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ISSN : 1598-6721(Print)
ISSN : 2288-0771(Online)
The Korean Society of Manufacturing Process Engineers Vol.19 No.5 pp.14-20
DOI : https://doi.org/10.14775/ksmpe.2020.19.05.014

Air Flow Analysis on Driving Truck with or without Side Pairing

Kyekwang Choi*, Jaeung Cho**#
*Department of Metal Mold Design Engineering, Kongju National UNIV.
**Division of Mechanical and Automotive Engineering, Kongju National UNIV.
#Corresponding Author : jucho@kongju.ac.kr Tel: +82-41-521-9271, Fax:+82-41-555-9123
08/02/2020 18/02/2020 01/03/2020

Abstract


In this study, the overall states of the airflow when a truck with or without side pairing is driven at a maximum speed of 90 km/h, regulated by domestic law, were investigated through computational fluid dynamics numerical analysis. All the tested models showed that the airflow went under the truck body; specifically, the air did not flow along the underside to the rear of the truck but through the sides of its underside. The drag with the drag coefficient at model 3 was clearly higher than those for the other two models. The results of this study could help to improve the truck performance by reducing its resistance against the air flown from it in driving itself.



사이드 페어링 장착 유무에 따른 구동 트럭에서의 공기 유동 해석

최 계광*, 조 재웅**#
*공주대학교 금형설계공학과
**공주대학교 기계자동차공학부

초록


    © The Korean Society of Manufacturing Process Engineers. All rights reserved.

    This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

    1. Introduction

    The vehicles accounts for a large portion of domestic cargo transportation by land. Large trucks which are running the long-distance at high speeds play a big role in land transport. The fuel efficiency can be improved by reducing the air resistance. So, the small efficiency improvements can save a lot of money in a gas-guzzling car. By using the flow analysis on large truck as well as passenger car, many researches at Europe are being actively performed about the reduction of air resistance. In case of large trucks, the deflectors are installed mainly on the top of cap where the seat of driver is located for the purpose of improving the aerodynamic performance to reduce air resistance[1-5]. In this study, the overall states of air flow under the condition that the truck with or without side pairing is driving at a maximum speed of 90 km/h regulated by domestic law are investigated through CFD numerical analysis[6-11]. The drag by flow affects the recovery of pressure from the rear of the truck body[8-11]. The results of this study are thought to be the effective data at improving performance by reducing the resistance against the airflow flown from the truck in driving itself.

    2. Study Models and Boundary Conditions

    2.1 Study models

    In this study, each of the three-dimensional models on trucks is shown by Figs. 1 (a), (b) and (c), respectively. In this study, the truck at Fig. 1 (a) was modeled with no side-pairing. The truck at Fig. 1(b) was modeled with a shock absorber bar installed at the truck which is commonly driven on current roads rather than side-pairing. Finally, the truck at Fig. 1(c) was modeled with the side-pairing to cover the sidewall of the truck's body as much as possible. Table 1 shows the meshes of models 1, 2 and 3.

    2.2 Boundary conditions of models

    Flow analyses in this study were carried out by using the CFX program of ANSYS. Figs. 2 (a), (b) and (c) show the boundary conditions specified in fluid models 1, 2 and 3, respectively. The flow rate of inlet is designated as 90km/h(25m/s). And the temperature of air flow is 25℃.

    3. Flow Analysis Results

    3.1 Flow analysis result of model 1

    Figs. 3, 4 and 5 show the pressure contours and flow rates on the rear of the truck at model 1 with no side fairing. As shown by Fig. 3, the maximum pressure on the rear of truck is 7.629 × 10-6Pa. At Fig. 4, the maximum flow rate of 39.08 m/s is shown around the truck. Also, Fig. 5 shows the fastest flow rate passing through the top of the truck. By using the function calculator of CFX-Post, the drag(FD) acting on the truck body became -25.1686N at model 1. As the front section area of the truck was 0.111m2, the drag coefficient of the truck was 0.56116.

    3.2 Flow analysis result of model 2

    Figs. 6, 7 and 8 show the pressure contours and flow rates on the rear of the truck at model 2 equipped with a shock absorber bar. As shown by Fig. 6, the maximum pressure on the rear of truck is 8.306 × 10-2Pa. At Fig. 7, the maximum flow rate of 39.49 m/s is shown around the truck. Also, Fig. 8 shows the fastest flow rate passing through the top of the truck. By using the function calculator of CFX-Post, the drag(FD) acting on the truck body became -25.1831 N at model 2. As the front section area of the truck was 0.111m2, the drag coefficient of the truck was 0.56148.

    3.3 Flow analysis result of model 3

    Figs. 9, 10 and 11 show the pressure contours and flow rates on the rear of the truck at model 3 installed with a side-fairing. As shown by Fig. 9, the maximum pressure on the rear of truck is 1.317 × 10-1Pa. At Fig. 10, the maximum flow rate of 39.64m/s is shown around the truck. Also, Fig. 11 shows the fastest flow rate passing through the top of the truck. By using the function calculator of CFX-Post, the drag(FD) acting on the truck body became -26.6487N at model 3. As the front section area of the truck was 0.111 m2, the drag coefficient of the truck was 0.59416.

    3.4 Overall analysis results of models 1, 2 and 3

    Figs. 12, 13 and 14 show the pressure contours on the middle plane of the truck body at models 1, 2 and 3, respectively. And Figs. 15, 16, 17 show the streamlines that represent the velocity of air flowing around the body of truck at models 1, 2 and 3, respectively. As shown by these figures, the air flowing down the truck is not going out the body to follow the underside of truck body to the end until the rear of the truck. Instead, as the air escapes to the side of a truck, the pressure appears high near the truck's side of the lower ground.

    4. Conclusion

    In this study, the overall states of air flow under the condition that the truck with or without side pairing is driving at a maximum speed of 90 km/h regulated by domestic law are investigated through CFD numerical analysis. The study results are as follows;

    1. At model 3, the maximum pressure of 1.317 × 10-1Pa at the rear of the truck was shown to be the greatest among the three models. And the maximum flow rate of 39.64 m/s at model 3 was the largest among three models.

    2. The drag with drag coefficient at model 3 was clearly higher in comparison to those of the other two models.

    3. At all models, it can be seen that the air flow goes under the body of truck. This air does not flow along the underside of truck to the rear on the body of truck but through the sides of the underside.

    4. The results of this study are thought to be the effective data at improving performance by reducing resistance against the airflow flown from the truck in driving itself.

    Figure

    KSMPE-19-5-14_F1.gif
    Flow analysis models
    KSMPE-19-5-14_F2.gif
    Boundary conditions of models
    KSMPE-19-5-14_F3.gif
    Contour of air pressure at model 1
    KSMPE-19-5-14_F4.gif
    Air flow velocity at model 1
    KSMPE-19-5-14_F5.gif
    Air flow velocity at head of model 1
    KSMPE-19-5-14_F6.gif
    Contour of air pressure at model 2
    KSMPE-19-5-14_F7.gif
    Air flow velocity at model 2
    KSMPE-19-5-14_F8.gif
    Air flow velocity at head of model 2
    KSMPE-19-5-14_F9.gif
    Contour of air pressure at model 3
    KSMPE-19-5-14_F10.gif
    Air flow velocity at model 3
    KSMPE-19-5-14_F11.gif
    Air flow velocity at head of model 3
    KSMPE-19-5-14_F12.gif
    Contour of pressure at model 1
    KSMPE-19-5-14_F13.gif
    Contour of pressure at model 2
    KSMPE-19-5-14_F14.gif
    Contour of pressure at model 3
    KSMPE-19-5-14_F15.gif
    Streamline of air flow velocity at model 1
    KSMPE-19-5-14_F16.gif
    Streamline of air flow velocity at model 2
    KSMPE-19-5-14_F17.gif
    Streamline of air flow velocity at model 3

    Table

    Meshes of models 1, 2, 3

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