From ca83847aa8e4aa1b663d1291d9521ee4ed4e62d0 Mon Sep 17 00:00:00 2001
From: Albert de Montserrat <albert.de.montserrat@gmail.com>
Date: Wed, 3 Jul 2024 15:42:31 +0200
Subject: [PATCH] docs

---
 docs/make.jl                        |  1 +
 docs/src/man/boundary_conditions.md | 36 +++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)
 create mode 100644 docs/src/man/boundary_conditions.md

diff --git a/docs/make.jl b/docs/make.jl
index e34f462f..0824923f 100644
--- a/docs/make.jl
+++ b/docs/make.jl
@@ -16,6 +16,7 @@ makedocs(;
             "Installation" => "man/installation.md",
             "Backend"   => "man/backend.md",
             "Equations" => "man/equations.md",
+            "Boundary conditions" => "man/boundary_conditions.md",
             "Advection" => "man/advection.md",
             ],
         "Examples"  => Any[
diff --git a/docs/src/man/boundary_conditions.md b/docs/src/man/boundary_conditions.md
new file mode 100644
index 00000000..98665708
--- /dev/null
+++ b/docs/src/man/boundary_conditions.md
@@ -0,0 +1,36 @@
+# Flow boundary conditions
+
+Supported boundary conditions:
+
+1. Free slip
+
+    $\frac{\partial u_i}{\partial x_i} = 0$ at the boundary $\Gamma$
+
+2. No slip
+
+    $u_i = 0$ at the boundary $\Gamma$
+
+3. Free surface
+
+    $\sigma_z = 0 \rightarrow \tau_z = P$ at the top boundary
+
+## Defining the boundary contions
+Information regarding flow boundary conditions is defined in the `FlowBoundaryConditions` object. They can be switched on and off by setting them as `true` or `false` at the appropriate boundaries. Valid boundary names are `left` and `right`, `top` and `bot`, and for the 3D case, `front` and `back`. 
+
+For example, if we want to have free free-slip in every single boundary in a 2D simulation, we need to instantiate `FlowBoundaryConditions` as:
+```julia
+bcs = FlowBoundaryConditions(;
+    no_slip      = (left=false, right=false, top=false, bot=false),
+    free_slip    = (left=true, right=true, top=true, bot=true),
+    free_surface = false
+)
+```
+
+The equivalent for the 3D case would be:
+```julia
+bcs = FlowBoundaryConditions(;
+    no_slip      = (left=false, right=false, top=false, bot=false, front=false, back=false),
+    free_slip    = (left=true, right=true, top=true, bot=true, front=true, back=true),
+    free_surface = false
+)
+```
\ No newline at end of file