--- a/src/Grids/Grids.jl	Sat May 25 16:07:10 2024 -0700
+++ b/src/Grids/Grids.jl	Sun May 26 17:35:52 2024 -0700
@@ -18,6 +18,7 @@
 export eval_on
 export componentview
 export ArrayComponentView
+export orthogonal_grid
 
 export BoundaryIdentifier
 export TensorGridBoundary

--- a/src/Grids/equidistant_grid.jl	Sat May 25 16:07:10 2024 -0700
+++ b/src/Grids/equidistant_grid.jl	Sun May 26 17:35:52 2024 -0700
@@ -47,12 +47,12 @@
 """
 inverse_spacing(g::EquidistantGrid) = 1/step(g.points)
 
-
 boundary_identifiers(::EquidistantGrid) = (Lower(), Upper())
 boundary_grid(g::EquidistantGrid, id::Lower) = ZeroDimGrid(g[begin])
 boundary_grid(g::EquidistantGrid, id::Upper) = ZeroDimGrid(g[end])
 boundary_indices(g::EquidistantGrid, id::Lower) = (1,)
 boundary_indices(g::EquidistantGrid, id::Upper) = (length(g),)
+orthogonal_grid(g::EquidistantGrid, id::Union{Lower,Upper}) = g
 
 """
     refine(g::EquidistantGrid, r::Int)

--- a/src/Grids/grid.jl	Sat May 25 16:07:10 2024 -0700
+++ b/src/Grids/grid.jl	Sun May 26 17:35:52 2024 -0700
@@ -128,6 +128,16 @@
 function boundary_indices end
 
 """
+    orthogonal_grid(g::Grid, id::BoundaryIdentifier)
+
+The grid for the coordinate direction orthogonal to that of the boundary
+with given id
+"""
+function orthogonal_grid end
+
+function boundary_indices end
+
+"""
     eval_on(g::Grid, f)
 
 Lazy evaluation of `f` on the grid. `f` can either be on the form `f(x,y,...)`

--- a/src/Grids/tensor_grid.jl	Sat May 25 16:07:10 2024 -0700
+++ b/src/Grids/tensor_grid.jl	Sun May 26 17:35:52 2024 -0700
@@ -95,6 +95,9 @@
     return LazyTensors.concatenate_tuples(b_ind...)
 end
 
+orthogonal_grid(g::TensorGrid, id::BoundaryIdentifier) = g.grids[grid_id(id)]
+
+
 function combined_coordinate_vector_type(coordinate_types...)
     combined_coord_length = mapreduce(_ncomponents, +, coordinate_types)
     combined_coord_type = mapreduce(eltype, promote_type, coordinate_types)
@@ -133,3 +136,4 @@
         return (I, d-cumsum(nds)[I-1])
     end
 end
+

--- a/test/Grids/equidistant_grid_test.jl	Sat May 25 16:07:10 2024 -0700
+++ b/test/Grids/equidistant_grid_test.jl	Sun May 26 17:35:52 2024 -0700
@@ -79,6 +79,12 @@
 
     end
 
+    @testset "orthogonal_grid" begin
+        g = EquidistantGrid(0:0.1:1)
+        @test orthogonal_grid(g, Lower()) == g
+        @test orthogonal_grid(g, Upper()) == g
+    end
+
     @testset "refine" begin
         g = EquidistantGrid(0:0.1:1)
         @test refine(g, 1) == g

--- a/test/Grids/tensor_grid_test.jl	Sat May 25 16:07:10 2024 -0700
+++ b/test/Grids/tensor_grid_test.jl	Sun May 26 17:35:52 2024 -0700
@@ -184,6 +184,17 @@
         @test boundary_indices(TensorGrid(g₄,g₁), TensorGridBoundary{2, Lower}()) == (1,)
         @test boundary_indices(TensorGrid(g₄,g₁), TensorGridBoundary{2, Upper}()) == (11,)
     end
+
+    @testset "orthogonal_grid" begin
+        g₁ = EquidistantGrid(range(0,1,length=11))
+        g₂ = EquidistantGrid(range(2,3,length=6))
+        g₃ = EquidistantGrid(range(4,5,length=7))
+    
+        @test orthogonal_grid(TensorGrid(g₁, g₂, g₃), TensorGridBoundary{1, Lower}()) == g₁
+        @test orthogonal_grid(TensorGrid(g₁, g₂, g₃), TensorGridBoundary{2, Lower}()) == g₂
+        @test orthogonal_grid(TensorGrid(g₁, g₂, g₃), TensorGridBoundary{3, Upper}()) == g₃
+    end
+
 end
 
 @testset "combined_coordinate_vector_type" begin