# Basics : Free Convection flow — Welcome to LS-DYNA Examples

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This LS-DYNA simulation shows a simple ICFD free convection problem. Since the solver is incompressible, density is a constant. Instead, the tiny density variations due to the rise in temperature are approximated by a external force applied on the system and function of the fluid’s thermal expansion coefficient, gravity and fluid temperature (Boussinesq approximation). Depending on the Raleigh number value, different vortex behaviors can be observed.

## Description

This LS-DYNA simulation shows a simple ICFD free convection problem. Since the solver is incompressible, density is a constant. Instead, the tiny density variations due to the rise in temperature are approximated by a external force applied on the system and function of the fluid’s thermal expansion coefficient, gravity and fluid temperature (Boussinesq approximation). Depending on the Raleigh number value, different vortex behaviors can be observed.

## Animated Result

Fluid temperature fringes and velocity vectors

## Keywords

*KEYWORD
*TITLE
*DATABASE_BINARY_D3PLOT
*DEFINE_CURVE_TITLE
*ICFD_BOUNDARY_PRESCRIBED_TEMP
*ICFD_BOUNDARY_NONSLIP
*ICFD_CONTROL_TIME
*ICFD_DATABASE_TEMP
*ICFD_INITIAL
*ICFD_MAT
*ICFD_PART
*ICFD_PART_VOL
*ICFD_SECTION
*INCLUDE
*MESH_SURFACE_ELEMENT
*MESH_SURFACE_NODE
*MESH_VOLUME
*PARAMETER
*END

## Reduced Input

\$-----------------------------------------------------------------------------
\$
\$ Example provided by Iñaki (LSTC)
\$
\$ E-Mail: info@dynamore.de
\$ Web: http://www.dynamore.de
\$
\$ Copying for non-commercial usage allowed if
\$ copy bears this notice completely.
\$
\$X------------------------------------------------------------------------------
\$X
\$X 1. Run file as is.
\$X    Requires LS-DYNA MPP R8.0.0 (or higher) with double precision
\$X
\$X------------------------------------------------------------------------------
\$# UNITS: Dimensionless.
\$X------------------------------------------------------------------------------
\$X
*KEYWORD
*TITLE
ICFD Natural convection flow
*INCLUDE
mesh.k
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
\$                                                                              \$
\$                             PARAMETERS                                       \$
\$                                                                              \$
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*PARAMETER
R    T_end      30.0
R  dt_plot      1.00
\$
\$--- Fluid
\$
Rrho_fluid      37.8
R mu_fluid        1.
R dt_fluid     0.010
RTemp_init     0.000
RTemp_w1       1.000
RTemp_w2       0.000
R HC_fluid       0.7
R TC_fluid        1.
Rthc_fluid        1.
R grav            1.
\$ Prandtl number : 0.7
\$
\$ Raleigh number : ( grav thc_fluid L^3 rho_fluid^2 hc_fluid ) / ( tc_fluid) : 10e3
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
\$                                                                              \$
\$                           ICFD CONTROL CARDS                                 \$
\$                                                                              \$
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*ICFD_CONTROL_TIME
\$#     ttm        dt
&T_end &dt_fluid
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
\$                                                                              \$
\$                       ICFD PARTS/ SECTION/ MATERIAL                          \$
\$                                                                              \$
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*ICFD_SECTION
\$#     sid
1
*ICFD_MAT
\$#     mid       flg        ro       vis
1         1&rho_fluid &mu_fluid
\$#      hc        tc      beta
&HC_fluid &tc_fluid&thc_fluid
*ICFD_PART
\$#     pid     secid       mid
1         1         1
*ICFD_PART
\$#     pid     secid       mid
2         1         1
*ICFD_PART
\$#     pid     secid       mid
3         1         1
*ICFD_PART
\$#     pid     secid       mid
4         1         1
*ICFD_PART_VOL
\$#     pid     secid       mid
10         1         1
\$#   spid1     spid2     spid3     spid4
1         2         3         4
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
\$                                                                              \$
\$                    ICFD BOUNDARY/INITIAL CONDITIONS                          \$
\$                                                                              \$
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*ICFD_BOUNDARY_NONSLIP
\$#     pid
1
*ICFD_BOUNDARY_NONSLIP
\$#     pid
2
*ICFD_BOUNDARY_NONSLIP
\$#     pid
3
*ICFD_BOUNDARY_NONSLIP
\$#     pid
4
*ICFD_BOUNDARY_PRESCRIBED_TEMP
\$#     pid      lcid
1         3
*ICFD_BOUNDARY_PRESCRIBED_TEMP
\$#     pid      lcid
2         4
*ICFD_INITIAL
\$#     pid        vx        vy        vz      temp
0                              &Temp_init
*DEFINE_CURVE_TITLE
Temp wall 1
\$#    lcid      sidr       sfa       sfo      offa      offo    dattyp
3                    &Temp_w1
\$#                a1                  o1
0.0                 1.0
10000.0                 1.0
*DEFINE_CURVE_TITLE
Temp wall 2
\$#    lcid      sidr       sfa       sfo      offa      offo    dattyp
4
\$#                a1                  o1
0.0            &Temp_w2
10000.0            &Temp_w2
\$#    lcid       sf
1        1
*DEFINE_CURVE_TITLE
Gravity force
\$#    lcid      sidr       sfa       sfo      offa      offo    dattyp
1                    &grav
\$#                a1                  o1
0.0                 1.0
10000.0                 1.0
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
\$                                                                              \$
\$                            ICFD MESH KEYWORDS                                \$
\$                                                                              \$
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*MESH_VOLUME
\$#   volid
5
\$#    pid1      pid2      pid3      pid4
1         2         3         4
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
\$                                                                              \$
\$                             DATABASE (OUTPUT)                                \$
\$                                                                              \$
\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*ICFD_DATABASE_TEMP
\$#     pid
3
*ICFD_DATABASE_TEMP
\$#     pid
4
*DATABASE_BINARY_D3PLOT
&dt_plot
*END