This LS-DYNA simulation shows a simple FSI coupling problem using weak/loose/explicit FSI. A rigid cylinder has a prescribed displacement in the Y direction. After five seconds, the inlet velocity boundary condition is triggered pushing the cylinder to the right. Since the coupling is loose, the two solvers retain their own independent timesteps and the solid mechanics solver runs in explicit. The FSI uses a boundary fitted approach. The fluid mesh must have a boundary with the structure. The meshes do not have to coincide but the geometries must remain close. When FSI is triggered, the fluid mesh moves in a Lagrangian way while the fluid flow evolves in a Eulerian way.
Fluid velocity fringes
*BOUNDARY_PRESCRIBED_MOTION_RIGID *KEYWORD *TITLE *CONTROL_TERMINATION *CONTROL_TIMESTEP *DATABASE_BINARY_D3PLOT *DEFINE_CURVE_FUNCTION *DEFINE_CURVE_TITLE *ELEMENT_SHELL *ICFD_BOUNDARY_FREESLIP *ICFD_BOUNDARY_FSI *ICFD_BOUNDARY_PRESCRIBED_VEL *ICFD_BOUNDARY_PRESCRIBED_PRE *ICFD_BOUNDARY_NONSLIP *ICFD_CONTROL_FSI *ICFD_CONTROL_TIME *ICFD_DATABASE_DRAG *ICFD_MAT *ICFD_PART *ICFD_PART_VOL *ICFD_SECTION *INCLUDE *MAT *MESH_BL *MESH_SURFACE_ELEMENT *MESH_SURFACE_NODE *MESH_VOLUME *NODE *PARAMETER *PART *SECTION *END
$-----------------------------------------------------------------------------
$
$ Example provided by Iñaki (LSTC)
$
$ E-Mail: info@dynamore.de
$ Web: http://www.dynamore.de
$
$ Copyright, 2015 DYNAmore GmbH
$ 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 Cylinder flow - Weak FSI
*INCLUDE
mesh.k
*INCLUDE
struc.k
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
$ $
$ PARAMETERS $
$ $
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*PARAMETER
R T_end 40.0
R dt_plot 0.20
$
$--- Fluid
$
R v_inlet 1.0
Rrho_fluid 1.0
R mu_fluid 0.005
R dt_fluid 0.050
$
$---+----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
*ICFD_CONTROL_FSI
$# owc
0
$---+----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
*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_PRESCRIBED_VEL
$# pid dof vad lcid
1 1 1 1
*ICFD_BOUNDARY_PRESCRIBED_VEL
$# pid dof vad lcid
1 2 1 2
*ICFD_BOUNDARY_PRESCRIBED_PRE
$# pid lcid sf death birth
2 2
*ICFD_BOUNDARY_FREESLIP
$# pid
3
*ICFD_BOUNDARY_NONSLIP
$# pid
4
*ICFD_BOUNDARY_FSI
$# pid
4
*DEFINE_CURVE_TITLE
Velocity inlet
$# lcid sidr sfa sfo offa offo dattyp
1
$# a1 o1
0.0 0.
5.0 0.
6.0 &v_inlet
10000.0 &v_inlet
*DEFINE_CURVE_TITLE
Pressure outlet
$# lcid sidr sfa sfo offa offo dattyp
2
$# a1 o1
0.0 0.0
10000.0 0.0
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
$ $
$ ICFD MESH KEYWORDS $
$ $
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*MESH_VOLUME
$# volid
10
$# pid1 pid2 pid3 pid4
1 2 3 4
*MESH_BL
$# pid nelth
4 2
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
$ $
$ DATABASE (OUTPUT) $
$ $
$---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
*ICFD_DATABASE_DRAG
$# pid
4
*DATABASE_BINARY_D3PLOT
&dt_plot
*end
This LS-DYNA simulation shows a simple FSI coupling problem using weak/loose/explicit FSI. A rigid cylinder has a prescribed displacement in the Y direction. After five seconds, the inlet velocity boundary condition is triggered pushing the cylinder to the right. Since the coupling is loose, the two solvers retain their own independent timesteps and the solid mechanics solver runs in explicit. The FSI uses a boundary fitted approach. The fluid mesh must have a boundary with the structure. The meshes do not have to coincide but the geometries must remain close. When FSI is triggered, the fluid mesh moves in a Lagrangian way while the fluid flow evolves in a Eulerian way.