Boundary conditions for flow past a cylinder

General
1

Hello everyone, I saw a tutorial on Flow past a cylinder(Test problem 2: Flow past a cylinder (DFG 2D-3 benchmark) — FEniCSx tutorial), where the benchmark specifies the outflow boundary condition as \nu \partial_{\eta} u - p \eta = 0.

However, the program in the tutorial indicates the outflow boundary condition as p=0. Could anyone explain why this is the case?

Additionally, how should this boundary condition be implemented if it is based on divergence conforming discontinuous Galerkin method?

2

Could you be more specific as to where it indicates this?
The tutorial sets phi=0 on the outlet, which is not the same as setting p to zero.
I’ve explained the bcs in more detail at Splitting schemes — Oasisx