Challenge

Week 4 Challenge : CFD Meshing for BMW car

JJagaveerapandiyan Selvaraj1 Apr 2023

CFD

Aim

To Mesh BMW car for CFD External flow analysis

OBJECTIVE

volumetric Mesh of external tunnel for analysis

To PROCESS

clean up

2D Mesh

external tunnel Volume

3D Mesh

clean up Aim

Clean up of BMW Car by deleting the symmetry portion except for Symbol which is not a symmetry model for ready for meshing

objective for cleanup

BMW car makes sure all the parts are without single cons except the body half the portion, only the external profile needs to capture removing internal surface surface

Meshing Aim

To obtain 2D shell tetra mesh with satisfying Quality criteria

objective

to obtain mesh quality criteria we need to make sure & maintain the mesh min length of coons

Volume Meshing Aim

To obtain volumetric mesh only the profile of the car at tunnel volume with minimum mesh size at the study area ( car region) and maximum mesh size at the top of the tunnel

volume Meshing objective

volume mesh the tunnel model without any error in quality criteria

COMMAND USED

Decks

select the solver to mesh- open form

view common

macros- visibility of surface

crosshatches- visibility of split surface define

single cons- free edges without any connection to surface

Double cons- connection of two surface

Triple cons- connection of three surfaces at a time

SURFACE CREATION & EDIT

TOPOMODE- classic

surface creation & cleanup mode

HOTPOINT

below operation will be performed in the following command & use that command to create, manipulate & delete hot points

insert(create), Project,multi-project, parametrical ( create with reference by % or by distance), Delete, intersect, release

CONS

below operation is used to perform create an edit of surface

past (merge two edges of the surface), release (make 1 step degrade of edges), project( project edge to face), fill hole (patch the holes)

FACES

below operation used for surface create delete & manipulate

Cut - cut & uncut split the surface or Faces, Delete, unDelete, new-conns or fitted (create from coons), TOPO (level up conns), PROJECT Cut (project the surface & cut), OFFSET, intersect (can split intersect & also delete surface), extend

POINTS

create & manipulate points using the below option

NEW (create from co-ordinate& inline- from coons selected), Relative- (with respective points), Delete, Undelete

Curve

creation and manipulation of curves by the below operation

create (concerning points), Delete, undelete

MESH CREATE & EDIT

Meshmode-classic

Mesh create & edit mode

Perimeters

length -macros - surface, Perimeter- edges or coons, Spacing- controlling nodal points & distribution of nodes

Grids

mesh manipulation

Move (nodes), Past (nodes)

Mesh Generation

2D shell mesh generated by using the below commands

spot mesh- (select, visible, regenerative), erase, Reconstruction

Auxillary

Fine(to make a smooth surface)

Measure tool

measure between node & coons

PROCEDURE

delete car Half the portion except the logo which is not symmetry

make the inside mode hollow and remove all unwanted surface

split each model to clean up the model without free edge assign a name to the respective model after cleaning up

check each part for error to troubleshoot

check-geometry

Names assign

BODY

LIGHT

GRILL

RIM & TIRE

OPTICAL REAR-VIEW MIRROR

WINDOW

by using the surface clean-up tool all bodies prepared

Mesh Quality criteria

check out the minimum measurement of each body and store it to assign the minimum element size

Assign Quality criteria

fixed parameters

max angle Quards- 0.7

max angle trias -0.7

skewness -0.3

OPTICAL REAR-VIEW MIRROR

minimum-1 mm

max- 3 mm

average-2 mm

WINDOW

minimum-1 mm

max- 3 mm

average-2 mm

RIM & TIRE

minimum-1 mm

max- 3 mm

average-2 mm

LIGHT

minimum-2 mm

max- 6 mm

average-4 mm

GRILL

minimum-0.4 mm

max- 2 mm

average-1 mm

BODY

minimum-1 mm

max- 5 mm

average-3 mm

TUNNEL

MINIMUM- 15 MM

MAXIMUM- 25 MM

AVERAGE-20 MM

Assign length parameters & macros as average mesh size for all except body-only macros assign as average mesh size perimeter will vary mesh size according to the attachment to the body

MESH OUTPUT

As conform to the mesh quality criteria by unlocking the hidden mode

overall

FRONT

TOP

REAR

Grills & LOGO

windows

Lights

TIRES & RIMS

MIRROR

SILENCER

BODY

After individual parts are meshed use Transformation-copy-symmetric (set a base 3 points) to mirror all parts to concerning the plan

WHOLE BODY

Tunnel volume creation

create a tunnel reference point

#tunnel parameter
# created by Jagaveerapandiyan.S
#length of car x
x=1306.02
#referance point
r=882.72
#tunnel
inlet=4*x+r
outlet=6*x+r
top=3*x+r
bottom=750 
#width of tunnel
t=x*2
print('parameter point creation for tunnel')
print('inlet=',inlet)
print('outlet=',outlet)
print('top=',top)
print('bottom=',bottom)
#width created referance from base point
print('thickness from referance=',t)