Paper Reference No. F2012-E03-005
Vehicle Wading Simulation
with STAR-CCM+
1Zheng
Xin; 2Qiao Xin; 3Kong Fanhua
Brilliance Automotive Engineering Research Institute
SUMMARY
INTRODUCTION
 CALCULATION MODEL ESTABLISHMENT AND PROJECT
ANALYSIS
 RESULTS AND ANALYSIS
 CONCLUSION

INTRODUCTION
Serious car wading would result in situations below:
 Waded car is easy to have its circuit interface and
sockets wetted;
 Firewall seepage;
 Short circuit, water entering air inlet pipe will lead to
air cylinder watering;
 Poor lubrication, increasing parts wearing and fuel
consumption, and so on.
INTRODUCTION
Because of the firewall seepage;
 To find out the main point of water seepage;
 The CFD software STAR-CCM+ was employed
to simulate the car wading.

CALCULATION MODEL
ESTABLISHMENT
Based on a CAD car model;
 All parts and units inside the
engine bay, front grille, wheels
and car body’s outer surface were chosen respectively
to generate a simulation space.
 First, creat the triangular meshes with Hypermesh，as
shown at above Figure, that makes model connection and
mesh quality improvement relatively easy. Then, provide
the output format of Nastran.

CALCULATION MODEL
ESTABLISHMENT
The surface grids


Hypermesh Surface Mesh
About 200,000 grids
The volume grids


STAR-CCM+ Volume Mesh
About seven million
PROJECT ANALYSIS
Table 1 Projects
projects
(I)
(II)
(III)
(IV)
Wading depth
100mm
100mm
200mm
200mm
Driving speed
30kph
10kph
30kph
20kph
Two fluid media of water and air was used in the analysis.
 Speed entrance boundary conditions were used for
entrance.
 Entrance speed was set according to actual road
condition speed, as shown in table 1 .

RESULTS AND ANALYSIS
project I
project II
project III
project IV
Display Volume Fraction of Water on Firewall at Different Wading Depths
and Driving Speeds
RESULTS AND ANALYSIS
Road Test Compared to project IV
RESULTS AND ANALYSIS
Added protective panel
 It has been seen from project IV that there was a lot of water in the center of firewall,
where water seepage could always be seen.
 For this concern, a protective panel was added to the engine bottom, as shown in
above Figure
 Aiming at stopping water back firing from the bottom and impacting the firewall.
RESULTS AND ANALYSIS
(1) project IV
(2) Modified project
Figure 1, water entering the engine bay was divided into two. One went
from grille, passing through intermediate cooler, condenser, radiator and fan,
and impacted the engine body. The other washed the engine bottom, turned
upward through the firewall and impacted the engine at the reverse side.
Figure 2, water washed the firewall from the engine bottom was stopped
by the newly added engine bottom protective panel, which cut off the water
flowing directly to and impacting the firewall.
RESULTS AND ANALYSIS
Volume Fraction of Water on Firewall
(1) project IV
(2) Modified project
Pressure Distribution over Firewall
CONCLUSION
(1) More accurate pressure distribution and water-on volume
fraction of all parts and units during the whole process of car
wading.
 (2) By adding the engine bottom protective panel, water
seepage at firewall was reduced. The modified project is
rational.
 (3) By use of CFD in product development, greatly shorten
the development cycle and save the development cost.
 (4) Analysis results are of important value for reference to the
design and development staff in optimizing product design.
 Deficiency of this article is that it lacks verification of overheat
that might occur in the engine bay due to addition of the engine
bottom protective panel. That will be covered later in our work.

Thanks for your attention
Contact Me



Name: Zheng Xin
E-mail: xin.zheng@brilliance-auto.com
Phone: 15802450824