--- a/src/SbpOperators/volumeops/derivatives/second_derivative.jl	Tue Feb 07 21:55:07 2023 +0100
+++ b/src/SbpOperators/volumeops/derivatives/second_derivative.jl	Wed Jul 26 21:35:50 2023 +0200
@@ -1,46 +1,37 @@
 """
-    second_derivative(grid::EquidistantGrid, inner_stencil, closure_stencils, direction)
+    second_derivative(g::EquidistantGrid, stencil_set, direction)
 
-Creates the second-derivative operator `D2` as a `LazyTensor`
-
-`D2` approximates the second-derivative d²/dξ² on `grid` along the coordinate dimension specified by
-`direction`, using the stencil `inner_stencil` in the interior and a set of stencils `closure_stencils`
-for the points in the closure regions.
+Creates the second derivative operator `D2` as a `LazyTensor`
 
-On a one-dimensional `grid`, `D2` is a `VolumeOperator`. On a multi-dimensional `grid`, `D2` is the outer product of the
-one-dimensional operator with the `IdentityTensor`s in orthogonal coordinate dirrections.
+`D2` approximates the second-derivative d²/dξ² on `g` along the coordinate
+dimension specified by `direction`.
 
-See also: [`volume_operator`](@ref).
+See also: [`VolumeOperator`](@ref), [`LazyTensors.inflate`](@ref).
 """
-function second_derivative(grid::EquidistantGrid, inner_stencil, closure_stencils, direction)
-    h_inv = inverse_spacing(grid)[direction]
-    return SbpOperators.volume_operator(grid, scale(inner_stencil,h_inv^2), scale.(closure_stencils,h_inv^2), even, direction)
+function second_derivative(g::TensorGrid, stencil_set, direction)
+    D₂ = second_derivative(g.grids[direction], stencil_set)
+    return LazyTensors.inflate(D₂, size(g), direction)
 end
 
-
 """
-    second_derivative(grid, inner_stencil, closure_stencils)
+    second_derivative(g::EquidistantGrid, stencil_set::::StencilSet)
 
-Creates a `second_derivative` operator on a 1D `grid` given `inner_stencil` and `closure_stencils`.
+The second derivative operator on an `EquidistantGrid`. 
+Uses the `D2` stencil in `stencil_set`.
 """
-second_derivative(grid::EquidistantGrid{1}, inner_stencil::Stencil, closure_stencils) = second_derivative(grid, inner_stencil, closure_stencils,1)
-
+function second_derivative(g::EquidistantGrid, stencil_set::StencilSet)
+    inner_stencil = parse_stencil(stencil_set["D2"]["inner_stencil"])
+    closure_stencils = parse_stencil.(stencil_set["D2"]["closure_stencils"])
+    return second_derivative(g, inner_stencil, closure_stencils)
+end
 
 """
-    second_derivative(grid, stencil_set, direction)
+    second_derivative(g::EquidistantGrid, inner_stencil::Stencil, closure_stencils)
 
-Creates a `second_derivative` operator on `grid` along coordinate dimension `direction` given a `stencil_set`.
+The second derivative operator on an `EquidistantGrid`, given `inner_stencil` and
+`closure_stencils`.
 """
-function second_derivative(grid::EquidistantGrid, stencil_set::StencilSet, direction)
-    inner_stencil = parse_stencil(stencil_set["D2"]["inner_stencil"])
-    closure_stencils = parse_stencil.(stencil_set["D2"]["closure_stencils"])
-    second_derivative(grid,inner_stencil,closure_stencils,direction);
+function second_derivative(g::EquidistantGrid, inner_stencil::Stencil, closure_stencils)
+    h⁻¹ = inverse_spacing(g)
+    return VolumeOperator(g, scale(inner_stencil,h⁻¹^2), scale.(closure_stencils,h⁻¹^2), even)
 end
-
-
-"""
-    second_derivative(grid, stencil_set)
-
-Creates a `second_derivative` operator on a 1D `grid` given a `stencil_set`.
-"""
-second_derivative(grid::EquidistantGrid{1}, stencil_set::StencilSet) = second_derivative(grid, stencil_set, 1)
\ No newline at end of file