```
GROUP 1. Run title and other preliminaries
TEXT(Pipe Flow With Axial Free Convec
TITLE
DISPLAY
An extra momentum source is added to the axial momentum
equation to represent a buoyancy force, in order to simulate
free convection in a pipe flow.

. - .
/       \
|         |
|\       /|
Axial    g    |         | ^
buoyancy |    |         | |
force    v    |         | |z
acts as       |         |
momentum      |  . - .  |
source        |/       \|
|  ^   ^  |  Fixed mass,
\ |   | /---momentum and
| - |     enthalpy flux
-->    into inlet
r
ENDDIS

GROUP 3. X-direction grid specification
CARTES=F

GROUP 4. Y-direction grid specification
*** 20 grid cells are used in y-direction to cover
an extent of 0.01 m
IREGY=1; GRDPWR(Y,20,0.01,1.0)

GROUP 5. Z-direction grid specification
*** The flow is parabolic
PARAB=T; IREGZ=1; GRDPWR(Z,20,0.20,1.0)

GROUP 7. Variables stored, solved & named
#solvel
SOLVE(H1)

GROUP 9. Properties of the medium (or media)
Fluid is air at STP (standard temperature and pressure)
#fluidmat
setprps(1,air20)
PRNDTL(H1)=0.7
GROUP 13. Boundary conditions and special sources
1. Inlet boundary: uniform velocity

INLET(UNIFORM,LOW,#1,#1,#1,#NREGY,#1,#1,1,1)
VALUE(UNIFORM,P1,0.1); VALUE(UNIFORM,W1,0.1);VALUE(UNIFORM,H1,0.0)

2. Wall boundary: constant temperature (and therefore enthalpy)

WALL (PIPE,NORTH,#1,#1,#NREGY,#NREGY,#1,#NREGZ,1,1)
COVAL(PIPE,W1,1.0,0.0); COVAL(PIPE,H1,1.0,1.0e3)

3. Buoyancy source

#gravity
gravity acts in the negative z direction; reference enthalpy = 0
gravdir=6; href=0.0
#bouss

GROUP 16. Termination of iterations
LITHYD=30; TSTSWP=5

GROUP 22. Spot-value print-out
NPLT=1; NPRMON=30; IYMON=NY/4

GROUP 23. Field print-out and plot control
NYPRIN=2; NZPRIN=10
*** Plot exit profile of velocity and temperature
PATCH(EXIT,PROFIL,1,1,1,NY,NZ,NZ,1,1)
PLOT(EXIT,W1,0.0,0.0);PLOT(EXIT,H1,0.0,0.0)
dump fields at every z-step to parphi
IDISPA=1
PHOTON USE
p
parphi
10 1

up z
gr ou x 1
msg radial scal is enlarged by factor of 10
msg velocity vectors
vec x 1 sh
pause
msg enthalpy contours
con h1 x 1 fi;0.001
pause
msg presure contours
con p1 x 1 fi;0.001
pause
msg velocity contours
con w1 x 1 fi;0.001
ENDUSE

```