<s>
Gerris	B-Application
is	O
computer	B-Application
software	I-Application
in	O
the	O
field	O
of	O
computational	O
fluid	O
dynamics	O
(	O
CFD	O
)	O
.	O
</s>
<s>
Gerris	B-Application
was	O
released	O
as	O
free	B-License
and	I-License
open-source	I-License
software	I-License
,	O
subject	O
to	O
the	O
requirements	O
of	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
(	O
GPL	B-License
)	O
,	O
version	O
2	O
or	O
any	O
later	O
.	O
</s>
<s>
Gerris	B-Application
solves	O
the	O
Navier	O
–	O
Stokes	O
equations	O
in	O
2	O
or	O
3	O
dimensions	O
,	O
allowing	O
to	O
model	O
industrial	O
fluids	O
(	O
aerodynamics	O
,	O
internal	O
flows	O
,	O
etc	O
.	O
)	O
</s>
<s>
or	O
for	O
instance	O
,	O
the	O
mechanics	O
of	O
droplets	B-General_Concept
,	O
thanks	O
to	O
an	O
accurate	O
formulation	O
of	O
multiphase	O
flows	O
(	O
including	O
surface	O
tension	O
)	O
.	O
</s>
<s>
Actually	O
,	O
the	O
latter	O
field	O
of	O
study	O
is	O
the	O
reason	O
why	O
the	B-Application
software	I-Application
shares	O
the	O
same	O
name	O
as	O
the	O
insect	B-Application
genus	I-Application
.	O
</s>
<s>
Gerris	B-Application
also	O
provides	O
features	O
relevant	O
to	O
geophysical	O
flows	O
:	O
</s>
<s>
Flow	O
types	O
#1	O
to	O
#3	O
were	O
studied	O
using	O
the	O
shallow-water	O
solver	O
included	O
in	O
Gerris	B-Application
,	O
case	O
#4	O
brings	O
in	O
the	O
primitives	O
equations	O
and	O
application	O
#5	O
relies	O
on	O
the	O
spectral	O
equations	O
for	O
generation/propagation/dissipation	O
of	O
swell	O
(	O
and/or	O
wind	O
sea	O
)	O
:	O
for	O
this	O
purpose	O
Gerris	B-Application
makes	O
use	O
of	O
the	O
source	O
terms	O
from	O
WaveWatchIII	O
.	O
</s>
<s>
On	O
the	O
contrary	O
Gerris	B-Application
does	O
not	O
allow	O
the	O
modeling	O
of	O
compressible	O
fluids	O
(	O
supersonic	O
flows	O
)	O
.	O
</s>
<s>
Gerris	B-Application
belongs	O
to	O
the	O
finite	B-Algorithm
volumes	I-Algorithm
family	O
of	O
CFD	O
models	O
.	O
</s>
<s>
Gerris	B-Application
is	O
quite	O
different	O
on	O
this	O
respect	O
:	O
it	O
implements	O
a	O
deal	O
between	O
structured	O
and	O
unstructured	O
meshes	O
by	O
using	O
a	O
tree	O
data	O
structure	O
,	O
allowing	O
to	O
refine	O
locally	O
(	O
and	O
dynamically	O
)	O
the	O
(	O
finite-volume	O
)	O
description	O
of	O
the	O
pressure	O
and	O
velocity	O
fields	O
.	O
</s>
<s>
Gerris	B-Application
mainly	O
aims	O
at	O
DNS	O
;	O
the	O
range	O
of	O
Reynolds	O
available	O
to	O
the	O
user	O
thus	O
depends	O
on	O
the	O
computing	O
power	O
they	O
can	O
afford	O
(	O
although	O
the	O
auto-adaptive	O
mesh	O
allows	O
one	O
to	O
focus	O
the	O
computing	O
resources	O
on	O
the	O
coherent	O
structures	O
)	O
.	O
</s>
<s>
According	O
to	O
the	O
Gerris	B-Application
FAQ	O
the	O
implementation	O
of	O
turbulence	O
models	O
will	O
focus	O
on	O
the	O
LES	O
family	O
rather	O
than	O
RANS	O
approaches	O
.	O
</s>
<s>
Gerris	B-Application
is	O
developed	O
in	O
C	B-Language
using	O
the	O
libraries	O
Glib	B-Language
(	O
object	O
orientation	O
,	O
dynamic	O
loading	O
of	O
modules	O
,	O
etc	O
.	O
)	O
</s>
<s>
Moreover	O
Gerris	B-Application
is	O
fully	O
compliant	O
with	O
MPI	B-Application
parallelisation	O
(	O
including	O
dynamic	O
load	O
balancing	O
)	O
.	O
</s>
<s>
Gerris	B-Application
does	O
not	O
need	O
a	O
meshing	O
tool	O
since	O
the	O
local	O
(	O
and	O
time	O
dependent	O
)	O
refinement	O
of	O
the	O
grid	O
is	O
on	O
charge	O
of	O
the	O
solver	O
itself	O
.	O
</s>
<s>
Among	O
the	O
various	O
ways	O
to	O
output	O
Gerris	B-Application
results	O
,	O
let	O
us	O
just	O
mention	O
here	O
:	O
</s>
<s>
Graphical	O
output	O
in	O
PPM	O
format	O
:	O
images	O
can	O
then	O
be	O
converted	O
in	O
(	O
nearly	O
)	O
any	O
format	O
using	O
ImageMagick	B-Language
,	O
and	O
MPEG	O
movies	O
can	O
be	O
generated	O
thanks	O
to	O
FFmpeg	B-Library
(	O
among	O
others	O
)	O
.	O
</s>
<s>
Gfsview	O
,	O
a	O
display	O
software	O
shipped	O
with	O
Gerris	B-Application
,	O
able	O
to	O
cope	O
with	O
the	O
tree	O
structure	O
of	O
the	O
Gerris	B-Application
grid	O
(	O
a	O
data	O
structure	O
which	O
is	O
not	O
efficiently	O
operated	O
by	O
general	O
visualization	O
software	O
)	O
.	O
</s>
<s>
Gerris	B-Application
was	O
distributed	O
as	O
free	B-License
and	I-License
open-source	I-License
software	I-License
right	O
from	O
the	O
onset	O
of	O
the	O
project	O
.	O
</s>
<s>
Following	O
a	O
redesign	O
of	O
the	B-Application
software	I-Application
organization	O
,	O
Gerris	B-Application
became	O
Basilisk	O
,	O
which	O
allows	O
one	O
to	O
develop	O
its	O
own	O
solver	O
(	O
not	O
necessarily	O
in	O
fluid	O
mechanics	O
)	O
using	O
various	O
data	O
structures	O
(	O
including	O
of	O
course	O
the	O
quadtree/octree	O
)	O
and	O
optimized	O
operators	O
for	O
iteration	O
,	O
derivation	O
,	O
etc	O
.	O
</s>
<s>
Solvers	O
are	O
written	O
in	O
C	B-Language
,	O
more	O
specifically	O
the	O
Basilisk	O
C	B-Language
.	O
</s>
