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한국기계가공학회지 제 권 제 호, 19 , 5 , pp.14 20(2020.05) ISSN 1598-6721(Print)
Journal of the Korean Society of Manufacturing Process Engineers, Vol. 19, No. 5, pp.14~20(2020.05) ISSN 2288-0771(Online)
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https://doi.org/10.14775/ksmpe.2020.19.05.014
Copyright The Korean Society of Manufacturing Process Engineers. This is an Open-Access article distributed under the terms of the Creative Commons Attribution-Noncommercial 3.0 License(CC BY-NC 3.0 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
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.
사이드 페어링 장착 유무에 따른 동 트럭에서의 공기 유동
해석
최계 * 조재웅, **,#
*공주대학 금형설계공학과,
**공주대학 기계자동차공학부
(Received 8 February 2020; received in revised form 18 February 2020; accepted 1 March 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.
Key Words : 대형 트럭 사이드 페어링 공기 저항 유속Truck( ), Side Fairing( ), Air Resistance( ), Flow Rate( ),
항력Drag( )
# Corresponding Author : [email protected]
Tel: +82-41-521-9271, Fax:+82-41-555-9123
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Kyekwang Choi, Jaeung Cho 한국기계가공학회지 제 권 제 호: 19 , 5
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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
(a) Model 1 (b) Model 2
(c) Model 3
Fig. 1 Flow analysis models
Table 1 Meshes of models 1, 2, 3
Nodes Elements
Model 1 109947 344340
Model 2 110159 347040
Model 3 110512 357026
(a) Model 1 (b) Model 2
(b) Model 3
Fig. 2 Boundary conditions of models
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
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Air Flow Analysis on Driving Truck with or without Side Pairing 한국기계가공학회지 제 권 제 호: 19 , 5
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Fig. 3 Contour of air pressure at model 1
Fig. 4 Air flow velocity at model 1
Fig. 5 Air flow velocity at head 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 × . At
Fig. 4, the maximum flow rate of 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() acting on the truck body became
at model 1. As the front section area
of the truck was , the drag coefficient of
the truck was .
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 ×. At Fig. 7, the maximum flow
rate of 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() acting on the
truck body became at model 2. As the
front section area of the truck was , the
drag coefficient of the truck was .
Fig. 6 Contour of air pressure at model 2
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Kyekwang Choi, Jaeung Cho 한국기계가공학회지 제 권 제 호: 19 , 5
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Fig. 7 Air flow velocity at model 2
Fig. 8 Air flow velocity at head of model 2
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
×. At Fig. 10, the maximum flow rate
of 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() acting on the truck body
became at model 3. As the front
section area of the truck was , the drag
coefficient of the truck was .
Fig. 9 Contour of air pressure at model 3
Fig. 10 Air flow velocity at model 3
Fig. 11 Air flow velocity at head of model 3
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Air Flow Analysis on Driving Truck with or without Side Pairing 한국기계가공학회지 제 권 제 호: 19 , 5
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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.
Fig. 12 Contour of pressure at model 1
Fig. 13 Contour of pressure at model 2
Fig. 14 Contour of pressure at model 3
Fig. 15 Streamline of air flow velocity at model 1
Fig. 16 Streamline of air flow velocity at model 2
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Kyekwang Choi, Jaeung Cho 한국기계가공학회지 제 권 제 호: 19 , 5
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Fig. 17 Streamline of air flow velocity at model 3
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
× at the rear of the truck was
shown to be the greatest among the three
models. And the maximum flow rate of
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.
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Air Flow Analysis on Driving Truck with or without Side Pairing 한국기계가공학회지 제 권 제 호: 19 , 5
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