# Comsol for Dummies by B1J2u4

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• pg 1
```									This man is not a dummy
Maximum power, minimum weight
Isaac Newton (1643 -1727)

F=m*a

Also known from the Da Vinci Code
Robert Hooke (1635 – 1703)

Force (F)

F=k*s

Extension (s)
Daniel Bernoulli (1700 -1782)

½rv2+rgh+p=constant
Joseph Fourier (1768-1830)

q=k(T-Tref)/L
Georg Ohm (1787 – 1854)

V=I*R
James Maxwell (1831 – 1879)
Dmitri Mendelejev (1834 – 1907)
Science can be fun ... (1879-1955)

... and rewarding (1833-1896)
fun...      ...failure...

... and disaster...
This bridge should
have been modeled
Why modeling?
• Suppose the laws of physics were unknown

• Every idea must be tested...
...and tested
... and tested

• Trial and error: very expensive
.....
Why modeling?
Save money by
1 Describing the physics mathematically
2 Solving the mathematical problem
PHYSICS             IDEA BY      FORMULA        SOLUTION
dynamics:          Newton:      F=m*a         -> a=F/m
mechanics:          Hooke:       F=k*s         -> s=F/k
gas/liquid flow     Bernoulli:   ½rv2+rgh+p=c -> v=2√ [(c-rgh-p)/r]
heat:               Fourier:     q=k(T-Tref)/L    -> T=qL/k+Tref
current             Ohm:         V=I*R          -> I=V/R
..............
Why modeling with software
• Simple geometry => Single equation
• Complex geometries => lots of equations

F=k*s -> s=F/k

s=???
Why Comsol?
• Lots of physics, lots of software
– Elasticity           – Abaqus, Ansys, Nastran etc
– Air resistance       – Fluent, CFX etc
– Electronics          – Ansoft, Maxwell
– Heat transfer        – Flowterm
– Chemical reactions   – Aspen

• COMSOL covers all
Why Comsol?
• Do we need to model all physics?
• Not always. But Comsol is very userfriendly
Why Comsol?
• Many times physics influences other physics
–Chemical reactions produce heat
–Electronic get hot
–Hot devices expand or melt
• Other softwares then need to be bundeled
•expensive
•lots of work to write interfaces

• Comsol is specifically written for this
Comsol!
• for all your research and development
– Affordable
– Powerfull
– Userfriendly
– Competative
How does Comsol work?
• Geometry       -> create computerdrawing
• Physics        -> laws of nature (F=k*s etc.)
• Meshing        -> to handle complex geometry
together with the physics
• Solving         -> Mathematical operations
• Postprocessing -> Viewing the results
Graphical User Interface (GUI)
Meshing, solving and viewing
More detailed example
F=k*s

sleft                                     sright

Finternal=k*sinternal

sinternal ?      Fexternal ?
Geom -> Physics -> Mesh -> Equations
Nodes
Displacements

S5
S2
S7

S17
S44
S1         S4    S9         S23         S49
S18

S8

S3
Equations

S5
S2
F7=k7*S7+neighboring nodal influence

S17
S44
F1 = k1*S1          S9          S23
S4                                       S49
+ neighboring nodal influence
+ external force       S18

External force
External force

F8=k8*S8+neighboring nodal influence

S3
A large set of equations

F1=k1*S1+neighboring nodal influence + external force
.
.
.
.

F7=k7*S7 + neighboring nodal influence
F8=k8*S8 + neighboring nodal influence
.
.
.
.

F49=k49*S49+neighboring nodal influence + external force
Fully write out all equations

• Neighboring nodal influence must be
described mathematically
Can be put in a matrix equation
 K11       K12         K13      K14                         K1 46     K1 48        K1 48     K1 49   s1   F1 
                                                            K 2 46    K 2 47       K 2 48             s  F 
K 2 49   2   2 
 K 21      K 22        K 23     K 24
. . .
 K 31      K 32        K 33     K 34                        K 3 46    K 3 47       K 3 48    K 3 49   s3   F3 
                                                                                                         
 K 41      K 42        K 43     K 44                        K 4 46    K 4 47       K 4 48    K 4 49   s4   F4 
                   .                      .                                    .                       .   . 
                                                                                                         
                   .                            .                              .                      .    . 
                   .                                  .                        .                       .   . 
K         K 46 2       K 46 3    K 46 4                   K 46 46    K 46 48       K 46 48   K 46 49   s   F 
 46 1                                                                                                  46   46 
 K 47 1   K 47 2       K 47 3    K 47 4                   K 47 46    K 47 47       K 47 48   K 47 49   s   F 
K         K 48 2       K 48 3    K 48 4
. . .
K 48 46    K 48 47       K 48 48             47   47 
K 48 49  s   F 
 48 1                                                                                                    48     48
 K 49 1   K 49 2       K 49 3    K 49 4                   K 49 46    K 49 47       K 49 48                
K 49 49  s
                                                                                                       49   F49 
which can then be solved

Remember F=k*s => s=F/k => s=(1/k)*F

K ] s  F 
s   F   1 * F 
K ] K ]
And finally.... viewing the results
• Results can be viewed
Even by animations
Comsol’s next topmodel?