Functions
	inlet_profile (H, S, nz, U_in)

	reattachment (u_bottom)

	run (Re, S=16, Lr=12, U_in=1.0, nz=4, dt=0.2, max_steps=24000)

	main ()

Detailed Description

Verification (sdflow): the backward-facing step (BFS) -- the canonical separated-flow benchmark, and
the showcase for the per-face INLET PROFILE. Geometry is the Gartling (1990) expansion-ratio-2 step: a
channel of full height H = 2S (S = step height) with no-slip walls top/bottom; flow enters ONLY the upper
half (y in [S, 2S]) with the developed parabolic channel profile and is zero over the lower half (the step
face); it leaves through the outflow. Behind the step a recirculation bubble forms on the bottom wall; the
reattachment length x_r/S grows with Re. Quasi-2D (periodic z).

The step is realized purely as the inlet condition via set_domain_bc_profile (no immersed solid): the
parabola vanishes at y=S (the step lip) and y=2S (top wall), exactly the developed upper-channel profile.

We de-risk in the laminar regime (Re_S = U_in*S/nu = 100, 200) -- a bubble must form, x_r/S must grow with
Re, mass is conserved and the flow stays divergence-free -- then push toward Gartling Re=800 and report the
reattachment for comparison (Gartling lower-wall reattachment ~6.1 H = ~12 S). Re_S = U_in * S / nu, with
U_in the mean inlet velocity over the open upper half.

Function Documentation

◆ inlet_profile()

verify_bfs_sdflow.inlet_profile	(	H,
		S,
		nz,
		U_in
	)

Developed parabola over the open upper half y in [S, 2S], zero over the step face y in [0, S].

Definition at line 28 of file verify_bfs_sdflow.py.

Referenced by run().

◆ reattachment()

verify_bfs_sdflow.reattachment ( u_bottom )

End of the primary bubble = the first - -> + crossing of the near-bottom-wall streamwise velocity
AFTER the flow has actually reversed behind the step (skip any thin positive sliver at the step lip).

Definition at line 38 of file verify_bfs_sdflow.py.

Referenced by run().

◆ run()

verify_bfs_sdflow.run	(	Re,
		S = `16`,
		Lr = `12`,
		U_in = `1.0`,
		nz = `4`,
		dt = `0.2`,
		max_steps = `24000`
	)

Run the backward-facing step at Reynolds number `Re` (Re_S = U_in*S/nu) and return its diagnostics.

Step height S, full channel height 2S, channel length Lr*S; a partial parabolic inlet feeds the upper
half, the lower half is the step face. Marches to steady state and returns a dict with the lower-wall
reattachment length (x_r/S, x_r/H), bubble presence, mass-conservation error and max divergence.
Returns None off root.

Definition at line 50 of file verify_bfs_sdflow.py.

References inlet_profile(), and reattachment().

Referenced by main().

◆ main()

verify_bfs_sdflow.main ( )

Run the laminar de-risk (Re_S 100, 200) and optional Re=800 push; print results and set exit code.

Definition at line 109 of file verify_bfs_sdflow.py.

References main(), and run().