibration model is required to predict in advance the vibration level of a large vehicle which carries sensitive electronic/mechanical equipments and drives often on the unpaved and/or off-road conditions. Central tire inflation system(CTIS) is recently adopted to improve the mobile operation of military and bulletproof vehicles. In this paper, full vehicle model(FVM) having 11 degrees of freedom and equipped with CTIS has been developed for a large vehicle which has $8\times8$ wheels$\times$driving wheels. Usability of the developed model is validated via road tests for three different modes (i.e. highway, country, and mud/sand/snow modes) and for various velocity conditions. The developed FVM can be used to predict the vibration level of the large vehicle as well as to determine the driving velocity criterion for different road conditions.

• International Journal of Automotive Technology
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• v.7 no.6
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• pp.715-720
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• 2006

This research investigates injury values and vehicle deformation for vehicle frontal crash compatibility. To investigate compatibility in an individual case, it is possible to impact two vehicles and evaluate the injury values and deformations in both vehicles. In this study, four tests were conducted to evaluate compatibility. A large and mini vehicle were subjected to a frontal car-to-car crash test at a speed of 48.3 km/h with an offset of 40%. An inclination car-to-car crash test using the large and small vehicle were conducted at 30 km/h at a $30^{\circ}$ angle. The results of the 48.3 km/h, car-to-car frontal crash revealed extremely high injury values on the chest and upper leg of the Hybrid III 50% driver dummy with seatbelt in the mini vehicle compared to the large vehicle. For the 30 km/h, car-to-car inclination crash, however, injury values in the small vehicle were 1.5 times higher compared to the large vehicle.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.135-141
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• 2005

Currently many safety assessment tests are conducted by crashing a vehicle against a rigid or deformable barrier. It is quite rational to evaluate crash performance of a vehicle in a barrier test in terms of vehicle stiffness and strength. However, there has been a lot of debate on whether barrier testing is a duplicate of real world crash collisions. One of the issues is car to car compatability. There are two essential subjects in compatability. One is partner-protection when crashing into another vehicle and the other is self-protection when struck by another vehicle. When considering a car to car frontal crash between a mini car and a large heavy car, it is necessary to evaluate human body stiffness of each vehicle. In this study, in order to evaluate the compatability of cars in car-to-car crashes, four tests were conducted. Test speed of each car is 48.3km/h, and the overlap of the mini and large car is $40\%$, and the overlap of the small cars is $100\%$. In all tests, only a drive dummy is used. The test results of the car to car crash test show that vehicle safety standard of mini car is not satisfied compared with large heavy car and HIC value of mini car is higher than large car. In this case observed that the relatively lower stiffness and weight of the mini car resulted in absorbing a large share of the total input energy of the system when crashed into the large heavy car.

• Journal of Auto-vehicle Safety Association
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• v.13 no.3
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• pp.54-59
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• 2021

Diesel engines emit PM and NOx during combustion. This is the main culprit of fine dust, which seriously affects the atmospheric environment. In particular, large-sized diesel vehicles over 3.5 tons emit a greater amount of pollutants because of their large displacement. The occurrence of vehicle abnormalities in this large-scale diesel vehicle causes even greater problems in the atmospheric environment. It was confirmed that there were many problems caused by natural regeneration DPF among large-sized diesel vehicles. Therefore, the most effective maintenance plan is suggested.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.6
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• pp.773-783
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• 2019

A numerical analysis of a turbulent flow with a 'large-eddy breakup device(LEBU)' was performed to investigate the influence of the device on the drag of underwater vehicle using commercial CFD code, FLUENT. In the present study, the vehicle drag was decomposed to skin-friction coefficient(C_f) and pressure coefficient(C_p). The variation of the vehicle C_f and C_p were observed with changing location of the device and Reynolds number. As a result, the device decreased the vehicle C_f because it suppressed the turbulent characteristics behind the device. The larger Reynolds number, the higher reduction effect when the device was placed in front part of, and near the vehicle. On the other hand, the device increased/decreased the vehicle C_p with increasing/decreasing turbulent kinetic energy at recirculating flow region behind the vehicle. The total drag change by the device was caused by C_p rather than C_f.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.159-163
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• 2008

The trend of Development Projects has been changing through a few recent years. Small-scale development projects in the past were usually for building residences or officetel in a big cities. making lots of profits. These projects made not only lots of profits but also unbalance between the urban centers and the suburbs. So government made some regulations to prevent the things from being worse anymore, planned to develop the country in balance and began to lead large-scale development project such as Inno city and Newtown. At first, in this study, the phases and the characteristics of development project's change will be looked around. And then, after overview about PFV(project financing vehicle) used a lot in large-scale development projects will be seen, the better ways to use PFV in large-scale development projects are going to be proposed by considering the problems in PFV's conformation.

• Journal of the Korean Society for Railway
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• v.13 no.1
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• pp.16-22
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• 2010

Various programs for dynamic simulation of the railway vehicle have advantages and disadvantages. These programs have limitation that cannot express a large deformable body for an wire of the railway vehicle. In this study, a program for dynamic simulation of the railway vehicle is developed. And the rigid, flexible and large deformable body can be simulated using this program. Its reliability is verified by comparison with a commercial program. Also, a wire is considered as the large deformable body and a sliding joint which connects the rigid body to the large deformable body is included. Moreover, as the wheel-rail contact module is added, the dynamic simulation of the railway vehicle can be analyzed using the developed program.

• Journal of the Korean Regional Science Association
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• v.6 no.1
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• pp.57-68
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• 1990

The purpose of this study is to develop the models to predict the noise PCE (Passenger Car Equivalence) of large running vehicles through noise prediction models. The noises were measured at the distance of 7.5M, 11.0M, and 14.5M from the noise source with test vehicles running at the speed of 40 Km/h, 60 Km/h, and 80 Km/h while normal traffic were detoured. Total noise levels were measured while vehicles were running at given speeds, Engine noise level was considered as the noise of its idle running at the three vehicle speeds shown above friction noise level was ascertained by moving the vehicle at given speeds without the engin operating. The noise prediction models for each noise source were developed by factors which affect to the each noise level. As a result of this paper, the reduction of total vehicle noise by increasing the distance to the noise source from 10 M to 15 M is as much as that by dropping its speed from 60 Km/h to 40 Km/h. Also, the reduction of PCE of total noise of large vehicle by making the noise source to that by reducing its speed from 80 Km/h to 60 Km/h. Enging noise PCE, which is in range between 65 and 160, is larger than friction noise PCE which is in range 3.5 and 5.5. Engin noise is the main noise of the large vehicles while friction noise is that of the small vehicles. Machine noise for large vehicles, and engin noise for small vehicles should be tightly controlled to reduce the vehicle noise. A low noise engine and tire, and the shape of vehicle body are needed to be developed to reduce noise further.

• Journal of Auto-vehicle Safety Association
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• v.13 no.2
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• pp.42-49
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• 2021

In this paper, we proposes a study on the derivation of inspection factors for the periodic inspection of large buses equipped with AEBS and LDWS. we investigate the safety evaluation (NCAP) of domestic and foreign vehicles and safety standards for the two functions currently in operation and analyze the evaluation factors, measurement methods and evaluation scenarios and so on. In addition, the test scenario was derived by analyzing the vehicle safety evaluation data already held, Therefore, we use an real large bus and the inspection elements for the periodic inspection were derived.