Week 4 Challenge : CFD Meshing for BMW car

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)

output surface created with reference from the point by using relative command and coons created curve command the surface created by face-new-coons

use face- offset (top parameter)

face-new-conn (to create a new surface) to create & finish the entire surface of the tunnel 

overall volume

Mesh 

Bottom

on mesh -parameter- spacing

biasing-geomentry

Dstart-20

Dlimit-100

factor-1.1

to create a fine region at car & core region away from car

create volume

volume-define- detect on the whole body

only tunnel study area with care profile volume needed rest not necessary for volumetric mesh

After volume mesh is done by using

check geometry to check errors & conform for volumetric mesh

 volume mesh

side view

Problem faced 

symbol

 minimum size & Quality criteria not obtained in the logo which is troubleshot by deleted & recreated the symbol's small surface

INFERENCE

Each PID is cleaned up & 2D mesh to extract volume mesh for tunnel volume is created and volumetric mesh is done successfully without any error 

Ready for external flow analysis