Challenge

Week 4 Challenge : CFD Meshing for BMW car

RRagul Raj9 Mar 2023

Aim:-

The Aim of this challenge is to create a surface mesh for the given model and its wind tunnel. The other main focus is identifying different volumes for volume mesh and choosing the most pertinent one.

Procedure:-

We explore the model looking for geometrical errors. Our basic idea is that the car must be a single shell with an internal volume.
we notice that the model is symmetrical, so we delete half of it and work on the other half.
Now using the wireframe view mode we see the errors such as single cons and triple cons.
So according to that we work on the areas where they are present
Now keeping in mind that our model must be shell like and form a single inner volume, the topo errors are cleared.
The grill for example when viewed from outside forms a surface and when viewed from inside forms an internal volume.This is to be achieved without losing the shape and features of the said grill.
Now the finished topological features and surface looks like this:
Now we assign PID'S to each distinct Part such as windshield , wheels, grills etc
Now we start surfacing meshing of the model with target lengths specified in the question.
We start with parts which are not in contact with each other like headlights ,grills etc. and move on to the body which is in contact with multipl parts.
For such cases like grill and body in contact we give the perimeter and macros length as a range from 1-3 mm.(1mm for grills and 3mm body).The result will be as follows:
We can see there is varying mesh length along the border of the body-grill contact.
After completely meshing we move on to wind tunnel construction.
For the wind tunnel construction (a rectangular box) we assume that the length of the car x mm and height is y mm.
the dimensions of the wind tunnel are -> height = 100mm (surface below the car) + y(height of the car) + 3x (above the car)
breadth -> 2x
length -> 6x(behind the car) + (car's length)x + 4x (infront of the car)
We mesh the surface of the newly formed surfaces with 100 mm as the mesh length for all the side surfaces and 20 mm for the top and bottom surfaces.
We use spacing tool for creating meshing where the 100 mm and 20 mm surface is in contact with each other.
Now we go to volumetric mesh and choose the define option.
When it detects all the open volumes we must choose the appropriaate one.
Except the selected one we delete the other volumes and we can continue to re-mesh this volume.
Since the Volume meshing for this model will take upto 2 days that part is not attached here.