# Basics : Rayleigh-Taylor

Home » Knowledge Base » ICFD / Incompressible CFD » Basics Examples » Basics : Rayleigh-Taylor

This example shows how to set up a simulation of two-phase flow with surface tension. Rayleigh-Taylor instability occurs when a fluid is on top of a lighter one.

## Keywords

```*TITLE
*KEYWORD
*DATABASE_BINARY_D3PLOT
*DEFINE_CURVE_TITLE
*ICFD_BOUNDARY_FREESLIP*ICFD_BOUNDARY_NONSLIP
*ICFD_CONTROL_TIME
*ICFD_MAT
*ICFD_PART
*ICFD_PART_VOL
*ICFD_SECTION
*INCLUDE
*MESH_INTERF
*MESH_SURFACE_ELEMENT
*MESH_SURFACE_NODE
*MESH_VOLUME
*PARAMETER
*END

```

## Reduced Input

`\$X------------------------------------------------------------------------------\$# UNITS: SI. \$X------------------------------------------------------------------------------\$X*KEYWORD*TITLE\$#                                                                         titleICFD Rayleigh-Taylor instability*INCLUDEmesh.k\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8\$                                                                              \$\$                             PARAMETERS                                       \$\$                                                                              \$\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8*PARAMETER\$#   prmr1      val1R    T_end       4.0R  dt_plot       0.1R dt_fluid      1e-2R     ro_h       1.2R     ro_l      0.17R     mu_h     0.003R     mu_l     0.003R     grav       1.0R     st       0.015\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8\$                                                                              \$\$                       ICFD PARTS/ SECTION/ MATERIAL                          \$\$                                                                              \$\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8*ICFD_MAT\$#     mid       flg        ro       vis        st           1         1     &ro_l     &mu_l       &st  *ICFD_MAT\$#     mid       flg        ro       vis           2         1     &ro_h     &mu_h  *ICFD_SECTION\$#     sid            1*ICFD_PART_TITLE\$#     pid     secid       mid   upper horizontal boundary         1         1         2   *ICFD_PART_TITLE                 \$#     pid     secid       mid   upper left vertical boundary              2         1         2   *ICFD_PART_TITLE                 \$#     pid     secid       mid   upper right vertical boundary              3         1         2   *ICFD_PART_TITLE\$#     pid     secid       mid   lower horizontal boundary         4         1         1   *ICFD_PART_TITLE                 \$#     pid     secid       mid   lower left vertical boundary              5         1         1   *ICFD_PART_TITLE                 \$#     pid     secid       mid   lower right vertical boundary              6         1         1   *ICFD_PART_TITLE                 \$#     pid     secid       mid   initial interface position                7         1         1   *ICFD_PART_VOL\$#     pid     secid       mid            8         1         1\$#   spid1     spid2     spid3           4         5         6         7  *ICFD_PART_VOL\$#     pid     secid       mid            9         1         2\$#   spid1           1         2         3         7  \$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8\$                                                                              \$\$                    ICFD BOUNDARY/INITIAL CONDITIONS                          \$\$                                                                              \$\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8*ICFD_BOUNDARY_FREESLIP\$#     pid            2         3         5         6*ICFD_BOUNDARY_NONSLIP\$#     pid            1         4*LOAD_BODY_Y\$#    lcid        sf                1        1          *DEFINE_CURVE_TITLEGravity force\$#    lcid      sidr       sfa           1               &grav\$#                a1                  o1                 0.0               &grav             10000.0               &grav\$\$---+----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 MESH KEYWORDS                                \$\$                                                                              \$\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8*MESH_VOLUME\$#   volid              1\$#   spid1     spid2             1         2         3         4         5         6*MESH_INTERF\$#   volid             1\$#   spid1             7    \$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8\$                                                                              \$\$                             DATABASE (OUTPUT)                                \$\$                                                                              \$\$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8*DATABASE_BINARY_D3PLOT\$#      dt  &dt_plot  *END`