Forward Facing Step — Welcome to LS-DYNA Examples

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This is a well known benchmarking problem for supersonic flow shock capturing. An incoming shock wave hits a forward facing step and reflects on the different walls, creating a transient shock wave pattern.

Description

This test is transient, compressible, inviscid flow. The wind tunnel has 1 length unit wide and 3 length units long. The step is 0.2 length units high and is located 0.6 length units from the left-hand end of the tunnel. The tunnel is assumed to have an infinite width in the direction orthogonal to the plane of the computation (i.e., “slab symmetry” is assumed). So, we treat it as a two-dimensional problem. Initially the wind tunnel is filled with a gamma-law gas, with ϒ = 1.4, which everywhere has density 1.4, pressure 1.0, and velocity 3. Gas with this density, pressure, and velocity is continually fed in from the left-hand boundary.

References:

[1] “ANSY Fluid Dynamics verification Manual”, 2019 R3

[2] Woodward, P., Colella, P., “The Numerical Simulation of Two-Dimensional Fluid Flow with Strong Shocks”, Journal of Computational Physics, Vol 54, pp. 115-173, 1984

Animated Result

forward_facing_step_pre.gif

Keywords

*DUALCESE_MODEL

*DUALCESE_CONTROL_SOLVER

*DUALCESE_CONTROL_TIMESTEP

*DUALCESE_CONTROL_LIMITER

*DUALCESE_INCLUDE_MODEL

*DUALCESE_BOUNDARY_PRESCRIBED_SEGMENT_SET

*DUALCESE_BOUNDARY_NON_REFLECTIVE_SEGMENT_SET

*DUALCESE_BOUNDARY_REFLECTIVE_SEGMENT_SET

*DUALCESE_BOUNDARY_SOLID_WALL_SEGMENT_SET

*DUALCESE_INITIAL

*DUALCESE_PART

*DUALCESE_EOS_IDEAL_GAS

*DUALCESE_D3PLOT

*CONTROL_TERMINATION

*DATABASE_BINARY_D3PLOT

*DATABASE_BINARY_D3DUMP

Reduced Input

*KEYWORD

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

*DUALCESE_CONTROL_SOLVER

$    ieqns     igeom iframeref

Euler        2D     fixed

*DUALCESE_CONTROL_TIMESTEP

$     iddt       cfl     dtint

2       0.5    0.0001

*DUALCESE_CONTROL_LIMITER

$    idlmt      alfa      beta      epsr

0       2.0       1.      0.001

$

*DUALCESE_INCLUDE_MODEL

fluid_m1q.k

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

$ Setup the boundary conditions for fluid

$ Prescribed inlet BC (left)

*DUALCESE_BOUNDARY_PRESCRIBED_SEGMENT_SET

$     ssid

1

$   lcid_u    lcid_v    lcid_w    lcid_d    lcid_p    lcid_t

-1

$     sf_u      sf_v      sf_w      sf_d      sf_p      sf_t

3.0       0.0       0.0       1.4       1.0

$ Outflow BC

*DUALCESE_BOUNDARY_NON_REFLECTIVE_SEGMENT_SET

$     ssid

2

$ Solid BC_3 (tunnel wall)

*DUALCESE_BOUNDARY_SOLID_WALL_SEGMENT_SET

$     ssid

3

*DUALCESE_BOUNDARY_REFLECTIVE_SEGMENT_SET

$     ssid

5

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

$ Setup the initial conditions for fluid

*DUALCESE_INITIAL

$      uic       vic       wic     rhoic       pic       tic       hic

3.0       0.0       0.0       1.4       1.0

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

$ Setup fluid properties

*DUALCESE_PART

$      pid       mid     eosid

1                   5

*DUALCESE_EOS_IDEAL_GAS

$    eosid        cv        cp

5  0.198413  0.277778

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

$ Handle output of flow variables

*DUALCESE_D3PLOT

density

pressure

velocity

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

*END

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