Syntax on BC

[erny123]

I'm looking into the NS convergence test: https://github.com/trixi-framework/Trixi.jl/blob/main/examples/dgmulti_2d/elixir_navierstokes_convergence.jl

For the Euler hyperbolic system ya'll implement the Slip-Wall BC.

However, I'm not understanding this syntax in line 189:

# define inviscid boundary conditions boundary_conditions_hyperbolic = (; :top_bottom => boundary_condition_slip_wall)

In lines 22-23 the top_bottom() function is defined along with the Dict().

If I want the BC to be a Slip-Wall but with a velocity using u_inner defined here:

https://trixi-framework.github.io/Trixi.jl/stable/reference-trixi/#Trixi.boundary_condition_slip_wall-Tuple{Any,%20AbstractVector,%20Any,%20Any,%20Any,%20CompressibleEulerEquations2D}

How would I go about doing that with the syntax given in this elixer example?

[DanielDoehring]

I am not sure if I understand your question correctly. Do you want a moving wall? The function you are referencing is indeed the BC invoked by the solver, with u_inner being internally assigned (i.e., from the fluid cell next to the wall).

[ranocha]

The code

Trixi.jl/examples/dgmulti_2d/elixir_navierstokes_convergence.jl

Lines 188 to 189 in fa43fb2

	# define inviscid boundary conditions
	boundary_conditions = (; :top_bottom => boundary_condition_slip_wall)

sets the boundary condition at the boundary named :top_bottom to boundary_condition_slip_wall. The boundary name :top_bottom is defined in

Trixi.jl/examples/dgmulti_2d/elixir_navierstokes_convergence.jl

Lines 22 to 26 in fa43fb2

	top_bottom(x, tol = 50 * eps()) = abs(abs(x[2]) - 1) < tol
	is_on_boundary = Dict(:top_bottom => top_bottom)
	cells_per_dimension = (16, 16)
	mesh = DGMultiMesh(dg, cells_per_dimension; periodicity = (true, false), is_on_boundary)