Paper Reference No. F2012-E03-005

Vehicle Wading Simulation with STAR-CCM+ 1Zheng Xin; 2Qiao Xin; 3Kong Fanhua

Brilliance Automotive Engineering Research Institute

INTRODUCTIONCALCULATION MODEL ESTABLISHMENT AND

PROJECT ANALYSISRESULTS AND ANALYSISCONCLUSION

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.

INTRODUCTIONBecause 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 theengine 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 gridsHypermesh Surface MeshAbout 200,000 grids

The volume gridsSTAR-CCM+ Volume MeshAbout seven million

PROJECT ANALYSIS

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 .

projects (I) (II) (III) (IV)

Wading depth 100mm 100mm 200mm 200mm

Driving speed 30kph 10kph 30kph 20kph

Table 1 Projects

 RESULTS AND ANALYSIS

project I project II

project III project IVDisplay Volume Fraction of Water on Firewall at Different Wading Depths

and Driving Speeds

 RESULTS AND ANALYSIS

Road Test Compared to project IV

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

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

(1) project IV (2) Modified project

Volume Fraction of Water on Firewall

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.

Name: Zheng Xin E-mail: xin.zheng@brilliance-auto.comPhone: 15802450824

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