Week 4 Challenge : CFD Meshing for BMW car
Aim
To Check and solve all geometrical errors , Assigning appropriate PID's & to perform a CFD mesh on a BMW car with the given target length and element quality criteria.
Procedure
1.The file is opened in ANSA as it is.
2.Since the geometry of the car was axisymmetric the half portion was removed and all the errors were removed .
3.The PID's were assigned on the parts of the cars as given below.
4.All the errors were rectified and the correct diagram was meshed on the half portion first. The meshing was first done to individual PID's of the target length given in the question.
5.Then the model was joined with the help of transform tool and meshed with quality critertia conditions.
Skewness = 0.5
Min length = 0.1mm
Max Length = 7mm
The correct image without error is as give below;
6.After meshing the car ,a windtunnel was created . For this a point was created at the centre in the car as reference.
The calculation required to make a windtunnel is as given below;
The length of the car ,x = 1300mm approx.
The distance from reference point to the front and back face of the car = 650mm approx.
The distance from reference point to the side faces of the car = 370mm approx.
The distance from reference point to the top face of the car = 400mm approx.
Calculation 1
From the refrence point another point was created below the car at 200mm distance so that the bottom wall does not intersect with wheels of the car.
Calculation 2
The length required to build the front wall of the wind tunnel from the front face of the car = The distance from reference point to the front face of the car + 4x
The total distance will be = 650+(4*1300)
= 5850mm
Calculation 3
The length required to build the back wall of the wind tunnel from the back face of the car = The distance from reference point to the back face of the car + 6x
The total distance will be = 650+(6*1300)
= 8450mm
Calculation 4
The length required to build the walls on both sides of the car = The distance from reference point to the side faces of the car + x
The total distance is = 370+1300
= 1670mm
Calculation 2
The length required to build the top wall of the wind tunnel from the top face of the car = The distance from reference point to the top face of the car + 3x
The total distance is = 400 + (3*1300)
= 4300mm
7.The walls were made and the PID's were assigned to them as given below.
8.After assigning the PID's the walls were meshed one-by-one.The bottom wall was meshed with a target legth of 20mm.
9.The top wall was meshed with a target length of 100mm
10.A growing mesh condition was applied to the side walls of range 20-100mm with growth factor of 1.2.
11.The final mesh is as shown below.
Result
The gemetrical errors were checked and the model was meshed with the given target length values and quality criteria.A wind tunnel was also created with the help of calculations shown above and meshed with the given target length values.